Separation Science and Technology, Vol.38, No.14, 3591-3607, 2003
Gold recovery by pH-switching process via cloud point extraction
Poly(oxyethylene)-9-nonylphenyl ether (PONPE-9) was employed for cloud point extraction of gold(Ill) ion and its phase separation behavior under different experimental conditions was evaluated. The effect on extraction efficiency, including equilibration time, ratio of PONPE-9 to gold, settling temperature, and pH of the solution, was demonstrated. The results indicate that PONPE-9 can be utilized for the extraction of gold in a manner akin to previous work using PONPE-7.5. The optimum experimental results obtained were applied to design a process scheme, pH switching via CPE, to overcome the drawback of the difficulty of separating gold from a gold-entrapped surfactant. The utility of the proposed scheme was demonstrated through the application of recovering gold(III) ion from a multimetal solution. Recoveries of greater than 63% of gold were obtained. Even if this is not so high a percentage recovery, it indicates the feasibility of the process scheme. On the other hand, it proved to be an even simpler and easy method for recovering gold from the leaching solution of printed substrates without spending harmful organic solvent.