Sorption of Nickel Ions from Aqueous Solutions by Lignite

Abstract

The sorption of nickel ions from aqueous solutions by lignite is investigated. Five lignite samples from different fields are considered. The samples are characterized by different ash content and yield of volatiles, as well as different elemental compositions and atomic ratios H/C and O/C. The sorptional capacity of lignites for nickel ions is found to be 0.25–0.33 mg/g. The degree of extraction is 80–97%. Comparison of the sorption properties shows that the lignite samples have greater sorptional capacity and degree of extraction for nickel ions than industrial AG-3 sorbent (by 0.2 and 62.0%, respectively). It is found that lignite removes nickel ions from solution by simple monomolecular adsorption, as described by the Langmuir equation. The adsorption process is described by a pseudo-second-order kinetic model. The time to reach sorptional equilibrium and maximum sorptional capacity is 30–40 min.