Interpenetrating Networks Of Silica/Calcium Alginate-xanthan Gum Composites For Pb²⁺ Removal From Aqueous Solution

In our work, silica was synthetically interpenetrated andcondensed into the polymer networks of calcium alginate (CA)-xanthangum (XG) gel beads through sol-gel process. The silica/CA-XGcomposites were characterized by Fourier-transform infraredspectroscopy (FT-IR), scanning electron microscopy (SEM),thermogravimetric analysis (TGA), and Brunauer-Emmet-Teller (BET)surface area. Adsorption of Pb(II) on silica/CA-XG composites inaqueous solution and regeneration ability of the composites wasinvestigated. The removal and recovery of Pb2+from battery industrialwastewater and rain water in Shanghai by the composites was alsostudied.Various parameters were optimized including dosage, contacttime, pH, temperature, salt ionic strength and co-existing metal ions,. Equilibrium data fitted well for Langmuir isotherm model, and themaximum adsorption capacity for Pb(II) ions was18.87,23.31, and25.84mg/g at20,30, and40℃, respectively. Thermodynamic studies of ΔG0(-5kJ/mol,20℃)，ΔH0(7.20kJ/mol)，ΔS0(18.02J/mol·K) revealed thenature of adsorption was spontaneous and endothermic. The adsorptionkinetics followed the pseudo-second-order model with R2>0.99. After25adsorption-desorption cycles, the composites still had an efficientregeneration using0.5mol/L HCl. Approximately100%of Pb2+could beremoved and93%of the targeted Pb2+could be recovered for2.0mg/Lsampled lead-bearing battery industrial wastewater after40h successivetreatment using the composites in a fixed-bed adsorption column. Themetal ions in rain water can be removed in different degrees by thecomposites.