Promotion Mechanism Of Nitric Acid Modified Activated Carbon On Bioavailability Of Hematite

Iron is the fourth most abundant element in the earth's crust,mainly in the form of Fe???oxide in the natural environment.The bio-reduction of Fe???oxide can degrade the macromolecular organics in groundwater and landfill leachate,which is of great significance to the treatment and restoration of water body in the environment.Fe???oxide mostly exists in the form of hematite.Compared with Fe???oxide with weak crystal and amorphous structure,hematite has strong crystal structure and low bio-availability.In recent years,it has been found that HNO3modified activated carbon can promote the bioavailability of Fe???oxide?Pyrite?with weak crystal structure,but the mechanism of promoting the bioreduction efficiency of Fe???with strong crystal structure is still unclear.In this study,hematite was used as an electron acceptor,Shewanella Putrefaciens is a microorganism with iron reducing function.By adding the activated carbon modified by HNO₃,the electron shuttle is formed,and the promoting effect and influencing factors of the activated carbon modified by HNO₃on the bioavailability of Fe???in hematite are explored;the promoting principle of the activated carbon modified by HNO₃on the bioavailability of Fe???in hematite is explored through the comparative experiment under the best reaction conditions.In addition,the best reaction conditions of hematite biodegradation organic matter were determined by batch experiments,and a column experiment reaction device was constructed.The organic matter degradation experiment was carried out in the groundwater polluted by an informal landfill in Tianjin.The main conclusions are as follows:?1?HNO₃modified activated carbon can promote the bio-availability of Fe???in hematite and the effect is better than that of unmodified activated carbon.The reduction rate of Fe???increased with the increase of modifier concentration and the decrease of hematite concentration,and the best carbon source was sodium lactate.The interaction of the three factors was low.The best value was hematite concentration 5mmol/L,modifier concentration 60%,and the type of carbon source was sodium lactate.?2?The addition of HNO₃modified activated carbon has little effect on the species and abundance of microorganisms,but the activated carbon modified by HNO₃has rich surface quinone functional groups.Through its oxidation and reduction,the electron transfer between hematite and microorganisms,the generation of secondary minerals and the crystal structure of hematite can be reduced,so as to improve the bio-availability of hematite.?3?The optimal conditions for the bioreduction of hematite are 8.3 mmol/L of iron ore,13.4 mmol/L of organic matter and 5%of nitric acid modifier.The column experiment was carried out on the groundwater polluted by an informal landfill in Tianjin.The COD degradation rate of the control group was only 67.36%,while that of the experimental group was increased to 84.24%.It was proved that under one-dimensional flow of water in the environment,the HNO₃modified activated carbon could still promote the biological reduction of organic matters in hematite,and the concentration of humic acid and protein-like in the water decreased after the reaction,and the concentration of aromatic acid decreased The aroma decreased and the degree of humification decreased.In this study,the electron shuttle formed by HNO₃modified activated carbon was used to promote the bio-availability of Fe???in hematite,and the related reaction mechanism was elucidated.This research has significant innovation and is of great significance to the regulation and control of carbon,nitrogen,oxygen and other elements in nature.It can provide a new method,new idea and new way for environmental remediation and pollution control.