Simultaneous adsorption of chromium and acidic dye from leather tannery model wastewater using a novel modified nanoclay

Simultaneous removal of Cr3+ and acidic dye from model tannery wastewater was investigated using local nano-clay modified by 3-chloro-2-hydroxypropyltrimethylammonium chloride surfactant. X-ray fluorescence, Fourier-transform infrared spectroscopy, X-ray diffraction, scanning electron microscopy, carbon, hydrogen, nitrogen and sulfur analysis, Brunauer-Emmet-Teller analysis and pH of zero-point charge (pH(ZPC)) analyses were carried out for characterization of the adsorbent, and adsorptive properties of the modified clay were investigated by batch experiments. The effects of essential parameters, such as adsorbent dosage, initial solution pH, initial solution concentration, contact time, and temperature, were studied. Maximum adsorption values (99.74% for Cr3+ and 83.26% for dye) were obtained in the following conditions: pH of 4, initial concentration of 100 mg/L, adsorbent dosage of 15,000 mg/L, contact time of 30 min. The effect of contaminants' concentration was also investigated through response surface methodology, central composite face-centered design and an empirical model was presented. The results of kinetic models' studies demonstrated that simultaneous adsorption of contaminants follows the pseudo-second-order model, and the adsorption data of single and binary solutions fitted nonlinearly to isotherm models showed that the adsorption of Cr (III) from binary and single solutions follow Langmuir and Dubinin-Radushkevitch isotherms, respectively. Adsorption of dye from both single and binary solutions follows Redlich-Peterson isotherm. Maximum adsorption capacities were obtained to be 193.1390 mg/g and 144.1782 mg/g for Cr3+ and dye, respectively. Synergistic and antagonistic adsorptions were observed in binary solutions.