Synthesis of functionalized biomaterials and its application in the efficient remediation of aquatic environment contaminated with Cr(VI)

Abstract

The aim of this study is to synthesize the three different hybrid materials precursor to natural biopolymer chitosan. The silanes viz., 3-mercaptopropyl trimethoxysilane, trimethoxy(octyl) silane and 3-aminopropyl triethoxysilane were grafted with the chitosan network and were named as CHMS, CHTS and CHAS, respectively. The materials were characterized by the FT-IR spectrometry, SEM–EDX and XPS analyses. These solids were then employed in the efficient removal of Cr(VI) from aqueous solutions using batch and column reactor operations. The functionalized biomaterials possessed extremely high percent removal of Cr(VI) compared to bare chitosan at wide pH range i.e., pH ∼3.0 to 8.0. A fast uptake of Cr(VI) was occurred and high percentage removal was obtained at wide range of Cr(VI) initial concentrations (7.7–100.58mg/L). The equilibrium state sorption data were utilized for the Langmuir and Freundlich adsorption isotherm studies. Similarly, an increase in background electrolyte concentrations from 0.0001 to 0.05mol/L NaNO3 was assessed for the uptake of Cr(VI) by these hybrid materials. Relatively a fast uptake of Cr(VI) by these hybrid materials were obtained and further the time dependence data were fitted well to the pseudo-second-order and fractal-like pseudo-second-order kinetic models rather a pseudo-first-order kinetic model. Furthermore, a detailed sorption mechanism was included with the help of FT-IR, TOC and XPS analyses. In addition, CHMS and CHTS were used for dynamic studies under column reactor operations. The breakthrough curves were then used for the non-linear fitting of the Thomas equation and the loading capacity of the column for Cr(VI) were estimated.