Sorption-Active Materials Based on an Acid-Nonresistant Aluminosilicate Nepheline, Used for Defluorination of Industrial Sewage

Abstract

A method for obtaining sorption-active materials based on a solidifying mineral dispersion composed of nepheline, hydrochloric acid, and water was suggested. The hardening processes and conditions under which sorption-active compounds are formed were studied. The mechanism of sorption of F ! ions on the sorbents developed was determined.A topical environmental problem of the Kola region is purification of mine water and underground water to remove fluoride ions. All the methods presently used for this purpose can be divided into two groups:(1) coprecipitation and coagulation on freshly synthesized aluminum and magnesium hydroxides and calcium phosphate and (2) ion exchange of fluorineselective ion exchangers, e.g., activated aluminum oxide, which is a strongly basic anion exchanger. However, use of these expensive ways to defluorinate water is unacceptable in the case of large-tonnage wastes. Defluorination of sewage from mining plants require granulated sorbents, which can be used by creating check dams before discharging, e.g., mine water into natural water basins. To solve this problem, it is suggested to prepare sorption-active materials by the technology of self-hardening binder systems. By binders (self-hardening) are understood systems containing, in certain relative amounts, the solid and liquid phases that can interact to give new condensed phases and are capable of hardening [1,2]. It is known that condensed reaction products formed in hardening of water-containing binder systems, with aluminosilicates used as a solid phase, are salts of complex composition. These salts contain oxyhydrates, hydrosilicates, and hydroaluminates, which exhibit sorption properties under certain conditions [5].In development of sorbents for defluorination of wastewater, the mineral phase of the self-hardening binder system should be composed of acid-nonresistant aluminum-containing minerals that can interact with aqueous solutions of acids to give hydroxo compounds of aluminum, which are anion-active sorbents under certain conditions [4]. The search for starting raw materials was limited to the natural resources of the Kola Peninsula. Preference was given to nepheline-containing raw materials, whose advantage over other types of raw materials consists in larger resources, fast decomposition by acids, and high content of alumina (up to 30 wt % Al 2 O 3 ). In view of the fact that aluminum hydroxides exhibiting the highest activity toward fluoride ions are formed in hydrolysis of its oxychlorides [4], a hydrochloric acid solution was chosen as the second component of the binder system for synthesis of a fluorine-selective sorbent.The aim of this study was to find conditions under which granulated sorption-active materials to be used in treatment of mine wastewater can be formed by the binder technology in the system constituted by nepheline, hydrochloric acid, and water and to determine the optimal application conditions of the materials obtained.We used a nepheleine concentrate produced by the Apatit Open Joint-Stock Company,...

Direct Lithium Extraction from α-Spodumene through Solid-State Reactions for Sustainable Li2CO3 Production

“…This material may be used for glass manufacturing (in the place of feldspar) or as a filler in paints, plastics, foam rubbers, and sorbents. 31 The findings presented in this work demonstrate the feasibility of spodumene as a lowcost Li source, which can increase the adoption of domestically sourced ores for cathode production. Our work also shows that α-spodumene itself can be used as an effective precursor, which opens new opportunities for the direct synthesis of battery materials from raw ores.…”

“…Following the washing procedure used to isolate Li 2 CO 3 , we are left with NaAlSiO 4 as a primary byproduct. This material may be used for glass manufacturing (in the place of feldspar) or as a filler in paints, plastics, foam rubbers, and sorbents . The findings presented in this work demonstrate the feasibility of spodumene as a low-cost Li source, which can increase the adoption of domestically sourced ores for cathode production.…”