Most of the chemical waste generated in the laboratory falls into five categories:
- a) Inorganic solids
- b) Aqueous solvents
- c) Organic solids
- d) Organic solvents
- e) Chlorinated solvents
Inorganic solid waste in the laboratory comes primarily from inorganic qualitative salt analysis. Examples of inorganic solids commonly handled in the lab are sodium chloride, sodium sulfate, calcium chloride, alumina, and silica gel as well as TLC plates. These wastes are to be discarded in the container labeled ‘inorganic solids.
Along these, aqueous inorganic wastes are also be generated in the laboratory. Organic synthetic and analytical experiments also result in the formation of an aqueous layer that is not used and must be discarded. Accordingly, this and any other solutions involving water as the solvent must be poured into the container labeled “aqueous waste.”
Organic solids are produced as end products of synthetic reactions. Once the appropriate analysis is over, these are to be discarded into the container labeled “organic solid.” Organic solids usually include naphthalene, glucose, urea, benzoic acid, nitroanilines etc.
Almost all the reactions require solvents to proceed smoothly. Moreover, extraction of organic compounds, recrystallization etc also require organic solvents. Chlorinated solvents are stored separately as they can contaminate surface and ground water. Halogenated solvents present in water may undergo a series of dehalogenation reactions leading to the formation of more toxic daughter compounds. The presence in water of both parent and daughter halogenated compounds constitutes a risk to aquatic ecosystems and human health. As far as halogenated solvents are considered, only chlorinated solvents are used in the laboratory and they include dichloromethane, chloroform and chlorobenzene. Used solvents/waste solvents in this category are to be discarded into the container labeled ‘chlorinated solvents.” Commonly used non-halogenated solvents include diethyl ether, ethyl acetate, hexane, toluene etc. These solvent wastes should be disposed into the container labeled “Organic Solvents.”
MISPLACED WASTE CREATES SERIOUS PROBLEMS FOR THE ECOSYSTEM AND THE ENVIRONMENT. IF IN DOUBT, PLEASE CONSULT YOUR TEACHER RATHER THAN CARELESSLY DUMPING WASTE INTO THE WRONG CONTAINERS.