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. 2021 Aug 10;6(33):21265–21275. doi: 10.1021/acsomega.1c01329

Fate of Lead and Cadmium in Precalciner Cement Plants and Their Atmospheric Releases

Yiming Huang †,‡, Jinling Liu †,*, Lu Yang ‡, Xinyu Li §,∥, Guojia Hu ‡, Guan Wang †,‡, Guangyi Sun §,∥, Zhonggen Li ‡,§,*
PMCID: PMC8387992  PMID: 34471731

Abstract

graphic file with name ao1c01329_0009.jpg

Disclosing the fate of lead (Pb) and cadmium (Cd) during the cement production process is the key to control their atmospheric emissions, which have not attracted much attention yet. In this study, three precalciner cement plants (CPs) using different raw materials in Guizhou Province in Southwest China were investigated. It showed that the concentrations of Pb and Cd in different raw materials and the associated total metal input of these materials were different among CPs; the behavior of Pb and Cd were almost the same during the clinker production process that there has been no accumulation of these two elements inside the system, and nearly all input of Pb and Cd were discharged by the clinker. Although the temperature of clinkerization was pretty high of 1450 °C, the atmospheric emission ratio of both metals was negligible (<0.006% for Pb and <0.002% for Cd of the total output, respectively); the main reason might be that the two elements were incorporated into the minerals of clinker, either as silicate or sulfate. The long-term environmental impacts of some high Pb-and Cd-laden clinkers and cement need to be monitored and evaluated.

1. Introduction

The manufacturing of cement involves the calcining of raw materials in a kiln to produce clinker;1 it is thus an energy-consuming industry; at the same time, a range of atmospheric pollutants, such as particulate matters (PM) and heavy metals, as well as greenhouse gas CO2, would be released into the ambient atmosphere during this high-temperature process.2−6 Therefore, the environmental impact of the cement industry, especially the heavy metal emissions concerning their toxicity and persistency, has received more and more attention.7,8

Nriagu and Pacyna9 estimated the atmospheric emissions of 16 trace metals from the cement plants (CPs) in the world and found the emission varied considerably for each element due to the large uncertainties in the emission factors (EMFs). In order to reduce the atmospheric emissions of heavy metals from CPs and eliminate their negative environmental impacts, the fate of heavy metals in CPs should be clarified first. However, aside from Hg, which has been studied with a couple of field investigations,7,10,11 research on other metals is relatively scarce. As two toxic and semi-volatile heavy metals, lead (Pb) and cadmium (Cd) can volatilize during the simulated clinker sintering process at 1450 °C,12,13 while they were found to be not totally volatilized in the rotary kiln, with the resultant clinker containing considerable content of Pb (16.8 mg·kg–1) and Cd (3.1 mg·kg–1) in filed investigation,14 and the loss of Pb and Cd in CPs with precalciner process was in the range of 39–57% by comparing the concentrations of Pb and Cd in raw meal and clinker.15 However, Cd was mainly discharged via the flue gas dust, while the emissions of Pb were dependent on the process conditions of some industrial process.16 Hence, the behavior of Pb and Cd inside the CPs could be more complicated than thought. In addition, due to the lack of information of Pb and Cd contents in different raw materials and the intermediate products, it is still not clear about the detailed behaviors of Pb and Cd during the clinker and cement production process.17,18 Furthermore, the estimation of atmospheric emissions of Pb and Cd from CPs would be vital to assess the environmental impacts of this industry.4,19−21

China has been the largest producer of cement in the world for more than three decades, and now, it produces more than one half of the world’s total cement products.22 The dominant production technique for cement in China has changed from using shaft kilns before 2000 to precalciner kilns, or suspension pre-heater kilns, since 2010.5 Guizhou Province in Southwest China is one important cement production base in China due to its rich limestone and coal deposits, and the cement output in this province has increased by 7 times during 2005–2018 and accounted for 5% of the national total in 2018.23−25 Our previous studies revealed the distinctive Hg emission levels from different precalciner CPs in Guizhou and found Hg was enriched and accumulated inside the clinker production process and Hg isotope signals of this source was different from other important sources, for example, non-ferrous smelters.7,26 In this study, three precalciner CPs (CP #1, CP #2, and CP #3) in Guizhou Province are systematically investigated; these three CPs all have a preheater and precalciner process and with a capacity of 4500–5000 tonnes clinker each line per day; the basic information of the instigated CPs is shown in Table S1. All input/output solid materials in the entire production process had been collected and analyzed, and the sampling locations are illustrated in Figure 7. The aims are to (1) detect the Pb and Cd concentrations in all materials during the entire production process; (2) find out whether there has been an enrichment of Pb and Cd inside the clinker production process; (3) quantify the atmospheric EMFs and the total atmospheric emissions of these two pollutants from CPs in Guizhou Province and the whole country; (4) assess the potential environmental impacts of Pb and Cd flowing through the cement production process. To the best of our best knowledge, this is the first detailed report on the two elements during the whole cement production process in China. Hence, results from this study will provide important basic information to reveal the fate of Pb and Cd during the precalciner cement production and the factors that control Pb and Cd emissions in CPs, which are needed to assess the possible impacts of Pb and Cd pollution caused by CPs.

Figure 7.

Figure 7

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Schematic diagram of the preheater/precalciner cement manufacturing facility and sampling points.

2. Results and Discussion

2.1. Concentrations of Pb and Cd in Different Solid Materials

The concentrations of solid materials in precalciner CPs are discussed in three parts, for example, different raw materials and coal, intermediate products (raw meal and kiln dust), and materials in clinker to cement production process. The detailed information about the concentrations of Pb and Cd in these materials are shown in Tables 1 and 2, respectively. In addition, their daily material input and output are provided in Table S2 of Supporting Information.

Table 1. Pb Concentration in Different Materials during the Entire Production of the Studied CPs.

      Pb concentration (mean ± SD, mg·kg–1)
materials     CP #1 CP #2 CP #3
material inputs during the clinker production raw materials limestone 319 ± 243 (n = 3)a 5.8 ± 4.7 (n = 3)a 2.9 ± 0.7 (n = 3)a
    sandstone 7.9 ± 0.9 (n = 3) b b
    shale 35 ± 14 (n = 3) 11.4 ± 2.0 (n = 3) 14.4
    coal gangue 50 ± 2 (n = 2) b b
    iron-rich materials 52 ± 3 (n = 3) 1619 ± 70 (n = 3) b
    beneficiation waste b b 12.1 ± 1.1 (n = 2)
    yellow phosphorus slag b b 21.1 ± 2.8 (n = 3)
    carbide slag b b 9.9 ± 2.5 (n = 2)
    coal slag b b 19.4 ± 0.9 (n = 3)
  fuel coal 17 ± 4 (n = 2) 13.1 ± 0.6 (n = 3) 8.6 ± 0.6 (n = 3)
  weighted mean   244.7 36.2 4.36
intermediate products raw meal   251 ± 15 (n = 3) 32 ± 1 (n = 3) 5.0 ± 0.1 (n = 3)
  kiln tail dust   527 ± 73 (n = 6) 30 ± 5 (n = 6) 6.0 ± 0.3 (n = 3)
  kiln head dust   234 ± 55 (n = 3) 117 ± 23 (n = 3) 23.2
  stack flue gas at the kiln tail   0.84c 0.16c 0.05c
  stack flue gas at the kiln head   0.21c 0.54c 0.33c
material during the clinker to cement production additives fly ash of CFPPs 133 ± 25 (n = 2) 22 ± 11 (n = 3) 51.8 ± 0.2 (n = 3)
    desulfurization gypsum 14 ± 14 (n = 3) 1.7 ± 0.05 (n = 3) 1.2 ± 0.04 (n = 3)
    limestone 319 ± 243 (n = 3) 5.8 ± 4.7 (n = 3) b
    bottom ash of CFPPs b b 19.4 ± 0.9 (n = 3)
    basalt b b 6.7 ± 0.2 (n = 3)
    black stone b b 14.5 ± 1.1 (n = 3)
  weighted mean   141.6 12.3 30.0
  clinker   407 ± 7 (n = 3)a 42 ± 3 (n = 3)a 8.1 ± 0.3 (n = 3)a
  cement products   542 ± 57 (n = 4) 40 ± 8 (n = 6) 11.1 ± 1.4 (n = 6)
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a

n is the sample numbers.

b

Not applicable.

c

Unit in μg·m–3 for Pb concentration in flue gas.

Table 2. Cd Concentration in Different Materials during the Entire Production of the Studied CPs.

      Cd concentration (mean ± SD, mg·kg–1)
materials     CP #1 CP #2 CP #3
material inputs during the clinker production raw materials limestone 5.49 ± 0.20 (n = 3)a 0.02 ± 0.02 (n = 3)a 0.04 ± 0.01 (n = 3)a
    sandstone 0.03 ± 0.002 (n = 3) b b
    shale 0.19 ± 0.01 (n = 3) 0.53 ± 0.28 (n = 3) 0.16
    coal gangue 7.85 ± 0.64 (n = 2) b b
    iron-rich materials 0.87 ± 0.03 (n = 3) 10.06 ± 0.92 (n = 3) b
    beneficiation waste b b 1.5 ± 0.04 (n = 2)
    yellow phosphorus slag b b 0.26 ± 0.8 (n = 3)
    carbide slag b b 0.28 ± 0.5 (n = 2)
    coal slag b b 0.23 ± 0.3 (n = 3)
  fuel coal 0.11 ± 0.01 (n = 2) 0.08 ± 0.01 (n = 3) 0.10 ± 0.01 (n = 3)
  weighted mean   4.26 0.24 0.13
intermediate products raw meal   5.02 ± 0.15 (n = 3) 0.23 ± 0.01 (n = 3) 0.15 ± 0.03 (n = 3)
  kiln tail dust   7.00 ± 0.32 (n = 6) 0.20 ± 0.02 (n = 6) 0.16 ± 0.04 (n = 3)
  kiln head dust   6.53 ± 1.19 (n = 3) 0.44 ± 0.05 (n = 3) 0.26
  stack flue gas at the kiln tail   0.01c 0.001c 0.001c
  stack flue gas at the kiln head   0.01c 0.002c 0.004c
material during the clinker to cement production additives fly ash from CFPPs 2.23 ± 0.54 (n = 2) 0.30 ± 0.14 (n = 3) 1.94 ± 0.02 (n = 3)
    desulfurization gypsum 0.30 ± 0.30 (n = 3) 0.02 ± 0.01 (n = 3) 0.05 ± 0.01 (n = 3)
    limestone 5.49 ± 0.20 (n = 3) 0.02 ± 0.02 (n = 3) b
    bottom ash from CFPPs b b 0.23 ± 0.03 (n = 3)
    basalt b b 0.20 ± 0.01 (n = 3)
    black stone b b 0.26 ± 0.07 (n = 3)
  weighted mean   2.43 0.15 1.01
  clinker   6.88 ± 0.23 (n = 3) 0.31 ± 0.01 (n = 3) 0.33 ± 0.08 (n = 3)
  cement products   7.14 ± 0.04 (n = 4) 0.32 ± 0.06 (n = 6) 0.35 ± 0.06 (n = 6)
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a

n is the sample numbers.

b

Not applicable.

c

Unit in μg·m–3 for Cd concentration in flue gas.

2.1.1. Raw Materials and Coal

Large variations in the Pb and Cd concentrations in different raw materials and coal were observed for these three CPs (Tables 1 and 2). Especially, the concentrations of Pb and Cd in limestone (319 ± 243 mg·kg–1 for Pb; 5.5 ± 0.2 mg·kg–1 for Cd) of CP #1 were much higher than that of the other two CPs (5.8 ± 4.7 mg·kg–1 for Pb, 0.02 ± 0.02 mg·kg–1 for Cd in CP #2; 2.9 ± 0.7 mg·kg–1 for Pb, and 0.04 ± 0.01 mg·kg–1 for Cd in CP #3), with the latter two cases having similar contents of Cd as previous reports (0.030–0.065 mg·kg–1).27 The high Pb and Cd concentrations in limestone found in CP #1 might be related to the oolitic limestone, which has been found to contain high levels of heavy metals due to geological reasons, and as high as 4.9 mg·kg–1 of Cd concentration was found in oolitic limestone in Europe,28,29 which was comparable to CP #1 of this study (5.5 ± 0.2 mg·kg–1). Moreover, iron-rich materials from nonferrous smelters used in CP #2 contained astonishing high Pb (1619 ± 70 mg·kg–1) and Cd (10.06 ± 0.92 mg·kg–1) compared to other raw materials (Tables 1 and 2), which were about 100 times higher than other raw materials. Pb and Cd in coal and most other raw materials possessed low concentrations in the three CPs (<50 mg·kg–1 for Pb and <0.3 mg·kg–1 for Cd), with except of coal gangue and beneficiation waste that contained moderate Cd concentrations (1.5–7.8 mg·kg–1).

2.1.2. Intermediate Products

Pb and Cd concentrations in intermediate products, which includes raw meal and dust captured from the air pollution control devices (APCDs) at kiln tail, are shown in Figure 1 and Tables 1 and 2. Pb and Cd concentrations in intermediate products of CP #1 were also much higher than that of CPs #2 and #3, which was consistent with the variation of Pb and Cd contents in limestone (Figure 1).

Figure 1.

Figure 1

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Comparison of the Pb and Cd concentration in different solid materials during the clinker production process in three CPs.

In CP #1, the concentration of Pb and Cd in raw meal (251 ± 15 mg·kg–1 of Pb; 5.0 ± 0.2 mg·kg–1 of Cd) were roughly equal to that in raw mix materials (weight mean: 244.7 mg·kg–1 of Pb; 4.26 mg·kg–1 of Cd) but significantly lower than that in kiln tail dust (527 ± 73 mg·kg–1 of Pb; 7.0 ± 0.3 mg·kg–1 of Cd) and in clinker (407 ± 7 mg·kg–1 of Pb; 6.88 ± 0.23 mg·kg–1 of Cd). In CP #2, there was a tiny gap in the concentrations of Pb and Cd in raw meal (32 ± 1 mg·kg–1 of Pb; 0.23 ± 0.01 mg·kg–1 of Cd), in kiln tail dust (30 ± 5 mg·kg–1 of Pb; 0.20 ± 0.02 mg·kg–1 of Cd), and in raw mix materials and coal (36.2 mg·kg–1 of Pb; 0.24 mg·kg–1 of Cd), and all of them were lower than that in clinker (42 ± 3 mg·kg–1 of Pb; 0.31 ± 0.01 mg·kg–1 of Cd). Similarly, the Pb and Cd contents in raw meals (5.0 ± 0.1 mg·kg–1 of Pb; 0.15 ± 0.03 mg·kg–1 of Cd) and in kiln tail dust (6.0 ± 0.3 mg·kg–1 of Pb; 0.16 ± 0.04 mg·kg–1 of Cd) were almost indistinguishable, and both of them were slightly higher than that in raw mix materials (4.36 mg·kg–1 of Pb; 0.13 mg·kg–1 of Cd) but lower than that in clinker (8.1 ± 0.3 mg·kg–1 of Pb; 0.33 ± 0.08 mg·kg–1 of Cd). The much higher metal concentration found in clinker than that of raw meal might be related to the mass reduction (ca. 1.6:1 for raw meal to clinker) during the clinker production,30 and the slightly higher metal concentration in kiln tail dust than raw meal indicates the capture of metal in flue gas within the raw mill and detained by the dust collector, which was consistent with the research of Wang et al.31 It should be noted that the concentration of Pb and Cd in raw meal of CP #1 has exceeded the reference limits of metals in raw meal in China (GB 30760—2014),32 which has a limit of 67 mg·kg–1 for Pb and 1 mg·kg–1 for Cd, while raw meal of CPs #2 and #3 was within this limit.

2.1.3. Materials in Clinker-to-Cement Production Process

During the clinker-to-cement production process, the input materials were clinker, dust captured by APCDs at kiln head, additives, and retarder, while the output was the kiln head stack gas and cement products. The concentrations of Pb and Cd in kiln head dust, clinker, and cement products of CP #1 were also much higher than those of CPs #2 and #3. The contents of Pb and Cd in kiln head dust (average 124.7 mg·kg–1 of Pb; 2.4 mg·kg–1 of Cd) was generally similar to that in clinker (average 152.7 mg·kg–1 of Pb; 2.5 mg·kg–1 of Cd) (Tables 1 and 2). Fly ash of coal fired power plants (CFPPs) used in the three CPs as additives contained much higher concentrations of Pb (68.9 mg·kg–1 on average) and Cd (1.49 mg·kg–1 on average) than that of gypsum. In the last, Pb and Cd concentrations in cement products (average 197.7 mg·kg–1 of Pb; 2.6 mg·kg–1 of Cd) were increased slightly compared to that of the clinker (Tables 1 and 2).

Pb and Cd in clinker and cement products were compared in this study and others (Table 3). Pb contents in clinker (408 ± 7 mg·kg–1) and cement (542 ± 57 mg·kg–1) in CP #1 of this study were approximately 100 times higher than that of a CP in Nigeria (4.4 mg·kg–1 in clinker; 3.9 mg·kg–1 in cement) and CP in United States of America (3 mg·kg–1 in cement),33 and similarly, Cd contents in clinker and cement products of CP #1 were 10–100 times higher than other CPs. Pb contents of cement products in CP #3 (11.1 ± 1.4 mg·kg–1) were only one ninth of that of a CP in South Korea (91 mg·kg–1),34 and Cd in cement products of CP #2 (0.32 ± 0.06 mg·kg–1) were only a quarter of a CP in Peninsular Malaysia (1.3 mg·kg–1, Table 3).35

Table 3. Comparison of Pb and Cd Concentrations in Clinker and Cement Products of Different CPs.
    concentration (mg·kg–1)
  
materials CPs Pb Cd references
clinker CP #1 (Guizhou province, China) 408 6.9 this study
  CP #2 (Guizhou province, China) 42 0.3 this study
  CP #3 (Guizhou province, China) 8.1 0.3 this study
  CP in Nigeria 4.4 0.5 (33)
  CP in Beijing, China 16.8 3.1 (14)
cement CP #1 (Guizhou province, China) 542 7.1 this study
  CP #2 (Guizhou province, China) 40 0.3 this study
  CP #3 (Guizhou province, China) 11 0.4 this study
  CP in Nigeria 3.9 0.6 (33)
  CP in USA 3 0.05 (33)
  CP in South Korea 91 1.3 (34)
  CP in Peninsular Malaysia 71 1.3 (35)
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Moreover, the reference limit of Pb in clinker in China was 100 mg·kg–1 and that of Cd was 1.5 mg·kg–1 (GB 30760—2014);32 thus, CP #1 exceeded the standard both for Pb and Cd, while CPs #2 (42 ± 3 mg·kg–1 of Pb; 0.31 ± 0.01 mg·kg–1 of Cd) and #3 (8.1 ± 0.3 mg·kg–1 of Pb; 0.33 ± 0.08 mg·kg–1 of Cd) were within the standard. Therefore, the limestone and iron-rich materials with low heavy metal concentrations were recommended to be the preferred materials to produce clinker. Otherwise, the cement products with high heavy metal concentrations deserved further research considering their possible impact on the environment and human health.

2.2. Atmospheric Emissions of Pb and Cd

Surprisingly, the Pb and Cd concentrations of stack flue gas in CP #1 were close to that of two other CPs. This might be caused by the high PM removals by electrostatic precipitator (ESP) or ESP-combined fabric filter (FF) and most Pb and Cd in flue gas were attached to the PMs in the lower temperature range (<200 °C). We compared the concentrations of Pb and Cd in this study and other previous studies, and the results are shown in Table 4. The concentrations of Pb in stack flue gas in the three CPs were 0.05–0.84 μg·m–3 (average 0.36 μg·m–3, Table 1), while that of Cd were 0.001–0.01 μg·m–3 (average 0.005 μg·m–3; Table 2). Since the cement industry emission standards do not have separate restrictions on Pb and Cd, the emission limit for inorganic chemical industry was selected for comparison and all concentrations of the stack flue gas in the three CPs were below this standard limit (2 mg·m–3 of Pb, 0.5 mg·m–3 of Cd) (GB 31573—2015).36 Furthermore, they were also much lower than most contents investigated by previous studies such as CP in India (34 μg·m–3 of Pb, 14.6 μg·m–3 of Cd; Table 4).37 However, Pb and Cd contents of flue gas in our study were close to the results investigated by Yan et al.38 (0.72 ± 0.01 μg·m–3 of Pb, 0.04 ± 0.01 μg·m–3 of Cd; Table 4).

Table 4. Comparison of Pb and Cd Concentration in Stack Flue Gas of Different Studies.

metals concentration (μg·m–3) references
Pb 0.05–0.84 this study
  0.72 (38)
  34 (37)
  0.3–88 (39)
  2.26–893 (40)
  0.65–50.4 (41)
Cd 0.001–0.01 this study
  0.04 (38)
  14.6 (37)
  0.1–37 (39)
  0.19–0.83 (40)
  0.02–0.3 (41)
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To quantify the atmospheric emissions of Pb and Cd from CPs, the atmospheric EMFs of Pb and Cd from CPs were established to estimate the emissions from kiln tail/head based on eqs 5 and 6, and the results are shown in Table S3. The difference in emissions between kiln tail and kiln head was not significant as other volatile elements, such as Hg.7

The average daily production capacity of the three CPs studied was 4500–5000 tonnes clinker·day–1 line–1 (Table S1), and the atmospheric Pb emission was estimated to be 3.08 kg·yr–1 on average per cement production line by using EMF1 of Pb (average: 1.81 mg Pb·tonne–1 clinker). Similarly, the atmospheric Cd emission was 0.038 kg·yr–1 on average per cement production line by using EMF1 of Cd (average: 0.022 mg Cd·tonone–1 clinker) (Table S3).

The production of clinker in Guizhou Province in 2018 was 8.03 × 107 tonnes,42 and the total provincial atmospheric Pb emission of cement industry in 2018 was estimated to be 145.3 kg·yr–1, while Cd emission was estimated to be 1.77 kg·yr–1 on average, which was much lower than the emissions from CFPPs in the same province (430 kg·yr–1 of Pb; 51.4 kg·yr–1 of Cd).43,44

Moreover, the production of clinker in the whole country was 1.43 × 109 tonnes in 2018;45 thus, the total national atmospheric Pb emission was 2.58 tonnes·yr–1, while Cd was around 31 kg·yr–1. The values of Pb and Cd emissions obtained in this study were much lower than previous research results,5 which gave the annual Pb emissions of 259–1129 tonnes·yr–1 and Cd emissions of 5.7–26.3 tonnes·yr–1 from Chinese CPs in 1980–2012. Similarly, Shao et al.19 estimated that Cd emission from Chinese CPs in 2010 to be 19 tonnes, which was also much higher than this study.

2.3. Mass Balance of Pb and Cd during the Cement Production Process

Limestone was the main material for clinker production, which accounted for 75–83% of the raw material mass of the three CPs studied (Table S2), while, other raw materials, for example, shale, sandstone, coal gangue, iron-rich materials, beneficiation waste, and bottom ash from CFPPs, as well as coal accounted for 7–10% of the raw material mass (Table S2). Combined with the metal concentration in different input/output materials (Tables 1 and 2) and the associated material mass flow (Table S2), the proportion of each material in the Pb and Cd input and output during the clinker production process is calculated (Figures 2 and 3). The detailed information of input and output of Pb and Cd flow during the whole cement production process in each CPs are shown in Figures 5 and 6.

Figure 2.

Figure 2

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Daily Pb input and output during the clinker production process of the three CPs.

Figure 3.

Figure 3

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Daily Cd input and output during the clinker production process of the three CPs.

Figure 5.

Figure 5

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Mass flow of Pb in three CPs. (Values are based on one day).

Figure 6.

Figure 6

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Mass flow of Cd in three CPs. (Values are based on one day).

Limestone in CP #1 and iron-rich materials in CP #2, which contained ultra-high Pb and Cd contents, completely dominated the input volume of Pb and Cd (Figures 2 and 3). In CP #2, the iron-rich material contributed more than three quarters of Pb and Cd input, albeit it only accounts for 2% of total mass material (Table S2). In CP #3, high Cd content of beneficiation waste accounted for more than half of the Cd input (59%), while limestone accounted for most of the Pb input (55%). As for the output of Pb and Cd, the clinker accounts for almost all the Pb and Cd output in the three CPs (93–99.7%). Meanwhile, the daily input and output of Pb and Cd during the clinker production process are roughly equal in three CPs (Figures 2 and 3), which indicates that almost all Pb and Cd input from different raw materials and fuels were ended up in the clinker. Moreover, low levels of Pb and Cd in flue gases resulted in minimal atmospheric emissions.

The output/input ratios of Pb in the clinker production and clinker-to-cement production were 95 and 118% on average of three CPs (Figures 2 and 5), respectively. Similarly, the output/input ratios of Cd in the clinker and clinker-to-cement production were 109 and 119% (Figures 3 and 6). Meanwhile, the enrichment factors of Pb and Cd from three CPs were established based on eq 4. The results are shown in Figure 4, and the enrichment factors of Pb and Cd in three CPs were all around 1, in particular, the enrichment factors of Pb were 0.96, 0.91, and 1.03, while those of Cd were 1.1, 0.99, and 1.03 in CP #1, CP #2, and CP #3, respectively. However, the enrichment factors of Hg and Tl in the three CPs were 5.9, 104, and 397 and 148, 85, and 93,46 respectively (Figure 4). The high enrichment factors of Tl and Hg indicated the obvious enrichment in the system of CPs; thus, close to 1 of enrichment factor of Pb and Cd in this study suggests Pb and Cd were roughly balanced during the clinker productions, namely, the daily Pb or Cd output is equal to the daily input.

Figure 4.

Figure 4

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Enrichment factors of different heavy metals in the three CPs (Hg in CP #3 is internal unpublished data, Tl in the three CPs are quoted from ref (46) and Hg in CPs #1 and #2 are quoted from ref (7); re-use this figure with permission from Elsevier).

Pb input from different raw materials (1760 kg·day–1 of CP #1; 263 kg·day–1 of CP #2; 36 kg·day–1 of CP #3) and coal (10.8 kg·day–1 of CP #1; 9.5 kg·day–1 of CP #2; 5.6 kg·day–1 of CP #3) almost all ended up in the clinker (1729 kg·day–1 of CP #1; 209 kg·day–1 of CP #2; 42 kg·day–1 of CP #3), and it further entered to cement products (2839 kg·day–1 of CP #1; 208 kg·day–1 of CP #2; 76 kg·day–1 of CP #3) (Figure 5). In other words, the Pb flow mainly followed the sequence of from raw materials to raw meal, then to clinker, and finally to cement products.

Similarly, most of the Cd input (30.8 kg·day–1 of CP #1; 1.8 kg·day–1 of CP #2; 1.3 kg·day–1 of CP #3) were also entered into the clinker first (29.2 kg·day–1 of CP #1; 1.6 kg·day–1 of CP #2; 1.7 kg·day–1 of CP #3) and then to cement products in three CPs (37.4 kg·day–1 of CP #1; 1.7 kg·day–1 of CP #2; 2.2 kg·day–1 of CP #3) (Figure 6). These phenomena were much different to that of Hg and Tl, which have hardly been found in the clinkers.7,46

In addition, the results of this study were also different to previous speculations that Pb and Cd been volatilized at high temperature and concentrated in kiln tail dust.12,13 This might be controlled by many factors that would restrict the volatilization of these elements during the clinker sintering process (clinkerization) in preheater, precalciner, and rotary kiln. According to previous studies, the main form of Pb in the clinker sintering process could be lead sulfate and lead chloride,47,48 and it was eventually dissolved in the clinker with sulfate. Cd was dominated by cadmium oxide/hydroxide and cadmium chloride in that process.47,49 These compounds have high stability than others at high temperatures; Cd could also form the solid solution of Cd sulfate salts in the clinker,50 thus, they were easier to be consolidated into the clinker. In addition, sulfur in raw meal could lower the surface tension and the viscosity of the melt (above 1338 °C)51 and promotes the solidification of Pb and Cd,52,53 while chlorine would reduce the solidification ability of clinker over Pb and Cd by decreasing the interstitial phases during the clinkerization.54 Moreover, due to the reaction of SiO2 with heavy metal oxides and chlorides, which are shown in eqs 1–3, silicate of heavy metals might be formed eventually during the clinkerization process, which might be the main way for Pb and Cd to exist in the clinker production process.55 Therefore, the extremely high content (>20%) of SiO2 during the cement production process could also have a great inhibition effect on the volatilization of Pb and Cd. Under the combined action of the above reasons, the volatilization of Pb and Cd was greatly inhibited during the clinkerization.

2.3. 1
2.3. 2
2.3. 3

where M stand for heavy metals; x and y are stoichiometric number.

A small part of Pb and Cd might be volatilized in the rotary kiln at 1450 °C, while, as the hot flue gas goes to the five-stage preheaters and precalciner where the temperature drops dramatically (from 1450 to 300 °C), Pb and Cd would condense and adhere to the raw meal powder and re-entered the rotary kiln; thus, this will reduce the atmospheric emissions of Pb and Cd, and the cycling of Pb and Cd should be constrained between the rotary kiln and the preheater; the formation of silicate of Pb or Cd will lead to the discharge of these metals out of the kilns in the form of clinker. Therefore, it was difficult for Pb and Cd to pass through the preheater and precalciner and return to the raw meal soils, and almost all Pb and Cd end up in the clinker during clinkerization. In addition, the modern APCDs, especially PM removers, can remove almost all (>99.9%) PM that contains Pb and Cd, thus leading to a negligible atmospheric of these two elements, which is different to Hg, with the latter which may exist in gaseous form (elemental or oxidized) and penetrate the dust collector.

3. Conclusions

Based on the field investigations of three precalciner CPs, it was found that the semi-volatile elements Pb and Cd do not enrich inside the clinker production system, especially in raw meal and kiln tail dust, as that found for Hg and Tl; this resulted in a dynamic equilibrium with almost all daily Pb and Cd input from different raw materials and fuels ended up in the clinker, and very little portions (<0.006%) of Pb and Cd were atmospheric-lost. The mechanism was the formation of specific stable metal compounds of Cd and Pb during the clinkerization process, such as Pb/Cd silicate or sulfate, which were easier to be consolidated into the clinker. Limestone used in some plant may contain high levels of Pb (e.g., 319 ± 243 mg·kg–1) and Cd (5.5 ± 0.2 mg·kg–1), which lead to high Pb and Cd in the clinker and the final products of cement. However, raw materials with high Pb and Cd concentration did not lead to a much increase in atmospheric emissions from stack gas. The total emission of cement industrial in Guizhou was estimated to be 145.3 kg·yr–1 for Pb and 1.77 kg·yr–1 for Cd in 2018, and the total national atmospheric emission from this industry was estimated to be 2.58 tonnes·yr–1 for Pb and 31 kg·yr–1 for Cd. The results of the estimation of atmospheric emissions in this study indicated that atmospheric emissions of Pb and Cd from the cement industry had been effectively controlled, but some cement products containing high metals needed to be monitored and to be evaluated for their long-term environmental impacts.

4. Experimental Section

4.1. Description of CPs

Three precalciner CPs in Guizhou Province were selected to study the fate of Pb and Cd during the cement production, with CP #1 located in the east of the province, #2 in the central, and #3 in the west of the province. In these three CPs, limestone and other raw materials were produced locally. Coal used in CP #1 was produced from Henan and Shaanxi Provinces, which are located in central China. However, the coal used in CP #2 and CP #3 was produced from the central and western areas of Guizhou Province, respectively; both of the above areas are the main coal-producing areas in Guizhou, and coal is either bituminous or anthracitic and formed in the late Permian.

APCDs used in kiln tail were different in the three CPs studied (Table S1). The devices used at kiln tail consisted of a selective non-catalytic reduction (SNCR) unit combined with an ESP in CP #1 for NOx and PM controls, respectively; an SNCR plus ESP-FF for CP #2, and an SNCR plus FF for CP #3, while the same ESP was used at kiln head.

4.2. Sample Preparation and Determination

Solid samples, including different raw materials (limestone, clay, sandstone, etc.), coal, intermediate products (raw meal and kiln dust from APCDs), clinker, additives, and cement products were collected simultaneously (about 1 kg per sample) for 3–6 times over a 2–3 day sampling period for each CP, and the specific sampling locations are shown in Figure 7. The stack flue gas and contained PM were not measured in this study, but the PM concentration in flue gas as well as other material input and output information were provided by these CP companies. Since the temperature in the stack gas (70–100 °C) was lower than any elemental or ionic Pb/Cd vapor, it is therefore assumed that all Pb/Cd in the stack gas was in particulate form and their atmospheric emissions were calculated based on the Pb/Cd content in particles (kiln dust) and the particle content in the stack flue gas. Simultaneously, information about various input and output material quantities and flue gas flow was gathered from the CP companies, which is shown in Table S2 of Supporting Information.

All solid samples were air-dried and ground to sizes smaller than 0.15 mm. The sample digestion method used was developed by Liang and Grégoire in 200056 with the following procedures, 50 mg powders were weighed into Teflon digestion bottles, and 1 mL HF and 1 mL HNO3 were added to the samples and then placed in an oven pre-heated at 190 °C for 24 h. After cooling, samples were heated on a hot plate at 120 °C to evaporate the solution to incipient dryness. Subsequently, 0.5 mL of HNO3 was added to the Teflon bottles and continuously heated on a hot plate until dry. Then, 200 ng of Rh as an internal standard, 2 mL of HNO3, and 2 mL of deionized water were added sequentially and placed in an oven pre-heated to 150 °C for 5 h. Finally, 0.4 mL of the digestion solution was transferred into a 15 mL centrifuge tube, and deionized water was added to obtain a volume of 10 mL. The Pb and Cd in this solution was measured by inductively coupled plasma mass spectrometry (Analytik Jena, Germany). The data of solid samples were reported based on their air-dried masses.

4.3. Quality Assurance and Quality Control

All Teflon bottles used for digestion were washed with 20% nitric acid (HNO3) and rinsed with deionized water. HF and HNO3 were distilled twice to remove impurities. Quality assurance and quality control were checked using blanks, duplicate samples, and certified reference materials. Certified reference materials of limestone (JLS-1; JDO-1), coal (NIST 1632d), fly ash (NIST 1633c), and soil (GSS-5) were also digested and analyzed along with solid samples from the CPs. The resulting recovery of Pb was in the range of 96–99% and Cd was in 95–116%.

4.4. Calculations of Enrichment Factors and Atmospheric EMFs

4.4.1. Enrichment Factors

To assess the degree of enrichment of Pb and Cd in the clinker production system, the enrichment factor is calculated according to a method for Hg,7,57 which is to divide the total amount (gram or kilogram) of the target trace element in the clinker production system by the daily input (gram or kilogram) from different raw materials and fuels, as follows

4.4.1. 4

when the enrichment factor is approximately equal to 1, it means there is no enrichment of Pb or Cd that occurred in the clinker production system; if the enrichment factor is greater than 1, it represents that Pb or Cd has been enriched or retained during the process, and a higher value means a higher enrichment of Pb or Cd inside the system.

4.4.2. Atmospheric EMFs

To quantify the atmospheric emissions of Pb and Cd from these three CPs, EMFs of Pb and Cd from precalcined CPs are estimated from the emissions from the kiln tail and head. Atmospheric EMF from a CP is either based on the clinker production (EMF1 in eq 5 in the unit of mg·tonne–1 clinker) or the cement production (EMF2 in eq 6 using unit of mg·tonne–1 cement), as follows

4.4.2. 5
4.4.2. 6

where MPb or Cd is the amount of Pb or Cd emitted into the atmosphere per day (g·day–1), which is calculated by the total amount of PM emissions and the Pb or Cd concentration in kiln head/tail dust; Mclinker is the daily output of clinkers (tonne·day–1), and Mcement is the daily output of cement products (tonne·day–1).

Acknowledgments

We appreciate the hard work of sampling and experimental preparation by Ji Chen, Li Tang, Tingting Wu, and Shan Li.

Supporting Information Available

The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.1c01329.

  • Basic information of the studied CPs; more detailed information of daily input and output quantities of different materials in the three CPs; and atmospheric EMFs of Pb and Cd for the three studied CPs (PDF)

Author Contributions

Z.L. involved in the conception of the study. Z.L., L.Y., and G.H. performed the field investigation. X.L., G.S., Y.H., G.W., L.Y., and G.H. were involved in the experimental analysis. Y.H. wrote the main manuscript. J.L. and Z.L. edited and revised the manuscript. All authors have read and approved the final manuscript.

This work was financially supported by the Guizhou Provincial Natural Science Foundation (no. Qian-Ke-He-Ji-Chu-ZK[2021]Zhong-Dian 044), the National Natural Science Foundation of China (no. U1612442), and the Doctoral Foundation Project of Zunyi Normal College (no. Zun-Shi BS [2018]15).

The authors declare no competing financial interest.

Supplementary Material

ao1c01329_si_001.pdf (73.8KB, pdf)

References

  1. Usón A. A.; López-Sabirón A. M.; Ferreira G.; Sastresa E. L. Uses of alternative fuels and raw materials in the cement industry as sustainable waste management options. Renewable Sustainable Energy Rev. 2013, 23, 242–260. 10.1016/j.rser.2013.02.024. [DOI] [Google Scholar]
  2. Pacyna E. G.; Pacyna J. M.; Fudala J.; Strzelecka-Jastrzab E.; Hlawiczka S.; Panasiuk D.; Nitter S.; Pregger T.; Pfeiffer H.; Friedrich R. Current and future emissions of selected heavy metals to the atmosphere from anthropogenic sources in Europe. Atmos. Environ. 2007, 41, 8557–8566. 10.1016/j.atmosenv.2007.07.040. [DOI] [Google Scholar]
  3. Pacyna J. M.; Pacyna E. G.; Aas W. Changes of emissions and atmospheric deposition of mercury, lead, and cadmium. Atmos. Environ. 2009, 43, 117–127. 10.1016/j.atmosenv.2008.09.066. [DOI] [Google Scholar]
  4. Cutillas-Barreiro L.; Pérez-Rodríguez P.; Gómez-Armesto A.; Fernández-Sanjurjo M. J.; Álvarez-Rodríguez E.; Núñez-Delgado A.; Arias-Estévez M.; Nóvoa-Muñoz J. C. Lithological and land-use based assessment of heavy metal pollution in soils surrounding a cement plant in SW Europe. Sci. Total Environ. 2016, 562, 179–190. 10.1016/j.scitotenv.2016.03.198. [DOI] [PubMed] [Google Scholar]
  5. Hua S.; Tian H.; Wang K.; Zhu C.; Gao J.; Ma Y.; Xue Y.; Wang Y.; Duan S.; Zhou J. Atmospheric emission inventory of hazardous air pollutants from China’s cement plants: temporal trends, spatial variation characteristics and scenario projections. Atmos. Environ. 2016, 128, 1–9. 10.1016/j.atmosenv.2015.12.056. [DOI] [Google Scholar]
  6. Arfala Y.; Douch J.; Assabbane A.; Kaaouachi K.; Tian H.; Hamdani M. Assessment of heavy metals released into the air from the cement kilns co-burning waste: Case of Oujda cement manufacturing (Northeast Morocco). Sustainable Environ. Res. 2018, 28, 363–373. 10.1016/j.serj.2018.07.005. [DOI] [Google Scholar]
  7. Li X.; Li Z.; Wu T.; Chen J.; Fu C.; Zhang L.; Feng X.; Fu X.; Tang L.; Wang Z.; Wang Z. Atmospheric mercury emissions from two pre-calciner cement plants in Southwest China. Atmos. Environ. 2019, 199, 177–188. 10.1016/j.atmosenv.2018.11.011. [DOI] [Google Scholar]
  8. Olatunde K. A.; Sosanya P. A.; Bada B. S.; Ojekunle Z. O.; Abdussalaam S. A. Distribution and ecological risk assessment of heavy metals in soils around a major cement factory, Ibese, Nigeria. Sci. Afr. 2020, 9, e00496 10.1016/j.sciaf.2020.e00496. [DOI] [Google Scholar]
  9. Nriagu J. O.; Pacyna J. M. Quantitative assessment of worldwide contamination of air, water and soils by trace metals. Nature 1988, 333, 134–139. 10.1038/333134a0. [DOI] [PubMed] [Google Scholar]
  10. Mlakar T. L.; Horvat M.; Vuk T.; Stergaršek A.; Kotnik J.; Tratnik J.; Fajon V. Mercury species, mass flows and processes in a cement plant. Fuel 2010, 89, 1936–1945. 10.1016/j.fuel.2010.01.009. [DOI] [Google Scholar]
  11. Wang F.; Wang S.; Zhang L.; Yang H.; Wu Q.; Hao J. Mercury enrichment and its effects on atmospheric emissions in cement plants of China. Atmos. Environ. 2014, 92, 421–428. 10.1016/j.atmosenv.2014.04.029. [DOI] [Google Scholar]
  12. Cipurkovic A.; Trumic I.; Hodžic Z.; Selimbašic V.; Djozic A. Distribution of heavy metals in Portland cement production process. Adv. Appl. Sci. Res. 2014, 5, 252–259. [Google Scholar]
  13. Cong J.; Yan D.; Li L.; Cui J.; Jiang X.; Yu H.; Wang Q. Volatilization of heavy metals (as, Pb, Cd) during Co-processing in cement kilns. Environ. Eng. Sci. 2015, 32, 425–435. 10.1089/ees.2014.0175. [DOI] [Google Scholar]
  14. Lu H.; Wei F.; Tang J.; Giesy J. P. Leaching of metals from cement under simulated environmental conditions. J. Environ. Manage. 2016, 169, 319–327. 10.1016/j.jenvman.2015.12.008. [DOI] [PubMed] [Google Scholar]
  15. Lin S. M. Release and pollution of heavy metals in cement production of different kilns. Guangdong Chem. Ind. 2008, 08, 113–116. [Google Scholar]; (In Chinese)
  16. Trinkel V.; Mallow O.; Thaler C.; Schenk J.; Rechberger H.; Fellner J. Behavior of chromium, nickel, lead, zinc, cadmium, and mercury in the blast furnace-a critical review of literature data and plant investigations. Ind. Eng. Chem. Res. 2015, 54, 11759–11771. 10.1021/acs.iecr.5b03442. [DOI] [Google Scholar]
  17. Landrigan P. J.; Boffetta P.; Apostoli P. The reproductive toxicity and carcinogenicity of lead: a critical review. Am. J. Ind. Med. 2000, 38, 231–243. . [DOI] [PubMed] [Google Scholar]
  18. Zhang Y.; Shang P.; Wang J.; Norris P.; Romero C. E.; Pan W.-p. Trace element (Hg, As, Cr, Cd, Pb) distribution and speciation in coal-fired power plants. Fuel 2017, 208, 647–654. 10.1016/j.fuel.2017.07.064. [DOI] [Google Scholar]
  19. Shao X.; Cheng H.; Li Q.; Lin C. Anthropogenic atmospheric emissions of cadmium in China. Atmos. Environ. 2013, 79, 155–160. 10.1016/j.atmosenv.2013.05.055. [DOI] [Google Scholar]
  20. Wang C.; Yang Z.; Zhang Y.; Zhang Z.; Cai Z. PAHs and heavy metals in the surrounding soil of a cement plant Co-Processing hazardous waste. Chemosphere 2018, 210, 247–256. 10.1016/j.chemosphere.2018.06.177. [DOI] [PubMed] [Google Scholar]
  21. Kolo M. T.; Khandaker M. U.; Amin Y. M.; Abdullah W. H. B.; Bradley D. A.; Alzimami K. S. Assessment of health risk due to the exposure of heavy metals in soil around mega coal-fired cement factory in Nigeria. Results Phys. 2018, 11, 755–762. 10.1016/j.rinp.2018.10.003. [DOI] [Google Scholar]
  22. National Bureau of Statistics of China . China Statistical Yearbook; China Statistics Press, 2019. (In Chinese). [Google Scholar]
  23. Mao J.; Xu H.. Prediction and Evaluation of Coal Resources in China; Science Press: Beijing, 1999. (In Chinese). [Google Scholar]
  24. Bureau of Statistics of Guizhou Province . Guizhou Statistical Yearbook; China Statistics Press, 2006. (In Chinese). [Google Scholar]
  25. Bureau of Statistics of Guizhou Province . Guizhou Statistical Yearbook; China Statistics Press, 2019. (In Chinese). [Google Scholar]
  26. Li X.; Chen J.; Tang L.; Wu T.; Fu C.; Li Z.; Sun G.; Zhao H.; Zhang L.; Li Q.; Feng X. Mercury isotope signatures of a pre-calciner cement plant in Southwest China. J. Hazard. Mater. 2021, 401, 123384. 10.1016/j.jhazmat.2020.123384. [DOI] [PubMed] [Google Scholar]
  27. Rambeau C. M. C.; Baize D.; Saby N.; Matera V.; Adatte T.; Föllmi K. B. High cadmium concentrations in Jurassic limestone as the cause for elevated cadmium levels in deriving soils: a case study in Lower Burgundy, France. Environ. Earth Sci. 2010, 61, 1573–1585. 10.1007/s12665-010-0471-0. [DOI] [Google Scholar]
  28. Jacquat O.; Voegelin A.; Juillot F.; Kretzschmar R. Changes in Zn speciation during soil formation from Zn-rich limestones. Geochim. Cosmochim. Acta 2009, 73, 5554–5571. 10.1016/j.gca.2009.05.069. [DOI] [Google Scholar]
  29. Quezada-Hinojosa R. P.; Matera V.; Adatte T.; Rambeau C.; Föllmi K. B. Cadmium distribution in soils covering Jurassic oolitic limestone with high Cd contents in the Swiss Jura. Geoderma 2009, 150, 287–301. 10.1016/j.geoderma.2009.02.013. [DOI] [Google Scholar]
  30. Cui J.; He J.; Xiao Y.; Li J.; Di Y. Characterization of input materials to provide an estimate of mercury emissions related to China’s cement industry. Atmos. Environ. 2021, 246, 118133. 10.1016/j.atmosenv.2020.118133. [DOI] [Google Scholar]
  31. Wang L.; Jin Y.; Nie Y.; Li R. Recycling of municipal solid waste incineration fly ash for ordinary portland cement production: a real scale test. Resour., Conserv. Recycl. 2010, 54, 1428–1435. 10.1016/j.resconrec.2010.06.006. [DOI] [Google Scholar]
  32. GB 30760. Technical Specification for Coprocessing of Solid Waste in Cement Kiln; National Standard of The People’s Republic of China, 2014. (In Chinese).
  33. Ogunbileje J. O.; Sadagoparamanujam V.-M.; Anetor J. I.; Farombi E. O.; Akinosun O. M.; Okorodudu A. O. Lead, mercury, cadmium, chromium, nickel, copper, zinc, calcium, iron, manganese and chromium (VI) levels in Nigeria and United States of America cement dust. Chemosphere 2013, 90, 2743–2749. 10.1016/j.chemosphere.2012.11.058. [DOI] [PubMed] [Google Scholar]
  34. Chang S. W.; Shon W. J.; Lee W.; Kum K. Y.; Baek S. H.; Bae K. S. Analysis of heavy metal contents in gray and white MTA and 2 kinds of Portland cement: a preliminary study. Oral Surg. Oral Med. Oral Pathol. Oral Radiol. 2010, 109, 642–646. 10.1016/j.tripleo.2009.12.017. [DOI] [PubMed] [Google Scholar]
  35. Halim N. A.; Kusin F. M.; Mohamed K. N. Heavy metal exposure from co-processing of hazardous wastes for cement production and associated human risk assessment. Int. J. Environ. Sci. Technol. 2018, 15, 733–742. 10.1007/s13762-017-1431-y. [DOI] [Google Scholar]
  36. GB 31573. Emission Standards of Pollutants for Inorganic Chemical Industry; National Standard of The People’s Republic of China, 2015. (In Chinese).
  37. Gupta R. K.; Majumdar D.; Trivedi J. V.; Bhanarkar A. D. Particulate matter and elemental emissions from a cement kiln. Fuel Process. Technol. 2012, 104, 343–351. 10.1016/j.fuproc.2012.06.007. [DOI] [Google Scholar]
  38. Yan D.; Peng Z.; Yu L.; Sun Y.; Yong R.; Karstensen K. H. Characterization of heavy metals and PCDD/Fs from water-washing pretreatment and a cement kiln co-processing municipal solid waste incinerator fly ash. Waste Manage. 2018, 76, 106–116. 10.1016/j.wasman.2018.03.006. [DOI] [PubMed] [Google Scholar]
  39. Zemba S.; Ames M.; Green L.; Botelho M. J.; Gossman D.; Linkov I.; Palma-Oliveira J. Emissions of metals and polychlorinated dibenzo(p)dioxins and furans (PCDD/Fs) from Portland cement manufacturing plants: Inter-kiln variability and dependence on fuel-types. Sci. Total Environ. 2011, 409, 4198–4205. 10.1016/j.scitotenv.2011.06.047. [DOI] [PubMed] [Google Scholar]
  40. Wang X. F.Research on non-conventional air pollutants emission characteristics from new dry process cement kiln. MA Thesis, Beijing University of Chemical Technology, 2017. (In Chinese with English abstract). [Google Scholar]
  41. Conesa J. A.; Gálvez A.; Mateos F.; Martín-Gullón I.; Font R. Organic and inorganic pollutants from cement kiln stack feeding alternative fuels. J. Hazard. Mater. 2008, 158, 585–592. 10.1016/j.jhazmat.2008.01.116. [DOI] [PubMed] [Google Scholar]
  42. Liu Z. Y. Perspective of supply and demand in Guangxi, Guizhou, and Yunnan cement markets. J. Build. Mater. 2019, 08, 106–115. [Google Scholar]; (In Chinese)
  43. Li X.; Bi X.; Li Z.; Zhang L.; Li S.; Chen J.; Feng X.; Fu X. Atmospheric Lead Emissions from Coal-Fired Power Plants with Different Boilers and APCDs in Guizhou, Southwest China. Energy Fuels 2019, 33, 10561–10569. 10.1021/acs.energyfuels.9b02188. [DOI] [Google Scholar]
  44. Zhou X.; Bi X.; Li X.; Li S.; Chen J.; He T.; Li Z. Fate of cadmium in coal-fired power plants in Guizhou, Southwest China: With emphasis on updated atmospheric emissions. Atmos. Pollut. Res. 2020, 11, 920–927. 10.1016/j.apr.2020.02.004. [DOI] [Google Scholar]
  45. Li C. Cement industry structure adjustment report in 2019. China Cem. 2020, 08, 16–21. [Google Scholar]; (In Chinese)
  46. Huang Y.; Liu J.; Feng X.; Hu G.; Li X.; Zhang L.; Yang L.; Wang G.; Sun G.; Li Z. Fate of thallium during precalciner cement production and the atmospheric emissions. Process Saf. Environ. Prot. 2021, 151, 158–165. 10.1016/j.psep.2021.05.013. [DOI] [Google Scholar]
  47. Xue J. C.; Yang Y. F.; Huang Q. F. Heavy metal species in cement products from co-processing waste in cement kilns. Res. Environ. Sci. 2010, 23, 1300–1305. [Google Scholar]; (In Chinese with English abstract)
  48. Cui S. P.Recycling analysis of domestic waste incineration ash in cement industry. Proceedings of Chinese Ceramic Society Annual Conference on Cement-Based Materials in 2003, 2003; pp 158–162. (In Chinese).
  49. Murat M.; Sorrentino F. Effect of large additions of Cd, Pb, Cr, Zn, to cement raw meal on the composition and the properties of the clinker and the cement. Cem. Concr. Res. 1996, 26, 377–385. 10.1016/s0008-8846(96)85025-3. [DOI] [Google Scholar]
  50. Pomiès M.-P.; Lequeux N.; Boch P. Speciation of cadmium in cement Part II. C3S hydration with Cd2+ solution. Cem. Concr. Res. 2001, 31, 571–576. 10.1016/s0008-8846(00)00477-4. [DOI] [Google Scholar]
  51. Telschow S.; Frandsen F.; Theisen K.; Dam-Johansen K. Cement formation. A success story in a black box: high temperature phase formation of Portland cement clinker. Ind. Eng. Chem. Res. 2012, 51, 10983–11004. 10.1021/ie300674j. [DOI] [Google Scholar]
  52. Zhang B.; Bogush A.; Wei J.; Zhang T.; Xu W.; Yu Q. Influence of sulfur on the fate of heavy metals during clinkerization. Constr. Build. Mater. 2018, 182, 144–155. 10.1016/j.conbuildmat.2018.06.084. [DOI] [Google Scholar]
  53. Zhang B.; Wei J.; Zeng Z.; Xu W.; Yu Q. Effects of Sulfur on the Solidification of Cadmium during Clinkerization. ACS Sustainable Chem. Eng. 2018, 6, 10645–10653. 10.1021/acssuschemeng.8b01970. [DOI] [Google Scholar]
  54. Zhang B.; Bogush A.; Wei J.; Xu W.; Zeng Z.; Zhang T.; Yu Q.; Stegemann J. Influence of Chlorine on the Fate of Pb and Cu during Clinkerization. Energy Fuels 2018, 32, 7718–7726. 10.1021/acs.energyfuels.8b01111. [DOI] [Google Scholar]
  55. Wang L.; Jin Y. Y.; Li R. D. Effect of CaO/SiO2 on heavy metals volatilization during melting treatment of fluidized bed incinerator fly ash. Environ. Pollut. Control 2009, 31, 16–19. [Google Scholar]; (In Chinese with English abstract)
  56. Liang Q.; Grégoire D. C. Determination of trace elements in twenty-six Chinese geochemistry reference materials by inductively coupled plasma-mass spectrometry. Geostand. Geoanal. Res. 2000, 24, 51–63. 10.1111/j.1751-908x.2000.tb00586.x. [DOI] [Google Scholar]
  57. Wang F.; Wang S.; Zhang L.; Yang H.; Wu Q.; Hao J. Characteristics of mercury cycling in the cement production process. J. Hazard. Mater. 2016, 302, 27–35. 10.1016/j.jhazmat.2015.09.042. [DOI] [PubMed] [Google Scholar]

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