Effect of Optimization Parameters on Photocatalytic Performance of g-C3N4 towards Industrial Wastewater Treatment and Antibacterial Activity

D.R. Paul, S.P. Nehra
Deenbandhu Chhotu Ram University of Scienece and Technology,
India

Keywords: g-C3N4, Co-Doping, Antibacterial activity, Photocatalysis

Summary:

Increased sense of living style and fashion in individuals has lead to high demand and production for textile products. Also, use of synthetic dyes in other sectors like food, cosmetics, pharmaceuticals, plastics and paper industries have jointly put up to dye effluents in water reservoirs leading to severe environmental pollution problems. Organic dyes in these effluents can transform to various toxic and carcinogenic compounds thus marking their presence to be undesirable. In addition, microbial contamination of water is another dreadful issue posing severe problems as numerous people suffer from diseases like cholera, cryptosporidiosis and protozoan infection etc. generated by contaminated water. Graphitic Carbon nitride (g-C3N4) is a visible light responding 2-dimensional carbon based material featuring outstanding photocatalytic properties in the field of energy and environment. In this study the urea derived g-C3N4 was synthesised at different calcination temperature ranging from 350 °C to 700 °C. Interestingly, it has been observed that the calcination temperature for the synthesis of g-C3N4 along with factors (pH and catalyst loading) influencing the photodegradation process, can make an impactful improvement in its photodegradation activity towards organic pollutants and antibacterial properties. All the prepared samples were characterised and compared using various techniques. XRD and FTIR analysis revealed that synthesis of g-C3N4 took place at temperature higher than 450 °C and the polymerisation/condensation degree of material could be further improved up to 550 °C. SEM analysis showed the temperature dependent evolutionary changes related to morphology of the samples. BET and DRS analysis revealed that g-C3N4 prepared at 550 °C had the highest specific surface area and smallest optical band gap value respectively, supporting the fact for its highest photodegradation potential towards pollutant from textile industry (methylene blue) under visible light irradiation. The effect of other parameters (pH and catalyst loading) were further analysed and discussed. It was observed that appropriate calcination temperature, pH and catalyst loading optimized the photodegradation efficiency of photocatalyst and found to enhance the apparent rate constant value up to 12 times. Additionally, The photocatalytic ability of prepared g-C3N4 under visible light irradiation was analyzed for set of various anionic dye pollutants (methyl orange, phenol red, cresol red, xylenol orange) and cationic dye pollutants (rose bengal, auramine O, crystal violet, methylene blue, rhodamine b). The calculated degradation efficiencies and apparent rate constant values for all dye pollutants under consideration indicated that cationic dyes are more actively degraded on the surface of g-C3N4 than anionic dyes. Also, the prepared samples were analysed and compared for their anti bacterial activity towards pathogenic bacteria (Escherichia Coli and Klebsiella pneumonia). Further, high stability of the photocatalyst was observed for four cyclic runs of the photocatalytic reaction. Hence, g-C3N4 can be considered as a potential candidate for industrial wastewater remediation against organic and pathogenic pollutants.