| Heavy metal pollution in water which caused a great threat to the environment and human health on account of its large emissions, high toxicity, easy moving and accumulating that was increasingly serious. Meanwhile, the traditional methods of removing the Cr (Ⅵ) costed high whereas the new method by microorganisms often appeared the problems of unstable, strain degeneration and so on. Its application was restricted consequently and the research on how to improve the microbial removal efficiency and Cr (Ⅵ) stability had become a meaningful way. In this paper, the municipal sludge and fly ash as the main raw material was used for preparation of porous lightweight Ceramsite which could improve its biological carrier performance. FeCl3 and Fe3O4 was used on the magnetic/positive modification of the ceramsite surface to change the electricity of the ceramsite surface and increase the magnetic field of the surface. The main results of this paper are as follows:(1)The porous ceramsite was prepared by municipal sludge and fly ash which can meet the demand for carrier in water treatment. Raising the proportion of mixed sludge appropriately will increase the flux components then improve the expansion effect of the ceramsite. The finding indicate that the optimal proportion of dry sludge and fly ash quality was 1:1, sintering process optimal preheating temperature was 400℃, the preheating time 20min and 1125℃, 10min. The apparent density of ceramsite was 0.8～0.9 g/cm3,the bulk density 0.7～0.8 g/cm3 and the porosity was 43%～45%, all the indicators meet with the artificial ceramsite for water treatment. The use of sludge in ceramsite can be fixed heavy metals properly which provided an effective way for resource utilization of municipal sludge, had good prospects.(2) FeCl3 and Fe3O4 were used on the surface magnetic/positive modification processing of ceramsite, the results showed that the concentration of FeCl3 was 1 mol/L, the dosage of Fe3O4 was 10%(mass fraction representing FeCl3),activation temperature was 600℃,the activation time was 3 h, which were the optimal modification contitions. The modified ceramsite was red brown due to the addition of iron oxide, the surface electric of the ceramsite by negatively charged became positively charged, the strength of the magnetic field is about 4～5mT. The XRD result showed that the modified ceramsite was attached to a surface of the iron oxide layer, a layer with porous structure, the main crystal phase of alpha were Fe2O3 and Fe3O4.(3) The unmodified and modified ceramsite were used as biological carrieres. Loading dominant bacteria treated the Cr (VI) simulated wastewater, the Cr (VI) concentration was 50 mg/L, the inoculation quantity was 1%(V/V), ceramisite added 10g/50 mL, under temperature of 30 °C. The removal Cr (VI) efficiency of the modified ceramsite hanging membrane could reach 97.9%after 8 h, which was 1.9 times higher than unmodified ceramsite. By the contrast experiment, the removal Cr (VI) were mainly reduced to Cr (III) by Microorganism, a little were adsorpted by the ceramsite or reduced by nutrients in the water. |
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