Synergistic adsorption-photocatalytic remediation of methylene blue dye from textile industry wastewater over NiFe LDH supported on tyre-ash derived activated carbon

Abstract

The photocatalytic performance of the multilayered NiFe LDH/Activated Carbon was evaluated for the degradation of methylene blue (MB) in industrial textile wastewater, considering prior adsorption on the photocatalyst surface. The XRD, XPS, BET, TEM and FE-SEM results confirmed that the highly exposed mesoporous layers, carbon backbone, and interlayer anions serve as active sites responsible for the adsorption of MB dye due to the expected electrostatic interactions. Electrochemical methods such as CV, LSV and EIS revealed the improved conductivity and supported the interactions observed. Encouraged by these interactions, the irradiation of visible light enabled the degradation of methylene blue, and the degradation products were monitored using UPLC chromatograms and MS spectra. The removal efficiencies of the MB dye were found to be 17.5 %, 51.2 %, 67.1 %, 84.8 %, and 94.2 % due to photolysis, adsorption, and degradation on AC, NiFe LDH nanosheets, and NiFe LDH/AC nanocomposite, respectively. The results of the UPLC chromatograms and MS spectra suggested that MB was mineralized into simpler fragments after 30 min of visible light irradiation. Scavenging studies were examined using a series of scavenging agents. However, the maximum photodegradation was attained in the absence of the scavengers. The reusability studies showed that the MB photodegradation efficiency declined by 20.8 %, possibly due to the loss of the catalyst during the washing step. Nonetheless, the NiFe LDH/AC structure remained intact, suggesting the strong stability of the photocatalyst. The plausible degradation mechanism and probable degradation pathway of MB were outlined and supported by the chromatographs and MS results. The overall results suggest that photocatalysis of cationic dyes such as MB on NiFe LDH/AC should be encouraged to work towards sustainable solutions for textile water treatment.