Optimizing decolorization of Acid Fuchsin and Acid Orange II solution by MnO2 loaded MCM-41

• MnO2/MCM-41 was prepared, used as adsorbent and characterized.
• Removal of Acid Fuchsin and Acid Orange II by MnO2/MCM-41 was optimized by RSM.
• MnO2/MCM-41 exhibits high adsorption capacity for Acid Fuchsin and Acid Orange II.

MnO2 loaded MCM-41 (MnO2/MCM-41) was synthesized and characterized by Fourier transform infrared spectra, X-ray diffraction and X-ray fluorescence. Acid Fuchsin and Acid Orange II adsorbed by MnO2/MCM-41 were investigated. Moreover, the response surface methodology design with three interacting parameters (pH, adsorbent dosage and initial dye concentration) was used to optimize the adsorption processes. The maximum removal efficiencies of Acid Fuchsin (93.2%) and Acid Orange II (91.9%) were achieved at pH 2.5, adsorbent dosage 0.11 g and initial dye concentration 200 mg/L. Results showed the adsorption processes were pH dependent. Besides, adsorption of Acid Fuchsin and Acid Orange II followed Freundlich and Dubinin–Radushkevich model with the maximum adsorption capacity was 716.17 mg/g for Acid Fuchsin and 909.99 mg/g for Acid Orange II by MnO2/MCM-41. In addition, the pseudo-second-order kinetic model described the kinetic data better than pseudo-first-order model, while external and intraparticle diffusion were found to be the rate controlling steps. Thermodynamic analysis revealed that the adsorption processes were spontaneous, and Acid Orange II adsorption was endothermic, while Acid Fuchsin adsorption was exothermic.