I. V. Tananaev Institute of Chemistry and Technology of Rare Elements and Mineral Raw Materials (Kola Science Center, RAS), Apatity, Russia:

M. V. Maslova, Leading Researcher, e-mail: maslova@chemy.kolasc.net.ru
L. G. Gerasimova, Chief Researcher

Adsorption properties of ion-exchange material based on spherical hydrous TiO₂ particles (HTD) in regards to non-ferrous metal cations has been investigated. TiO₂ particles were synthesized by the sol-gel method. The high stable titanium sol (IV) was obtained by the method of limited hydrolysis of ammonium titanyl sulfate (NH₄)₂TiO(SO₄)₂·H₂O (ATS) solution without the usage of organometalic compounds. The presence of ammonium ion in sol prevents the polymerization of gels, which has a positive impact on porosity of the obtained compounds and, consequently, on ion-exchange properties. The synthesized material is weakly-acidic ion-exchanger, pK value of functional groups to be determined as рК₁ = 5.28 and рК₂ = 7.88. The total ion-exchange capacity equals 4.0 mg-eq/g towards sodium cation. This article presents the adsorption behavior of non-ferrous metal cations using HTD during technological wastewater purification. The cations were selected based on their ubiquity in wastewater of different industrial processes. The maximum ion-exchange capacity of the researched cations as well as quantitative characteristics of the sorption process was estimated. According to the maximum exchange capacity the selectivity order of the metal ions on HTD is determined as follows: Pb²⁺ > Co²⁺ > Cu²⁺ > Ni²⁺ > Sn²⁺ > Cd²⁺ > Zn²⁺. The obtained sorption data are best elucidated by the Freundlich model for cadmium and lead cations, and by Langmuir and Freundlich models in the case of sorption of zinc, copper and nickel cations. The sorption kinetics of these metal ions on HTD shows that the internal diffusion processes play a main role. The tests on purification of water from hardness salts and polyvalent metals in dynamic regime were performed to evaluate the functional properties of HTD. It was shown that HTD has an increased capacity in regards to divalent metal cations and low selectivity to hardness cations as compared to carboxylic cation exchanger С-104 (“Purolite”). In the case of wastewater treatment in tannery industry, the sorption of chrome cations by HTD exceeds 99% in all the researched systems, whilst the remaining concentration of chromium ions (III, VI) in the solution is lower than PMC.

The researches were conducted with the financial support of Russian Science Foundation (RSF) as a part of the scientific project 17-19-01522.

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