College of Environmental Science and Engineering, Hunan University, Changsha, 410082, Hunan, China.
Key Laboratory of Environmental Biology and Pollution Control (Hunan University), Ministry of Education, Changsha, 410082, Hunan, China.
Environ Sci Pollut Res Int. 2020 Jan;27(3):2786-2796. doi: 10.1007/s11356-019-07140-4. Epub 2019 Dec 13.
The effects of humic acid (HA) and its different molecular weight (MW) fractions on the sedimentation of nanoscale zero-valent iron (NZVI) in the absence and presence of cations (i.e., Na/Mg/Ca) were investigated. Ultrafiltration (UF) was used as the method of fractionation to obtain four different MW fractions (separated by ultrafiltration membranes of 10 kDa, 50 kDa, and 100 kDa). Differing sedimentation behavior was observed for NZVI with different MW fractions of HA. Generally, the degree of settling of NZVI particles in the presence of high MW fractions of HA was lower than that of low MW fractions of HA and that without HA. The results were mainly attributed to the steric stabilization provided by the high MW fractions of HA. The presence of Na/Mg/Ca alone had insignificant influence on the settling of NZVI, but both Mg and Ca exerted an obvious influence on the settling of NZVI in the co-presence of HA. The settling behavior of NZVI was further examined in the co-presence of different MW fractions of HA and Ca. The co-presence of low MW HA fractions and Ca led to a lower settling of NZVI. This might be due to the formation of a layer of HA-Ca complex on the particle surface, providing stronger steric stabilization. Nevertheless, in the co-presence of high MW HA fractions and Ca, the settling of NZVI was initially reduced but accelerated with time, which might be due to the gradual aggregation of NZVI with time resulted from the bridging effect of HA-Ca complex.
研究了腐殖酸（HA）及其不同分子量（MW）级分在不存在和存在阳离子（即 Na/Mg/Ca）时对纳米零价铁（NZVI）沉淀的影响。超滤（UF）被用作分级方法，以获得四个不同的 MW 级分（通过 10 kDa、50 kDa 和 100 kDa 的超滤膜分离）。HA 的不同 MW 级分对 NZVI 的沉淀行为存在差异。通常，在存在高 MW 级分 HA 的情况下，NZVI 颗粒的沉降程度低于低 MW 级分 HA 和无 HA 的情况。结果主要归因于高 MW 级分 HA 提供的空间稳定作用。单独存在 Na/Mg/Ca 对 NZVI 的沉降没有明显影响，但 Mg 和 Ca 在 HA 共存时对 NZVI 的沉降有明显影响。进一步在不同 MW 级分 HA 和 Ca 共存的情况下研究了 NZVI 的沉降行为。低 MW HA 级分和 Ca 的共存导致 NZVI 的沉降较低。这可能是由于在颗粒表面形成了一层 HA-Ca 配合物，提供了更强的空间稳定作用。然而，在高 MW HA 级分和 Ca 共存的情况下，NZVI 的沉降最初减少但随着时间的推移加速，这可能是由于 HA-Ca 配合物的桥接作用导致 NZVI 随着时间的推移逐渐聚集所致。
