Comparative study of methylene blue adsorption using alkali-activated pumice from Bali and Banten

Abstract

This study presents the comparison of methylene blue (MB) adsorption using alkali-activated pumice from Bali (A-P1) and Banten (A-P2). Pumice samples were activated under alkaline solution and followed by simple hydrothermal treatment in a polypropylene bottle at 100 °C for 24 hours. The X-ray diffraction (XRD) patterns showed that both treated pumices have different peak characteristics, where only A-P1 was dominated by the mineral phase of GIS-NaP1 zeolite. The change of amorphous to zeolite phases increased negative sides and caused A-P1 to have a higher adsorption capacity than A-P2. Based on the adsorption data of AP1 and AP2, the Langmuir isotherm model shows a better fit with high correlation values (R2) compared to the Freundlich model. This means the interaction between the treated pumice and MB followed the assumption of monolayer coverage on homogeneous surfaces, in which the maximum values of MB adsorption were found to be 51.546 mg/g for A-P1 and 27.027 mg/g for A-P2. In addition, A-P1 and A-P2 were also potentially used as heterogeneous catalysts for MB degradation through Fenton-like process due to the presence of iron oxide contents.