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Zirconium (Zr) and hafnium (Hf) are very important in nuclear and high-temperature applications, but their similar physical and chemical properties bring great challenges to separation. The current extraction methods have defects, such as low efficiency at high metal concentration. In this article, a zirconium (Zr)/hafnium (Hf) solvent extractive separation from sulfuric acid solutions using trioctylamine (TOA) as the extractant was researched at room temperature. The aqueous solution is prepared using zirconium sulfate (containing Hf), and the concentration of metal ions (Zr4+ and Hf4+) was about 1.096 mol·L−1. The effects of the aqueous acidity, the concentration of TOA, the contacting time, and the organic to aqueous O/A ratio on the separation of Zr and Hf were investigated. It is observed that the Zr can be extracted in the organic phase selectively, and the optimal conditions were: TOA concentration of 40 vol%, organic to aqueous O/A ratio of 3, contacting time of 5 min. Under these conditions, the single-stage extraction rate of Zr is 61.23%, while the Hf is almost not extracted. The mechanism of Zr extraction by TOA was studied through the saturation capacity and slope methods. Based on the results, it is believed that the structure of the extracted complex may be [R3NH]2[Zr(SO4)3]. This study provides a new approach for the development of industrialized Zr-Hf separation.

The separation of valuable elements from nitric acid solutions containing ytterbium alloy components was investigated. The extraction and separation efficiency of N235 in a nitric acid system was evaluated by examining the effects of solution acidity, chloride ion concentration, and extractant ratio. The experimental data were analyzed using dynamic calculations. The results indicated that the partition rate of iron increases exponentially with higher chloride ion and hydrochloric acid concentrations, while the partition rate of ytterbium remains unaffected. Iron demonstrated a higher partition ratio in pure hydrochloric acid compared to nitric acid solutions containing ammonium chloride, likely due to the absence of nitrate ions, which inhibits complex formation with N235. The extraction rates of both iron and ytterbium increased with higher trioctylamine concentrations and longer extraction times. Back-extraction experiments revealed that the back-extraction rate of iron gradually decreased with increasing acidity of the back-extraction solution. Emulsification of the organic phase was observed when the acidity was below 0.1 mol/L. Overall, ytterbium and iron were successfully separated through a four-stage extraction process, achieving a ytterbium purity of 99.98%. These findings provide a foundation for the development of ytterbium recovery technologies.

Wastewater containing methanesulfonic acid (MSA) mainly originates from the production process of metal detergent, which also contributes significantly to environmental pollution. This study investigates the extraction of MSA from wastewater using trioctylamine (TOA). A thorough investigation was carried out into the factors that affect extraction efficiency, such as the type of extractant, phase ratio (O/A), temperature, stirring speed, and extraction time. An extraction efficiency of 96.1% was achieved using TOA at 25 °C, 1400 r·min − 1 , and an extraction time of 30 min. Various techniques including FT-IR, XPS, and high-resolution ESI-MS were employed to investigate the extraction mechanism. The results of different techniques revealed that the complexation between TOA and MSA occurred through ionic and hydrogen bonding interactions. Moreover, TOA was successfully regenerated through back-extraction with sodium hydroxide. The proposed extraction system is advantageous for eco-friendly engineering applications.

Germanium is an important element used in crucial industry sectors like optical fibers for telecommunication or IR optics for night vision systems. However, its global output is limited. It is estimated that its annual global production is ca. 140 tons. Therefore, many world economies, including USA and EU, consider it as a critical raw material. One of the potential sources of germanium is zinc metallurgy. It is assumed that only 3% of germanium present in processed zinc ores is recovered. It was found that during the technological processes of Polish zinc smelters some by-products containing elevated germanium concentrations are produced. In the paper, potential germanium sources, including copper-cobalt cake obtained during the purification of zinc electrolyte and dross from the feeding furnace, are presented. The main components of the cake are cadmium, zinc, copper, nickel, cobalt, and lead, while the dross contains mainly zinc (>65%). Results of leaching tests for both materials using aqueous sulfuric acid solutions are shown. In the case of the cake, wet and dried material was investigated. It was found that the germanium leaching yield for the dried material reached 99%, while for the wet one was 46-86%, depending on leaching conditions (without or with oxidant). On the other hand, the germanium leaching yield for the dross reached 55%. Further processing of the solutions obtained after germanium leaching from the copper-cobalt cake was also analyzed. Two ways were proposed, including precipitation with tannic acid and solvent extraction with addition of complexing agents using a trioctylamine extractant.

Reactive extraction is a significant technique employed for the removal of organic acids such as carboxylic acid which are usually present in low concentrations in aqueous solutions. This technique was explored by applying Response Surface Methodology (RSM) in process parameter optimization for malic acid recovery from aqueous streams using Trioctylamine as extractant and 1-decanol as organic diluent. Malic acid, a C 4 dicarboxylic acid has a wide variety of applications in the polymer, food, chemical and pharmaceutical industries. The optimization of the response function: extraction efficiency was systematically carried out using three process parameters for reactive extraction: temperature, initial malic acid concentration and extractant (Trioctylamine) composition. Response Surface Methodology in combination with Box-Behnken design involving seventeen experimental runs was employed for malic acid reactive extraction in this study. A statistical second-order polynomial predicted an extraction efficiency of 97.53%. The optimum conditions of the process variables were found to be: temperature: 304.73 K, acid concentration: 0.25 kmol/m 3 , Trioctylamine composition: 23.54% (v/v). Under these optimum conditions, the experimental response of extraction efficiency of 93.25% was obtained. The experimental results obtained was in close conformity with the predicted values by numerical optimization using Response Surface Methodology. These findings can pave the way for the reactive separation process design for recovery of carboxylic acids from dilute aqueous waste streams as well as a fermentation broth.

This paper focuses on the reactive extraction of levulinic acid (LA) from aqueous solution by reactive extraction. This goal is achieved using eugenol, a green alternative in the industry, as a solvent in the liquid-liquid equilibrium (LLE) measurements for the ternary system of LA + Eugenol + H 2 O and quaternary systems of LA + Eugenol/ Methanol (MeOH) + H 2 O + Tri-n-octylamine (TOA) at T  = 293.15 K. Additionally, the distribution coefficients ( K D ) were calculated for LA using the two diluents. Also, the ability of different diluents with TOA, in the extraction of LA were compared. The distribution coefficient of eugenol with TOA ( K D = 9.44) is compared with other organic diluents which indicated that eugenol is a suitable option. MeOH, being the shortest chain alcohol, also turned out to be a diluent that could be utilized for extraction of LA with TOA. Furthermore, the Non-Random Two-Liquid (NRTL) excess Gibbs energy model was applied to correlate the measured phase equilibria. The obtained parameters were further validated using a decanter model.

Levulinic acid (LA), a carboxylic acid with a keto-acid structure, has recently been gaining increasing attention as a promising biorefinery platform chemical due to its potential to be feasible and sustainable. This work focuses on using trioctylamine (TOA) to separate LA from an aqueous solution by liquid–liquid extraction. For that, binodal curves and tie lines were determined at T  = (293.15, 313.15, and 333.15) K under atmospheric pressure. The slope of the determined tie lines demonstrates that higher extraction efficiencies are possible with higher acid concentrations. Furthermore, infrared spectroscopy (FT-IR) was applied to better understand the behavior of phase diagrams. This study detected the acid-extractant complex formation between (LA) and (TOA). Finally, the experimental data were successfully correlated with the NRTL model at all the measured temperatures. The obtained parameters were applied using a decanter model.

The uptake of 75 Se and 73 As on trioctylamine-impregnated resin from HCl solutions was studied with batch uptake, kinetics, and column studies. Selenium-75 extracts well ( D w  ~ 900) at high HCl concentrations (≥ 10 M) with and no extraction of 73 As at any HCl concentration. The uptake kinetics were slow with low extraction ( D w  < 100) for time periods ≤ 15 min and no clear equilibrium achieved even after 24 h. Column studies were performed to characterize the separation of 75 Se and 73 As; 75 Se is retained from conc. HCl while arsenic is eluted with high yields and high radiopurity.

The hazardous chemicals discharged from various dyeing industries adversely impact human health and the environment. Therefore, it is essential to treat wastewater containing dyes with technology that outperforms conventional methods. In the current study, liquid-liquid extraction (LLE) based on pseudoprotic ionic liquids (PPILs) was employed as an efficient tool to remove anionic dyes from simulated and real dye effluent. PPIL derived from trioctylamine and octanoic acid was used for the extraction studies. Initially, simulated dye samples were prepared using different anionic dyes, namely alizarin yellow, rose Bengal, and methyl orange, identical to the real industrial dye effluent composition, and LLE studies were carried out. After a series of screenings, the essential experimental parameters required for deploying a pre-pilot plant scale study have been optimized systematically. After successful optimization, similar experimental parameters were deployed for the removal of dyes from the industrial dye effluent collected from Angeripalayam common effluent treatment plant limited (ACETP), Tirupur, Tamil Nadu, India. While most optimized reaction conditions remained unaltered, adjustments were made to some, such as pH, to suit practical scenarios. Moreover, the dyes were back-extracted with dilute diethylamine and the regenerated extractant was reused in subsequent LLE cycles.

The paper has aimed at studying the transfer of indole 3-acetic acid ( IAA ) from a feed aqueous solution to a stripping aqueous solution of NaOH using a chloroform bulk liquid membrane and trioctylamine ( TOA ) as a ligand ( L ). Initial molar concentrations of IAA in the feed phase, c IAA,F 0 (10 –4 –10 –3  kmol/m 3 ), of TOA in the membrane phase, c L,M 0 (10 –2 and 10 –1 kmol/m 3 ), and of NaOH in the stripping phase, c NaOH,S 0 (10 –2 and 1 kmol/m 3 ), were selected as process factors. Their effects on the final values of IAA concentration in the feed phase ( c IAA,Ff ) and stripping solution ( c IAA,Sf ), extraction efficiency ( E F ), distribution coefficient ( K D ), and recovery efficiency ( E R ) were quantified using multiple regression equations. Regression coefficients were determined from experimental data, i.e . , c IAA,Ff,ex  = 0.02–1 × 10 –4 kmol/m 3 , c IAA,Sf,ex  = 0.22–2.58 × 10 –3 kmol/m 3 , E F,ex  = 90.0–97.9%, K D,ex  = 9.0–46.6, and E R,ex  = 66.5–94.2%. It was found that c IAA,F 0 had the most significant positive effect on c IAA,Ff and c IAA,Sf , whereas c NaOH,S 0 had a major positive effect on E F , K D , and E R . A deterministic model based on mass transfer of IAA was developed and its parameters, i.e . , mass transfer coefficient of IAA-L complex in the liquid membrane (0.82–11.5 × 10 –7  m/s) and extraction constant (1033.9–1779.7 m 3 /kmol), were regressed from experimental data. The effect of c L,M 0 on both parameters was significant.