ABSTRACTThe graphene-coated iron oxide (GCIO) was used for the removal of Pb2+ and As3+ ions from aqueous solution. For the characterization of GCIO, several techniques (FTIR, XRD, EDX, SEM, TEM, TGA, DSC and vibrating sample magnetometry) were used which indicated the interaction of Pb2+ and As3+ with adsorbent. In addition, the effects of adsorbate concentration, different composition of adsorbent, temperature, pH of the solution and contact time of adsorbate-adsorbent were studied. After analysis of these experiments, it was found that GCIO offered very fast removal of Pb2+ and As3+ with small amount of GCIO (0.09 g) in 100 mg/L adsorbate solution. The maximum removal of Pb2+ ions (up to 97.62%) was achieved when 100 mg/L standard solution of metal ion was treated with GCIO for 35 min at 45°C in weak acidic medium (5 pH). The adsorption of Pb2+ ions followed Freundlich model with high correlation coefficient 0.98 R2. In case of As3+ ions, maximum removal of metal ion (up to 86.62%) was attained when 100 mg/L adsorbate solution is treated with GCIO for 25 min in slightly acidic medium (6 pH) at 25°C. The adsorption of As3+ ions followed D-R model with 0.98 R2 value. The adsorption of both metal ions (Pb2+ and As3+) follows second-order kinetic model. The high percentage removal of metal ions with little quantity of GCIO confirmed that GCIO is an excellent, effective and economic adsorbent.
Keywords: Adsorption; As3+; Pb2+; graphene; maghemite.