Synthesis of manganese zinc ferrite using ferrous pickle liquor and pyrolusite ore

The possibility of utilizing hydrochloric acid-based waste pickle liquor (WPL) and medium-grade pyrolusite ore to synthesize manganese zinc ferrite was explored. The excess acidity of the WPL was neutralized using mild steel turnings. The unreacted mild steel scrap and suspended solids were removed by filtration. Partial precipitation technique was employed to reduce the impurities. The purified WPL was treated with medium-grade pyrolusite ore to prepare the leach liquor to which the required quantities of ferrous chloride and zinc granules were added to maintain stoichiometry in the resultant compound. The hydroxy carbonate of manganese, zinc and iron was precipitated by the addition of a hot solution (70°C) of sodium carbonate (20% v/v), which upon sintering in argon atmosphere yielded manganese zinc ferrite. The addition of sodium lauryl sulfate (SLS) helped in preventing agglomeration of the particles. Sintering at 450°C for 30 min in argon atmosphere has resulted in mixed phases of (Zn,Mn,Fe) (Fe,Mn)₂O₄ and Mn₃O₄, which indicates lack of phase purity. Sintering at temperatures higher than 950°C for 5 h in argon atmosphere enabled complete ferritization. The extent of ferritization was found to be a function of sintering time at 950°C. The manganese zinc ferrites synthesized using WPL and medium-grade pyrolusite ore exhibited soft magnetic characteristics.