Ferrous sulphate (FeSO 4 ) is a kind of salt with many applications in medicine and agriculture. It is used for the treatment of iron deficiency in the pharmaceutical industry and as fertilizer in agriculture. Convertor sludge is a residual in the steel industry that is produced by the oxidation of iron in LD convertors and is separated by spraying water in a venturi. Due to the high iron content in this material and also to reduce waste steel residual, this study was conducted to produce iron sulphate from it. The main purpose of this study was to produce the sulfate salts of ferrous and ferric species from the leaching solutions of the sludge of Esfahan Zob-Ahan in laboratory scale. In this regard, the experimental conditions and critical parameters of ferrous sulphate crystallization process were investigated. In the first stage, the reduction of ferric iron into ferrous iron in the leach solutions was conducted. Various reductants such as metallic iron powder, iron sponge powder, in place-made SO 2 gas and sodium metabisulphate were used to convert the leached ferric iron to ferrous iron. The results showed that metallic iron, SO 2 gas and sodium metabisulphate were not effective reductants during the atmospheric pressure and themperature of up to 90?C. The rate and the extent of iron reduction for these materials were at a low level. Results showed that the pwdere of sponge iron which was a by-product of Zob Ahan Complex and could not be used in the industrial steel making process was a suitable ferric reductant. The rate and extent of iron reduction was at a high level and the concentration of iron ions were increased in the leach soloutions which was suitable in the crystallization process. Multi-stage evaporation-crystallization method was employed for the production of pure ferrous sulphate crystals. The analysis of the final product by X-ray floursence and X-ray diffractometery showed that the product can be used in the agricultural apllications. In addition, in order to generate ferric sulphate crystalls, hydrogen peroxide was used in the leach stage. The results showed that ferric sulphate could be successfully produced from the leach soloutions of LD-sludge.
