磷石膏脱硫钙渣浸取液中杂质对碳酸钙晶型的影响

摘要

磷石膏脱硫钙渣是磷石膏化学分解后产生的以氧化钙为主要成分的尾渣。以氯化铵溶液浸取磷石膏脱硫钙渣并碳化浸取液以制备轻质碳酸钙是一种有效利用磷石膏脱硫钙渣中钙资源的方法。本文分析了该方法在不同氯化铵浓度下浸取液的组成、钙浸出率及pH，同时为了研究浸取液中NH4+、铁、铝、镁等对产品碳酸钙晶型的影响，配制了含有杂质离子的NH4Cl–NH3·H2O溶液，比较了其碳化产品与相同条件下脱硫钙渣碳化产品的晶型差异。结果表明，随氯化铵浓度升高，浸取液pH降低，铝含量降低，铁、镁含量升高。在氯化铵浓度范围内， NH4+对球霰石形成有促进作用，而铁、镁杂质对方解石形成有促进作用，由于铝离子存在形态不同，铝在1mol/L时对形成球霰石有促进作用，在大于1mol/L时对形成方解石有促进作用。当氯化铵浓度小于4mol/L时，各种杂质相互作用形成球霰石晶型，氯化铵浓度等于4mol/L时，各种杂质相互作用形成球霰石和方解石混合晶型。%Phosphogypsum(PG)desulfurization slag is the residue from chemical decomposition of PG, of which the main component is CaO. Leaching PG desulfurization slag with an ammonium chloride solution and carbonating with CO2 to prepare calcium carbonate is an effective way to utilize the calcium in the slag. In this paper,the composition,calcium leaching rate and pH of leaching liquid in different concentrations of ammonium chloride were analyzed. To find out the influence of ions such as ammonia,iron,aluminum and magnesium in the leaching liquid on the crystal form of calcium carbonate,NH4Cl-NH3·H2O solution containing impure ions were prepared and the XRD crystal forms of products were compared with the products obtained by PG desulfurization slag under the same conditions. It turned out that with the increasing of ammonium chloride concentration,pH value and content of aluminum decreased,while the content of iron and magnesium increased. Within the scope of the concentration of ammonium chloride,NH4+has a promoting effect on the formation of vaterite; iron and magnesium facilitate the formation of calcite. Because aluminum’s form is different with the increasing of ammonium chloride concentration,aluminum facilitates the formation of vaterite when the concentration of ammonium chloride was 1mol/L,but facilitates the formation of calcite when the concentration of ammonium chloride was up to 1mol/L. The interaction of impurities made the crystalform of vaterite when the concentration of ammonium chloride was below 4mol/L. However,when the concentration of ammonium chloride was 4mol/L,the interaction of impurities made the product a mixture crystal form of vaterite and calcite.