Experimental Investigation and Thermodynamic Modeling of Zn+۲ and Ni+۲ Extraction from Zn Plant Residue using D۲EHPA

Zinc plant filter cake contains valuable metals that can be reused as a source for obtaining these metals. This study  describes an experimental two stage study on the extraction of zinc and nickel from waste zinc filter cake which includes acid leaching of zinc filter cake followed by organic phase aided extraction of metals from the leaching solution. To determine the optimum leaching condition a comprehensive study of the recovery of chemical elements from spent plant residues was experimentally studied at different levels of acid concentrations at different temperatures while measuring chemical elements concentration with respect to time. Experimental results showed that ۹۹% recovery of Ni۲+, Zn۲+ and ۸۹% recovery of Pb۲+ can be achieved at following optimum conditions: ۲M nitric acid, T= ۳۵۸.۱۵ K after ۱.۵ h of acid leaching at S/L=۱/۱۰. Then, the extraction of Zn۲+, Ni۲+, and Pb۲+ was carried out by di-(۲-ethylhexyl) phosphoric acid (D۲EHPA) that was diluted with kerosene in equal phase ratio and the effect of extractant concentration and pH was studied at T = ۲۹۸.۱۵ K. Results showed that an increase in pH and extractant concentration can greatly increase zinc and nickel extraction to a maximum achievable amount of ۹۵% and ۹۰ % for Zn۲+ and Ni۲+, respectively by ۲۵ (v/v%) D۲EHPA at pH = ۵.۵ and organic to aqueous phase ratio (O/A) = ۱/۱. For modeling of equilibrium concentrations in organic and aqueous phases and activity coefficients calculation, Electrolyte-UNIQUAC-NRF, UNIQUAC-NRF, NRTL and NRTL-based local composition models were used. After that, adjusted parameters were successfully used for calculation of the equilibrium constant of the unknown parameters and the extraction reaction. The obtained results of thermodynamic modeling were in well agreement with the experimental data.

Keywords:

Thermodynamic Modeling , Solvent extraction , D۲EHPA , Zinc Residue , Activity coefficient , Gamma model