Separation of Rare-Earth Elements from Nitrate Solutions by Solvent Extraction Using Mixtures of Methyltri-n-octylammonium Nitrate and Tri-n-butyl Phosphate

The article presents data on the solvent extraction separation of rare-earth elements (REEs), such as La(III), Ce(III), Pr(III), and Nd(III), using synergic mixtures of methyltrioctylammonium nitrate (TOMANO3) with tri-n-butyl phosphate (TBP) from weakly acidic nitrate solutions. Specifically, experimental results on separation of REEs, for the pair Ce(III)/Pr(III) for quaternary mixtures of REEs (La(III), Ce(III), Pr(III), Nd(III)) and for the pair La(III)/Pr(III) for solutions containing La(III), Pr(III), and Nd(III), are presented. It was shown that effective separation for the pair Ce(III)/Pr(III) from a solution containing 219 g Ce(III)/L, 106 g La(III)/L, 20 g Pr(III)/L, 55 g Nd(III)/L, and 0.1 mol/L HNO3, was achieved using 56 steps of a multistage, counter-current solvent extraction cascade with scrubbing, at an organic-to-aqueous phase volume ratio (O/A) equal to 2/1 on the extraction section and O/A equal to 4/1 on the scrubbing section, using 3.3 mol/L solutions of the mixture TOMANO3-TBP with molar ratio 0.15:0.85 in dodecane. Separation for the pair La(III)/Pr(III) could be achieved using a solvent extraction cascade with scrubbing in 32 steps at O/A equal to 2/1 on the extraction section and O/A equal to 2.8/1 on the scrubbing section of the solvent extraction cascade from a solution containing 258 g La(III)/L, 58 g Pr(III)/L, 141 g Nd(III)/L, and 0.1 mol/L HNO3 with 3.0 mol/L solution of the mixture TOMANO3-TBP with molar ratio 0.2:0.8 in dodecane.

Gold recovery from waste printed circuit boards of mobile phones by using microwave pyrolysis and hydrometallurgical methods

Recycling of waste printed circuit boards (PCBs) has attracted increasing attention because of its high annually produced amount and high content of gold. In this study, gold recovery from waste PCBs was carried out by using the processes including microwave pyrolysis, acid leaching, solvent extraction and oxidative precipitation. The leaching efficiency of copper was approximately 95% when using a lixiviant composed of sulfuric acid and hydrogen peroxide, and the leaching efficiencies of gold were approximately 59, 95 and 95% by using thiourea, thiosulfate and aqua regia, respectively. The gold ions contained in the leachate previously produced by the leaching processes were not satisfactorily extracted by using organic solvents including di-(2-ethylhexyl)phosphoric acid, tributyl phosphate, dibutyl carbitol and trioctylamine, so the leachate was decided to bypass solvent extraction and directly apply to the oxidative precipitation process. By using the oxidants of hydrogen peroxide and perchloric acid, the precipitation efficiencies of gold were approximately 95 and 99%, and the final recovery rates were approximately 90 and 93%, respectively. The high recovery rates of gold can be attributable to the use of microwave pyrolysis that prevents the loss of gold caused by shredding and grinding processes. In addition, perchloric acid can provide higher selectivity for gold recovery than hydrogen peroxide. The maximum processing capacity of microwave pyrolysis of waste PCBs would be approximately 1.23 kg. The gold recovered from 1 t of waste PCBs can be sold for approximately USD 10,000, and thus the return on investment can be as high as approximately 1400%.

IR spectroscopy for analysing solvent extraction efficiency of oil extracts

Solvent extraction is a method for purifying oil extracts, which are used as oil-plasticisers for industrial rubber goods, from cancerogenic hydrocarbons. The efficiency of this method is mainly determined by the selectivity and solvent properties of a separating agent. However, when carrying out a comparative analysis of promising extraction methods, it is necessary to use real-time methods for studying the composition of the resulting products. The purification efficiency of oil extracts from polycyclic aromatic components, including carcinogenic hydrocarbons (benzo[a]pyrene, benzo[e]pyrene, benzo[a]anthracene, chrysene, benzo[b]fluoranthene, etc.), was evaluated depending upon the nature of selective solvents. The structure-group composition of the purified oil extracts and those at the second-stage of purification was determined by FTIR spectroscopy. It was found that the extraction efficiency of the studied solvents towards polycyclic aromatic hydrocarbons from oil extracts increases in the following order: dimethyl sulfoxide < N-methylpyrrolidone + 10 wt% ethylene glycol <N-methylpyrrolidone +50 wt% triethylene glycol. When using a solvent comprising N-methylpyrrolidone + 50 wt% triethylene glycol, the proportion of polyalkyl-substituted and condensed aromatic structures in the purified oil extract decreases by 16.8%; the oil extract yield increases by over 25 wt% in contrast to extraction with N-methylpyrrolidone + ethylene glycol mixture, which meets the requirements of the European Union for oil extract purification (Directive No. 2005/69/EC). Therefore, we recommend the solvent comprising N-methylpyrrolidone + 50 wt% triethylene glycol for purifying oil extracts from components having a technogenic impact on the environment and human health and IR spectroscopy for efficiency assessment of solvent extraction of oil extracts.

Ionic Liquids as Components of Systems for Metal Extraction

This review addresses research and development on the use of ionic liquids as extractants and diluents in the solvent extraction of metals. Primary attention is given to the efficiency and selectivity of metal extraction from industrial wastewater with ionic liquids composed of various cations and anions. The review covers literature sources published in the period of 2010–2021. The bibliography includes 98 references dedicated to research on the extraction and separation of lanthanides (17 sources), actinides (5 sources), heavy metals (35 sources), noble metals, including the platinum group (16 sources), and some other metals.

Investigating matrix interference in the pharmacopeial limit test for aluminum in citric acid: a re-examination, for revision of the method

In many pharmacopoeias, the limit test used for determining the level of aluminum in citric acid labeled for use in the manufacture of dialysate, is based on solvent extraction using 8-hydroxyquinoline and measurement of fluorescence. However, the fluorescence intensity (F.I.) readout from the extract of citric acid samples has been found to be highly dubious, showing low value, and even lower than that of a blank solution. The aim of this work therefore was to examine what effects the matrix has on the test. The comparison of the two standard curves of aluminum solutions in water, against those prepared in citric acid solutions revealed that they differed greatly in terms of slope and y-intercept. In addition, the F.I. values on the plot of the citric acid solution were much lower than that prepared in the water. In another experiment, a decrease in the F.I. of aluminum solution was clearly seen when the co-existing concentration of citric acid was increased. The results inferred that citric acid interfered with the test due to its acidity and metal-chelating capabilities. Based on this evidence, the pharmacopeial limit test for aluminum in citric acid should be revised; otherwise, it could yield results that underestimate aluminum levels and lead to inaccurate conclusions

Process intensification in Desalination operation in mesoscale systems

Development of desalination technologies has been identified as vital to fulfilling future water demand. Directional solvent extraction is one of the promising membrane-less seawater desalination method. Membrane based desalination technologies incur a higher cost and are subjected to fouling after certain period of time of operation and needs regular maintenance and monitoring. It is believed that, overcoming these drawbacks is possible by working in the millimeter scale through the incorporation of pulsatile flow and air damper. This work presents a theoretical approach designed for a certain nominal length of an air damper, placed on the top of the extraction column, with the flow in the desalination unit being semi pulsatile combined with secondary pulsation generated due to air suspension during solvent extraction applied for desalination operation. Henceforth a theoretical approach based on the above stated parameters, it is found theoretically that with increase in flow pulsation amplitude and frequency the extracted salt concentration in solvent increases. The application of infra red radiation in preheating section with the help of a infrared heating device is the crucial part of DSE process, cooling is planned to achieve via a heat exchanger or atmospheric cooling. The total exergy and energy calculations will be conducted to see the energy requirement for the process. It is planned to calculate the salt separation efficiency of sea water (on the basis of WHO guidelines) to fresh water, alongwith flow rate and processing time.