铝和锆改性沸石对太湖底泥-水系统中溶解性磷酸盐的固定作用

通过试验方法考察了2种不同底泥改良剂(铝和锆改性沸石)对太湖底泥-水系统中SRP(可溶解性磷酸盐)的固定作用. 改性沸石改良前后太湖底泥对水中较高浓度磷的吸附平衡数据可用Langmuir和Freundlich等温吸附方程进行描述,吸附动力学过程可用准二级动力学模型进行描述. 太湖底泥、铝和锆改性沸石改良太湖底泥的最大磷吸附量分别为395、613和1 009 mg/kg. 被改良太湖底泥中,铝改性沸石所吸附的磷主要以NaOH-rP(NaOH提取态磷)形态存在,锆改性沸石所吸附的磷主要以NaOH-rP和Res-P(残渣态磷)形态存在. 当水中初始ρ(SRP)很低时,太湖底泥和改性沸石改良太湖底泥均释放出磷,其中后者的释磷量较低. 改性沸石改良太湖底泥中的w(BAP)(BAP为生物有效磷)低于太湖底泥,w(liable-P)(liable-P为弱吸附态磷)也明显偏低. 铝改性沸石改良太湖底泥中的w(BD-P)(BD-P为氧化还原敏感态磷)与太湖底泥相比差异不显著,而锆改性沸石改良太湖底泥中的w(BD-P)明显低于太湖底泥. 可见,铝和锆改性沸石均可用于控制太湖底泥磷的释放,其中锆改性沸石的控制效果更好. 

Immobilization of Phosphate in Taihu Lake Sediment-Water Systems Using Aluminum-Modified Zeolites and Zirconium-Modified Zeolites as Amendments

Adding sorbents to sediments has been suggested as an effective technology for contaminated sediment remediation. In this study, two types of modified zeolites, including aluminum-modified zeolites (AlMZs) and zirconium-modified zeolites (ZrMZs) were prepared and used as sediment amendments to control the release of phosphorus (P) from Taihu Lake sediments. The sorption of phosphate-P from Taihu Lake sediment-water systems on AlMZs and ZrMZs was investigated through a series of experiments. The Langmuir and Freundlich isotherm models were found to be quite useful to describe the sorption equilibrium data of P on the raw and amended sediments at a high initial P concentration (1-10 mg/L). The sorption kinetics of phosphate on the raw and amended sediments followed a pseudo-second-order model. Based on the Langmuir isotherm model, the maximum phosphate-P sorption capacities for the raw, AlMZs-amended and ZrMZs-amended sediments were 395,3 and 1009 mg/kg, respectively. Sequential extractions of P from the raw and amended sediments after phosphate sorption indicate that most of phosphate sorbed by AlMZs existed in the form of NaOH-rP (P extracted with NaOH), and most of phosphate sorbed by ZrMZs existed in the forms of NaOH-rP and Res-P (residual P). Phosphate-P could be released from the raw and amended sediments at a very low concentration of P in water. The amount of phosphate-P released from the modified zeolites-amended sediment was less than that from the raw sediment. The contents of bioavailable P including water-soluble P (WSP), readily available P (RDP), NaHCO₃-extractable P (olsen-P) and algal-available P (AAP) in the sediments reduced after the sediments were mixed with AlMZs or ZrMZs, making P in the sediments more stable. The content of liable-P (P extracted with NH₄Cl) in the modified zeolites-amended sediment was less than that in the raw sediment. The content of BD-P (P extracted with bicarbonate dithionite) in the raw sediment was higher than that in the ZrMZs-amended sediment, but was no significant difference to that in the AlMZs-amended sediment. Results of this work indicate that AlMZs and ZrMZs are promising amendments for controlling phosphate-P release from Taihu Lake sediments, and ZrMZs are more suitably used as sediment amendments to control phosphate-P release than AlMZs.