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Production of Polyferric Sulphate from Industrial Wastewater by Microwave Heating Oxidation
Polyferric Sulfate(PFS),Microwave Heating Oxidation,Coagulation,Composite inorganic coagulants,Preparation,
|Publication Year :||2017|
(3) 通過對洗衣廢水之杯瓶實驗來評估硫酸鐵產品的去除效率。本研究在試驗開始前記錄下200毫升洗衣廢水的初始濁度和化學需氧量。而後調節每個燒杯的pH值並添加遞增劑量的硫酸鐵溶液，接著開啓混凝機。杯瓶實驗過程如下：快混100rpm 3min，慢混30rpm 15min，靜置12min。實驗結果顯示，最適pH值為7，最適添加劑量為0.2-0.4毫升。濁度和化學需氧量的去除率皆超過90%，表明製備出的硫酸鐡有良好的混凝效果。
The coagulation process is an effective environmental protection technology, which is widely used in the wastewater treatment facilities, such as purification treatment of industrial and agricultural waste water, for the destabilization of colloids suspensions and for the removal of suspended solids along with the removal of turbidity and Chemical Oxygen Demand (COD). In recent years, more and more researchers are interested in the synthesis of composite inorganic coagulants. A characteristic example is Polyferric Sulfate(PFS), which is a relatively new poly inorganic coagulation with high cationic charge. In this study, the Microwave Heating Oxidation process, a new preparation method for Polyferric Sulfate was investigated, including types of chemical oxidant, doses of chemical oxidant, reaction temperature (or microwave power), reaction time. And the optimum preparation operation was evaluated by the role of major parameters, including ferrous concentration, total iron concentration, pH value, Alkalinity.
Firstly, the optimum condition of coagulant PFS preparation was investigated, by comparing different oxidants (Hydrogen Peroxide, Sodium Chlorate, Nitric Acid). For Hydrogen Peroxide, the optimum condition decided by experiments are as follows: 39.33mL of Hydrogen Peroxide were added to the raw materal, 100mL of ferrous industrial wastewater, reacting in microwave oven, under 127W, for 50min. Besides, for Sodium Chlorate, the optimum condition decided by experiments are as follows: 1.86g of Sodium Chlorate were added to the raw materal, 100mL of ferrous industrial wastewater, reacting in microwave oven, under 36W, for 40min. Additionally, for Nitric Acid, the optimum condition decided by experiments are as follows: 6.03mL of Nitric Acid were added to the raw materal, 100mL of ferrous industrial wastewater, reacting in microwave oven, under 127W, for 40min. Thus, the product liquid polyferric could be obtained.
Secondly, using Sodium Hydroxide could raise the basicity of Polyferric Sulfate theoretically, hence, the optimum operation of adding Sodium Hydroxide into coagulant PFS was investigated, by comparing different dosages of Sodium Hydroxide. The condition decided by experiments are as follows: 6, 9 and 12mL of Sodium Hydroxide were added to the coagulant products, 50mL of Polyferric Sulfate, under stirring. And the basicity increased from 3-4% to nearly 8-11% respectively. The experiment proved that adding appropriate doses of Sodium Hydroxide could raise the basicity of PFS products significantly.
Thirdly, operation cost was an important factor for evaluating feasibility of the three kinds of PFS products. The highest cost was 9.73 Taiwanese dollars per liter for Hydrogen Peroxide and the mediate cost was 2.73 Taiwanese dollars per liter for Nitric Acid. The lowest cost was 1.09 Taiwanese dollars per liter for Sodium Chlorate.
Finally, the coagulation efficiency of Polyferric Sulfate products in treating laundry wastewater was evaluated by jar test. In this study, we recorded the turbidity and Chemical Oxygen Demand of 200mL laundry wastewater before beginning, and used the prepared solution of PFS, dosed each beaker with adjusted pH values and increased amounts of solution. After dosing each beaker, turned on the stirrers. The jar test would be performanced as follows: Operated the stirrers at 100 rpm for 3 minutes, then reduced the speed to 30 rpm for 15 minutes and allowed setting for 12 minutes. According to the results, the best pH values were about 7 and the proper dosages were 0.2-0.4mL. Turbidity and COD removal rate were more than 90%, which showed that prepared Polyferric Sulfate had very good coagulation performance.
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