Sorption of zinc chloride complexes from acid-based solutions by using anionic resins: process optimization and modelling

The sorption of zinc chloride ions from hydrochloric acid-based solutions using anionic resins was investigated. A two-stage experiment was planned. In the first stage, parameter optimization was performed using the Taguchi experimental optimization approach for type of anionic resins, initial Zn (II) ion concentration, resin dose, agitation rate, and temperature and time of the process as process parameters. According to the signal—to—noise ratio values calculated with the larger better-quality feature; the optimum parameter levels were determined as chloride form resin, 10 g/L, 1200 mg/L, 200 rpm and 35 °C and 90 min, respectively. Under optimum operating conditions, the sorption capacity of the resin for zinc chloride complex ions was 46.52 mg/g. The energy dispersive X-Ray analyses confirmed that zinc chloride complexes bind to the resin’s surfaces. In the second step, equilibrium and kinetic tests were performed under the optimum parameters. The tests results were compared with six equilibrium isotherm models with 2 or more parameters and four kinetic models. The non-linear solution approach was applied for all models. Langmuir isotherm and the general order models were the best fit. The values of \({K}_{L}\) and \({q}_{m,L}\) for the Langmuir model were 2.15*10^–3 L/g and 66.08 mg/g, respectively. The kinetic model can be given by an equation of order 3.26. Accordingly, \({k}_{n}\) and \({q}_{e,n}\) were 2.18*10^–5 min/(g mg)^2.26 and 60.03 mg/g, respectively. The process mechanism was a typical chemical sorption. According to the results of desorption tests conducted using 1 M HCl, the desorption efficiency was 65%.