Water Hyacinth Leaf Protein Concentrate Composites for Removal of Hexavalent Chromium

Abstract

Water Hyacinth Leaf Protein Concentrate/Graphene Oxide/Chitosan/polyvinyl alcohol (WHLPC/GO/CS/PVA) composite was synthesized for the removal of Cr (VI) from wastewater. About 80% of the prepared composite material constitutes WHLPC which is extracted from water hyacinth plant leaf. The prepared material was characterized by FT-IR and XRD. The process variables such as pH, contact time, dosage, initial Cr (VI) concentration, and temperature were optimized using a batch mode experiment. Kinetic studies were conducted using pseudo-first-order and pseudo-second-order models and it was observed that the chemosorptive pseudo-second-order model described the adsorption system in a better way, with a high value of R2. The highest adsorption capacity of 202.59 mg/g was achieved at pH 1.0, and equilibrium was achieved within 330 min. Langmuir and Freundlich isotherm models were analyzed using non-linear fitting. It was found that the Langmuir model gives the best fit indicating monolayer adsorption of Cr (VI) on the WHLPC/GO/CS/PVA. The reuse efficiency of the synthesized material was also found to be greater than 65% for five consecutive cycles. Thermodynamic studies were conducted and results revealed that the adsorption was natural and endothermic.