摘要:
氧微纳气泡改性矿物可改善富营养化引起的水体和表层沉积物的缺氧/厌氧问题,但微纳气泡的生成和增氧机理尚不明确。该研究以天然多孔矿物凹凸棒石和蒙脱石为例,研究了改性矿物的氧微纳气泡释放和对水体的增氧性能,并分析了氧微纳气泡的生成和增氧机理。光学显微镜和NanoSight测试结果表明两种改性矿物均能有效释放微米气泡(约100μm)和纳米气泡(80.0~213.9nm),凹凸棒石比蒙脱石有更高的氧微纳气泡释放量和气泡固定效率,其释放量为0.12mg/g,是蒙脱石的4倍。在本实验体系下,改性凹凸棒石和蒙脱石应用24h可将材料空隙水DO从1.6mg/L分别升高到7.3和5.6mg/L;应用72h可将上覆水DO从1.5mg/L分别升高到4.6和4.4mg/L。研究发现材料将氧携带到水体后,表面孔对从材料中脱附的氧起分散作用,进而生成了氧微纳气泡。
Abstract:
Oxygen micro/nano-bubbles (MNBs) modified natural minerals have been proved as an effective manner to combat eutrophication induced DO depletion and hypoxia/anoxia of surface sediment in natural water. However, the generation and the oxygenation mechanisms by such oxygen MNBs are still unclear. In this study, attapulgite and montmorillonite were selected as the model natural porous minerals to evaluate the releasing performance and oxygenation effect of oxygen MNBs, and also the oxygenation mechanisms. The results of light microscope and NanoSight showed that both minerals could release oxygen microbubbles (with diameter of about 100 μm) and nanobubbles (with diameter distributed mainly in 80.0~213.9 nm) effectively. The modified attapulgite had higher oxygen MNBs releasing capacity and stabilized more interface MNBs than montmorillonite, with the releasing capacity of 0.12 mg/g, which was 4 times of that for montmorillonite. After 24 h of the experiment, the DO concentrations of the interstitial water improved from 1.6 mg/L to 7.3 and 5.6 mg/L for modified attapulgite and montmorillonite, respectively. In another experiment, DO concentrations of the overlying water were improved from 1.5 mg/L to 4.6 and 4.4 mg/L, respectively, after applying the modified attapulgite and montmorillonite for 72 h. The results revealed that when oxygen was brought into water by mineral, it was the physical dispersion of mineral surface pores to oxygen that was desorbed from minerals to water, that caused the generation of oxygen MNBs.
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