Effect Of Hydrogenotrophic Bacteria On Transport Of Chitosan-stabilized Nanoscale Zero-valent Iron

Nano-zero-valent iron?nZVI?is a material with large specific surface area and extremely strong reducibility.However,nZVI has a short migration distance in groundwater and cannot meet the needs of in-situ repair.However,groundwater environment is very complicated,present research focuses on the effect of hydrological parameters and water qualities conditions on the transport ability of nZVI,but little study pay attention to the effect of microorganism in groundwater.In this study,nZVI and CS-nZVI were synthesized by liquid phase reduction method,and the morphology of the material was characterized and analyzed by transmission electron microscopy?TEM?and scanning electron microscopy?SEM?.X-ray diffraction?XRD?and Raman spectroscopy were used to characterize the corrosion products of nZVI during transport.The effects of hydrogenotrophic bacteria?HTB?on the transport of nZVI and CS-nZVI under different water quality conditions were studied by static sedimentation experiments and transport experiments.The results are as follows:?1?nZVI particles have a spherical cluster structure with uniform particle size,and in the presence of HTB,nZVI was oxidized to needlelike substances.The results show that,the characterization results of XRD and Raman spectra indicate that the nanomaterials have obvious structural changes after adding HTB.The oxidation product of nZVI was mainly Fe₂O₃,while the oxidation product of CS-nZVI was mainly wüstite?FeO?and lepidocrocite??-FeOOH?.?2?When there was no HTB,the suspension stability of CS-nZVI particles was stronger than nZVI,and the transport ability in quartz sand column was higher than nZVI.HTB inhibits the sedimentation performance of nZVI,promote the sedimentation performance of CS-nZVI,and with the increase of HTB concentration,the promotion effect was more obvious.HTB inhibits the transport performance of nZVI and CS-nZVI,then promotion its transport ability,HTB has a stronger inhibitory effect on CS-nZVI.?3?HTB and HA can inhibit the sedimentation of nZVI and keep its suspension performance better,when the concentration of HA in the system was 10 mg/L,1/3 HTB has the most obvious inhibitory effect on sedimentation of nZVI,but it promote the sedimentation performance of CS-nZVI particles.HA can enhance the transport ability of nZVI and CS-nZVI,when the HA concentration was 10 mg/L,the promotion effect was the strongest;when the system contains 1/3 HTB and 10 mg/L HA,nZVI and CS-nZVI have the highest mobility,reaching 90%,therefore,when the system contains both HTB and HA,there was a certain synergistic effect.?4?Both K⁺and Ca²⁺promoted the sedimentation of nZVI and CS-nZVI,the smaller K⁺and Ca²⁺concentration,the smaller promotion effect on sedimentation of nZVI and Ca²⁺promoted the sedimentation of nZVI better than K⁺,When K⁺and HTB coexist,the nZVI suspension can maintain good stability,but when Ca²⁺and HTB coexist,the sedimentation rate of nZVI increases.Corresponding to the results of the sedimentation experiment,Both K⁺and Ca²⁺inhibited the transport ability of nZVI and CS-nZVI.?5?When there was no HTB,the breakthrough percentage of nZVI was 5.32%,and the breakthrough percentage of CS-nZVI was 15.71%.The breakthrough curves were higher in the presence of HTB,while the retained profiles were lower,indicating that the copresence of bacteria in suspension increased the transport and decreased the deposition of nZVI in porous media,but HTB reduces the breakthrough percentage of CS-nZVI and increases the retention percentage in quartz sand.In the high concentration of nitrate solution,the breakthrough percentage of nZVI and CS-nZVI decreases.