Alkali treated water chestnut<i>(Trapa natans L.)</i>shells<i>as a</i>promising phytosorbent for malachite green removal from water

Abstract

Search for eco-friendly adsorbents for sustainable dye treatment is on the rise. The present study demonstrated the enhanced removal of malachite green (MG) with alkali-modified shells of water chestnut (AWCN) under optimized physio-chemical parameters. Alkali treatment significantly reduces the lignocellulosic components which in turn increased the water stability. The material was been characterized by pHzpc, FTIR, FESEM-EDAX, and BET surface area analysis. pH-dependent adsorption was noticed and the maximum adsorption capacity was determined as 136.46<b> </b>mg/g. Adsorption followed pseudo-second-order kinetics (<i>R</i>²=0.99) and Langmuir isotherm model (<i>R</i>²=0.99). Thermodynamic parameters suggested that the adsorption process is spontaneous (ΔG°= -2.99<b> </b>kJ/mol), favorable and endothermic (ΔH°=34.72<b> </b>kJ/mol). Simple regeneration allows multi-cycle use with minimal loss of activity. The mechanism has been proposed to be a combination of electrostatic interaction, H-bonding, and π-π stacking between AWCN and MG. In conclusion, alkali modification of <i>Trapa natans L.</i> shells provides excellent removal of MG from water.