Studying the extraction of heavy-metal ions from galvanic wastewater by reagent method

Abstract

This paper presents the study of the possibility to increase the extraction degree of heavy metal ions (HMIs) from two types of galvanic wastewater (GWW 1 and GWW 2) by the reagent method. It is established that, as a result of interaction between GWW 1 components and Na2S pentahydrate, the largest amounts of the resultant precipitate were registered in alkaline medium, which is 13.4 and 91.5% greater than in neutral and acidic media, respectively. A greater precipitate weight increase was observed when using 0.7% of Na2S pentahydrate in alkaline medium than when using 0.14% of that solution. The following efficient conditions are determined for removing HMIs from GWW 1 by the reagent method: Na2S pentahydrate solution concentration of 0.7%; volumetric reagent/GWW ratio: 1:42; alkaline medium; and retention time of 20 minutes. Implementing the method proposed allows achieving the extraction degree of 99.97% for Cu2+ ions and 99.93% for Ni2+ ions. A greater efficiency of extracting HMIs from GWW 2 was identified with adding Na2CO3, as compared to Ca(OH)2 when depositing for 25 minutes. Implementing the technique proposed for cleaning of GWW 1, GWW 2 from HMIs leads to achieving the standards of threshold limit values for fishery water bodies.