Optimisation of activated carbon fabrication derived from spent coffee grounds for malachite green removal

As the impact of Malachite Green (MG) is insidiously deleterious to the environment, treatment of MG-bearing wastewaters is strictly necessary prior to the discharge. Accordingly, the key of reported work was to optimise the fabricating conditions of activated carbon (AC) used to sequester MG form aqueous solution via adsorption process. In this study, spent coffee ground was selected as a precursor in which impregnation ratio with ortho-phosphoric acid, activation temperature and activation time were simultaneously optimised to produce AC. The central composite design (CCD) of response surface methodology (RSM) was exploited to determine the optimum fabricating conditions that resulted in maximum removal of MG. The percentage removal of MG to the tune of 96.3% was achieved at the impregnation ratio of 0.50, activation temperature of 554 °C and activation time of 31.4 minute.Model that could predict the MG removal percentage was successfully developed and had been statistically confirmed to be significant. The experimental MG adsorption equilibrium data by the fabricated AC were fitted to the Langmuir, Freundlich and
Tempkin isotherm models with Langmuir model cropped up to be the best fit, indicating monolayer adsorption of MG was preponderant on AC surface. The findings from the this study unveil the potential of spent coffee grounds as an alternative precursor in fabricating low cost AC for the treatment of wastewater loaded with MG pollutant.