N‑(((2-((2-Aminoethyl)amino)ethyl)amino)methyl)-4-sulfamoylbenzamide Impregnated Hydrous Zirconium Oxide as a Novel Adsorbent for Removal of Ni(II) from Aqueous Solutions: Optimization of Variables Using Central Composite Design

In this study, N-(((2-((2-aminoethyl)­amino)­ethyl)­amino)­methyl)-4-sulfamoylbenzamide was impregnated into the hydrous zirconium oxide matrix to yield N-(((2-((2-aminoethyl)­amino)­ethyl)­amino)­methyl)-4-sulfamoylbenzamide/hydrous zirconium oxide composite (AESB/HZO). The composite material was used to remove Ni­(II) from aqueous environment. AESB/HZO was characterized using Fourier transform infrared, scanning electron microscopy with energy dispersive X-ray, and thermogravimetry–differential thermal analyses. An experimental design approach was utilized to model and optimize the variables of adsorption of Ni­(II) onto the AESB/HZO composite. Four experimental parameters were selected as independent variables: contact time, pH, adsorbent dose, and initial Ni­(II) concentration. A multivariable experimental design was used to establish quadratic model to describe the relationship between percent removal of Ni­(II) and four independent variables. At the optimum conditions (contact time: 85 min, pH: 6, adsorbent dose: 10 mg/20 mL, and initial Ni­(II) concentration: 20 mg L–1), high removal efficiency (99.35%) was achieved, which is reasonably well predicted by the quadratic model. The sorption of Ni­(II) is dependent on pH and ionic strength at pH < 6.0. At low pH, −NH and −NH2 groups are protonated, whereas the −SO2– group is available for binding with Ni­(II) and the sorption of Ni­(II) is mainly governed by outer sphere surface complexation. In the pH range 6.0–7.5, −NH, −NH2, and −SO2– groups are available for binding with Ni­(II) and the sorption is mainly governed by inner-sphere surface complexation. Adsorption isotherm data fitted well to the Langmuir model and the maximum adsorption capacity was found to be 96.03 mg g–1 at 303 K. The results of present investigation demonstrated that AESB/HZO has a good potential for Ni­(II) removal from aqueous solution.