Study On Synthetical Utilization Of Phosphate Tailings

With the contineous mining, the rich ore resources of phosphorite in China is nearly exhausted. Phosphate tailings as one of the solid waste slag are produced from the mining process.These phosphate tailings are treated by the ways of accumulation and desertion become source of serious environmental pollution, and loss most effective composition. With the development of the times, the amount of phosphate tailings in tailings reservoirs are becoming much bigger than before, the capacity of tailings reservoirs is insufficient. It will destroy the ecological environment to newly built tailings reservoirs. So comprehensive utilization of phosphate tailings has practical significance in our daily life. It will solve environmental pollution and obtain secondary resources. The overall development and utilization of tailings can solve the problems of environment pollution and land protection, these can provide great benefit for our economy, society and environment.Work in this paper is based on the tailings of phosphorite beneficiation in Haikou, Hainan. Firstly, pretreat the tailings with acid leaching to obtain slag and filtrate. Secondly, calcine the silicon slag with sodium salt, then dissolve the slag with water and filter it to get the water solubles. Thirdly, acidize the water solubles and add the surfactant at the same time, filter and wash the production, and then calcine it to obtain the white carbon black. The useful elements magnesium and phosphorus in the acid leaching filtrate are recycled as follows: Firstly, acidize the acid leaching filtrate to remove calcium. Secondly, concentrate the filtrate twice to get the coarse magnesium sulfate, then refine the coarse magnesium sulfate. Phosphorus is enriched through circulating acid leaching, and the diammonium phosphate can be produced from wet-process phosphoric acid purified with complex salt crystallization. Magnesium removal experiment is made by DTPMP from phosphate rock, and study on waste solution from demagging phosphate.?1? Analyse the phosphate tailings with high magnesium content with XRD, XRF, SEM as well as TG, results show that the tailings mainly contains dolomite, fluorapatite, silica and phosphogypsum. The tailings can be treated as the very low-quality phosphorite ore since it has a P₂O₅ content of 10.02% and a high Mg O content of 14.5%. The surface appearance of tailings is mainly flasky or massive, and the sizes of particles are not uniform. The tailings maintains stable when the temperature is below 600?. However, if the temperature increase to 600? to 800?, sustained weight loss will happen since dolomite decomposition happens in this temperature range.?2? In order to increase the concentration of phosphorus and magnesium and improve the recovery of tailings, exploration is performed to study the process route of decomposing tailings with hydrochloric acid. Conclusion shows that condition with a raw ratio of 2.25, a reaction temperature of 60? and a reaction time of 20 min is optimal for tailings decomposition.?3? Analyse the acid leaching residue of tailings with XRD, XRF, BET, results show that dolomite and fluorapatite in tailings are decomposed completely after acid leaching treatment, remained slag is mainly silica and illite. Silica content in acid leaching residue is 78.856%. Since specific surface area and pore size of the residue are both small, postprocessing is necessary to study the adsorption thermodynamics.?4? Study on the process conditions of extraction of magnesia from phosphate tailings acidolysis solution: the results on calcium reduction by 98% sulfate acid were better than which by 50% sulfate acid, the concentration ratio at the first time is 0.65, and the second one is 0.2.?5? The concentration of P₂O₅ and Mg O of acidolysis solution and the precipitation rate of Mg SO₄ and CaSO₄ along with the cycle number increased at the same time. The precipitation rate of Mg SO₄ and CaSO₄ respectively reach 75.5% and 99.8% after 5 cycles. The concentration of Mg O in the condensed filtrate decreased with the increase of cycle number, while the concentration of P₂O₅ increased gradually, the concentration of P₂O₅ in the condensed filtrate reach about Research conclusions are as follows: 17%, which meet the requirement of extraction of phosphoric acid by organic base.?6? According to the test process and operating conditions, the silica product meet the quality requirements of GB3061-2009, the heptahydrate magnesium sulfate meet the quality requirements of the first grade of GB2680-2009, the diammonium phosphate meet the quality requirements of superior product of GB1025-2009.?7? During magnesium removal experiment, the optimal conditions are obtained: decomposing original ores in DTPMP directly, particle size 200 mesh, the terminal p H is 2, mol ratio is 2.66, reaction time is 60 min, reaction temperature is 70 ?. Under the optimum condition, eliminating ratio of magnesium is above 65%, loss rate of phosphorus is under 1.5%. The grade of phosphate rock is improved from 25.14% to 28.89% by use of DTPMP.?8? During the process of preparation of composite flame retardant, the optimal ratio of A/PER is 4:1, the optimal ratio of B/ME is 1:3. Under the optimum ratio, both the two products have a great effect on PP with 30% composite flame retardant, and UL-94 at V-0.The innovation of this paper are as follow:?1?The silicon slag and the phosphogypsum separated completely after phosphate tailings were decomposed by acid by indirect sulfuric acid method, and the sincere silicon slags are convenient for comprehensive utilization of silicon. The slag phase and liquid phase are utilized effectively which provide theoretical and testing support.?2? It is the first time for the preparation of white carbon black by silicon slag. The prepared silicon slag meet the quality requirements.?3? The diammonium phosphate was prepared from phosphate tailings with high magnesium content by cycle acid leaching and crystallization method.?4? The mid low grade phosphate rock were decomposed by organic acid and prepare of composite flame retardant from waste liquid of magnesium. Efficient and comprehensive utilization of magnesium resources is excepted to obtain.