利用铁改性方解石作为活性覆盖材料控制水体内源磷的释放

虽然利用方解石作为一种活性覆盖材料控制水体内源磷释放具有较好的应用前景,但是其控制底泥中磷释放的效率仍然有待进一步提高.鉴于此,本文采用铁盐对方解石进行改性试图制备一种除磷性能更好的底泥活性覆盖材料——铁改性方解石,进而通过批量实验考察了铁改性方解石对水中磷酸盐的去除性能,以及通过底泥培养实验考察了铁改性方解石活性覆盖控制水体内源磷释放的效率.结果发现,采用铁对方解石进行改性,可以显著提高材料对水中磷酸盐的去除能力.铁改性方解石投加量的增加,有利于水中磷酸盐的去除.增加初始磷浓度,铁改性方解石对水中磷酸盐的单位去除量随之增加,最大的单位磷去除量可以达到3.09 mg·g~(-1).铁改性方解石覆盖可以有效地控制底泥中磷的释放,导致上覆水体中溶解态活性磷(SRP)浓度处于很低的水平.此外,铁改性方解石覆盖还可以促使底泥中少量的氧化还原敏感态磷(BD-P)和金属氧化结合态磷(NaOH-rP)向残渣态磷(Res-P)转变,使得底泥中磷的稳定性略微增强.固定到铁改性方解石覆盖层中的磷大多数(90.8%)以较为稳定和非常稳定的形态存在,且大部分磷以非生物可利用性磷形式存在,很难被重新释放出来.与方解石覆盖相比,铁改性方解石覆盖控制底泥中磷向上覆水体中释放的效率明显更高,且被铁改性方解石覆盖层所钝化的磷更为稳定.以上结果显示,铁改性方解石是一种非常有希望用于控制水体内源磷释放的底泥活性覆盖材料.

Use of Iron-modified Calcite as an Active Capping Material to Control Phosphorus Release from Sediments in Surface Water Bodies

The use of calcite (CA) as an active capping material has high potential for controlling the release of phosphorus (P) from sediments, but its efficiency still needs to be enhanced. To address this issue, an iron-modified CA (Fe-CA) was prepared, the removal performance of phosphate from aqueous solution by Fe-CA was studied, and the efficiency of the use of Fe-CA as an active capping material to prevent the liberation of P from sediments was investigated. The results showed that Fe-CA exhibited much higher phosphate removal ability than CA. The phosphate removal efficiency of Fe-CA increased with an increase in the Fe-CA dosage. Increasing the initial phosphate concentration gave rise to an increase in the amount of phosphate removed by Fe-CA, and the maximum amount of phosphate removed by Fe-CZ reached 3.09 mg·g^-1. Sediment capping with Fe-CA could effectively control the release of soluble reactive P (SRP) from the sediment into the overlying water, leading to a very low concentration of SRP in the overlying water. Additionally, the Fe-CA capping also resulted in the transformation of a small amount of redox-sensitive P (BD-P) and metal-oxide-bound P (NaOH-rP) in sediments to residual P (Res-P), leading to a slight increase in the stability of P in the sediment. The overwhelming majority (90.8%) of P bound by the Fe-CA capping layer existed in the form of NaOH-rP, calcium-bound P (HCl-P), and Res-P, which are relatively very stable. Furthermore, the percentage of bioavailable P (BAP) as a proportion of total extractable P in the P-bound Fe-CA capping layer was very low, and the bound P was re-released with difficulty into the water column for algae growth. Compared to CA capping, the efficiency for the control of sedimentary P release into the overlying water by Fe-CA capping was much higher, and the stability of P bound by the Fe-CA capping layer was also higher. The results of this work indicate that Fe-CA is a very promising active capping material for the interception of the release of P from sediments into the overlying water.