Recovery of zinc from galvanizing dross by a method of super-gravity separation

The hot dip galvanizing dross is a valuable by-product because it contains high levels of zinc, motivating a search for processes or technologies to allow the cost-effective recovery of the zinc content. In this work, the feasibility of recovering zinc from an industrial galvanizing dross by a novel method of super-gravity separation was investigated. The effects of gravity coefficient (G), separation time (t) and separation temperature (T) on the separation efficiency were evaluated. When the gravity coefficient was higher than 15, the galvanizing dross samples were separated into two parts, i.e. the upper residue and the lower filtered zinc. The majority of the dross particles were retained in the upper residue and the filtered zinc was purified significantly. At G ≥ 500, t ≥ 180 s and T = 510 °C, over 79 wt% zinc was recovered with a high purity of about 99 wt%. Increasing gravity coefficient and separating time favored the zinc recovery, but at G ≥ 500 and t ≥ 60 s, the zinc recovery increased at a very limited rate. Increasing separating temperature benefited the zinc recovery but reduced the iron removal. Also, cake mode filtration was determined to be the dominant mechanism of the super-gravity separation of galvanizing dross in this work. •Metallic zinc was recovered from a galvanizing dross by super-gravity separation.•The majority of Zn-Fe-Al intermetallic compounds were removed.•At optimal conditions over 79 wt% zinc was recovered with a high purity of 99 wt%.•Cake mode filtration was determined to be the dominant mechanism.