Today, biphasic aqueous systems have received more attention than conventional separation methods due to their advantages, such as biocompatibility, low cost, and easy operation. The extraction of cobalt ions from the aqueous phase with the absence and the presence of other ions was investigated using polyethylene glycol, and ammonium sulfate salt without using an extractant. The efficiency was evaluated using operating parameters such as aqueous pH, salt and polymer concentrations, phase volume ratio, and initial metal concentration. The higher temperature, and the lower aqueous pH showed a maximum transfer rate for cobalt ions into the PEG1000 phase. Extraction efficiency under optimal conditions equal to 50% (w/w) polyethylene glycol 1000, 4 M ammonium sulfate, aqueous pH = 2, and 15 min extraction time was over 98%. Results from infrared spectroscopy, and thermo-gravimetric analysis illustrated the presence of the PEG-cobalt ion complex. The observation demonstrated that the biphasic system is the proper technology for wastewater purification.

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In this study, response surface methodology was used to evaluate the extraction of cobalt ions using an aqueous two‐phase system (ATPS). This method is environmentally benign and low‐risk because water has replaced the poisonous and dangerous organic solvents in this extraction procedure. For the first time, a central composite design was employed to examine the effect of various factors on the extraction of cobalt ions. The findings of the experimental design revealed that the concentration and volume of cobalt ions had a considerable impact on the extraction percentage in the ATPS system. In contrast, the concentration of ammonium sulphate and pH had only a minor effect. The value of the correlation coefficient (R2 = 0.9565) clearly shows the agreement between the mathematical model and the experimental results. The maximum extraction percentage was attained in optimum conditions (50% polyethylene glycol concentration, 3.75 M salt concentration, 0.5 ml cobalt volume, and pH 4).

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