Crosslinked poly(vinylphosphonic acid) (PVPA) particles were successfully synthesized from vinylphosphonic acid and a crosslinker by water-in-oil (W/O) suspension polymerization using three silicone oils. The structure, morphology, and size of the PVPA particles were confirmed by Fourier transform infrared spectroscopy, scanning electron microscopy, and optical microscopy. The surface of the spherical particles was wrinkled, and their size ranged from 5 – 260 µm. The adsorption of divalent and trivalent metal ions (Cu²⁺, Zn²⁺, La³⁺, Tb³⁺, Lu³⁺) from aqueous solutions was studied using the synthesized PVPA particles under batch conditions at various metal ion concentrations and pHs for the first time. For all metal ions, pH-dependent adsorptions were observed. Partial charge neutralization of metal ions occurred because the PVPA particles are highly hydrophilic. The extraction efficiencies of La³⁺, Tb³⁺, and Lu³⁺ are higher than those of Cu²⁺ and Zn²⁺. The separation ability for La³⁺, Tb³⁺, and Lu³⁺ is not so high, but they can be used for the group extraction of these metal ions.

The extraction kinetics of forward extraction of boron by 2,2,4-trimethyl-1,3-pentanediol (TMPD) were investigated, using a Lewis cell. Factors affecting the extraction rate, including stirring speed, concentrations (TMPD and B(OH)₃), interfacial area, and temperature were examined. Results indicated that the extraction rate is controlled by chemical reaction at interface. The activation energy E_a was measured depending on experimental conditions. The extraction rates of B(OH)₃ and TMPD are first-order dependent with respect to B(OH)₃ and TMPD concentrations, and rate equation is proposed. The rate-determining step is to form the complex at the interface, and the derived extraction mechanism is in good agreement with the experimental results. Based on the above-mentioned regime, an extraction mechanism for boron was also presented.

Using hexane-1,6-diyl bis (4,4,4-trifluoro-3-oxobutanoate) (H₂hdfob), the mechanism for extracting rare earth metal ions to the organic phase was evaluated. From slope analysis, it was clarified that one divalent metal hydroxide ion reacts with two H₂hdfob where one of the protons is dissociated from each ligand. Such a complexation formed the 1 : 2 metal–ligand neutral complex. Such a complex formation reaction is very similar to that of Co²⁺ or Ni²⁺, which form a 1 : 1 metal–ligand neutral complex.

The heat-stable salts (HSS) in flue gas desulfurizer 1,4-bis-(2-hydroxypropyl)-piperazine (HPP) are separated by HPP forming an aqueous two-phase system (ATPS) with Na₂SO₄, which is the main component of HSS. In this work, SO₄^2–, NO₃^–, Cl^–, K⁺, PO₄^3– and SO₃^2– were selected to study the separation performance in the HPP+Na₂SO₄ ATPS. The results indicate that the partition coefficients of the above ions in the ATPS are related to their structures. Furthermore, the partition coefficients of anions are related to the charge numbers and salting out capacity. Simultaneously, with the increase of pH in ATPS, the partition coefficients of ions decrease first and then have no significant change. These findings provide an effective reference for the process design of separating HSS from HPP by ATPS.

The extraction of trivalent rare earth ions (RE³⁺) from HNO₃ solution using a triamide amine, tris(N,N-di-2-ethylhexyl-ethylamide)amine (DEHTAA), was conducted, and the extraction mechanism was estimated from extraction behavior of HNO₃ and RE³⁺. A DEHTAA molecule dominantly formed a DEHTAA⸱HNO₃ at 1.0 M HNO₃ and a DEHTAA⸱(HNO₃)₂ at 6.0 M HNO₃ in the acid-equilibrated organic phase. This would provide the unique dependence of E% for the light RE³⁺ on the HNO₃ concentration, in which the E% value had a minimum and maximum at ~0.5 M and ~2 M HNO₃, respectively. The results of the slope analyses for the distribution ratios for RE³⁺ suggested that the dominant RE³⁺ complex was RE(NO₃)₃DEHTAA(DEHTAA⸱HNO₃) at 1.0 M HNO₃. The E% for RE³⁺ decreased from La³⁺ to Lu³⁺ at 1.0 M HNO₃; however, those increased from La³⁺ to Nd³⁺ at 0.25 M HNO₃ and from La³⁺ to Sm³⁺ at 6.0 M HNO₃.

In this work, deep eutectic solvent (DES) combined with ultrasonic-assisted extraction was proposed to extract free seleno-amino acids from Cardamine hupingshanensis. The contents of seleno-amino acids in the extract were determined by high-performance liquid chromatography with a fluorescence detector (HPLC-FLD). Response surface design was used to optimize the extraction conditions such as ultrasonic time, ultrasonic temperature, and liquid-solid ratio. The results showed that DES prepared by choline chloride and ethylene glycol had the highest extraction efficiency of seleno-amino acids. The main free seleno-amino acids in Cardamine hupingshanensis were selenocystine (SeCys₂) and selenomethylcysteine (SeMeCys). The optimal extraction conditions were as follows: liquid-solid ratio of 50 mL·g^–1; extraction temperature of 40 °C; and extraction time of 45 min. Under the optimal extraction conditions, the SeCys₂ and SeMeCys contents were 356 μg·g^–1 and 147 μg·g^–1, respectively. This study shows that DES has great potential in extraction and separation.

If calixarenes can be dissolved in a relatively safe non-halogen solvent, they can be used in a liquid-liquid extraction process suitable for mass processing. In the present study, extraction behavior of metal ions using a calix[4]arene carboxylic acid derivative (^tOct[4]CH₂COOH) dissolved in aromatic ethers was investigated. The solubility of ^tOct[4]CH₂COOH in aromatic ethers decreases with increase of the length of aliphatic side chain of the ethers. The solubility of ^tOct[4]CH₂COOH in 1-butoxybenzene (BB) was 28.0 mmol/L, which is smaller than that in chloroform but is higher than those in hexane and toluene. Divalent metal ions Mn(II), Co(II), Ni(II), Cu(II), Zn(II), and Pb(II) were extracted using ^tOct[4]CH₂COOH in BB through proton exchange reaction at similar pH range in toluene, which is higher than that in chloroform. The extraction reaction of Cu(II) using ^tOct[4]CH₂COOH in BB was determined by slope analysis and loading test. The stoichiometry between ^tOct[4]CH₂COOH and Cu(II) was 2:1.

In this study, the selective extraction and mutual separation of Sc(III) and Y(III) from Ni(II), Co(II) and Mn(II) in acidic media were performed with N-lauroylsarcosine (NLS) in toluene. The experimental results were quantitatively analyzed using the conventional slope analysis method. This method reasonably elucidated reasonably the extraction equilibrium formulation of these metals with LNS. Isostearic acid with only a carboxylic acid group in the molecule extracted Sc(III) and Y(III) in a higher pH region compared with that with LNS having amide and carboxylic acid moieties. Therefore, we found that the amide group included in the molecule structure of NLS plays an important role to extract these metals. Mutual separation of Sc(III) and Y(III) was carried out by a one-step extraction using NLS from Ni(II), Co(II) and Mn(II) in acidic media. Sc(III) is more strongly extracted than Y(III) with NLS, and the separation factor of the metals is quite high at 4.68×10³. Furthermore, the stripping of Sc(III) and Y(III) extracted into the organic phase was achieved using appropriate concentrations of various acids.

This research focuses on emulsification solvent extraction for purifying wet-process phosphoric acid. The effects of various parameters, including stirring speed, phase ratio and emulsification time on the extraction yield and droplet size distribution were investigated. The optimal conditions were determined. The influence of time and physical properties of solvent on average droplet diameter was fitted by dimensional analysis. The results showed that the mathematical model has a strong agreement with the experimental data. This model was reliable to predicting the droplet size in different conditions of manufacturing emulsion.