微波干燥污泥重金属及有机物固定化机理研究

Immobilization of heavy metals and organic substances in drying sludge by means of microwave radiation

为研究不同干燥方法对污泥中重金属及有机物的固定作用,采用微波辐射和鼓风加热为污泥干燥方法,并进一步分析微波辐射对污泥中污染物有效固定的机理.实验表明：900 W微波辐射8 min可实现污泥低能耗、快速干燥,促进干污泥中污染物的固定,水平震荡浸取微波干燥污泥有机物的浸出浓度仅为鼓风加热的28%;拟自然条件下微波干燥污泥Cu^2＋、Cr^6＋、Zn^2＋、Pb^2＋的浸出浓度远低于鼓风加热干燥污泥,微波辐射对污泥中重金属固定作用排序为Pb^2＋〉Zn^2＋〉Cr^6＋〉Cu^2＋.通过SEM及XRD手段分析干污泥的化学组成、结晶状况、孔径结构认为：微波辐射通过破壁、堆积、包埋、固定、成孔过程将重金属及有机物有效闭塞在干污泥0.075～0.75μm的孔径中,实现污染物与干污泥的紧密结合.

The objective of present study was to investigate the heavy metals （ Cu^2＋ , Cr^6 ＋ , Zn^2 ＋ and Pb^2 ＋ ） and organic substances behavior during leaching procedure of sludge which was dried by microwave radiation and blast heating respectively. And the immobilization mechanism of contaminations in microwave drying sludge was discussed further. It was found that the wet sludge could be dried quickly in the 900W microwave and the energy consumption was much lower than the blast heating. The efficiency of stabilization of drying sludge was evaluated from the results of leaching tests. The results showed that the concentration of organic substances in the supernatant liquid from the microwave drying sludge in the aclinic shake leaching test was declined by 28% compared with the sludge dried by blast heating. And also the heavy metals concentrations of microwave drying sludge in the leaching test of simulated natural waters conditions were much less than the blast heating one. The immobilizing effect of heavy metals in microwave drying sludge was determined in descending order as Pb^2＋, Zn^2＋ , Cr^6＋ , Cu^2＋. The chemical composition, crystal condition and pore structure were explored by scanning electron microscopy and X-ray diffraction. And it was revealed that organic substances and heavy metals could be fixed into the 0. 075 um～ 0. 75 um pores of stabilized matrices by five important immobilization procedures, crack the cell wall in the wet sludge, pile up the fragments of cell wall, package up the organic substances and metals in the fragments, fixing the organic substances and metals, and fusing to form pores.