The published article contains an error in the unit of concentration. The unit of TCE concentrations must be in mg/L instead of ppm in the abstract, manuscript, figures, and tables.
Page 28080, abstract: The increase in temperature showed increase in the adsorption capacity.
Corrected: The increase in temperature showed a decrease in the adsorption capacity.
Page 28080, abstract: The Langmuir and Freundlich isotherm models showed accurate fits with R2 values of 0.99067 and 0.99142, respectively.
Corrected: The Langmuir and Freundlich isotherm models showed accurate fits with R2 values of 0.990 and 0.991, respectively.
Page 28080, second paragraph (first column): (1.1 g·L–1 at 25 °C).
Corrected: (1.1 g/L at 25 °C).
Page 28081, second paragraph (first column): 0.6–6.5 mg TCE/L N2.
Corrected: 0.6–6.5 mg TCE/l N2.
Page 28081,Table 1: Density (g/cm3) - 1.4642
Corrected: Density (g/cm3) - 1.46
Page 28082, Table 2:
Corrected:
Page 28082, Section 2.2.3 (first column): 50–60 mg.
Corrected: 50 ± 10 mg.
Page 28082, Section 2.2.4 (second column): 40 mL/min
Corrected: 40 mL/min
Page 28083, first paragraph (first column): For 710 μm, the adsorption capacity achieved was 94.8307 mg/g, whereas for 500 μm it was found to be 413.064 mg/g. However, for the finer particle size 355 μm, the adsorption capacity was the highest of 523.252 mg/g.
Corrected: The amount of gas mixture adsorbed in the pressure range of 0 < P/P0 < 0.5 is essentially the adsorption in the micropore region of the adsorbent surface. The micropore region of the smaller particle size of 355 μm was more dominant, which showed better adsorption. The adsorption capacity was observed to increase at higher pressures (P/P0) indicating the heterogeneous surface of the activated carbon. The multilayer adsorption of TCE-air molecules was continued at higher pressures increasing the adsorption capacity of the activated carbon particles at saturation pressure. For 710 μm, the adsorption capacity achieved was 349.198 mg/g, whereas for 500 μm it was found to be 367.432 mg/g, and for the finer particle size 355 μm, the adsorption capacity was the highest of 477.62 mg/g when the adsorption capacity of air was neglected.
Page 28083, Section 3.2 (first column): The adsorption capacities for inlet concentrations of 100, 150, 200, and 250 ppm were 523.252, 575.844, 593.181, and 624.044 mg/g, respectively.
Corrected: The adsorption capacities for inlet concentrations of 100, 150, 200, and 250 mg/L were 481.62, 530.212, 547.548, and 578.415 mg/g, respectively, neglecting the adsorption of air on activated carbon particles.
Page 28083, first paragraph (second column): 8000 μg/L
Corrected: 8000 μg/l
Page 28084, first paragraph (first column): The adsorption capacity at equilibrium for an experiment carried out at 50 °C is 489.104 mg/g. The maximum adsorption capacity of the activated carbon at 100 °C was 262.245 mg/g.
Corrected: The adsorption capacity at equilibrium for an experiment carried out at 50 °C is 443.472 mg/g, and the maximum adsorption capacity of TCE on the activated carbon at 100 °C was 216.613 mg/g when the adsorption of air is neglected.
Page 28084, first paragraph (first column): The adsorption capacity on activated carbon at 30 °C was observed to be around 523.256 mg/g.
Corrected: The adsorption capacity of TCE on activated carbon at 30 °C was observed to be 477.624 mg/g, neglecting the adsorption of air.
Page 28084, Section 3.4 (first column): As seen in Figures 4a,b, both the Langmuir isotherm and the Freundlich isotherm were in agreement with the experimental plot, with the R2 values of 0.99142 and 0.99067, respectively. The Langmuir isotherm plot slightly over predicted the adsorption capacity with a standard error of 29.7801%.
Corrected: As seen in Figure 4a,b, both the Langmuir isotherm and the Freundlich isotherm were in agreement with the experimental plot, with the R2 values of 0.990 and 0.991, respectively. The Langmuir isotherm plot slightly over predicted the adsorption capacity with a standard error of 29.78%.
Page 28084, Section 3.5: Desorption of Adsorbed TCE Vapor. It was observed that all the samples were completely desorbed within 30–35 min. The complete desorption was achieved at a temperature of approximately 350 °C. Figure 5 shows the desorption of different concentrations of TCE–vapor-loaded activated carbon samples. The samples with a higher concentration of adsorbed TCE (250 ppm) showed faster desorption. However, the desorption curve became less steep as the concentration of TCE adsorbed decreased. Also, the time required for complete desorption was comparatively higher for the lower concentration adsorbed sample. The weak forces between the TCE molecules and the carbon surface resulted in the fast and easy desorption, which suggests the physical nature of adsorption. (38) The desorption of TCE at higher temperatures may cause some oxidation of the effect of particle size of the adsorbent on the residual mass of TCE. The particle size 355 μm showed higher mass loss (49.093%) than the other two particle sizes (32.295 and 31.103%, respectively) because of the increase in the micropore volume. As the adsorption capacity was higher for 355 μm AC, the desorption was expected to be higher. The complete weight loss for the three samples was obtained below 350 °C. The desorption temperature mainly depends on the boiling point of the VOCs and their volatility. Also, for a higher concentration of TCE in the sample, the temperature and time required for complete desorption will be high. (40,41) Figure 7 shows that no significant effect was observed with the change in the purging gas. Nitrogen, argon, and carbon dioxide gases were used to study the effect on the residual mass. The effect of the heating rate of desorption is shown in Figure 8. It was observed that the heating rate has less impact on the desorption rate. From the analysis of the initial and residual mass of activated carbon particles, it was found that complete recovery of TCE vapor is possible by using activated carbon particles.
Figure 5.
(a) Adsorption isotherms of air (in absence of TCE vapor, i.e., only adsorption of nitrogen present in air) on activated carbon particles at 30, 50, and 100 °C and (b) comparison of the adsorption isotherms of TCE vapor in air and air (i.e., in absence of TCE vapor) on activated carbon particles at 30, 50, and 100 °C.
Figure 7.
Desorption of adsorbed TCE–vapor and air at 350 °C from activated carbon particles of different sizes (sizes 355, 500, and 710 μm) loaded with TCE vapor at different concentrations in air.
Figure 8.
Effect of different purging gas on the TPD curve.
Corrected/Addition: 3.5 Adsorption of Air on Activated Carbon. The adsorption isotherms of air on activated carbon particles at the temperatures of 30, 50, and 100 °C are shown in Figure 5a. The adsorption capacity of air was less than 50 mg/g at 30 °C. This indicates a weak interaction between air and activated carbon. Moreover, the adsorption capacity of air on activated carbon decreases with an increase in temperature. Figure 5b shows the comparison of adsorption isotherms of air on activated carbon particles in the presence of TCE vapor and in the absence of TCE vapor, respectively. The adsorption of air (in the absence of TCE vapor) was observed to be much less than that in the presence of a TCE–air mixture. These results indicate that there is a strong affinity between TCE molecules and the surfaces of activated carbon particles.
3.6. Desorption of Adsorbed TCE Vapor. It was observed that all the samples were completely desorbed within 30–35 min at more than 300 °C. The complete desorption was achieved at 350 °C. Figure 6 shows the desorption of different concentrations of TCE–vapor and air-loaded activated carbon samples. The samples with a higher concentration of adsorbed TCE vapor (250 mg/L) showed faster desorption. However, the desorption curve became less steep as the concentration of TCE–air mixture adsorbed decreased. Also, the time required for complete desorption was comparatively higher for the lower concentration adsorbed sample. The weak forces between the TCE molecules and the carbon surface resulted in the fast and easy desorption, which suggests the physical nature of adsorption (38). Desorption of TCE at higher temperatures may cause some oxidation of TCE, which might contaminate the TCE affecting its reusability (39). The TPD curves are shown in Figure 7 depicting the effect of particle size of the adsorbent on the residual mass of TCE. The particle size 355 μm showed higher mass loss (49.093%) than the other two particle sizes (32.295 and 31.103%, respectively) because of the increase in the micropore volume. As the adsorption capacity was higher for 355 μm AC, desorption was expected to be higher. The complete weight loss for the three samples was obtained below 350 °C. The desorption temperature mainly depends on the boiling point of the VOCs and their volatility. Also, for higher concentrations of TCE at the inlet, the temperature and time required for complete desorption will be high (40, 41). Figure 8 showed that no significant effect was observed with the change in the purging gas. Nitrogen, argon, and carbon dioxide gases were used to study the effect on the residual mass. The effect of the heating rate of desorption is shown in Figure 9. It was observed that the heating rate has less impact on the desorption rate. From the analysis of the initial and residual mass of activated carbon particles, it was found that efficient recovery of TCE vapor is possible by using activated carbon particles. Figure 10 shows the schematic representation of the experimental setup for the adsorption process.
Figure 6.
Desorption of adsorbed TCE-vapor and air at 350 °C from activated carbon particles loaded with TCE vapor at different concentrations in air.
Figure 9.
TPD curve of the residual mass of trichloroethylene on activated carbon at an increasing heating rate (5–20 K/min).
Figure 10.
Schematic representation of the experimental setup for the adsorption process (Legend: V1, V2, V3, V4, V5, and V6 are valves, P. Load measures the loading pressure of the gas, P. Equilibrium measures the equilibrium pressure of the gas in the sample chamber, and Primary and Turbo are the vacuum pumps).
Page 28084, Table 3:
Corrected:
Figure 5. Desorption of the activated carbon sample loaded with different concentrations of TCE.
Corrected/Addition:
NOTE: Because of the addition of revised Figure 5, the following figure numbers were changed as follows:
Page 28086: Acknowledgments: The authors sincerely thank the staff members of the Materials Development Section of the Alkali Metals and Material Division (AMMD), Bhabha Atomic Research Centre (BARC), Mumbai for their support during the experimental works.
Corrected: Acknowledgments: The authors sincerely thank the staff members of the Materials Development Section of the Alkali Material and Metal Division (AMMD), Bhabha Atomic Research Centre (BARC), Mumbai, for their support during the experimental work. The authors are grateful to Prof. J. Szulejku, Hanyang University, South Korea, for his valuable suggestions to improve the quality of this paper.
Acknowledgments
The authors sincerely thank the staff members of the Materials Development Section of the Alkali Metals and Material Division, Bhabha Atomic Research Centre, for their support during the experimental works.
Supporting Information Available
The Supporting Information is available free of charge at https://pubs.acs.org/doi/10.1021/acsomega.0c06102.
BET, density, and pore size distribution analyses, plotted data (PDF)
Supplementary Material
Associated Data
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