Preparation of modified chitosan with 3,4-dihydroxybenzaldehyde and investigation of its boron adsorption properties in aqueou solutions

In this study a novel adsorbent bearing poliol groups was prepared via modification of low molecular weight chitosan (LMWC) with 3,4-dihydroxybenzaldehyde. Adsorption conditions of boron onto bare and modified chitosan (MC) were investigated. Fort this, various adsorption parameters such as pH, initial concentration, temperature were investigated. Optimum pHs for boron adsorption were found to be 9,0 and 5,0 for LMWC and LC respectively. Very fast adsorption kinetics was determined for both adsorbent. Adsorption behaviour was obeyed Langmuir adsorption model for both adsorbents. Langmuir adsorption capacities for LMWC and LC were found to be 9,53 mg/g and 36,765 mg/g, respectively. It was observed that boron adsorption was a spontaneous process on both adsorbents. Adsorption reaction of boron on LMWC was found to be endothermic but conversly it was exothermic on LC. Adsorption of boron occured via electrostatic interaction on LMWC but for LC it was said to occur via hydrogen bonding and partially via electrostatic and hydrophobic interactios. Adsorption mechanizms were proposed for both adsorbents. Keywords: Boron, Chitosan, Adsorption, Adsorption Mechanisms