Executive Summary : | Continuous and nonregulated scrapping of electronic waste materials contribute towards environmental pollution. Weathering and aerial oxidation of the metals (33%), paints, plastics (30%), and other components present in the electronic wastes produce toxic chemicals and other contaminants. Lack of control strategy on the electronic waste management and inadequate awareness in the society poses a huge challenge on maintaining a sustainable green environment. To address the issue, a mild wet-chemical method is proposed here which use complexation and capping ability of saccharides (glucose, starch, cellulose, chitosan etc.) to dissolve and absorb constituent metal as metal ions [Sn(II), Li(I), Cu(II), Ag(I), Au(III), Ni(II), Al(III), Pb(II), Zn(II), Fe(III) etc.] from the waste materials. The charge generated during the process also facilitate the disintegration of the synthetic polymers such as, polytetrafluoroethylene (PTFE) and polypropylene in water. Reaction kinetics of such reactions are influenced through photon, thermal energy, and anions (CO32-, PO43- etc.) in the solution. However, systematic study in this regard has not been carried out in details. Mixing chitosan and cellulose with glucose following the dissolution of the reactive metal ions, such as, Sn(II), Li(I), Ni(II), Al(III), Pb(II), Fe(III), Zn(II) etc. leads to increase in viscosity of the solution but it helps to immobilize the metal ions and plastic fragments. Temperature control and the pH regulation of the solution would assist control releases of few absorbed metal ions, while other multivalent ions will maintain stable complex with the saccharides. Aqueous solution of glucose at 70 ℃ is suitable for the Ag ion extraction from the silver foil. Dissolution of copper and gold ion is observed from their respective metallic foils at the same condition, but the process is slow. Details kinetic study of such dissolution reaction will be done from the alloy containing Cu, Ag, and Au to simulate effect of corrosion resistant metals in the wastes. Though the leaching process of Ag is promoted upon addition of carbonate, phosphate or urea, interference of other metal ions is yet to be investigated. For the current project, leaching experiments will be tested from the other metallic foil (Cu, Au) or alloy (AuAg) sheets in presence of N-bromosuccinimide (NBS) and nicotinamide to make desirable selection of leaching of gold ion [Au(I)/Au(III)] over other ions. Mixing of other saccharides, such as, chitosan or cellulose is required for the gradual dissolution and trapping of remaining metal ions, Sn(II), Li(I), Ni(II), Al(III), Pb(II), Fe(II) etc. from the waste materials. Simultaneous generation and accumulation of charge during the reaction through mechanical stirring will help to disintegrate PTFE or polypropylene tribochemically. The coated plastic will be converted into insoluble nanosized plastics which will be separated from the reaction vessel. |