Rapid malachite green removal from aqueous solution by natural zeolite: Process optimization by response surface methodology

In this study, malachite green removal from aqueous solutions by natural zeolite was investigated. The interaction between zeolite and malachite green was determined by SEM/EDX and FTIR. The parameters like adsorbent dosage (0.1–1 mg/100 mL), initial malachite green concentration (40–200 mg/L) and the contact time (10–600 s) were optimized using the central composite design of response surface methodology. Maximum removal yield (99.70%) was obtained at an adsorbent dosage of 0.68 mg/100 mL, an initial malachite green concentration of 79.02 mg/L, and at 414 s contact time. The equilibrium process complied better with the Langmuir isotherm model, which exhibits a single layer adsorption, when compared with the Freundlich isotherm model. Adsorption kinetics followed the pseudo-second-order type kinetic and intra-particle diffusion played an important role onto adsorption mechanism of malachite green. The findings of this study demonstrated that zeolite which is found abundant on earth as a cheap and efficient adsorbent could be used for rapid malachite green adsorption from aqueous solutions.