Spent pickling effluents coming from hot-dip galvanizing processes contain high amounts of zinc and other metallic compounds in hydrochloric acid media. Thus, the effluent has a strong hazardous character and needs to be treated before disposal. Emulsion pertraction (EPT) with hollow fiber modules, can be considered as a clean alternative able to carry out the separation and recovery of zinc. After demonstrating the viability of EPT for the treatment of this kind of effluents in previous works using tributyl phosphate (TBP) as extractant agent and service water as back-extraction agent, several experiments were performed to analyse the influence on the extraction (EX) and back-extraction (BEX) kinetics of the main operation variables: (i) initial zinc concentration in the aqueous feed phase, (ii) organic phase/stripping phase volume ratio in the emulsion stream and (iii) emulsion volume.