Comprehensive Utilization Of Phosphate Tailings From Reverse Floatation

Phosphate tailings is the solid waste generated in the phosphate beneficiationprocess, it occupies a large area of land, pollutes the environment and causes a waste ofresources. In this paper, two kinds of phosphate tailings were researched, combining withtheir physical and chemical properties, the comprehensive utilization methods werecarried out: to magnesian phosphate tailings which has high dolomite content, it wasused to recovering light magnesium carbonate and the filter residue was used forlimestone admixture in concrete. To those hyperphosphate phosphate tailings with highcellophane content, with the preparation of light calcium carbonate and light magnesiumcarbonate, at the same time, the containing collophanite was recycled.The step by step decomposition characteristics of dolomite in phosphate tailings wasclarified by the method of thermal analysis combining with calcinations experiments firstof all during the research. Then the best calcination condition of phosphate tailings wasobtained. The optimum calcining conditions of magnesian phosphate tailings wascalcining temperature750℃holding60minutes, the mainly calcination product wereCaCO3and MgO. The best calcining process of hyperphosphate phosphate tailings wascalcining temperature850℃holding60minutes, the mainly calcination product wereCaO, MgO and apatite.By single factor analysis and orthogonal experiments, the optium experimentalconditions of recycling MgO from magnesian phosphate tailings to prepare lightmagnesium carbonate were with the liquid-solid ratio of7:1, adding some organic aminewith the concentration of6×10-2mol/L, at the reaction temperature of70℃with40minutes, the percent yield of light mangnesium carbonate can reach62.4%. The lightmagnesium carbonate product had good crystallinity and high purity, the particle size ofit was uniform and the average size was400nm. The residue after recovering MgO wasused to preparing concrete. It improved the early strength of the concrete block by adding15%residue of external blending method but had little influence on the late strength. Theaffection on the early and late strengths of the concrete block was very small by adding 20%of the residue with internal blending method.In the experiments of comprehensive recycling magnesium and calcium fromhyperphosphate phosphate tailings, at the calcium oxide recovery phase, the optimumprocesses by ammonia leaching method to prepare light calcium carbonate from CaOwere, with liquid-solid ratio of8:1, ammonium to calcium ratio of2.1, reactiontemperature of30℃，reaction time of25minutes. The optimum conditions of preparelight magnesium carbonate from MgO were, the liquid-solid ratio of8:1, reactiontemperature of70℃, reaction time of40minutes. the percent yield of light calciumcarbonate and light mangnesium carbonate reached81.16%and57.58%respectively.The light calcium carbonate product was spherical particles for good crystallinity, highpurity and uniform particle size distribution with the average particle diameter800nm.The mainly crystal morphology of the light magnesium carbonate product was sphericaland the component of it was relatively single. The particle size distribution of it wasuniform with the average diameter of900nm. The main mineral component of theresidue after recovering calcium and magnesium was collophanite with P2O5contentreaching33.8%. It had reached the requirement of the high grade phosphate rock.Therefore, the resource utilization of phosphate tailings was realized in this study basedon the physical and chemical properties of reverse flotation phosphate tailings.