Synthesis of PEI functionalized silica microsphere loaded polymeric network for simultaneous removal of Cr (III) & Cr (VI) from aquatic medium

Abstract

Current study presents a simple method for facile synthesis of Polyethylenimine (PEI) functionalized silica microsphere loaded polymeric hydrogel (PEI-SiO2MS-Ca-ALG) beads. Synthesis of SiO2MS involved two steps: synthesis of polystyrene (PS) core by sol-gel technique and growth of silica shell over PS particles using hydrolysis and condensation followed by subsequent removal of the PS core. These SiO2MS was functionalised with PEI followed by its loading into alginate matrix to form the PEI-SiO2MS-Ca-ALG nanohybrid beads. The developed products were characterized by FTIR, BET, DLA, SEM-EDS and zeta potential measurement. The PEI-SiO2MS-Ca-ALG polymeric hydrogel beads were used for efficient removal of both chromium (III) and chromium (VI) from groundwater (70–100% for concentration range of 0.1–100 µg mL−1) at pH 2–3. Sorption capacities of these beads for Cr(III) & Cr(VI) were 85.4 and 57.2 mgg−1 respectively as evaluated from Langmuir model for dry beads. Kinetics, thermodynamics, diffusion, isotherm studies were carried out for both Cr(III) & Cr(VI) uptake on the PEI-SiO2MS-Ca-ALG hydrogel beads. In-situ Cr(VI) to Cr(III) transformation by PEI before sorption of Cr(III) was investigated and explained by XPS analysis. Mechanism of Cr(III) & Cr(VI) uptake by beads was proposed based on fraction diagram, FTIR along with other experimental observations.