Metallic Affinity of Toxic and Noble Metals by Particles Produced from Sericin, Alginate and Poly-(Ethylene Glycol)

Abstract

Biosorbents have been used as a potential alternative to the conventional technologies for removal of toxic metals from water and wastewater. The use of waste material as adsorbent offers significant advantages like low-cost, availability, efficiency, biodegradability, etc. In this study, particles produced from a blend between sericin, alginate and Poly(ethylene glycol) diglycidyl ether (PEG) were used to remove toxic and precious metals from aqueous solutions. Precious metals are found in wastewaters of various industrial processes including metal, ore processing, electronic manufacturing and mining; and the recovery of these metals is profitable to those industrial processes. Sericin is a protein present in cocoon of silkworm (Bombyx mori) usually discharged in the effluent of silk production. Alginate is a natural polysaccharide extracted from abundant sources of brown algae (brown seaweed) properties to this material. The addiction of PEG into a blend of sericin-alginate induces chemical modification that can develop better properties to this material. The objective of this work is to evaluate the metallic affinity and adsorption capacity of particles produced by sericin-alginate blend and sericin-alginate- PEG blend. The blends were dripped in aqueous and alcoholic (ethanol) solutions of CaCl2 and Ca(NO3)2, and then the particles were dried at 100 °C. The simulation of speciation diagrams as functions of pH was performed using Hydra/Medusa software in order to establish the pH to be used in the experiments. The removal of chromium, cadmium, nickel, copper, lead, silver, palladium, platinum and gold ions from aqueous solution by sericin-alginate particles was evaluated through adsorption affinity testes. The results indicated that the presence of PEG improve the adsorption capacity of the biosorbents. For the noble metals the greatest values of reduction and adsorption capacity were obtained to gold (98 – 99 %) and palladium (87 – 89 %), and for the toxic metals it was obtained higher values of reductions to lead (66 – 83 %), cadmium (62 – 79 %), chromium (69 – 74 %) and copper (65 – 74 %).