After entering the food chain, they undergo biomagnification processes and finally accumulate in the human body. They tend to accumulate in living organisms. The persistent nature of these non-biodegradable pollutants is very dangerous. This pollution has an influence on air, water, and soil contamination by dust, industrial gases, sewage, waste, and coal combustion products containing heavy metals (Nocoń et al. It is required that the precipitation agents not only effectively remove metal ions from the solution but also effectively bind with dyes or metal complexes.Īs civilization develops, the level of environmental pollution with heavy metals intensifies. However, toxic byproducts are often produced. The possibility of improving the efficiency of metal precipitation is obtained by using a higher dose of precipitating agent. Dithiocarbamate (DTC) compounds are also used, e.g., sodium dimethyldithiocarbamate (SDTC), and ligands for permanent metal binding, e.g., 1,3-benzenediamidoethanethiol (BDETH 2), 2,6-pyridinediamidoethanethiol (PyDET), a pyridine-based thiol ligand (DTPY) or ligands with open chains containing many sulfur atoms, using of a tetrahedral bonding arrangement around a central metal atom. Potassium/sodium thiocarbonate (STC) and 2,4,6-trimercaptotiazine (TMT) are widely used. All these restrictions forced to search for new and effective precipitants. Disadvantages of that process are very low solubility of metal sulfides, highly sensitive process to the dosing of the precipitation agent, and the risks of emission of toxic hydrogen sulfide. ![]() ![]() On the other hand, use of sulfides is characterized by lower solubility compared with that of metal hydroxides, so a higher degree of metal reduction can be achieved in a shorter time. As a result, metal hydroxide is getting amphoteric and it can go back into the solution. However, during metal hydroxide precipitation, large amounts of solids are formed. Chemical precipitation using hydroxides or sulfides is one of the most commonly used methods for removing metals from water and wastewater. Restrictive requirements for maximum concentrations of metals introduced into the environment lead to search for effective methods of their removal.
0 Comments
Leave a Reply. |
AuthorWrite something about yourself. No need to be fancy, just an overview. ArchivesCategories |