Research on control of pH in solvent extraction of zinc by D2EHPA (P204)
In solvent extraction of zinc with D2EHPA(P204) as extractant, the pH was a main factor on extraction reaction. However, the extraction reaction results in replacement of hydrogen ions which inevitably reduces the pH value of the extraction system, thus reducing the equilibrium distribution ratio of extraction. And the pH further reduces with increase of amount of extracted zinc and initial zinc ions concentration. When zinc ions concentration increase to a certain extent, the decrease of pH would invariably limit the increase in extraction rate. Therefore, when high concentration of zinc was extracted by P204, neutralization of the replaced hydrogen ions serves as the essential prerequisite to improve the extraction ratio. In this paper, several methods were investigated on control of pH in the extraction system for the extraction of zinc in high concentration. The results showed that when alkali was added directly, the mixture emulsified because of the abrupt increase of pH in the vicinity of critical stoichiometric alkali easily, which made it hard to control the alkali addition. When the method of saponification pretreatment was used, the phenomenon of emulsification also appeaed easily in the process of saponification at higher saponification ratios, resulting in difficulty in separation of liquid phases. However, when some amount of a buffer was used in association with alkali, a favorable effect was obtained not only on stabilization of pH, but also on prevention of emulsification, which effectively ensured high extraction ratio. For a solution with 30 g/L zinc ion, the single-stage extraction ratio reached 99. 61％ by addition of a certain amount of buffering reagent under conditions of 40％ of extractant concentration and 1 : 1 of aqueous/oil ratio.
solvent extraction zinc pH control buffer saponification
Yongbin Yang Xianju Shi Qian Li Tao Jiang Wenjuan Wang Hongguang Nie
School of Minerals Processing and Bio-engineering, Central South University,Room 932, Lushan Road (S School of Minerals Processing and Bio-engineering, Central South University,Room 932, Lushan Road (S School of Minerals Processing and Bio-engineering, Central SouthUniversity,Room 932, Lushan Road (So Xian Design and Research Institute of Non-ferrous Metallurgy,710000, Xian, China
国际会议
The 19th International Biohydrometallurgy Symposium(第19届国际生物湿法冶金大会 IBS2011)
长沙
英文
808-812
2011-09-18（万方平台首次上网日期，不代表论文的发表时间）