Calcium sulphate recovery from solid waste generated at primary zinc process

Carolina Bittencourt de Abreu, Afonso Henriques Martins


Slurry generated at primary zinc process by a hydrometallurgical route presents metal species precipitated and substantial calcium sulfate (CaSO4). This paper presents the experimental results for acid leaching, using H2SO4, and recovery of CaSO4, for subsequent industrial use. The influence of the variables time and temperature of leaching, leach pulp density and concentration of sulfuric acid in the extraction of CaSO4 has been evaluated by a statistical approach using the Complete Factorial Method at two levels. Optimum experimental conditions for the maximum extraction of CaSO4 from the residue sample (leaching during 45 minutes, temperature at 45±2ºC, leach pulp density at 10g/l and sulfuric acid concentration at 0.33M), were determined from experimental results by the Statistical Method of the Ascending Step. It was recovered 32% of CaSO4 from the leach liquor of sulfuric acid leaching under optimized conditions. The sample of CaSO4 recovered from the residues was characterized technologically and it presented lower impurities content than standard samples of CaSO4 used in the agriculture and building materials industry.

Key words: calcium sulfate, leaching, recovery, characterization.

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ISSN: 1808-7310 - Best viewed in Mozilla Firefox

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