Degradation of mixed cationic dye pollutant by metal free melem derivatives and graphitic carbon nitride

Graphitic carbon nitride (GCN), a polymeric metal free catalyst is widely used to degrade the toxic organic dye from the aqueous pollution. However, its catalytic efficiency and effective simultaneous reduction of mixed dye is still a challenge. Here, we have tuned the physiochemical properties of the GCN and melem derivatives by facilely tuning the degree of polycondensation and examined their catalytic activity towards the removal of cationic dye individually and together in solution. Catalysts were synthesized by thermal treatment of low-cost melamine and characterized by XRD, FTIR, RAMAN, FE-SEM, EDX, UV-DRS, and FL spectroscopy to confirm materials' structure, phase, morphology and optical properties. A suitable phase of the catalyst (M-450) exhibited superior removal capacity with a high-rate constant compared to others. The results demonstrate that M-450 has a maximum loading efficacy of 2.13 and 1.12 mg g(-1) for methylene blue (MB) and Rhodamine B (RhB) dyes respectively in a single dye system. Attractively, when MB and RhB co-exist in the solution, the ef-ficacy increased by 14% (2.44 mg g(-1)) and 27% (1.43 mg g(-1)) for MB and RhB respectively. The adsorption kinetics, stability, effect of pH and reusability of M-450 catalyst was testified. Further, radical scavenger ex-periments and terephthalic acid tests were carried out to explain the reaction mechanism involved in the degradation of textile dyes. Moreover, electron paramagnetic resonance (EPR) analysis validated the availability of hydroxyl radicals in the photocatalytic reaction. Excellent stability and reusability were attained even after five successive cycles, demonstrating a suitable photocatalyst for the efficient degradation of mixed dye.

Automated summary

By tuning the physiochemical properties of GCN and melem derivatives, an efficient catalyst M-450 was synthesized with superior removal capacity for both single and mixed dye systems, demonstrating excellent stability and reusability in the degradation of textile dyes.