Adsorptive removal of nickel from water using volcanic rocks

• Published in: Applied geochemistry 2010-10, Vol.25 (10), p.1596-1602
• Main Authors: Alemayehu, Esayas, Lennartz, Bernd
• Format: Article
• Language: English
• Subjects: Adsorbents; Adsorption; Diffusion; Earth sciences; Earth, ocean, space; Engineering and environment geology. Geothermics; Exact sciences and technology; Geochemistry; Grains; Isotherms; Mathematical models; Pollution, environment geology; Rocks; Sorption
• ISSN: 0883-2927; 1872-9134
• DOI: 10.1016/j.apgeochem.2010.08.009

► Basic process characteristics were determined under batch conditions. ► Adsorption was found to be highly dependent on pH. ► Pseudo-second order equation best described the kinetics mechanisms of Ni(II) adsorption. ► VPum had a higher affinity than VSco towards Ni ions. ► Given that enough VPum or VSco are provided, Ni(II) could be removed even from a mixture matrix. This paper presents the results of a study on Ni(II) removal from water by adsorption using abundant and low-cost volcanic rock grains: Scoria (VSco) and Pumice (VPum), which could be used as an alternative approach to remove potentially harmful metals from contaminated water. Basic process characteristics were determined under batch conditions. The maximum adsorption capacities for Ni(II) on VSco and VPum were found to be 980 and 1187 mg kg −1, respectively. These results were obtained at the optimized conditions of pH (5.0), temperature (24.9 °C), contact time (24 h), adsorbent/solution ratio (1:20), particle size (fine) and with the variation of initial concentrations between 0.5 and 50 mg L −1. Competitive adsorption of Ni(II), Cd(II) and Cu(II) on the adsorbents present in binary as well as ternary mixtures were also compared with the single metal solution. Thus, given that enough volcanic rock grains are provided, Ni(II) ions could be removed even from a metal ion bearing matrix. A number of available models like Lagergren pseudo-first order kinetics, second-order kinetics, intra-particle diffusion and liquid film diffusion were utilized to evaluate the kinetics and the mechanism of the sorption interactions. The results revealed that the pseudo-second order equation best described the kinetics mechanisms of Ni(II) adsorption although the removal process was found to be complex. Moreover, three adsorption models have been evaluated in order to attempt to fit the experimental data, namely the Langmuir, the Freundlich and the Redlich–Peterson isotherm models. It was found that the first two isotherms most closely described the adsorption parameters.