SOLAR PHOTOCATALYTIC DEGRADATION OF ORGANIC POLLUTANTS IN LOCAL DYEING WASTEWATER USING NEEMMODIFIED GRAPHITIC CARBON NITRIDE (g-C3N4)

SOLAR PHOTOCATALYTIC DEGRADATION OF ORGANIC POLLUTANTS IN LOCAL DYEING WASTEWATER USING NEEMMODIFIED GRAPHITIC CARBON NITRIDE (g-C3N4)

ABSTRACT

The discharge of dyeing wastewater containing high concentration of contaminants from the local dyeing industry has caused a serious environmental concern. The present study reports the synthesis of graphitic carbon nitride and itsutilization in degradation of dyeing effluent pollutants under solar irradiation. The synthesized g-C3N4 was modified using the aqueous leaves extract of AzadiratchaIndica (Neem plant): a clean, non-hazardous and environmentally friendly procedure (green modification route). The morphology, elemental composition, crystallography, Surface area and adsorption bands of the synthesized modified and unmodified g-C3N4 samples were comprehensively examined using SEM, EDS, XRD, FT-IR and BET characterization techniques. The photo-oxidation of organic pollutants in the local dyeing wastewater by the modified and unmodified g-C3N4nanomaterials under sunlight irradiation in a batch reactor system was tested. The photocatalytic degradation efficiency of the local dyeing wastewater by the photocatalysts was assessed using chemical oxygen demand (COD) as the indicator parameter. Different experimental conditions such as the effects of solution pH, time, and Photocatalyst dosage on the efficiency of COD degradation process were investigated and then optimum conditions were established. The SEM and XRD analysis of the modified and unmodified g-C3N4demontrated the formation of crystalline tri-s-triazine unit and agglomerated morphology. The BET surface analysis displayed that the surface area of the g-C3N4nanopaticles increased from 58.88 cm3 /g to 141.0 cm3 /g upon modification, while the EDS analysis demonstrated the existence of C and N as the major constituents of the as-synthesized nanomaterials. The study found that the modified g-C3N4 nanoparticle exhibited significant higher catalytic activity of 61% COD removal compared to the unmodified g-C3N4nanoprticle (40% COD removal). It was established from the optimization study that pH of 9.8 and photocatalyst dosage of 0.7 g/200ml were the optimum conditions. The experimental data obtained were evaluated ii using three different kinetic models: first order, second order and Behnajady-Modirshahla-Ghanbery (BMG). It was found that the Behnajady-Modirshahla-Ghanbery model best described the data based on the correlation coefficient (R2 ). This study demonstrated that the modified g-C3N4 nanoparticle showed better photocatalytic activity in comparison to the unmodified g-C3N4. The enhancement in performance is because of its high surface area which signifies more active sites for reaction, small bulk diffusion length and strong redox ability of charge carriers.

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