Efficient graphene-coated iron oxide (GCIO) nanoadsorbent for removal of lead and arsenic ions

The 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.