Alkali treated water chestnut(Trapa natans L.)shellsas apromising phytosorbent for malachite green removal from water

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 mg/g. Adsorption followed pseudo-second-order kinetics (R2=0.99) and Langmuir isotherm model (R2=0.99). Thermodynamic parameters suggested that the adsorption process is spontaneous (ΔG°= -2.99 kJ/mol), favorable and endothermic (ΔH°=34.72 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 Trapa natans L. shells provides excellent removal of MG from water.Waste shells of water chestnut (Trapa natans L.), a waterborne fruit have been modified using sodium hydroxide solution and tested for removal of malachite green by batch method. Excellent adsorption capacity (136.46 mg/g) was obtained under ambient conditions. As of now, very little work has been reported on water chestnut shells for the removal of dyes from wastewater. The present work shows an excellent adsorption capacity among all the previous work on water chestnut for dye remediation. Alkali activation significantly reduces hydrophilic/lignocellulosic components within the shells, which in turn makes the material more water stable and sustainable.