Multivariate optimization of the degradation conditions of methylene blue using a catalyst recovered from electronic waste.

Improper disposal of electronic waste and the release of industrial effluents containing toxic dyes in aquatic bodies are two worrying environmental problems worldwide. Mobile phones are omnipresent components of the electronic scrap. Lithium cobalt oxide (LiCoO 2) present in cathodes of discarded lithium-ion batteries (LIBs) has been reused in several ways. In this study, it was made a multivariate optimization (using response surface methodology) of the experimental conditions of a catalytical degradation process of methylene blue dye (MB) utilizing LiCoO 2 (from disposed mobile phones) as catalyst in an advanced oxidation process supported by H 2 O 2 and heating. Simultaneous effects analysis of the factors H 2 O 2 (mol L^–1), MB (mg L^–1), LiCoO 2 (mg) and temperature (ºC) showed that temperature was the most significant factor in the degradation process, followed by the quantity of LiCoO 2 and the concentration of H 2 O 2. The mathematical model obtained for the experimental design presented statistical significance (R² = 0.9330) and no lack of fit. The optimization process indicated that for H 2 O 2 = 1.71 mol L^–1, MB = 6.0 mg L^–1, LiCoO 2 = 32 mg and temperature = 32 °C, the degradation reaches a value of 93.30 ± 2.51. [ABSTRACT FROM AUTHOR]