Optimization of photo: active carbon dots for reactive dyes degradation by response surface methodology—an industrial approach

Carbon Quantum Dots are stable photocatalyst which are synthesized from Spirulina platensis by microwave assisted technology. The synthesized CQDs contain rough surface and distributed in less than 10 nm size and exhibited strong blue fluorescence under UV transilluminator and PL spectra analysis. CQDs effectively degraded 150 ppm concentration of Reactive Blue MR, Reactive Orange M2A and Reactive Yellow M4G by the ratio of 1:10 (Catalyst and Dye) and required 4, 8 and 10 h for complete degradation, respectively. But in case of mixture of reactive dyes, 1:5 of catalyst and dye were used and it requires 10 h for complete degradation under sunlight. We also statistically studied optimized conditions for dye degradation using Response Surface Methodology for process parameters such as concentration, pH, volume, and time. The degradation reaction follows first order kinetics, and the removal of CQDs from treated water is attained by charcoal as an adsorbent. Modification of functional groups during dye degradation was analyzed by using FTIR. Various physico-chemical parameters such as BOD, COD, TOC, TIC and metal ions were studied to determine the quality of degraded water. 95% of various reactive dye can be effectively degraded by biosynthesized metal ion or chemical free natural CQDs. Hemolytic effect and cytogenetic effect of CQDs and treated water proved synthesized CQDs are non-toxic to living organism.