Mg/Li Co-doped g-C3N4 Visible Light Driven Photocatalyst: Synthesis, Characterization and Their Application for Photo Induced Bacterial Disinfection and Removal of Organic Pollutants from Water

D.R. Paul, S.P. Nehra
Deenbandhu Chhotu Ram University of Science & Technology, Murthal (Haryana), India,
India

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

Summary:

The adverse effects of microbial contamination and effluents from textile industries on the aquatic and human life make it a mandatory issue to be addressed. Solar light driven photocatalytic degradation is an economical and easy method for the decomposition of harmful organic pollutants into less dangerous minerals and complete bacterial disinfection. Recently, among various two-dimensional carbon materials, graphitic carbon nitride (g-C3N4) has caught severe focus by researchers for various environmental applications. In this study, a novel visible light responding photocatalyst series based on Mg and Li co-doped g-C3N4 (GCNML(x,y)) was prepared by following a facile strategy of thermal copolymerization. The prepared photocatalysts have been characterised and compared for various structural, optical and morphological aspects. FTIR and XRD analysis confirmed synthesis and successful doping of obtained materials. XPS analysis indicated existence of both Li and Mg in GCNML. BET and pore volume analysis revealed the mesoporous nature of both GCNML and GCNP. The resulted photocatalyst exhibited superior photocatalytic activity in comparison to its mono-metallic counterparts (GCNM, GCNL) and pristine g-C3N4 (GCNP). Photocatalytic reactions towards methylene blue (MB) dye results revealed that GCNML(0.5,2) achieved photocatalytic degradation efficiency of 93% in 60 min followed by GCNML(0.5,3) (80 %) in 80 min > GCNML(0.25,2) (77 %), GCNML(1,2) (71 %),GCNML(0.5,1) (not noticeable) in 120 min and monometallic counter parts (GCNL (90 %) > GCNM (81 %) > GCNP (62 %) in 120 min under visible light irradiation. This degradation process was fitted to the pseudo first order dynamic model and it was deduced that the synergistic effect of Mg and Li in GCNML(0.5,2) can enhance rate of photocatalytic degradation of MB dye to about 0.04411 min-1 which is 5.4 times in comparison to GCNP and nearly 3.2 times to its monometallic doped counterpart samples. The results of photocatalytic reactions of GCNML(0.5,2) further revealed its spectacular activity for degradation of other toxic organic dyes like crystal violet, methylene blue, methyl orange, rhodamine b and rose bengal under natural solar irradiation. In addition, prepared samples were analysed and compared for their splendid anti bacterial activity towards pathogenic bacteria (Escherichia Coli and Klebsiella pneumonia). The improved photoactivity and antibacterial activity of GCNML is primarily attributed to better absorption ability of visible light, reduced optical band gap and retarded recombination rate of photo-induced holes and electrons supported by DRS and PL analysis and were not affected majorly by specific surface area of the respective materials. The pH of dye solution in alkaline range can further enhance its photocatalytic performance. Moreover, GCNML (0.5, 2) showed good reusability and stability up to four cyclic experimental runs. Mechanism exploration found the enhanced photocatalytic and antibacterial activity was mainly ascribed to the strong oxidizability of active species generated on visible light responding GCNML(x,y). The performed study revealed that GCNML can act as a potential solar light responding photocatalytic material for eco-friendly contaminants remediation from aquatic environment.