Facile synthesis of a porous sorbent derived from the rice husk biomass: A new and highly efficient material for water remediation

Abstract

This study describes a novel semi-synthetic sorbent for the sorption of cadmium nanoparticles (Cd-NPs) made from rice husks functionalized with nitric acid (NT-RH). Powder X-ray diffraction (PXRD) analysis verified the NT-RH synthesis and Cd sorption at the NT-RH (Cd@NT-RH). The surface functionalities of NT-RH that contributed most to the sorption of Cd-NPs were discovered using FTIR analysis. Scanning electron microscopic (SEM) examination shows that the acid-functionalized rice husk-based sorbent has a porous structure resembling a network with macro-sized voids. These voids practically vanish in the Cd@NT-RH, indicating their effective contribution to the sorbent's overall sorption activity. The elemental analysis further supports the PXRD and FTIR results and confirms the formation of NT-RH and its sorption potential for Cd-NPs. Furthermore, the effect of varied working temperatures, sorbent dosages, sorbent-sorbate contact period, and pH values on NT-RH sorption performance was investigated. Since the NT-RH's point of zero charge was determined to be 6.6, the sorbent's Cd-NPs elimination capacity was found to be highest at pH = 7, where a minimal quantity of competing (H+) and precipitating (OH–) ions is present. Cd sorption on NT-RH was better described by the Langmuir isotherm and pseudo-2nd order kinetics model. Thermodynamic analysis of Cd sorption at NT-RH demonstrates that the sorption process is exothermic and occurs spontaneously.