Study On Preparation Of Electrolysis Manganese Residue Fertilizer

Heavy metal elements in electrolysis manganese residue are dangerous to human health and pollute environment. Actually, producting agriculture fertilizer with manganese residue is an effective way to resolve the problem and create economic value. According to existing researches, the calcium sulfate in electrolysis manganese residue causes soil hardened and impervious. To resolve the problem, calcium sulfate was turned into calcium carbonate. The difficulty degree of transforming calcium sulfate to calcium carbonate from thermodynamics and kinetics was discussed in this paper. The fertilizer efficiency of electrolysis manganese residue and preparation method were studied from the mechanism and experiments. According to national standards, the manganese residue fertilizers were prepared.The feasibility of transforming CaSO4to CaCO3was analysed by comparing solubility and solubility product. The result showed that it was easy for precipitation conversion. The spontaneity of the reactions between CaSO4and NH4HCO3,(NH4)2CO3, K2CO3, K2HPO4was analysed by the thermodynamic calculation. The results showed both enthalpy changes and Gibbs free energy changes were less than zero. It indicates that the reactions could happen spontaneously.The optimum reaction conditions of the reaction between CaSO4and NH4HCO3were confirmed by single factor and orthogonal experiments. The prefered conditions were showed as follows:reaction temperature is30癈, molar ratio of NH4HCO3and CaSO4is2.3:1, the reaction time is90min, the concentration of NH4HCO3solution is1.75mol/L. The best conversion of reaction reached97.01%.The influence of temperature and molar ratio of raw materials on conversion of the reactions between CaSO4and NH4HCO3,(NH4)2CO3, K2CO3, K2HPO4was investigated. The result indicated that the conversions increased with the addition of temperature and molar ratio. Reaction products were analysed by XRD, SEM. The apparent activation energy of the reactions between CaSO4and NH4HCO3,(NH4)2CO3, K2CO3were18.9296kJ/mol,18.3410kJ/mol,11.1098kJ/mol, respectively. It indicates that the reactions could happen easily and belong to diffusion-controlled reactions.According to the nutritional requirements of tea, acacia and phytolacca, five fertilizer formulases were designed by adding basic fertilizers of nitrogen, phosphorrs and potassium. Sealed placing after seven days, the compaction status was observed and the effective components were tested. The results showed that the effective phosphorus of1#fertilizer was slightly lower than the national standard and other indexes were qualified. Its content of water-soluble phosphorus was95.6%of effective phosphorus and the content of chloride ion was only2.6%. The N, P2O5, K2O contents of2#,3#and4#fertilizer reached the national standards. But their chloride ion contents were higher than3.0%.