Zn0.94Mn0.06O for adsorption and photo-degradation of methyl orange dye under visible irradiation: Kinetics and isotherms study

Three photocatalyst-adsorbents consist of Zn0.97Mn0.03O, Zn0.94Mn0.06O, and Zn0.92Mn0.08O were synthesized by hydrothermal method and calcined at 800 °C. The structural and optical properties of the sample Zn0.94Mn0.06O were characterized by using XRD; TEM; SEM; EDS; DLS; and DRS. The surface of the sample Zn0.94Mn0.06O consists of nano-particles (<100 nm) and nano-holes (18.4 nm), also the band-gap of it was obtained 2.89 eV. Adsorption and photo-degradation of methyl orange (MO) dye was investigated in darkness and under visible light irradiation (200 W tungsten). The sample Zn0.94Mn0.06O showed the most decolorization efficiency in the shortest time, so that 0.15 g of it adsorbed and destroyed the MO dye molecules (99 ± 1 %) in 40 s under irradiation. The most adsorption capacity of Zn0.94Mn0.06O was obtained 30.06 mg/g and the mechanism of the dye adsorption was investigated by using BET analysis and zeta potential. Also the adsorption isotherm and kinetics were calculated for describing the adsorption of MO onto the Zn0.94Mn0.06O.