羟基磷灰石改性膨润土对铀的吸附效果及其机制

Study on adsorption effect and mechanism of uranium by hydroxyapatitemodified bentonite

伴随我国核能的开发与高效利用,铀已成为我国地表水、地下水和土壤的常见污染物之一,从含铀废水中去除U(VI)已成为亟需解决的环境问题。本工作以膨润土(BTN)、磷酸氢二钠、硝酸钙为原料,采用简单易行的一步水热法成功制备出羟基磷灰石(HAP)改性膨润土复合材料(HAP/BTN)。考察了HAP/BTN对水溶液中铀的吸附性能,利用单因素试验和正交试验探讨了pH、转速、温度、投加量、时间对吸附性能的影响。试验结果表明,在p H=6.0、转速=100 r·min^(-1)、室温(298.15 K)、HAP/BTN投加量1 g·L^(-1)、吸附时间t=30 min时,该吸附材料对10 mg·L^(-1)含铀废水的去除率可达98%,最大吸附量为186.45 mg·g^(-1)。吸附过程更符合Langmuir模型和准二级动力学,热力学参数表明HAP/BTN对铀的吸附是自发吸热的过程,结合XPS及XRD的结果证实了HAP/BTN吸附铀主要归因于络合反应、化学吸附、静电吸附和离子交换作用。

With the development and efficient utilization of nuclear energy in China,uranium has become one of the common pollutants in surface water,groundwater and soil.The removal of U(VI)from uranium-containing wastewater has become an urgent environmental problem to be solved.Hydroxyapatite modified bentonite composite hydroxyapatite modified bentonite(HAP/BTN)was successfully prepared by a simple one-step hydrothermal method using bentonite,disodium hydrogen phosphate and calcium nitrate as raw materials.The adsorption performance of HAP/BTN on uranium in wastewater was investigated.The effects of pH,rotation speed,temperature,dosage and time on the adsorption performance were discussed by orthogonal test.The results showed that under the conditions of pH=6.0,rotation speed=100 r·min^(−1),room temperature(298.15 K),HAP/BTN dosage of 1 g·L^(−1) and adsorption time t=30 min,the removal rate of 10 mg·L^(−1) uranium-containing wastewater could reach 98%,and the maximum adsorption capacity was 186.45 mg·g^(−1).The adsorption process was more in line with the Langmuir model and pseudo-second-order kinetics.Thermodynamic parameters show that the adsorption of uranium on HAP/BTN was a spontaneous endothermic process,combined with XPS and XRD results,confirmed that the adsorption of uranium by HAP/BTN was mainly attributed to complexation reaction,chemical adsorption,electrostatic and ion exchange.