Removal and recovery of zinc from solution and electroplating effluent using Azolla filiculoides

The removal of zinc ions from aqueous solutions and electroplating rinse effluent by Azolla filiculoides on batch and column studies was investigated. The maximum zinc uptake by Azolla in batch systems at an optimum pH of 6.0 was found to be 45.2 mg/g, The dried Azolla filiculoides showed good mechanical stability and flow-permeability in repeated column operations. The zinc uptake in column operation at pH 6.2 and 60% breakthrough was between 25.8-30.4 mg/g with varying Row rates (from 32 to 160 ml/h.g). Complete desorption of bound zinc was accomplished with 120 mi of either 0.2 N H2SO4 or HCl. The data from regeneration efficiencies for six cycles, evidenced that the reusability of Azolla in the treatment of Zn2+-laden wastewater is viable. An effluent-free, closed loops of zinc treatment system, with Azolla biomass as the sorbent, is proposed. (C) 1999 Elsevier Science Ltd. All rights reserved.