Thiol functionalised silica microsphere loaded polymeric hydrogel: Development of a novel hybrid sorbent for removal of lead and cadmium

Current study presents a facile synthesis method for thiol functionalised silica microsphere loaded polymeric hydrogel. Silica microspheres were synthesised as core shell particles by sol-gel method followed by hydrolysis and condensation reaction to form the silica core. The silica was functionalised with thiol and the functionalised silica microsphere was subsequently impregnated into polymeric alginate matrix to form thiol functionalised silica microspheres loaded alginate hydrogel beads (SH-SiO₂MS-Ca-Alg). The developed components and final products were characterised by BET, FTIR, DLS, SEM-EDS. The developed SH-SiO₂MS-Ca-Alg hydrogel beads were used for efficient removal of Pb and Cd [72-97 % for Pb; 60-85 % for Cd at concentration range of 0.1-100 μg mL^-1 and optimum pH 5-7] from aquatic medium. The sorption capacities evaluated for Pb and Cd from Langmuir isotherm were 127.99 and 70.68 mgg^-1 respectively. Uptake kinetics, isotherm, thermodynamics, intraparticle diffusion studies were carried out for both Pb (II) and Cd (II). Mechanism of Pb (II) and Cd (II) removal by SH-SiO₂MS-Ca-Alg hydrogel hybrid beads was proposed with the help of zeta potentials of SH-SiO₂MS at different pH along with fraction diagram of Pb and Cd.