Abstract
Presented work concerns the application of synthetic oxide adsorbent in the removal of cadmium ions from its model, water solutions. In this study, a novel magnesium–silicon (Mg–Si) binary oxide adsorbent was prepared by a modified co-precipitation method, utilizing sodium silicate and magnesium sulphate solutions as precursors of silica and magnesium oxide, respectively. The material was thoroughly characterized in order to evaluate chemical composition (AAS, EDS and gravimetric method), crystalline structure (XRD), morphology (SEM), particle size distribution (DLS), characteristic functional groups (FTIR) and porous structure parameters (BET and BJH models). It was proved that the adsorbent is amorphous, with a micrometric-sized, irregular-shaped particles and relatively large surface area of 540 m2/g. Batch adsorption experiments were conducted to investigate the adsorption of Cd(II) ions on the prepared adsorbent, including evaluation of adsorption kinetics, the intraparticle diffusion model, the effect of pH, contact time, mass of the adsorbent, temperature and the effect of competitive Cl− and NO3 − anions. During the study, it was confirmed that the adsorption of Cd(II) ions reached equilibrium within 30 min, which was found to fit well with a pseudo-second-order kinetic model type 1 (r 2 = 0.998–0.999). The Mg–Si adsorbent exhibited high adsorption capacity for Cd(II) ions at pH above 7, and the maximum quantity of cadmium(II) ions adsorbed in optimal time was achieved for the highest metal ion concentrations: 18.22 (Cl−) and 15.46 (NO3 −) mg/g. The competitive anions present in the model cadmium salt solutions hindered adsorption in the sequence Cl−>NO3 −.
Highlights
IntroductionAmong many technologies, which enable the removal of impurities from aqueous solutions, adsorption (Du et al 2011; Salam and Burk 2010; Zheng et al 2009), ion exchange, photocatalysis, filtration, coagulation, chemical precipitation, and electrodialysis or reverse osmosis (Chen et al 2012; Gupta et al 2012a, b, c; Maturana et al 2011; Mungray et al 2012), can be mentioned
The results showed that the resulting oxide system has a completely amorphous structure
The investigated properties of Mg–Si binary oxide adsorbent confirm its high level of activity and ability to adsorb hazardous metals ions (such as cadmium(II) ions) from aqueous solutions
Summary
Among many technologies, which enable the removal of impurities from aqueous solutions, adsorption (Du et al 2011; Salam and Burk 2010; Zheng et al 2009), ion exchange, photocatalysis, filtration, coagulation, chemical precipitation, and electrodialysis or reverse osmosis (Chen et al 2012; Gupta et al 2012a, b, c; Maturana et al 2011; Mungray et al 2012), can be mentioned. The continual development of technologies enabling the production of synthetic systems, including recycling of waste materials, with specific porous structure parameters (synthetic adsorbents) is very important (Saleh et al 2013, 2014). There are many reports in the literature concerning how the method of
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