Heliyon (Sep 2019)
Adsorption of heavy metal ions (Cu2+, Ni2+, Co2+ and Fe2+) from aqueous solutions by natural zeolite
Abstract
The process of remove copper, nickel, cobalt and iron ions by natural zeolite of the Yagodninsky deposits, Kamchatka region, from water resources within a concentration range of 0.5–3.5 mg-eq/L has been experimentally investigated. The specified concentrations range was chosen according the contents of heavy metals in the waste water of the mining enterprise of Kamchatka region The values of maximum sorption capacity have been determined. On the basis of studies using X-ray powder diffraction (XRD) it has been established by the Rietveld method of calculation that the zeolite tuff of the Yagodninsky deposit consists of clinoptilolite-Na (23.0 %), clinoptilolite-Ca (52.1 %) and modernite (12.9 %). It has been established that exchange cations are sodium, calcium, potassium and magnesium. The Gibbs free energy has been calculated which is equal for copper ΔG = –25.6 kJ/mol, iron – ΔG = –23.7 kJ/mol, nickel – ΔG = –21.5 kJ/mol and cobalt – ΔG = –20.0 kJ/mol. The obtained results show that natural zeolite can be used as an effective sorbent for extracting of ions Cu2+, Ni2+, Co2+ and Fe2+ from polluted waters. On the basis of the analysis of the parameters of the mordenite crystal lattice a decrease in sizes in the direction of the a- and b-axes and, consequently, of the elementary cell volume of the treated zeolite is observed as compared with the initial zeolite in the Cu > Ni > Co > Fe row. New knowledge about the sorption properties of the Yagodninsky deposit zeolites can be interesting for the industrial areas of South-Eastern Asia such as China, Japan, Korea, etc.
