Enhanced coconut shell-based activated carbon for water desalination using an adsorption-capacitive deionization hybrid system

Freshwater scarcity is a global issue, and most water purification technologies are energy-intensive, making them unaffordable for low-income societies. Adsorption-capacitive deionization (ACDI) offers a low-energy solution, making it a potential solution for these societies. This study utilized coconut shells to prepare pristine activated carbon (PAC) electrodes for ACDI by KOH activation at temperatures 700 and 800 ˚C. To enhance the performance of coconut shell-activated carbon electrodes, Tetramethylammonium bromide ((CH3)4N+ Br-) which is a cationic surfactant was used to create positive charges on the surface of PAC to make enhanced activated carbon (EAC) for an ACDI hybrid system application. The surface functional groups were identified by using Fourier Transform Infrared Spectroscopy (FTIR) and pore size distribution and surface area (SA) were identified by the Barret-Joyner-Halenda (BJH) and Brunauer-Emmett-Teller (BET) method under N2 adsorption/desorption isotherm respectively. The PAC and EAC attained maximum specific SA of 175.03 and 751.43 m2/g respectively. The electrochemical properties of PAC electrodes such as specific capacitance (SC) and electrical conductivity were examined using cyclic voltammetry (CV) and electrochemical impedance spectroscopy (EIS) in 6 M of KOH electrolyte using a CS 350 electrochemical cell. The SC of PAC from activated carbon was 376.29 F/g while EAC increased to 628.20 F/g. The salt adsorption capacity of PAC and EAC were 2.78 and 10.96 mg/g respectively. It can be seen that enhancing the AC led to the improvement of specific SA, SC, and salt removal capacity of AC during the desalination experiment.