Risk assessment and green chemistry applied to waste generated in university laboratories

Abstract

Chemical reagents have become fundamental products in daily life use, they contribute in several ways to establish a high level of social development. In the case of higher education, the use of reagents allows learning thought laboratory practices. These practices must be carried out under preventative measures, in order to avoid negative impacts on the environment and human health; this generates the need to identify and classify the chemical substances used and the waste generated. This research was developed at the Faculty of Environmental Engineering at Universidad Santo Tomás in the Villavicencio campus, the objective was to apply the concepts of Green Chemistry in the laboratory guidelines, in addition to guaranteeing the proper management of the chemical waste generated. Initially, the hazard of twenty-one (21) laboratory guides based on the Globally Harmonized System (GHS) ninth revised edition (2021) was determined. Subsequently, an update was performed by applying Green Chemistry to ten (10) of the laboratory guides that represented the greatest hazards, and finally, a manual was established for the management of chemical waste resulting from laboratory practices. The results determined that in the subject of Inorganic Chemistry the guidelines Physical and Chemical Properties of the Matter presents the highest hazard index, due to lead nitrate, which was evaluated as the most hazard reagent, because of its carcinogenicity (1B) and reproductive toxicity (1A). The proposed update to the guidelines was possible by replacing the chemical substances used in order to reduce by 24% the risk associated with them and the by 50% the use of reagents in relation to the same laboratory guidelines defined in the first stage.

Graphical abstract

Highlights

• •The principles of green chemistry and microscale chemistry are applied to the prioritized guides.
• •With the applied methodology, the risk analysis of the reagents was carried out, this through the Globally Harmonized System (GHS).
• •By replacing the chemical substances used, it is possible to reduce 24% of the associated risks.
• •Green Chemistry in the field of solid waste management applied in universities, presents successful results.

1. Introduction

Currently, one of the great concerns of society refers to the care and preservation of the environment [1], becoming more and more important [2]. In a system that revolves around economic growth and the development of civilization; with the exploitation of natural resources and different industrial processes, some of which involve the use and management of hazardous chemical substances, and the consequent environmental alterations [3]. Following the suggestion of the United Nations Conference on the Environment, Colombia adopted the application of the Globally Harmonized System of Classification and Labeling of Chemical Substances (GHS), with which it is intended to create a uniform classification system for chemical hazards, according to the properties of each substance [4]. Thus, all sectors that handle these substances must comply with these regulations, including educational institutions, which handle and generate hazards waste.

Industry is the sector that generates the greatest amount of hazards chemical waste, however, the education sector is the sector that generates the greatest variety of these [5], which results in a greater diversification of waste that can produce different exposure hazards, difficulty in handling and environmental impacts [6].

In the 1990s, the transition towards the concept of sustainability led to the emergence of "Green Chemistry", a term that seeks sustainability through the application of economically viable, socially acceptable and environmentally friendly processes. This concept spread throughout the world. World and today, industries, governments and educational institutions are working on its application [[7], [8], [9], [10]].

Green Chemistry has 12 principles: prevent the creation of waste; maximize the atomic economy; perform a less hazardous chemical synthesis; design less hazardous products and compounds; use safe solvents and reaction conditions; project energy efficiency; use renewable raw materials; avoid chemical derivatives; use catalysts; design products that are easily degradable at the end of their useful life; monitor chemical processes in real time to avoid contamination and prevent accidents [[10], [11], [12], [13], [14], [15], [16], [17], [18], [19], [20]].

Currently there is a transition from theory to practice, with a growing number of practical contributions that validate the application of Green Chemistry in the field of solid waste management applied in educational institutions such as universities [21], some of them already present successful results in your application [13,15,[22], [23], [24], [25], [26], [27], [28], [29]].

In this research, the application of the concept of Green Chemistry was proposed according to laboratory guides of the Faculty of Environmental Engineering at the Santo Tomas University, Villavicencio campus; the study was developed in three stages; The first was carried out through an analysis of the hazard of the chemical reagents used in twenty-one [21] laboratory guides based on the Globally Harmonized System (GHS) ninth revised edition [30], in order to prioritize the reagents and laboratory guides that represented the greatest hazard. A prioritization criterion for the classification of substances was their hazard of carcinogenicity, mutagenicity and toxicity for reproduction, highlighting Lead nitrate, Acetocarmine, Potassium dichromate, Phenol, Phenolphthalein, Formaldehyde and Sodium borate.

In the second stage, proposals for improvement were established in ten [10] prioritized laboratory guides, based on the evaluation of the hazard of the reagents used. Validation tests were carried out to determine their effectiveness, this, by means of proven laboratory methods, which allowed to propose changes in the use and management of reagents and laboratory waste. In the third stage, a stoichiometric analysis was carried out to determine the waste product of the execution of these laboratory guides and thus be able to elaborate a laboratory manual that would guide each of these generated waste towards the proper management, taking into account, in addition, strategies for the use of waste and chemical reagents.

The study is limited to the chemical reagents handled in the laboratory practices of the Faculty of Environmental Engineering, that is, the chemical reagents used in other Faculties of the University were not counted, so these reagents are not part of the prioritization, for Therefore, they are not considered in the substitution of chemical reagents, validation tests and the manual guide of the laboratory. In addition, it can be clarified that the validation tests and replacement of reagents are limited to the fulfillment of the objectives of the laboratory practices and the existing chemical reagents. However, it is important to mention that the faculty that has the highest volume of use of chemical reagents is the Faculty of Environmental Engineering.

2. Materials and methods

The present study lasted 12 months, developed in three stages [1]: Hazard ranking of laboratory guides [2], Application of the principles of green chemistry and [3] Chemical waste management manual, and are described below.

2.1. Hazard ranking of laboratory guides

The analysis of the hazardous of the laboratory guides was based on and adapted from the methodology established in the Lithner study [31]. In the work done here, the most recent version of the GHS, ninth revised edition [30], was used and, unlike Lithner, physical hazards were added. In addition, the evaluation criteria were adapted for this case study, as will be described below.

In order to establish an analysis of the hazardous of the laboratory guides, a consolidation of the types, classes and categories of hazard present in the GHS [30] was carried out. From there, an Excel matrix was elaborated that categorizes physical, human health and environmental hazards into five levels (V) according to their category of hazard, giving them an exponential value (degree of hazard) that varies between 1 and 10,000 according to Table 1, assigning 1 to the reagents they represent the least hazard and 10,000 to the reagents with the greatest hazard.

Table 1.

Hazard categorization.

Hazard class (category)	Hazard level	Hazard level
Based on the categories of physical, health and environmental hazards defined in the GHS [30].	V	10,000
	IV	1,000
	III	100
	II	10
	I	1

Once the evaluation instrument was established, the 53 laboratory guides that use reagents in the practices of the Faculty of Environmental Engineering were analyzed and, from there, a matrix was developed that lists each reagent, the total amount used and its categories hazardous. In total, 106 reagents were identified. The hazard categories were obtained from the Safety Data Sheet - MSDS and from the information in the categorization matrix, it was possible to determine the degree of hazard for each of these reagents.

Subsequently, each practical laboratory guide was assigned the value of the degree of hazard of each reagent that contained it, thus obtaining the sum of the degree of hazard of each guide. These values served as the first prioritization criterion to establish the classification of the guidelines according to hazard, based on the GHS, ninth revised edition [30].

Another prioritization criterion for classification was substances that had a hazard class of carcinogenicity, mutagenicity, and toxicity to reproduction. For the case study, reagents with these hazard classes were selected regardless of their hazard category. In total, 16 reagents were identified with these hazard classes and 21 laboratory guides that contained between 1 and 4 of these reagents. Since many of the reagents contained a carcinogenicity, mutagenicity and toxicity hazard for reproduction, it was decided to prioritize them in the most hazard categories (1A and 1B), based on the Lithner study [31] finally determining 7 reagents and 13 laboratory guides as exemplified in Table 2.

Table 2.

Prioritization of reagents according to the hazard class.

Reagents	Guides Code	Hazard Class and Category
		Mut.	Car.	Rep. Tox.
Lead nitrate	QI2	–	1B	1A
Acetocarmine	B5	–	2	1A
Potassium dichromate	EA1	1B	1B	1B
Phenol	QO3	1B	–	1B
Phenolphthalein	B6, TAR1, EQ1, QI8, QO6, QI7, QI6	2	1B	2
Formaldehyde	QO7	1	1B	–
Sodium borate	QO9	–	–	1B

Mut: Mutagenicity, Car: Carcinogenicity, Rep Tox.: Reproductive toxicity. QI2: Guide to Physical and Chemical Properties of Matter, B5: Guide to Mitosis and meiosis, EA1: Guide for the characterization of Organic Substrates, QO3: guide to recognize the properties of compounds, B6: Photosynthesis and cellular respiration, TAR1: Wastewater Neutralization Guide, EQ1: Guide to Spontaneous Reactions, Galvanic Cells, and Hydrolysis, QI8: Chemical reactions and stoichiometry, QO6 Recognition of alcohols, QI7: Guide for the preparation of solutions, QI6: Inorganic Functions, QO7: Aldehyde, ketone and lipid reactions, QO9: Polymerization.

2.2. Application of the principles of green chemistry

In this second stage the principles of green chemistry were applied [32] and microscale chemistry was implemented [33], on the prioritized guides based on the scenarios proposed in the first stage, that is, the first 5 guides categorized in Table 3 and the first 5 categorized in Table 4 were selected.

Table 3.

Laboratory guides selected according to the hazardous ranking of values higher than 100,000. In Table 3, the first 5 laboratory guides are presented according to the scores obtained from the categorization by hazards defined in Table 1. In this table, there are mainly laboratory guides associated with the area of chemistry, in particular, those related to practices where chemical reactions are analyzed.

GUIDE CODE	LABORATORY GUIDE	DEGREE OF TOTAL HAZARD
QO7	Aldehyde, ketone and lipid reactions	157,622
QO8	Identification of carboxylic acids and esterification reactions	151,510
QI8	Chemical reactions and stoichiometry	126,733
QO6	Recognition of alcohols	113,011
QO4	Identification of functional groups by solubility	100,110

Table 4.

Laboratory guides selected according to the hazardous ranking of highly hazardous reagents.

GUIDE CODE	LABORATORY GUIDE	DEGREE OF TOTAL HAZARD
QI2	Physical and chemical properties of matter	68,552
B5	Mitosis and meiosis	12,310
EA1	Characterization of Organic Substrates	60,021
QO3	Determination of the melting point of a pure substance. Obtaining hydrocarbons	75,531
B6	Photosynthesis and cellular respiration	23,210

Table 4 shows the first 5 guides of laboratories selected according to the hazardous of the classes of reagents used.

Once the 10 guides that were to be updated had been determined, a bibliographic database search was carried out, in which updated proposals were established for each of these, applying the concepts of green chemistry and microscale chemistry.

Subsequently, validation tests were developed in the laboratory in order to verify the effectiveness of these updated guidelines in relation to the original guidelines, this identified if they met the initial objective of the laboratory practice. In addition, an estimate of the amount of chemical waste generated in these new guides and the way in which their waste could be managed was generated [34,35].

2.3. Chemical waste management manual

Stoichiometric calculations of 42 laboratory guides were carried out using the trial-and-error method in an Excel calculation book, in which the proportions between reagents, products and subproducts were determined in cases where the nature of the practice can generate them in a chemical reaction. (See Equation (1)). For substances that required the drip procedure, the value of 0.05 g was used to standardize the unit of mass measurement.

2.4. Equation (1). Stoichiometry

Input |Reagent₁+Reagent_n| = |Product₁+ Subproduct_n| Output (1)

Chemical waste was classified according to the methodology used at the National University of Colombia, see Table 5, taking into account the Globally Harmonized System (GHS) and hazardous waste management [36]. For the classification, those products and subproducts that were generated in greater quantity (ml) were considered, prioritizing waste based on production.

Table 5.

Assignment of hazardous waste types.

Waste type	Description
1–5	Container waste.
6–10	Mixed solid waste.
11–13	Aliphatic hydrocarbon waste.
14–16	Aromatic hydrocarbon waste.
17–19	Cyclic hydrocarbon waste.
20–27	Organic waste with different functional groups.
28–35	Aromatic organic waste with different functional groups.
36–39	Inorganic acid waste.
40–43	Alkaline waste.
44–49	Residues of salts and aqueous solutions of heavy metal.
50–53	Sludge.
54	Contents of pressure vessels

In total, 20 types of chemical waste generated in the laboratory practices were classified. For all of them, risk reduction processes were proposed, so that they can be arranged in a better way. Finally, the potential for taking advantage of the types of waste was determined, all this applied under the principles of green chemistry, [37]. For each type of waste generated, a protocol was established that describes the generalities of the waste, the security measures, the treatment and finally the possible use under the principles of green chemistry.

Finally, the laboratory waste manual is structured with the following items: introduction, objectives, scope, safe work in the laboratory, bearing in mind the responsibility of the personnel entering the laboratory, as well as the Personal Protection Elements (PPE), the manipulation of chemical substances, the procedures according to the classification of 20 types of chemical waste generated in the laboratories where practices of the Faculty of Environmental Engineering are carried out, in which the hazard, incompatibilities, treatment that must be applied to each group and exploitation mechanisms.

3. Results and discussions

3.1. Hazard ranking of laboratory guides

According to the established methodology, the reagents for lead nitrate, acetocarmine, potassium dichromate, phenol, phenolphthalein, formaldehyde and sodium borate are found in the upper part of the hazard scale and in 13 laboratory guides, the first being as follow: Physical and chemical properties of matter- QI2, Mitosis and meiosis- B5 and Characterization of Organic Substrates- EA1.

Thus, the degree of total hazard of the laboratory guides is not presented in descending order, since the ranking arrangement corresponds to the prioritization of the hazard of carcinogenicity, mutagenicity and toxicity for reproduction, as shown in Table 6. It is emphasized that this does not mean that the hazard that each laboratory guide represents is not important, but that it is necessary to pay special attention to those that contain reagents with prioritized categories of hazard, since they represent a hazard to the health of those who handle them. Regardless of the concentration used.

Table 6.

Ranking of hazardous of the guides. QI2: Physical and chemical properties of matter, B5: Mitosis and meiosis, EA1: Characterization of Organic Substrates, QO3: Determination of the melting point of a pure substance. Obtaining hydrocarbons, B6: Photosynthesis and Cellular Respiration Guide, TAR1: Wastewater Neutralization Guide, EQ1: Guide to Spontaneous Reactions, Galvanic Cells, and Hydrolysis, QI8: Guide to Chemical Reactions and Stoichiometry, QO6: Guide for the recognition of alcohols and phenols, QI7: Guide for the preparation of solutions.

Ranking	Guides Code	Degree of total Hazard
1	QI2	68,552
2	B5	12,310
3	EA1	60,021
4	QO3	75,531
5	B6	23,210
6	TAR1	21,320
7	EQ1	19,340
8	QI8	126,733
9	QO6	113,011
10	QI7	47,341

In this way, it was determined that the laboratory guide with the greatest hazard is IQ2 (Guide No. 2 of Inorganic Chemistry, called: Physical and chemical properties of matter) with a value of the total degree of hazard of 68,552, and the reagent The most hazard is lead nitrate, with a total hazard value of 23,011, being included in the categories of carcinogenicity (1B) and toxicity for reproduction (1A), in addition to being an oxidizing solid, which can produce acute toxicity and eye damage.

With this study it was also possible to obtain a general knowledge of the types and quantities of reagents used by the Faculty of Environmental Engineering at the Villavicencio campus in one semester, ethyl alcohol being the most used with a total of 32,342 ml and sodium chloride the most used with a value of 2,021.6 g.

3.2. Application of the principles of green chemistry

Adjustments were made to the laboratory guides by applying the principles of green chemistry considering principle 1 (Prevent waste), principle 3 (Less Hazardous Chemical Syntheses) and principle 12 (Inherently safer chemistry for accident prevention), taking that by eliminating highly dangerous reagents and replacing them with reagents of lesser degree of danger, less dangerous waste is produced; microscale chemistry was also applied as shown in Table 7. These guides were validated by conducting laboratory practices in the university facilities. In addition, the table adds the hazard values for chemical reagents used, it must be considered that in the chemical reagents used in original guides, among them acetocarmine and phenol, it must be substituted for having health hazards in the category of Carcinogens and reproductive toxicity.

Table 7.

Proposed reagents for each selected laboratory guide according to the hazardous ranking.

Lab guide	Original reagents	Total Hazard	Proposed reagents	Total Hazard
QI2 -Physical and chemical properties of matter	− Potassium Iodide − Lead Nitrate	− 1,000 − 23,011	− Sodium Carbonate − Calcium Chloride	− 1,000 − 1,010
B5 - Mitosis and meiosis	− Acetocarmine	− 10,310	− Safranina − Hydrochloric acid	− 10,000 − 10
EA1 -Characterization of organic substrates	− Potassium dichromate	− 28,011	− Potassium Permanganate	− 2.011
QO3 - Recognition of properties of organic compounds …	− Phenol − Pyrocatechol	− 22,300 − 22,400	− Not included (Procedures that used phenol or pyrocatechol were eliminated)	–
B6 -Photosynthesis and cellular respiration	− Phenolphthalein	− 1,200	− Methyl Orange	− 100
QO7 -Reaction aldehydes, ketones and lipids	− Formaldehyde − Potassium Permanganate − Acetone	− 24,300 − 2,010	− Glutaraldehyde (2%) − Schiff's reagent − Benzaldehyde − Acetone	− 1,200 − 10 − 3,020 − 2,010
QO8 -Identification of carboxylic acids and esterification reactions	− Formic acid − Acetic acid	− 20,010 − 20,011	− Benzoic acid − Acetyl chloride	− 12,000 − 21,000
QI8 -Chemical reactions and stoichiometry	− Cupric sulfate − Copper powder − Phenolphthalein − 5% hydrochloric acid − Methylene blue	− 4,010 − 0 − 1,200 − 10 − 20	− Iron filing − Methyl orange	− 1,100 − 100
QO6 -Acohol recognition	− Phenol − Metanol − Phenolphthalein − Hydrochloric Acid − Zinc Chloride	− 22,300 − 2,100 − 11,230 − 1,200 − 10 − 12,010	− Isopropanol − Terbutanol − Propylene glycol − Methyl orange − Lucas's reagent	− 2,110 − 3,000 − 0 − 100 − 2,010
QO4 -Identification of functional groups by solubility	–	–	− For this case, a micro-scale work is proposed, since it is not prudent to modify the reagents used, in addition, it would seek to identify chemical substances with few chemical hazards.	–

Once the validation tests were carried out in the laboratories, it was found that the 10 proposed laboratory guides were effective, meeting the same objectives set out in the original guides.

The hazards of the new proposed laboratory guides were determined based on the methodology outlined in this article, and they were compared with the hazards of the original guides. In Fig. 1 You can see the comparison of the hazards of the proposed guides with the original ones, in relation to the class of hazard of the reagents (carcinogenic, mutagenic and toxic for reproduction).

Fig. 1.

Comparison of the hazards of the original guidelines versus the proposed guidelines in relation to the hazard class.

QI2: Physical and chemical properties of matter, B5: Mitosis and meiosis, EA1: Characterization of organic substrates, QO3: Recognition of properties of organic compounds, B6: Photosynthesis and Cellular Respiration Guide.

In Fig. 1 it is observed that the most representative changes are in EA1 and QO3, which correspond to the substitution of potassium dichromate in the practice "Characterization of organic substrates" of the course of "Alternative energies (EA1)" and to the substitution of phenol for the practice of "Recognition of properties of organic compounds" of the course "Organic Chemistry (QO3)". In general, a 36% reduction in hazard was obtained in relation to the original guidelines.

In Fig. 2 you can see the comparison of the hazards of the proposed guides with the original ones, in relation to the hazardous of the reagents.

Fig. 2.

Comparison of the hazards of the original guides versus the proposed guides in relation to the hazardous ranking.

QO7: Reaction to aldehydes, ketones and lipids, QO8: Identification of carboxylic acids and esterification reactions, QI8 - Chemical reactions and stoichiometry, QO6 - Recognition of alcohols, QO4 - Identification of functional groups by solubility.

In Fig. 2 the most representative change occurred in QO6, which represents the practice of recognition of alcohols, in this practice methanol is replaced by other alcohols with higher molecular weight, thus reducing part of the hazards to which the university community will be exposed.

Applying green chemistry and work at the microscale, the new guide is generated with different chemical substances that meet the needs of the practice and reduce physical hazards, health hazards and environmental hazards. Methyl orange enters as a substitute for phenolphthalein, other hazardous substances such as tert-butyl alcohol (Ter butanol), ethyl ether and zinc chloride are eliminated.

The reduction in the use of chemical substances with a high hazard characteristic implies a reduction in the generation of highly hazardous chemical waste, with the proposed guidelines a 36% reduction in hazard characteristics is achieved in the reagents used, which in turn implies a reduction with respect to waste by a similar percentage; For example, the elimination of lead nitrate as a chemical reagent, because it generated a heavy metal as a waste, which involved a more complex and expensive management in the chain of management of a hazardous waste, which would no longer be necessary, by making this change, since it now generates a similar volume of hazardous waste. However, it would no longer have the same hazard characteristics.

The procedure in which lead nitrate was used was replaced by a safer one, which proposes a chemical reaction between sodium carbonate and calcium chloride [38] As shown in Table 8. As in the previous change in the procedure, other proposals were made in which as a result, when applying the work at the microscale, a decrease in the volume of hazardous waste generation was achieved and by substituting key reagents eliminates or mitigates hazard characteristics.

Table 8.

Stoichiometric calculation sample of the proposed procedure to replace lead nitrate.

Involved Chemical Reaction (Calcium Carbonate)
CaCl2 + Na2CO3 → CaCO3 + 2NaCl
Compound	Name	Input	Output
CaCl2	Calcium chloride	1,047 g	≈ 0 g
Na2CO3	Sodium carbonate	1 g	≈ 0 g
H2O	Water	26 ml	> 26 ml
CaCO3	Calcium carbonate	0 g	> 1.04 ml
2NaCl	Sodium chloride	0 ml	> 1.007 ml
N/A	Filter paper	2.05 ml	>2.053 g

3.3. Chemical waste management manual

Regarding the quantification carried out by means of the stoichiometric calculations of the laboratory guides of the Faculty of Environmental Engineering, a total theoretical value of 3,285.68 ml of liquid chemical waste was generated, of which 52% belongs to type 20 "Aliphatic Alcohols ”See Fig. 3, being the one with the highest quantity, due to factors such as: they are used as solvents, in the same way for cleaning the laboratory equipment before and after each practice. Next, sulfur salt residues are positioned with 27% and hydrocarbons with 7%. On the contrary, the percentage of halogenated salts is close to zero.

Fig. 3.

Classification of waste generated in the laboratory practices of the Faculty of Environmental Engineering. Note. The type of waste generated is identified as: Aliphatic alcohols (Type20), sulfur salts (Type46), hydrocarbons (Type11), sodium hydroxide (Type40), hydrochloric acid (Type37), sulfuric acid (Type36), nitric acid (Type38), aldehydes and ketones (Type21), hydrocarbons (Type13), aromatic alcohols (Type28), nitrogenous salts (Type45), aliphatic esters (Type23), inorganic acids (Type39), aromatic esters (Type31) (carboxylic acids (Type22), aqueous solutions (Type48), amines and amides (Type25), hydrocarbons (Type16), potassium hydroxide (Type41) and halogenated salts (Type44); the color assigned to each of the types mentioned above corresponds to the RESPEL PIRS UNAL classification (See Anexo 3.). Source: The authors, 2020.

The experimental processes generate chemical residues that cannot be eliminated in their original form, nor should they be directly discharged down the drain, which is why treatments are proposed in order to reduce their contaminating potential and that the effluent can be reused. Or spilled. In such case to be recovered. In Table 9, those liquid chemical wastes that due to their physicochemical characteristics can receive the same treatment, in order to reduce their contaminating potential, were grouped..

Table 9.

Proposed treatments for the management of liquid chemical waste at the point of generation.

Waste group	Chemical waste	Proposed process	Recommended products
Organic	Type 20: Aliphatic Alcohols Type 21: Aldehydes and aliphatic ketones	Thermal utilization	N/A
Acids Inorganic and organic	Type 36: Sulfuric Acid	Inorganic base neutralization	Sodium bicarbonate (NaHCO3)
	Type 37: Hydrochloric acid		Sodium carbonate (Na2CO3)
	Type 38: Nitric Acid		Sodium carbonate (Na2CO3)
			Sodium carbonate (Na2CO3)
	Type 22: Aliphatic carboxylic acids		Sodium carbonate (Na2CO3)
Bases and their solutions Inorganic	Type 40: Sodium Hydroxide	Neutralization with a dilute solution	Hydrochloric acid (HCl)
	Type 41: Potassium Hydroxide		Sulfuric acid (H₂SO₄)
Halogenated solvents Organic	Type 16: Hydrocarbons (methylene blue)	Thermal utilization	N/A
	Type 23: Alpha esters: sodium acetate and propanolate	Thermal utilization	N/A
	Type 25: Amines and aliphatic amides: Butylamine	Neutralize	Sodium bicarbonate (NaHCO3)
	Type 44: Halogenated salts (Iodine)	REDOX	Sodium carbonate (Na2CO3)
Metals Heavy	Type 48: Copper (Cu)	Reducing agent precipitation	Sodium borohydride (NaBH₄)

Thermal utilization is proposed as an option for the disposal of the waste groups mentioned in Table 9, seeking to take advantage of their calorific power. This use would be carried out with companies external to the institution which, since currently the university does not have the capacity to take advantage of waste with this technology.

The different types of waste generated in the laboratory can have very different characteristics and can be produced in variable quantities, aspects that directly affect the choice of the procedure for their elimination.

4. Conclusions

With the applied methodology, it was possible to carry out the analysis of the risk of the reagents through the Globally Harmonized System (GHS) and the adaptation to Decree 1496 of 2018 of Colombia with the aim of improving the handling of the reagents. These results reflect the need to review, especially the laboratory guides that are presented in high positions with respect to hazardous, and modify them under the principles of Green Chemistry, in order to reduce their degree of total hazard.

Based on the results of the ranking carried out, it was determined that the laboratory guide with the highest degree of total hazard is Guide N ° 2 of Inorganic Chemistry (QI2), called: Physical and chemical properties of matter, the one that contains the reagent with greater hazard, which is Lead Nitrate since it is an oxidizing solid, which can produce acute toxicity, eye damage, carcinogenicity, toxicity for reproduction and acute and chronic aquatic toxicity.

With the established proposals, it was possible to reduce 36% of the hazards based on the Globally Harmonized System (GHS) for the hazards of chemical reagents, out of the 10 prioritized guides, and an outlook was raised to carry out green chemistry studies in more laboratory practices, and even in other faculties.

20 types of hazardous waste were identified, resulting from laboratory practices, whose total volume obtained was 3,285.68 ml. 52% of these residues are of aliphatic alcohols, followed by residues of sulfur salts with 27% and 7% of hydrocarbons.

5. Recommendations

This first and second stage is an open panorama to enter into an investigation of how chemical substances can affect occupational health based on occupational diseases established in Decree 1477 of 2014 of the Ministry of Labor [39], This panorama has been studied before in Colombia, determining that the most critical substances for said country was tetrachloethylene [40].

The chemical waste manual must continue to be updated and given feedback in the face of changes in work procedures, as new substances arise that are not included in the classification, since the proposal is based on the laboratory guides that are currently in use.

It was found that there are opportunities for improvement in the management of both the reagents used and the hazardous waste generated, implementing pedagogical strategies aimed at the sustainability of laboratory practices, such as conducting micro-scale experiments, which in addition to reducing costs, reduces potential impacts on human health and the environment. In addition to contributing to the science and awareness of students about the hazards of certain reagents and the necessary safety procedures, contributing to the training of professionals who are more aware of their responsibility with health and the environment. Following the methodology of this work, it will be applied to the waste generated in the practical classes.

It is identified that there is a high generation of RESPEL from alcohols which, if they are properly separated, could take advantage of their calorific power as fuel in cogeneration operations.

Author contributions statement

Jonathan Steven Murcia Fandiño: Conceived and designed the experiments, Analyzed and interpreted the data, Contributed reagents, materials, analysis tools or data, Wrote the paper. Saúl Martínez Molina: Conceived and designed the experiments, Performed the experiments, Analyzed and interpreted the data, Wrote the paper. Valma Martins Barbosa: Conceived and designed the experiments, Wrote the paper, Analyzed and interpreted the data. Diana Paola Herrera Gómez: Conceived and designed the experiments, Performed the experiments, Analyzed and interpreted the data. Camila Alejandra Buitrago Barbosa: Conceived and designed the experiments, Performed the experiments, Analyzed and interpreted the data. Jairo Andres Velasquez Cuestas: Conceived and designed the experiments, Performed the experiments, Analyzed and interpreted the data. Francey Valentina Ruiz Gacha: Conceived and designed the experiments, Performed the experiments, Analyzed and interpreted the data. Maria Alejandra Torres Ardila: Conceived and designed the experiments, Performed the experiments, Analyzed and interpreted the data.

Data availability statement

Data included in article/supplementary material/referenced in article.

Declaration of competing interest

The authors declare that they have no known competing financial interests or personal relationships that could have appeared to influence the work reported in this paper.