Extraction technology of zinc from pyrolysis carbon black ash residue of waste tires

Waste tires were pretreated with kerosene, then pyrolyzed to form carbon black, and then calcined to form ash. The extraction of zinc from ash after calcination of waste tires pyrolyzed carbon black was studied. The zinc was finally recovered as zinc oxide by acid dissolution-step precipitation method. Four kinds of inorganic acids (HCl, HNO₃, H₂SO₄ and acetic acid) were used to acid dissolve the ash, and it was found that hydrochloric acid had the best acid dissolution effect on the ash. On this basis, the effects of acid concentration, liquid-solid ratio (acid volume/carbon black mass), leaching time, acidolysis temperature and other factors on the leaching effect of zinc ions were investigated. The optimal technological conditions for zinc leaching were as follows: acid concentration 2 mo1/L, temperature 20 ℃, leaching time 60 min and liquid-solid ratio 6:1 mL/g. Under these conditions, the leaching rate of zinc ions was about 91.4%. After precipitation and calcination of filtrate by step precipitation method, zinc oxide product with purity of about 98.2% was obtained, and the extraction rate of zinc from ash was about 81.4%.