Obtaining and production of metals from natural raw materials causes a large amount of liquid, solid, and gaseous wastes of various hazard classes that have a negative impact on the environment. In the production of titanium dioxide from ilmenite concentrate, hydrolytic sulphuric acid is formed, which includes various metal cations, their main part is iron (III) and titanium (IV) cations. Hydrolytic acid waste is sent to acid storage facilities, which have a high environmental load. The article describes the technology of ion exchange wastewater treatment of acid storage facility from iron (III) and titanium (IV) cations, which form compounds with sulphate ions and components of organic waste in acidic environments. These compounds are subjected to dispersion and dust loss during the evaporation of a water technogenic facility, especially in summer season. Sorption of complex iron (III) cations [FeSO4]+ and titanyl cations TiO2+ from sulphuric acid solutions on cation exchange resins KU-2-8, Puromet MTS9580, and Puromet MTS9560 was studied. Sorption isotherms were obtained both for individual [FeSO4]+ and TiO2+ cations and in the joint presence. The values of the equilibrium constants at a temperature of 298 K and the changes in the Gibbs energy are estimated. The capacitive characteristics of the sorbent were determined for individual cations and in the joint presence.
The issues of complex processing of mineral resources are relevant due to the depletion of available raw materials. So, it is necessary to involve technological waste, generated during the processing of raw materials, to obtain valuable components. In the process flow of apatite concentrate treatment using the sulfuric acid method, a large amount of phosphogypsum is produced with an average content of light rare earth metals (REMs) reaching 0.032-0.45 %. When phosphogypsum is treated with sulfuric acid solutions, a part of REMs is transferred to the sulfate solution, from which it can be extracted by means of ion exchange method. The study focuses on sorption recovery of light REMs (praseodymium, neodymium and samarium) in the form of anionic sulfate complexes of the composition [ln(SO 4 ) 2 ] – on polystyrene anion exchanger AN-31. The experiments were performed under static conditions at a liquid-to-solid ratio of 1:1, pH value of 2, temperature of 298 K and initial REM concentration in the solutions ranging from 0.83 to 226.31 mmol/kg. Thermodynamic description of sorption isotherms was carried out by the method based on linearization of the mass action equation, modified for the ion exchange reaction. As a result of performed calculations, the authors obtained the constants of ion exchange equilibrium for Pr, Nd and Sm, as well as the values of the change in the Gibbs energy for the ion exchange of REM sulfate complexes on the AN-31 anion exchanger and the values of total capacity of the anion exchanger. Calculated separation factors indicated low selectivity of AN-31 anionite exchanger for light REMs; however, the anion exchanger is suitable for effective recovery of a sum of light REMs. Based on the average value of ion exchange equilibrium constant for light REMs, parameters of a sorption unit with a fluidized bed of anion exchanger were estimated.
Rare earth elements (REEs) are valuable and strategically important in many high-technology areas, such as laser technology, pharmacy and metallurgy. The main methods of REE recovery are precipitation, extraction and sorption, in particular ion exchange using various sorbents, which allow to perform selective recovery and removal of associated components, as well as to separate rare earth metals with similar chemical properties. The paper examines recovery of ytterbium in the form of coordination compounds with Trilon B on weakly basic anion exchange resin D-403 from nitrate solutions. In order to estimate thermodynamic sorption parameters of ytterbium anionic complexes, ion exchange process was carried out from model solutions under constant ionic strength specified by NaNO 3 , optimal liquid to solid ratio, pH level, temperatures 298 and 343 K by variable concentrations method. Description of thermodynamic equilibrium was made using mass action law formulated for ion exchange equation and mathematically converted to linear form. Values of equilibrium constants, Gibbs free energy, enthalpy and entropy of the sorption process have been calculated. Basing on calculated values of Gibbs energy, a sorption series of complex REE ions with Trilon B was obtained over anion exchange resin D-403 from nitrate solutions at temperature 298 K. Sorption characteristics of anion exchange resin have been estimated: total capacity, limiting sorption of complex ions, total dynamic capacity and breakthrough dynamic capacity.
A complex heterogeneous process of ion exchange can be defined with an isotherm-isobar equation of the chemical reaction, which describes differential affinity between the process and its effect – the law of mass action. Ion exchange includes processes accompanied by changes in the charge of ions and functional groups caused by the passing of ionic bond into covalent one. Hence isotherm equations of ion exchange for such processes must differ from conventional stoichiometric equations, but they can be obtained by classical study approaches to ion exchange equilibrium. The paper describes a new thermodynamic model, based on linearization of mass action law, modified for the ion exchange equation. The application of this model allows to define stoichiometry of ion exchange and the shape of ions adsorbed by the solid phase of ion-exchange resins, as well as to estimate equilibrium constant and Gibbs free energy of the process. Comparative analysis has been carried out for the thermodynamic model of cerium sorption in the form of anionic complex with Trilon B from a multisalt solution with ionic strength of 1 mol/kg (NaNO 3 ) under рН = 3 and temperature 298 K on a test sample of weak-base anion-exchange resin Cybber EV009. Experimental isotherm of the sorption has been obtained. Calculations of thermodynamic parameters have been performed using Langmuir, Freundlich, Dubinin – Radushkevich, Temkin and Flory – Huggins models, as well as thermodynamic model of linearized mass action law, proposed by the authors. Calculated values of the equilibrium constant and Gibbs energy – K = 9.0±0.5 and ΔrG 0 298 = –5.54±0.27 kJ/mol – characterize the sorption of EDTA cerate ions by ion-exchange resin. The shape of adsorbed ions has been defined in Stern-Helmholtz layer of CeTr, and total capacity of anion resin EV009 for EDTA cerate ions has been estimated as q ∞ = 2.0±0.1 mol/kg.
Sorption isotherms was obtained in the form sulfate complex of cerium on the anion exchanger D-403 at a temperature of 298 K and pH = 2÷4 in the presence of various concentrations of magnesium sulfate. Thermodynamic description of the sorption isotherm sulfate complexes of cerium by the method, which based on linearization of the equations of the law of mass action modifed for the reaction of ion exchange. The values of the apparent constants of ion exchange and differential Gibbs energy calculated for the ions of Ce(SO 4 ) - 2 .
