pH effect on zinc recovery from the spent pickling baths of hot dip galvanizing industries

Abstract

In this work, the pH effect on the zinc electrowinning present in the spent pickling baths (SPBs) is analysed with the aim of decreasing the energetic cost of the process. Specifically, the effect of increasing the initial pH with and without its control during the whole electrolysis experiment is studied on synthetic solutions with concentration values similar to those present in the spent pickling baths. Finally, real SPBs are treated under pH control and the results obtained are also compared with those acquired with the direct electrolysis of these SPBs in a membrane reactor. The modification of the initial pH on synthetic solutions shows an increase in zinc deposition rate as the initial pH is risen. However, the zinc redissolution phenomenon is present during the whole experiment. On the other hand, when the pH is controlled, the results obtained are much better as zinc redissolution is prevented and the hydrogen evolution reaction rate is decreased. Comparing the behaviour between the reactor under pH control and that in the presence of an anion-exchange membrane, reflects zinc conversion values slightly higher for the membrane reactor due to the zinc precipitation occurring in the reactor under pH control, which is higher as the pH rises. However, the specific energy consumption is considerably higher in the membrane reactor mainly due to the ohmic drop introduced by the membrane.

Leaching of Zinc Ash with Hydrochloric Acid Solutions

“…To prevent any problem during zinc electrodeposition [27], solvent extraction can be used to purify the bath [28]. Literature data [29] shows that Kelex 100 can remove Fe(III) ions from acidic chloride solutions (pH 0-1), remaining zinc ions in the aqueous phase (extraction of zinc occurs at pH above 5).…”

High‐Capacity and Long‐Life Zinc Electrodeposition Enabled by a Self‐Healable and Desolvation Shield for Aqueous Zinc‐Ion Batteries

“…[6,9] The hydrogen evolution reaction (HER) accompanied by the increase of the local pH value promotes the corrosion of the Zn electrode and the formation of the Zn-contained by-products (such as Zn 4 -(SO 4 )(OH) 6 • 4H 2 O) on the surface of the anodes. [10][11][12]24] The intertwined Zn dendrite formation and sustained Zn corrosion significantly reduce the Coulombic efficiency (CE) and cycle life of the aqueous Zn batteries.…”

Entrepreneurship in the Raw Materials Sector

“…2010;. In this step, some acids, namely hydro chloric (HCl) or sulfuric (H 2 SO 4 ) acids are applied to remove the oxide layer (Abad et al 2017;Regel-Rosocka et al 2010). In practice, quite a large proportion of the products with faulty zinc coatings are returned to this step, which results in the enrichment of the pickling liquor in also zinc, beside iron, and the acid concentration decreases at the same time.…”