| With the development of urbanization and agriculture and industry, many important river source water were affected to different degrees of pollution in our country. Water pollution problems have become increasingly prominent. There is a wide variety of pollutants in micro-polluted water, which most are organic matter and ammonia nitrogen. Generally, it is difficult to remove organic matter and ammonia nitrogen effective by the conventional process in water plant. Therefore, we need to find a cost-effective treatment methods urgently to solve the problem of micro-polluted water effectively and protect people’s drinking water safety.Study at home and abroad, modified bentonite has good adsorption properties, it can effectively deal with micro-polluted water and sewage. But because of modified bentonite powdered is difficultly to separated from solid-liquid in water treatment and processing cost is high, thereby hindering its practical application in water treatment. So it will has a realistic significance to make bentonite powdered into a kind of easy recycling reuse bentonite granules.Microwave enhanced Al-bentonite(hereinafter referred to as M-Al-Bt) were prepared by using sodium bentonite as raw materials, AlCl3·6H2O as modifier and heated by microwave. Modified bentonite granules(MBG1, MBG2, MBG3, MBG4) were prepared by mixing with polyvinyl alcohol(PVA) as binder and pore former (sodium bicarbonate(NaHCO3), sodium alginate(SA), carrageenan, starch) and M-Al-Bt. MBG were prepared by orthogonal experiments and analyzed in the preparation process of different conditions. The characterize of MBG’s surface and internal stru were analyzed by SEM, EDS, XRD, FT-IR, BET and BJH. To investigate the mechanism of preparing MBG. The effect of MBG on UV254 and NH4-N in micro-polluted water under different reaction conditions were investigated. To explore the removal mechanism of MBG and investigate the regeneration effect of NaOH on MBGThe results of MBG preparation showed that the optimum preparation conditions of M-Al-Bt were Q=260 W, L/S=1ml/g, T=6 min, Al=12 mmol/lOg. The best preparation conditions of different MBG were PVA=10%, NaHCO3=5%, embedding quantity=10 for MBG1; PVA=11%, SA=3%, embedding quantity=9.5 for MBG2; PVA=11%, carrageenan=1%, embedding quantity=10 for MBG3; PVA=11%, starch=6%, embedding quantity=9 for MBG4. The granules forming effect of MBG 1 was better than MBG2, MBG3 and MBG4.The results of MBG characterization showed that the surface, internal pore structure and adsorption properties of MBGl had improved significantly compared to NBG, which were made by sodium bentonite. Compared to NBG, the specific surface area of MBG1 was 32.9452 m2/g, which was increased about 13 times, the average pore size of MBG1 significantly decreased and the pore volume increased about 12 times, the layer spacing of MBG1 increased from 1.25 nm to 1.57 nm.The removal experimental results of MBG showed that the removal efficiency of MBG1 on humic acid concentration of 20 mg/L and ammonia nitrogen concentration of 5 mg/L in micro-polluted water was better than NBG, MBG2, MBG3 and MBG4. Static adsorption experiments results showed that the removal rate of MBG1 on UV254 and NH4-N will be up to 98.54% and 20.56% in micro-polluted water under the following conditions, MBG1 dosage of 3 g/L, reaction time of 20 min, pH value of 7.0. The adsorption saturated MBG1 can effectively be recycled three times by using 1.5 mol/L NaOH solution, the removal rate of MBG1 after regeneration were over 70%(without adding new MBG1). In order to improve the effect of water treatment, after regeneration can add new MBG1 appropriately. Dynamic adsorption experiments results showed that the removal efficiency of MBG1 filtration column on humic acid concentration of 20 mg/L and ammonia nitrogen concentration of 5 mg/L in micro-polluted water was better than NBG filtration column. MBGl filtration column run in 50 h, the average removal rate on UV254, NH4-N and turbidity were 97.0%,48.4% and 69.3%, the average value of UV254, NH4-N and turbidity were 0.017 cm-1,2.6 mg/L and 0.5 NTU. |
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