Potentials of Some Waste Biomaterials as Sorbents for Gold- and Silver-Cyanide Removal from Aqueous Matrices

摘要

Plating, printed circuit board, jewellery units, photofinishing and mining industries emanate large-volume low-tenor effluents containing metal-cyanide (M_xCN) like gold- and silvercyanide. Since metal moiety of M_xCN being precious, non-renewable and finite resource; their complete removal from effluents is the key. Biosorption has immense potential of becoming efficient and economical alternative to recover the wasted metal resource over conventional methods. Twenty-eight low-cost biomaterials obtained from diverse sources were screened for gold- and silver-cyanide uptake. Study revealed that maximum uptake of both MxCN took place at acidic pH. Based on maximum uptake, Rice Husk (RH) and Eicchornia root (ER) biomass were selected for gold- and silver-cyanide sorption, respectively, for further studies. Optimal conditions for sorption were: pH (4.0-7.0), biosorbent quantity (1-3%), rate of uptake (40 min) and initial M_xCN concentration (5-500 μmol). Biosorption data obtained conformed to Freundlich and Langmuir adsorption models (R~2＞0.98). NaOH acted as an efficient desorbing agent (＞95%).