Enhanced Photocatalytic Degradation of Indigenous Dyeing Wastewater Of Sodium-Magnesium-Titanium Multiple Doped Zinc Tungstate Nanocomposites Under Natural Sunlight.

Abstract

The photocatalytic activity of the Na-Mg-Ti doped ZnWO4 nanocomposites were investigated by monitoring the degradation of Indigeneous dyeing wastewater under sunlight irradiation. ZnWO4 nanoparticle was synthesized by a simple sol-gel technique using zinc acetate, sodium tungstate (precursors) and water and ethanol (1:1) as solvents based on Box-Behnken Design. This was followed by doping of the metallic elements of different mole ratios onto ZnWO4 nanoparticles by wet impregnation method. The produced nanomaterials were analyzed by HRSEM, HRTEM, EDX, UV-Visible Spectrometer, FTIR, BET N2 Adsorption-desorption, XRD and XPS. HRSEM/HRTEM analysis confirmed the formation aggregated spherical shape irrespective of the synthesis conditions while XRD analysis demonstrated the formation of highly crystalline, monoclinic phase of ZnWO4 with a crystallite size of 14.51 nm at the optimum conditions of solution pH(7.5), reaction temperature(30°C) and stirring speed (2000 rpm) and addition of the dopants did not change the phase. The photocatalytic performance of 1%Na1%Mg1Ti, 1%Na1%Mg2%Ti, 1%Na2%Mg1%Ti, 1%Na1%Mg1%Ti doped ZnWO4 showed that ZnWO4 doped with equal mole ratio of Na, Mg and Ti (1:1:1) exhibited 81.5% degradation efficiency of the organic dyes in the wastewater under the following applied conditions: catalyst dose (0.4g), reaction time (60 minutes) and pH (3) respectively. The experimental data best suited to Langmuir isotherm and a reaction kinetic followed Intra-particles diffusion model. The treated decolourised water was also analysed for reduction in the amounts of contaminants such as sulphates, phosphates, carbonates and bicarbonates and it was found that 1%Na1%Mg1%Ti doped with ZnWO4 exhibited excellent catalytic activity than the undoped ZnWO4 counterpart.