Removal of Zinc(II) from Spent Hydrochloric Acid Solutions from Zinc Hot Galvanizing Plants

Abstract

The extraction of zinc(II) from spent pickling hydrochloric acid solutions obtained in zinc hot-dip galvanizing plants was studied. Tributyl phosphate and its mixtures with di(2-ethylhexyl)phosphoric acid (DEHPA), HOE F 2562, ALIQUAT 336, ALAMINE 304, ALAMINE 308, ALAMINE 310, ALAMINE 336, and CYANEX 301 were used as extractants. The acidic extractants (CYANEX 301 and DEHPA) did not extract both zinc(II) and iron(III) from 10% HCl. Precipitation occurred or stable emulsions were formed when ALAMINE 304, ALAMINE 308, and ALAMINE 310 were used. Each of the other reagents coextracted both zinc(II) and iron(III). The latter had to be reduced to iron(II) prior to extraction. Tributyl phosphate and HOE F 2562 showed the best extraction performance. ALAMINE 336 and ALIQUAT 336 induced the oxidation of iron(II) to iron(III), thus enhancing the coextraction of iron. Zinc(II) could be effectively stripped from the loaded phases containing TBP and HOE F 2562 with water. A higher efficiency of stripping was observed in the second stage.

A review on methods of regeneration of spent pickling solutions from steel processing

“…The author's research group has been working on selective zinc recovery from hydrochloric acid SPS for a couple of years applying not only diffusion dialysis and retardation but also classical [59][60][61][62][63][64][65][66] and membrane based [64,[67][68][69] solvent extraction (see Table 5). …”

“…After screening for the most suitable extractant from among a wide spectrum of compounds (Table 5), TBP (E Zn(II) ∼100%) and dibutyl(butyl) phosphonate (DBBP; E Zn(II) ∼80%) have been selected for further examination [59,61,64,70]. The criteria of extractant suitability for SPS regeneration confirmed by Australian researchers [71] are as follows: good phase disengagement after extraction and stripping, high selectivity of zinc extraction over iron(II) and easy zinc stripping with water.…”

“…The authors propose a flowsheet of spent pickling solution recovery (Fig. 5) based on equilibrium studies [59][60][61][62][63][64] followed by extraction and stripping examination in mixer-settler units [65,66]. Some other …”

Liquid–liquid extraction/separation of platinum(IV) and rhodium(III) from acidic chloride solutions using tri-iso-octylamine

“…Limited studies are reported on Alamine 308 as extractant for acids and transition metals [29][30][31][32].…”

Selective extraction of zinc(II) over iron(II) from spent hydrochloric acid pickling effluents by liquid–liquid extraction

“…1 that iron(II) exists exclusively as FeCl + while zinc occurs as neutral ZnCl 2 in both effluents. According to Regel et al [26] and Cierpiszewski et al [27] who used the program Medusa to roughly estimate the distribution of various chlorocomplexes in spent HCl pickling liquors, iron(II) may also exists as Fe 2+ additionally to FeCl + while zinc exists almost completely in the anionic forms as ZnCl 4 2− and ZnCl 3 − . Both analysis are theoretical and dependent on the species considered to exist in the aqueous system (and their respective concentrations as well), and also the stability constants used in the calculations.…”