| Boron slurry is one of main waste in boron industry. With the development of boron industry and the growing demand of borax and boric acid in china, the dumping of boron slurry also increases with years, which not only engrosses a great deal of the soil, but also produces severe contamination to environment. Boron slurry is a rich source of magnesium. Usually, the content of MgO in boron slurry exceeds 30%. The massive dumping of boron also makes a large waste of the magnesium resource. So looking for suitable method for recycling and utilizing magnesium in boron slurry can not only solve environment pollution problems but also make good use of magnesium resource and gain tremendous economic benefit. In this thesis, the recovery and utilization of magnesium in boron slurry was researched, and a new method of leaching magnesium from boron slurry was developed, which had a large handling capacity, simple process and lower cost. Then magnesium sulfate products such as fertilizer-grade magnesium sulfate, technical-grade magnesium sulfate and magnesium hydroxide sulfate hydrate (MHSH) whiskers were prepared. The concrete research contents are as follows.(1).New process of leaching magnesium from boron slurry was researched. The process conditions of leaching magnesium by heap leaching method and pond leaching method had been researched. The result shown that pond leaching method excelled the heap leaching method, which had higher leaching rate of magnesium from boron slurry and milder reaction rate. The optimal conditions of leaching Magnesium were concluded as follow:the concentration of sulfuric acid is about 14%, the amount of sulfuric acid is 110% of the theoretical value; leaching time is about 5 days.(2).Magnesium sulfate products such as fertilizer-grade magnesium sulfate and technical-grade magnesium sulfate were prepared. The leaching solution made from boron slurry contained some impurities such as iron, manganese, aluminium and so on. The magnesium sulfate obtained without purification contained 15.24%of MgO and 32.72% of SO3, which had met the demand of magnesium sulfate fertilizer. Using ammonium peroxydisulfate and light-magnesia as purifying auxiliaries, magnesium sulfate obtained after purification excelled the first-grade product of technical-grade magnesium sulfate, what's more, the content of iron and manganese impurities were both under 5 ppm, which had met the requirement of Analytical reagent standard.(3).The chemical reaction system and process conditions of MHSH whiskers were researched. Using the self-made high purity magnesium sulfate as raw mterial, MHSH whiskers were synthesized via a hydrothermal method at. The influential factors of magnesium hydroxide sulfate hydrate crystal growth, such as alkali source, reactants concentration, reactants proportion, hydrothermal temperature, reaction time, and so on, had been researched. And the best reaction system of MHSH whiskers preparation—magnesium sulfate and light-magnesia, was selected through experiments. The optimal conditions were: the concentration of magnesium sulfate in the slurry is 0.60mol/L, the reactants proportion is n(MgSO4):n(MgO)=2:1, the hydrothermal temperature is 180℃, and the reaction time is 6h.(4).The improvement of MHSH whiskers morphology was researched. The sector-like whiskers were inhibited through adding organic alcohol, and MHSH whiskers with a well dispersion and morphology were obtained. The MHSH whiskers obtained had a diameter of about 1μm and a length of 30～50μm, were smaller than which obtained without adding organic alcohol, but the structure of MHSH whiskers didn't changed.
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