Optimizing adsorption parameters in tannery-dye-containing effluent treatment with leather shaving waste

In the dyeing step in tanneries, it is necessary to add dyes till the fibrous texture of leather is deeply colored. That results in colored wastewater, which complicates the wastewater treatment. Adsorption is an advanced treatment operation that can increase the final wastewater quality. In this study, solid waste from tanneries, i.e., chromium-tanned leather shaving waste, was used as the adsorbent to treat dye-containing effluents generated through a wet end process, carried out in a pilot-scale tannery drum to investigate the possibility of using this technique as pretreatment in the wastewater process. Adsorption trials were conducted in laboratory-scale tannery drums to recreate the tannery conditions. Multiresponse optimization was used to optimize the adsorption parameters. Plackett–Burman factorial design was used to initially eliminate some factors from the seven selected important parameters: adsorbent concentration, pH, temperature, dye concentration, rotation speed, time, and particle size. Four important factors were selected: adsorbent concentration, pH, dye concentration, and rotation speed. Thereafter, a central composite rotatable design (CCRD) experiment was performed with desirability functions to achieve the optimal conditions, and to determine the maximum adsorption capacity at equilibrium (qe) and dye removal (R). The optimized responses were determined to be R = 87.37% and qe = 24.74 mg g−1. Finally, a confirmation study was executed in pilot-scale by using optimized levels of parameters which showed well response to the predicted model.