Adsorption-oxidation process for dyestuff removal from tannery wastewater

Abstract

In leather processing, dyeing is one of the most important operations. A significant amount of wastewater is emitted from the tannery after the dyeing operation. The dyeing wastewater harms aquatic life. Removal of dyestuffs from the real dyeing wastewater has become a great challenge to lessen the tannery's pollution load. In this work, the adsorption-oxidation process has been studied for acid dyestuff removal from real tannery effluent. The preparation of cost-effective adsorbent was performed through thermal alteration of liming sludge leftover from a tannery. Adsorbent had been distinguished, implementing Fourier Transform Infrared (FTIR) Spectroscopy, Energy Dispersive Spectrometer (EDS), Scanning Electron Microscope (SEM), and X-ray diffraction (XRD) both immediately before and following. The parameters of adsorbent dosage, oxidant dosage, contact time, settling time, oxidant reaction time, and initial pH were performed to maximize the efficiency of dyestuff removal from tannery wastewater. Adsorption was performed without prior regulating the initial pH to remove dyestuff and other pollutants present in the effluent. Then, oxidation was performed to degrade the remaining color of the dyestuff. After adsorption-oxidation, the treated effluent’s pH level was 6.9. The combined effect of adsorbent and oxidant results showed dyestuff removal at 75.82%. The co-efficient obtained from Pseudo-Second-Order (PSO) kinetics, Freundlichisotherm, and thermodynamic analysis, elucidated the adsorption responseof an exothermic chemisorption reaction, with significant interconnectivity between adsorbent and dyestuff molecules. The mechanism of adsorption of Green V dyestuff on liming sludge adsorbent was also studied. The reusability study revealed that the regeneration efficiency was 91.85% after the 4th cycle of the adsorption–regeneration process. Moreover, the process reduced biochemical oxygen demand (BOD) and chemical demand (COD) was 72.41%, and 58.63%, respectively from the dyeing wastewater. The present approach would be implemented as an affordable and sustainable methodology to remove acid dyestuff from real tannery wastewater.