Abstract
The adsorption of Ni2+ ions from water solutions by using hydrogels based on 2-hydroxyethyl acrylate (HEA) and itaconic acid (IA) was studied. Hydrogel synthesis was optimized with response surface methodology (RSM). The hydrogel with the best adsorption capacity towards Ni2+ ions was chosen for further experiments. The hydrogel was characterized by Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and atomic force microscopy (AFM) analysis before and after the adsorption of Ni2+ ions. Batch equilibrium experiments were conducted to investigate the influence of solution pH, hydrogel weight, ionic strength, adsorption time, temperature and initial concentration of nickel ions on the adsorption. Time-dependent adsorption fitted the best to the pseudo-second-order kinetic model. A thermodynamic study revealed that the adsorption was an exothermic and non-spontaneous process. Five isotherm models were studied, and the best fit was obtained with the Redlich–Peterson model. Consecutive adsorption/desorption studies indicated that the HEA/IA hydrogel can be efficiently used as a sorbent for the removal of Ni2+ ions from the water solution. This study develops a potential adsorbent for the effective removal of trace nickel ions.
Highlights
Wastes produced in different kinds of industries have become an important environmental problem at the global level [1,2]
The optimization of hydrogel synthesis was performed in order to produce adsorbents with good swelling properties and removal abilities for Ni2+ ions
The x and y axes show the two input parameters for hydrogel synthesis, which have the greatest influence on the adsorption properties of the hydrogel, mass of 2-hydroxyethyl acrylate (HEA) and itaconic acid (IA)
Summary
Wastes produced in different kinds of industries have become an important environmental problem at the global level [1,2]. Nickel is widely used in heavy metals that has many beneficial applications in human life, but it is very dangerous if dispatched into natural water [3,4]. Nickel is used in the production of metallic alloys, nonferrous metals, mineral processing, paint formulation, electroplating, batteries manufacturing, forging and production of coins [5,6,7]. There are several techniques for removing nickel ions from water: chemical precipitation, ion exchange, adsorption, membrane filtration and reverse osmosis [8]. The adsorption process has been widely used for the removal of heavy metals from water due to its high efficiency, ease of operation, cost-effectiveness and no secondary pollution [9,10,11,12]
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