Solar light-based advanced oxidation processes for degradation of methylene blue dye using novel Zn-modified CeO2@biochar.

Abstract

Herein, a novel nanocomposite, namely, Zn-modified CeO2@biochar (Zn/CeO2@BC), is synthesized via facile one-step sol-precipitation to study its photocatalytic activity towards the removal of methylene blue dye. Firstly, Zn/Ce(OH)4@biochar was precipitated by adding sodium hydroxide to cerium salt precursor; then, the composite was calcined in a muffle furnace to convert Ce(OH)4 into CeO2. The crystallite structure, topographical and morphological properties, chemical compositions, and specific surface area of the synthesized nanocomposite are characterized by XRD, SEM, TEM, XPS, EDS, and BET analysis. The nearly spherical Zn/CeO2@BC nanocomposite has an average particle size of 27.05nm and a specific surface area of 141.59 m2/g. All the tests showed the agglomeration of Zn nanoparticles over the CeO2@biochar matrix. The synthesized nanocomposite showed remarkable photocatalytic activity towards removing methylene blue, an organic dye commonly found in industrial effluents. The kinetics and mechanism of Fenton-activated dye degradation were studied. The nanocomposite exhibited the highest degradation efficiency of 98.24% under direct solar irradiation of 90min, at an optimum dosage of 0.2gl-1 catalyst and 10ppm dye concentration, in the presence of 25% (V/V) 0.2ml (4µl/ml) hydrogen peroxide. The hydroxyl radical generated from H2O2 during the photo-Fenton reaction process was attributed to the nanocomposite's improved photodegradation performance. The degradation process followed pseudo-first-order kinetics having a rate constant (k) value of 0.0274min-1.