镧改性沸石对太湖底泥-水系统中磷的固定作用

考察了不同反应时间、pH值、硅酸根离子浓度、DO浓度、老化时间以及初始磷浓度等条件下一种新型底泥改良剂-镧改性沸石对太湖底泥-水系统中磷的固定作用.当水中磷浓度很低时,太湖底泥和镧改性沸石改良太湖底泥均释放出磷.镧改性沸石改良太湖底泥的释磷量少于太湖底泥.镧改性沸石改良太湖底泥中金属氧化物结合态磷(NaOH-P)和钙结合态磷(HCl-P)等较为稳定形态磷含量多于太湖底泥,而镧改性沸石改良太湖底泥中氧化还原敏感态磷(BD-P)这种不稳定形态磷含量少于太湖底泥.太湖底泥和镧改性沸石改良太湖底泥对水中较高浓度磷酸盐的吸附平衡数据均可以采用Langmuir等温吸附模型加以描述.镧改性沸石改良太湖底泥对水中磷酸盐的吸附能力明显高于太湖底泥,且吸附能力随老化时间的增加而降低.被镧改性沸石所吸附的磷酸盐主要以NaOH-P和HCl-P等较为稳定形态磷存在,不容易被重新释放出来.上述结果表明,采用镧改性沸石对太湖底泥进行原位改良可以增强太湖底泥对磷的固定能力,减少太湖底泥磷的释放.

Immobilization of phosphorus in Taihu Lake sediment-water systems by lanthanum-modified zeolite

In-situ sorbent amendment is a promising contaminated sediment remediation technology. The immobilization of phosphorus (P) in Taihu Lake sediment-water systems using lanthanum-modified zeolite (LaMZ) as a novel amendment was investigated by conducting a series of experiments. P could be released from unamended and LaMZ-amended Taihu Lake sediments at a very low initial concentration of P in water. The amount of P released from LaMZ-amended Taihu Lake sediment was less than that from Taihu Lake sediment. The content of NaOH-P (P extracted with NaOH) or HCl-P (P extracted with HCl) in LaMZ-amended Taihu Lake sediment was higher than that in Taihu Lake sediment. The content of BD-P (P extracted with bicarbonate dithionite) in LaMZ-amended Taihu Lake sediment was less than that in Taihu Lake sediment. The equilibrium sorption of phosphate from aqueous solution at a high initial concentration of P (0.5~15mg/L) could be described by the Langmuir isotherm model. The phosphate sorption capacity for LaMZ-amended Taihu Lake sediment was much higher than that for Taihu Lake sediment. The phosphate sorption capacity for LaMZ-amended Taihu Lake sediment decreased with increasing aging time. Sequential extraction of P from phosphate-sorbed Taihu Lake sediment and LaMZ-amended Taihu Lake sediment indicated that most of sorbed phosphate onto LaMZ existed in NaOH-P and HCl-P forms, and was relatively stable and unlikely to be released under anaerobic condition. Results of this work indicate that in-situ LaMZ amendment is a promising method for controlling P release from Taihu Lake sediment.