Keywords: competitive biosorption, chitosan flakes, adsorbents, platinum recovery, binary dilute solutions, palladium recovery, metal recovery, metal recycling, Langmuir competitive model
Evaluation of chitosan flakes as adsorbent for palladium and platinum recovery from binary dilute solutions
In the recent years, special attention has been paid to the competitive recovery or separation of metals from industrial wastewaters or solid wastes that contain more than one chemical component. Platinum group metals (PGMs), particularly palladium and platinum, are used together in many fields such as industrial catalyst production. The recovery of these metals from industrial waste streams has required development of present processes and new technologies. In this work, the potential of chitosan for palladium and platinum recovery from aqueous solutions was investigated. The observed results showed that the optimum operating conditions for palladium and platinum recovery by chitosan were initially pH = 2, particle size of adsorbent = 0.21 mm and adsorbent dose = 10 g/L. Experimental results indicated that Freundlich isotherm and Langmuir models best fitted with the equilibrium data of platinum and palladium adsorption on chitosan in single solutions, respectively. In binary solutions, the competitive adsorption of palladium and platinum were successfully described by the Langmuir competitive model (LCM). As it was expected, experimental results indicated that, equilibrium capacity for each metal decreased in presence of another ion due to competition of palladium and platinum anions for active sites on the chitosan surface.