In this study,Schwertmannite,Akaganéite and ammoniojarosite were biosynthesized by different bacteria and characterized.The results showed that bacteria are critical in mediating the mineral formation process:the...In this study,Schwertmannite,Akaganéite and ammoniojarosite were biosynthesized by different bacteria and characterized.The results showed that bacteria are critical in mediating the mineral formation process:the morphology,crystallinity,grain size and specific surface area of each mineral varied upon different bacteria and culturing conditions.In addition,the formed minerals’elemental composition and group disparity lead to different morphology,crystallinity and subsequent adsorption performance.In particular,adsorption difference existed in iron minerals biosynthesized by different bacteria.The maximal adsorption capacities of Akaganéite,Schwertmannite and ammoniojarosite were 26.6 mg/g,17.5 mg/g and 3.90 mg/g respectively.Cr(VI)adsorption on iron-minerals involves hydrogen bonding,electrostatic interaction,and ligand exchange.The adsorption only occurred on the surface of ammoniojarosite,while for Akaganéite and Schwertmannite,the tunnel structure greatly facilitated the adsorption process and improved adsorption capacity.Thus,the molecular structure is the primary determining factor for adsorption performance.Collectively,the results can provide useful information in selecting suitable bacteria for synthesizing heavy-metal scavenging minerals according to different environmental conditions.展开更多
The behaviors of inorganic nitrogen species in three types of bioretention columns under an intermittently wetting regime were investigated. The mean NH+4—N, NO-3—N and total N(TN) removal efficiencies for the conve...The behaviors of inorganic nitrogen species in three types of bioretention columns under an intermittently wetting regime were investigated. The mean NH+4—N, NO-3—N and total N(TN) removal efficiencies for the conventional bioretention column(Col. T1) are 71%, 1% and 41%, for layered bioretention column with less permeable soil layer(Col. T2) the efficiencies are 83%, 84% and 82%, and for the bioretention column with submerged zone(Col. T3) the values are 63%, 31% and 53%, respectively. The best nitrogen removal is obtained using Col. T2 with relatively low infiltration rate. Adsorption during runoff dosing and nitrification during the drying period are the primary NH+4—N removal pathways. Less permeable soil and the elevated outlet promote the formation of anoxic conditions. 30%–70% of NO-3—N applied to columns in a single repetition is denitrified during the draining period, suggesting that the draining period is an important timeframe for the removal of NO-3—N. Infiltration rate controls the contact time with media during the draining periods, greatly influencing the NO-3—N removal effects. Bioretention systems with infiltration rate ranging from 3 to 7 cm/h have a great potential to remove NO-3—N.展开更多
基金Project(42277256)supported by the National Natural Science Foundation of ChinaProjects(HBKT-2021011,HBKT-2021014)supported by the Hunan Province Environmental Protection Research Program,ChinaProject(CDSKY-2023-05)supported by the Scientific Research of Project Hunan Provincial Urban Geological Survey and Monitoring Institute,China。
文摘In this study,Schwertmannite,Akaganéite and ammoniojarosite were biosynthesized by different bacteria and characterized.The results showed that bacteria are critical in mediating the mineral formation process:the morphology,crystallinity,grain size and specific surface area of each mineral varied upon different bacteria and culturing conditions.In addition,the formed minerals’elemental composition and group disparity lead to different morphology,crystallinity and subsequent adsorption performance.In particular,adsorption difference existed in iron minerals biosynthesized by different bacteria.The maximal adsorption capacities of Akaganéite,Schwertmannite and ammoniojarosite were 26.6 mg/g,17.5 mg/g and 3.90 mg/g respectively.Cr(VI)adsorption on iron-minerals involves hydrogen bonding,electrostatic interaction,and ligand exchange.The adsorption only occurred on the surface of ammoniojarosite,while for Akaganéite and Schwertmannite,the tunnel structure greatly facilitated the adsorption process and improved adsorption capacity.Thus,the molecular structure is the primary determining factor for adsorption performance.Collectively,the results can provide useful information in selecting suitable bacteria for synthesizing heavy-metal scavenging minerals according to different environmental conditions.
基金Project(2011ZX07303-002)supported by National Water Pollution Control and Management Technology Major Program,China
文摘The behaviors of inorganic nitrogen species in three types of bioretention columns under an intermittently wetting regime were investigated. The mean NH+4—N, NO-3—N and total N(TN) removal efficiencies for the conventional bioretention column(Col. T1) are 71%, 1% and 41%, for layered bioretention column with less permeable soil layer(Col. T2) the efficiencies are 83%, 84% and 82%, and for the bioretention column with submerged zone(Col. T3) the values are 63%, 31% and 53%, respectively. The best nitrogen removal is obtained using Col. T2 with relatively low infiltration rate. Adsorption during runoff dosing and nitrification during the drying period are the primary NH+4—N removal pathways. Less permeable soil and the elevated outlet promote the formation of anoxic conditions. 30%–70% of NO-3—N applied to columns in a single repetition is denitrified during the draining period, suggesting that the draining period is an important timeframe for the removal of NO-3—N. Infiltration rate controls the contact time with media during the draining periods, greatly influencing the NO-3—N removal effects. Bioretention systems with infiltration rate ranging from 3 to 7 cm/h have a great potential to remove NO-3—N.
