Development of watermelon rind derived activated carbon/manganese ferrite nanocomposite for cleaner desalination by capacitive deionization

Capacitive deionization (CDI) is one of the most efficient and emerging techniques for water desalination applications. This work reports the development, characterization and CDI studies of watermelon derived activated carbon (WMAC) and its MnFe2O4 composite (WMAC/MnFe2O4) for NaCl desalination. WMAC was prepared through single-step low-temperature pyrolysis by H3PO4 activation. Facile synthesis of spinel MnFe2O4 nanoparticles on WMAC surface was performed through the hydrothermal technique. Morphological, textural and physico/electro–chemical analysis showed the effect of MnFe2O4 incorporation on WMAC. The nanocomposite possessed definite crystallites, low structural disorders and sufficient magnetization for electrochemical applications. Also, the nanocomposite was dominantly composed of mesopores with a specific surface area of 483 m2/g. The high specific capacitance value of 425 F/g (scan rate – 10 mV/s) along with better stability and low charge resistance, confirmed the suitability of WMAC/MnFe2O4 as an efficient electrode material for CDI applications. NaCl removal studies using WMAC/MnFe2O4 showed an electrosorption capacity of 29.7 mg/g for the nanocomposite, with rapid desalination and good recyclability. A plausible mechanism of salt adsorption and desorption is also presented. WMAC/MnF2O4 exhibited significant application potential for the industrial desalination.