Development and characterisation of miscellaneous cationic sorbents based on lignocellulosic gourd shell

Abstract

The aim of this study is to develop miscellaneous cationic sorbents based on the lignocellulosic biomass of Lagenaria vulgaris fruit, with the property of efficient sorption of anionic pollutants from aqueous solutions. The lignocellulosic gourd shell (LGS biomass), as a potentially valuable agro-waste, was examined and used for the synthesis of sorbents. The preparation of synthesis precursor (LVAT) was performed by alkaline pretreatment of LGS biomass. Pretreatment under weak alkaline conditions with green carbonate solution was carried out for partial delignification and extraction of depolymerized hemicellulose, thereby achieving higher material porosity and activation of cellulose microfibrils. This activation involves the translation of available –OH functional groups into –ONa form (alkali-cellulose), while maintaining the initial biomass composition. Synthesis of the cationic sorbents was performed in three ways. Different N-reagents, such as tertiary amino and quaternary ammonium compounds, were used in the cation modification of LGS biomass and LVAT precursor, to determine the effects of reagent structure and hydrophobicity on the synthesis outcome, and primarily on the sorption properties of the resulting sorbents. The synthesized cationic sorbents were characterized by physico-chemical methods and tested for the removal of anionic pollutants from water, especially phosphates and nitrates. The various chemical modifications of lignocellulosic biomass provide a scientific contribution to a better understanding of the mechanism of anions sorption on the sorbent surface.