Activated Luffa derived biowaste carbon for enhanced desalination performance in brackish water

Abstract

Membrane capacitive deionization (MCDI) is an effective process to remove salt ions from brackish water. In this work, a systematic investigation was carried out to study the effects of applied potential and salt concentration on salt adsorption capacity (SAC), charge efficiency (Λ) and energy consumption in an MCDI system using Luffa biowaste derived carbon as electrodes. We studied the comparative MCDI performance of Luffa derived carbon as electrodes before and after activation. Furthermore, the desalination capacities of the electrodes were quantified by batch-mode experiments in a 2500 mg L⁻¹ NaCl solution at 0.8–1.2 V. Activated Luffa carbon showed a high SAC of 38 mg g⁻¹ at 1.2 V in a 2500 mg L⁻¹ NaCl solution with a low energy consumption of 132 kJ mol⁻¹ salt as compared to non-activated samples (22 mg g⁻¹, 143 kJ mol⁻¹). The adsorption mechanisms were investigated using kinetic models and isotherms under various applied potentials. Consequently, the excellent SAC of activated Luffa carbon can be attributed to the presence of micro/mesoporous network structure formed due to the activation process for the propagation of the salt ions.