Removal of Malachite Green Dye from Aqueous Solution by a Novel Activated Carbon Prepared from Baobab Seeds Using...

Two activated carbons were synthesized from baobab seeds (BSs) using two activators, sulfuric acid (BS-AAC) and sodium hydroxide (BS-BAC), for dye removal from aqueous solutions. Malachite green (MG) was used as a model dye. SEM, FTIR, TGA, and surface area were used to characterize the feedstock and synthesis activated carbons. According to the SEM results, the surface morphology differed significantly from that of the raw material due to the many pores created by activating agents during carbonization. Various surface groups existed on the activated carbon surface as shown by FTIR analysis. An oxidation process utilizing hydrogen peroxide (H₂O₂) was investigated for MG. Various reaction parameters such as pH value, H₂O₂ concentration, and activated carbon dosage were investigated for the oxidative degradation of MG. By using BS-AAC and BS-BAC, 97.9% and 78% dye degradation efficiency in aqueous solutions, respectively, was achieved under optimal conditions. This study reveals that MG dye degradation increases with solution pH, making BS-AAC and BS-BAC ineffective at low pH values. However, degradation declines above pH 6. Based on the BS-AAC data, MG removal kinetics were fitted with a first-order kinetic model, while BS-BAC data were fitted with a second-order kinetic model. It was demonstrated that activating baobab with sulfuric acid can form a novel activated carbon that can quickly remove MG from aqueous solutions. The results showed that the removal of malachite green was over 89% for AC-AAC and 77% for AC-BAC, even after four regeneration cycles.