Characteristics Of Red Mud By Washing It With Low Molecular Organic Acids

The experiment study on features washing technology of red mud,it can reduce the migration of heavy metals in red mud,decrease toxicity,change the chemical forms of heavy metals in the environment,easily reduces the amount of the forms of content conversion(weak acid extractable),while improving the adaptability of plants.The first step is to wash red mud by using of EDTA with low molecular weight organic acid such as citric acid,oxalic acid and tartaric acid in combination,controlling the pH and the way of washing it;and the next step is to analysis the forms of red mud by applying the method with BCR continuous extraction.The mainly experimental results show that(1)The heavy metal Cd:in the red mud Cd exists mainly in the non effective state of residual form,followed by a potential effective state(reducible and oxidizable),finally available(weak acid extractable);extraction effect of Cd by using EDTA+ citric acid is the highest.The best method to extract heavy metals Cd in red mud when the eluent pH=3,washing for 4h citric acid +4h EDTA and the highest rate can reach 54.5%,and the removal is mainly available(weak acid extractable)in Cd;the worst effect is a combination of EDTA+ oxalic acid,when the eluent pH=7,washing method is 8hEDTA+ of oxalic acid extraction of heavy metal Cd in red mud rate the lowest,only 28.4%.(2)The heavy metal As:in the red mud As mainly exists in the form of non effective residual state,followed by the effective state(weak acid extractable state),oxidized state,and finally reduced state.Extraction effect of As by using EDTA+ oxalic acid is the highest.The best method to extract heavy metals As in red mud when the eluent pH=3,washing for 4h oxalic acid +4h EDTA and the highest rate can reach 51%,effective state(weak acid extractable)and potential available(reducible and oxidizable)are significantly decreased in As weak acid extractable,reducible reduced 3.171mg/kg,reduced to 1.822 mg/kg,can be reduced to 1.009mg/kg oxidation state;the worst method is when the washing eluent pH=7,washing method is 8h EDTA+ citric acid and the As on heavy metals in red mud extract was the lowest,only 5.44%.(3)The heavy metal Hg:in the red mud Hg exists mainly in the non effective state of residual form,followed by a potential effective state(reducible and oxidizable),finally available(weak acid extractable);The best method to extract heavy metals Hg in red mud when the eluent pH=3,washing for 4h citric acid +4h EDTA and the highest rate can reach 41.84%,effective state(weak acid extractable)and potentially effective state(reducible and oxygen content in the Chinese state)of Hg were significantly reduced,weak acid extractable 0.2502mg/kg decreased,but the original state is reduced to 0.2760 mg/kg.Can reduce the oxidation state of 0.3636 mg/kg;the worst effect is a combination of EDTA+ oxalic acid,when the washing eluent pH=5,washing method is 8hEDTA+of oxalic acid extraction of heavy metal Hg in red mud was the lowest,only 10.72%.The final pot experiment shows that the turf seeds could grow on the red mud after washing and the germination rate could reach about 70%,indicating that the red mud could be preliminarily formed as soil after washing red mud.