Articles

The study focused on the solvent extraction of Cr(III) from sulfate media using Cyanex 302 (bis (2,4,4-trimethylpentyl) monothio-phosphinic acid). Various parameters were systematically evaluated, including phase contact time, initial pH, metal ion concentration, extractant concentration, sulfate ion concentration, temperature, and the type of diluent. Equilibrium was reached within 30 minutes, with the highest extraction efficiency occurring at pH 5.0. Adding more Cyanex 302 improved the extraction efficiency. The study showed that each Cr(III) ion paired with a single dimeric extractant molecule. The presence of sulfate ions was found to hinder extraction by forming non-extractable chromium complexes. The extraction process was endothermic, as indicated by positive enthalpy changes. Among the diluents tested, toluene showed the highest extraction efficiency; however, kerosene was chosen for practical reasons. The maximum loading capacity of Cyanex 302 for Cr(III) was determined to be 2.742 g per 100 g of the extractant. Research found that sulfuric acid was good for stripping, but HCl and HNO3 did not work in the conditions tested. Cyanex 302 had a medium level of extraction efficiency compared to other extractants. These results suggest that Cyanex 302 holds promise for industrial applications in Cr recovery processes, although further optimization may be required to enhance its effectiveness.

The extraction behaviour of vanadium (V) from nitric acid solutions was studied using technical grade D2EHPA in kerosene as an extractant. The effects of aqueous pH, the concentration of vanadium (V) and nitrate ion in the aqueous phase, and the concentration of D2EHPA in the organic phase were investigated. The extraction equilibration time was 30 min. Metal ion dependencies appeared non-ideal due to the non-constancy of the aqueous phase acidity and the equilibrium extractant concentration. Two types of extraction mechanisms originated from the study of pH dependency. The study conceded that the extraction of vanadium (V) occurred via ion exchange or chelation type of extraction when the pH (eq) <2.50. On the other hand, the solvated ion-pair extraction mechanism occurs when the pH (eq) was above 2.50. The extractant dependencies showed that vanadium (V) species were extracted by one molecule of D2EHPA. The salting-out effect was observed from the effect of nitrate ion concentration. The effect of various types of diluents on vanadium (V) extraction with technical grade D2EHPA was studied; kerosene appeared to be a suitable diluent. The temperature dependence data revealed that the system was exothermic with the &Delta;H value of -12.34 kJ/mol. The loading capacity was 6.11 g vanadium (V) per 100 g extractant. The H 2 SO 4 (0.5 mol/L) was the right stripping agent for the extracted species.