Naphthol green B Removal using a Novel Hydrogel Composite: Thermodynamics, Isotherms, Kinetics and Optimization by RSM

In this study, the efficiency of the Poly(4-vinylpyridine-co-acrylamide) doped with EuCl3 {(Poly(4-VP-co-AAM)/EuCl3)} hydrogel synthesized in the laboratory by free radical in-situ polymerization method in removing naphthol green B (NGB) from wastewater was investigated. The structural properties of the adsorbent have been described by Fourier transform infrared spectroscopy (FT-IR), thermogravimetric analysis (TGA), scanning electron microscopy (SEM) and X-ray diffraction (XRD) analyses. The dependence of NGB adsorption performance on varying such as the amount of adsorbent, initial NGB concentration and contact time were investigated in a batch system. To determine the interaction effects of the selected parameters on the adsorption process and to optimize the adsorption capacity of the process, the central composite design (CCD) in the response surface methodology (RSM) was used. Optimum conditions were found to be 110 mg/L NGB concentration, 0.05 g/100 mL Poly(4-VP-co-AAM)/EuCl3/EuCl3 dosage and 165.81 min contact time. The adsorption capacity and removal efficiency under these conditions were 206.46 mg/g and 92.50 %, respectively. Experimental equilibrium data were in better agreement with the Langmuir isotherm. The kinetic results indicated that the adsorption process can be defined by pseudo-second-order kinetic with internal diffusion as one of the rate-determining steps. The adsorption process was found to be exothermic and spontaneous. Experimental results showed that dye can be successfully removed from wastewaters using Poly(4-VP-co-AAM)/EuCl3 hydrogel as adsorbent.