Hazardous jarosite use in developing non-hazardous product for engineering application

Jarosite released from zinc metal extraction process is hazardous in nature and its world wide disposal has become a major environmental concern. In this study, an attempt has been made to immobilise and recycle the jarosite released from Hindustan Zinc Limited, India, using CCRs, so called fly ash, and clay soil. Results revealed that the particle size of jarosite was finer than that of CCRs and had higher porosity and water holding capacity due to fine textured materials resulting in high surface area (10,496.18 ± 30.90 cm2/g). Jarosite contain higher concentration of toxic elements (lead, zinc, sulphur, cadmium, chromium and copper) than that of CCRs. Concentrations of radionuclides such as 226Ra, 40K and 228Ac in jarosite found less than in CCRs are similar to that of soil. Statistically designed experiments on solidified/stabilised (s/s) sintered jarosite-CCRs products confirmed that the compressive strength of jarosite bricks reached as high as 140 kg/cm2 with 14.5% water absorption capacity at the combination of 3:1 ratio of jarosite and clay, respectively, but, concentrations of all the toxic elements recommended by United States Environmental Protection Agency (USEPA)-Toxicity Leachate Characteristics Procedure (TCLP) standard are not within the permissible limits. However, it is confirmed that the toxic elements leaching potentials of s/s-sintered products developed using 2:1 jarosite clay ratio with 15% CCRs comply with the USEPA-TCLP limits and also meet the quality for engineering applications.