Application of momordica charantia (Bitter gourd) waste for the removal of malachite green dye from aqueous solution

Abstract

Momordica charantia (bitter gourd) waste (BGW) as a low-cost adsorbent was successfully used to remove malachite green (MG) dye from aqueous solution in batch adsorption experiment. BGW was characterized by scanning electron microscopy and Fourier transform infrared spectroscopy. Optimal experimental conditions were ascertained for contact time, medium pH and ionic strength. Of the six models used, adsorption isotherm studies confirmed that the Sips model fitted well to the experimental data. Maximum adsorption capacity (qmax) of BGW for MG dye based on the Langmuir and Sips models was 96.4 and 240.0 mg g-1, respectively. The BGW-MG kinetics fitted well to the pseudo-second-order model. Adsorption of MG onto BGW was influenced, to some extent, by the presence of salts (KCl, KNO3 and NaCl). Studies showed that 0.1 mol dm-3 NaOH was able to regenerate BGW and improve its adsorption capability to 95% dye removal at 1st cycle, and subsequently maintaining its high adsorption ability throughout the five consecutive cycles.