磷酸盐通过不溶性金属磷酸盐沉淀而被广泛应用于镉、铅污染土壤的稳定修复.但是,环境中磷含量的增加会引起新的污染,而缓释磷酸盐因兼具稳定重金属和降低二次污染风险的特性而备受关注.本文制备了一种新型的缓释磷酸盐固定剂(SRPA),对其进行了BET,SEM,FTIR,溶胀率,磷含量等表征.结果表明,SRPA是一种内部具有网状结构的球体,除磷酸盐外,还含有羟基,羧基和其他官能团,比表面积为5~7.18 m2/g.SRPA的磷酸盐含量从5%增加到8%,Korsmeyer-Peppus模型表明,non-Fickian扩散过程对磷酸盐的释放起着主要控制作用.将SRPA应用于土壤后,我们发现与传统的磷酸盐改良剂相比,土壤中水溶性磷的浓度大大降低.SRPA比传统的磷酸盐改良剂对土壤的修复效果更好.水溶性镉(Cd)和铅(Pb)的修复效率分别从68.57%提高到97.09%,和从76.9%提高到97.89%.可生物利用的Cd和Pb分别从63.09%增加到71.85%,和从66.21%增加到76.47%.提取物的实验结果表明,随着残留重金属的增加,修复后土壤中重金属的可交换和碳酸盐结合的含量显着降低,表明重金属的稳定性增加.
Phosphate is widely used to immobilize cadmium (Cd) and lead (Pb) in soils through the insoluble metal phosphate precipitation. However, an increase in the phosphorus content of the environment can cause new pollution. In this study, five slow-release phosphate amendments (SRPAs) were synthesized and their characteristics including BET, SEM, FTIR, swelling ratio, and thephosphorus release were determined. The results show that SRPA was a sphere with a network structure with a specific surface area of 5 to 7.18 m2/g andcontained phosphate, hydroxyl, carboxyl and other functional groups. Among five SRPAs, S3 sample showed good performance for phosphate release. Phosphate release from SRPA was well fitted with Ritger-Peppas model with constant n between 0.45 and 0.85, indicating that the phosphate release was in accordance with non-Fickian diffusion. As compared with monocalcium phosphate (MCP), SRPA application led to a lower concentration of water-soluble phosphorus in the soil sample and higher remediation efficiencies of Cd and Pb. The remediation efficiencies of water-soluble Cd and Pb in soil with SRPA were 97.1%and 97.9%, respectively. The remediation efficiencies of bioavailable Cd and Pb were 71.85%and 76.47%, respectively. The results of Tessier extraction showed that the exchangeable and carbonatebound fractions of Cd and Pb in the soil sample after SRPA application significantly reduced,while the residual fraction increased, indicating the stability of heavy metals increased.