Arsenic Removal From Groundwater In Shanyin County By Nano Fe-Mn Oxides

The arsenide is widely distributed in various geological environment, and its toxicity can lead to chromosome or gene mutation, cancer induction, abnormal development of the embryo, and so on. As the geological environment is different, the concentration of arsenic in the groundwater is not the similar. But with the interference of natural geological changes and human factors, the possibility of exceeding the standard of arsenic content in groundwater is increasing. Before the groundwater exceeding the standard of arsenic is measured,which usually cannot be distinguished. Once the water containing arsenic goes into the municipal pipe network, which will result in a wide range of chronic arsenic poisoning. In some areas, where are under the states of water shortages, people know that arsenic content is out of standard limit in groundwater, but they have to drink. Therefore, the removal of arsenic in the groundwater becomes particularly important.Fe-Mn oxides, which are naturally exist in the roots of plants in the wetlands, they can effectively prevent enrichment of heavy metals inside plants from the soil, and they can be used as adsorbents of heavy metals. Nano Fe-Mn oxides have the advantages of nano materials in adsorption and the characteristics of iron and manganese oxides. The groundwater that the experiments used is from Shanyin County, the arsenic content is 240.4~340.8ug/L, water quality is reducibility, pH is 8.2~8.5. Experiment is under the same conditions of groundwater’s pH, in order to reduce environmental impact on groundwater.Firstly, the process of synthesizing Fe-Mn oxides were simulated by using The Geochemist’s Workbench, which’s a geochemical software. Main researches of simulation were adding sequence of raw materials, pH changed in the process of reaction, formation process of synthesis products. The simulation provided guidance for the synthesis experiment, and provided the reliable judgments to explain the mechanism of arsenic removal. The results of simulation showed that adding ferrous sulfate solution into potassium permanganate solution(forward synthetic process), the precipitations of iron and manganese oxides were produced at the same time. While, adding potassium permanganate solution into ferrous sulfate solution(reverse synthesis process), the iron oxide’s formation was prior to the manganese oxide’s in the synthesis process of redox co-precipitation of FeMn oxides. The simulation results showed that the adding sequence of raw materials was closely related to the characteristics of Fe-Mn oxides particles.Then, the pH was detected by the real-time monitoring in the synthesis process was to verify the accuracy of the simulation results. The results showed that there was a certain difference between the experiment’s pH and the simulated process’ s pH, but the trend was basically the same. During the experiment, scanning electron microscope(SEM), Energy dispersive spectrometer(EDS), Laser particle size distribution analyzer and X-ray diffraction(XRD) were used to the representation of Fe-Mn oxides. The results showed that the particle sizes of Fe-Mn oxides were below 21 nm in the forward and reverse synthesis process, and different synthesis process of Fe-Mn oxides had different surface condition.Finally, the soil and groundwater from Shanyin County were analyzed, this paper used nano Fe-Mn oxides to remove arsenic from the groundwater. So that, the removal capacity of nano Fe-Mn oxides was verified in real conditions. Experiments showed that the nano Fe-Mn oxides by forward synthetic process had stronger arsenic removal capacity, while, the nano Fe-Mn oxides by reverse synthetic process had higher adsorption efficiency.The experiments were combined with simulation, the synthesis process of nano Fe-Mn oxides was studied. On this basic, the synthesized Fe-Mn oxides were used to remove high arsenic from groundwater in Shanyin County. The results showed that changing the addition order of the synthetic materials in the process of synthesizing nano Fe-Mn oxides, the nano Fe-Mn oxides would have different characteristics. The nano Fe-Mn oxides had higher arsenic removal performance and could be used to the removal arsenic in the ground water. The research results of nano Fe-Mn oxides had important realistic significance and theoretical value to the practical application and theoretical explanation.