磷石膏/固硫灰渣复合材料对铀(Ⅵ)的吸附行为及机理研究

Adsorption Behavior and Mechanism of Phosphogypsum/Sulfur-fixing Ash Composite for Uranium(Ⅵ)

为了减少磷石膏(PG)和固硫灰渣(SFA)这两种工业固体废弃物在环境中的堆积以及避免其给自然环境带来的风险,最大化降低对环境的污染,以PG和SFA为原料,采用一步高温煅烧法制备了磷石膏/固硫灰渣(PG/SFA)新型复合吸附材料,同时采用批次静态吸附法研究了PG/SFA对的铀(Ⅵ)吸附性能。并利用PG/SFA较强的亲铀特性,对铀矿开采过程中产生的铀矿坑水开展了深度净化处理应用研究。最后,结合SEM、FTIR和XRD表征手段,探讨了PG/SFA对铀的吸附机理。结果表明:在p H=6.0、吸附剂PG/SFA投加量0.02g、吸附时间60min、铀初始浓度125mg/L、吸附温度40℃的条件下,PG/SFA对铀的吸附量可达84.6mg/g;PG/SFA对铀的吸附符合准二级动力学模型和Langmuir等温吸附模型;水中共存阴、阳离子(Ba^(2+)、Sr^(2+)、Ni^(2+)、Ca^(2+)、Cl~-、NO_(3)^(-)、CO_(3)^(2-)、F~-)对PG/SFA吸附铀的性能基本无影响。在真实铀矿坑水中,PG/SFA对铀的去除率可达99.8%,分配系数(K_d)高达1.46×10~6m L/g,出水铀浓度低至0.003mg/L。PG/SFA对铀的吸附机理主要为PG/SFA中的Ca^(2+)和PO_4^(3-)与UO_(2)^(2+)发生沉淀反应,并进一步在PG/SFA表面生成钙铀云母Ca(UO_(2))_2(PO_4)_2·3H_2O矿相结构。研究表明,利用工业固废磷石膏和固硫灰渣可作为铀矿坑水的高效吸附材料,从而实现“以废治废”的目标。

In order to reduce the accumulation of phosphogypsum(PG)and sulfur-fixing ash(SFA)in the environ-ment,avoid the risks to the natural environment and minimize the environmental pollution,a new composite adsorption material of phosphogypsum/sulfur-fixing ash(PG/SFA)was prepared by one-step high-temperature calcination method with PG and SFA as raw materials,and the uranium[U(Ⅵ)]of PG/SFA was studied by batch static adsorption method.Based on the strong U(Ⅵ)affinity of PG/SFA,the deep purification treatment of uranium mine water produced in the process of U(Ⅵ)mining was studied.Finally,the adsorption mechanism of PG/SFA for U(Ⅵ)was discussed by means of SEM,FTIR and XRD.The results show that the adsorption capacity of PG/SFA for U(Ⅵ)can reach 84.6 mg/g under the conditions of pH of 6.0,PG/SFA adsorbent dosage of 0.02 g,adsorption time of 60 min,initial concentration of U(Ⅵ)of 125 mg/L and adsorp-tion temperature of 40℃.The adsorption of U(Ⅵ)by PG/SFA accords with pseudo-second-order kinetic model and Langmuir isothermal adsorption model.The coexistence of anions and cations(Ba^(2+),Sr^(2+),Ni^(2+),Ca^(2+),Cl-,NO_(3)^(-),CO_(3)^(2-),F^(-))in water has little effect on the U(Ⅵ)adsorption performance of PG/SFA.In real uranium mine water,the removal rate of U(Ⅵ)by PG/SFA can reach 99.8%,the distribution coefficient(Kd)is as high as 1.46×106 mL/g,and the effluent U(Ⅵ)concentration is as low as 0.003 mg/L.The adsorption mechanism of U(Ⅵ)by PG/SFA is mainly that Ca^(2+)and PO3-4 in PG/SFA react with UO^(2+)2 by precipitation,and then autunite Ca(UO_(2))2(PO4)2·3H2O mineral phase structure is formed on the surface of PG/SFA.Therefore,the utilization of industrial solid waste phosphogypsum and sulfur-fixing ash can be used as efficient adsorption materials for uranium mine water,thus achieving the goal of"treating waste with waste".