A novel composite of SiO2 decorated with nano ferrous oxalate (SDNF) for efficient and highly selective removal of Pb2+ from aqueous solutions

Developing a material with high adsorption capacity and selectivity to remove lead from Pb2+ polluted wastewater is of vital importance for environment protection and resources utilization. In this study, a novel composite, SiO2 decorated with nano ferrous oxalate (SDNF), was prepared from natural biotite containing ores to remove Pb2+. Pseudo-first-order kinetic (R2 = 0.99) and Langmuir models (R2 = 0.99) fitted the data well, manifesting that Pb2+ adsorption process was monolayer adsorption. The maximum Pb2+ adsorption capacity was identified as 446.98 mg/g. SEM and TEM images showed that nano ferrous oxalate with average size of 11.51 nm was coated on the surface of ores, and their distributions were uniform. Results of XRD, XPS, FTIR and zeta potential indicated that ion exchange, surface complexation and electrostatic attraction interaction were involved in the remvoal of Pb2+, and the ion exchange between Fe2+ and Pb2+ played a major role. Moreover, both Cd2+ and Zn2+ removal efficiency are less than 2 % in Pb-Cd or Pb-Zn coexisted solution, indicating the composite possessed high selectivity for Pb2+ removal. All above results indicated that the composite was a material with high adsorption capacity and selectivity for Pb2+, which was suitable for remediation of Pb2+ pollution from Pb2+ containing wastewater.