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Removal of heavy metals using rice husk ash.

机译：使用稻壳灰去除重金属。

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The purpose of this research was to investigate the potential use of rice husk ash in removing heavy metals in wastewater. Two types of ash were used in the study; black ash and gray ash, both of which were obtained from Riceland, a rice mill which is located in Stuttgart, Arkansas.; The study was conducted in two phases; a batch study and a continuous flow study. In the batch study, the feasibility of using rice husk ash in adsorbing heavy metals was tested using metal solutions containing zinc, copper, cadmium, nickel, and chromium at various concentrations. Freundlich and Langmuir adsorption isotherms were developed to substantiate the adsorption characteristics of the ash.; In the continuous phase of the study, six bench-scale activated sludge units were used to simulate a wastewater treatment plant. All the units have a volume of approximately 8 liters, and they were fed with synthetic wastewater. The feed rate was controlled at 8 liters a day to each unit (using peristaltic pumps) to provide a hydraulic detention time of approximately 24 hours. The operating sludge age was maintained at about 20 days. Each reactor was seeded with mixed liquor from a WWTP to enhance simulation. All reactors received baseline wastewater and ran until steady state conditions (in terms of effluent BOD removals, effluent TSS removals) were achieved. Five of the reactors were then fed with heavy metal solution in their influent at known concentrations while one reactor (Reactor A) was used as a control. Four of these reactors received various concentrations of rice husk ash (black ash and gray ash) added to the aeration chamber. Reactor B only received the baseline wastestream with the metal solution with no ash added. The reactors were operated for a total time of approximately ten weeks.; From the research it was found that there is a potential in using rice husk ash as an adsorbent for heavy metals removal. Black ash was found to perform better in adsorbing copper compared to gray ash. However, gray ash performed better in adsorbing zinc than black ash. The use of ash in a biological treatment system also helps to prevent or reduce toxic impacts to the microorganisms when the influent metal concentration was slightly higher than the suspected inhibitory levels. This could be used as an immediate response to toxic upset caused by heavy metals in a biological wastewater treatment plant.
机译：这项研究的目的是研究稻壳灰在去除废水中重金属方面的潜在用途。在研究中使用了两种类型的灰；黑灰和灰灰，均购自位于阿肯色州斯图加特的碾米厂Riceland。该研究分两个阶段进行：批处理研究和连续流动研究。在批处理研究中，使用包含各种浓度的锌，铜，镉，镍和铬的金属溶液测试了使用稻壳灰吸附重金属的可行性。开发了Freundlich和Langmuir吸附等温线以证实灰分的吸附特性。在研究的连续阶段，使用六个台式规模的活性污泥装置模拟废水处理厂。所有单元的容积约为8升，并向它们注入了合成废水。每个单元的进料速度控制为每天8升（使用蠕动泵），以提供大约24小时的液压滞留时间。操作污泥的年龄保持在约20天。每个反应器中都注入了污水处理厂的混合液，以增强模拟效果。所有反应器均接收基准废水，并运行至达到稳态条件（就废水BOD去除，废水TSS去除而言）。然后向五个反应器中注入已知浓度的重金属溶液，同时将一个反应器（反应器A）用作对照。这些反应器中的四个接收了加入到曝气室内的各种浓度的稻壳灰（黑灰和灰灰）。反应器B仅在不添加灰分的情况下接收含金属溶液的基准废物流。反应器总共运行约十周。从研究中发现，稻壳灰有可能用作重金属去除的吸附剂。与灰灰相比，发现黑灰在吸附铜方面表现更好。但是，灰烬在吸附锌方面比黑灰表现更好。当进水金属浓度略高于怀疑的抑制水平时，在生物处理系统中使用灰分还有助于防止或减少对微生物的毒性影响。可将其用作对生物废水处理厂中重金属引起的有毒气体的立即反应。

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