Efficient Selective Sorption of Cationic Organic Pollutant from Water and Its Photocatalytic Degradation by AlVO4/g-C3N4 Nanocomposite

This study reports the synthesis, characterization and water remediation application of novel AlVO4/g-C3N4 nanocomposites. The nanocomposite has been synthesized by a low temperature solid-state reaction using graphitic carbon nitride (g-C3N4) obtained via calcination of melamine and AlVO4 prepared via assisted sonochemical technique. Powder X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), Fourier Transform Infrared spectroscopy (FTIR), ultraviolet-visible diffuse reflection spectroscopy (UV-vis DRS), and the N-2 gas adsorption Brunauer-Emmett-Teller (BET) method has been used to characterize the pristine and composite samples. AlVO4 and g-C3N4 interact with each other forming a hybrid composite, which shows excellent ability for selective sorption of cationic MB (methylene blue) dye from wastewater. The initial dye concentration pH and amount of sorbent has been varied and their effect on the adsorption process has been analysed. The photocatalytic efficiency of the MB dye adsorbed pristine g-C3N4, AlVO4:g-C3N4 (1:3) and AlVO4:g-C3N4 (1:1) composite has been tested under visible light. With increased proportion of AlVO4 in the samples, the photocatalytic efficiency improved and the best photodegradation has been observed for the AlVO4:g-C3N4 (1:1) sample. Photoluminescence (PL) studies, photocurrent response measurements and electrochemical impedance spectroscopy (EIS) indicates enhanced separation of the photogenerated electron/hole pairs leading to effective degradation of the MB dye solution in case of the AlVO4:g-C3N4 (1:1) composite sample. The photocatalytic mechanism has been elucidated and it could be inferred that photogenerated holes and superoxide anion radicals play a major role in the photocatalysis process.