Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certai...Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certain by-products, and identify cheaper replacements for expensive conventional PRB materials, especially pure metallic iron. The feasibility of reductive denitrification of nitrate by SIF was studied by batch experiments. Operational parameters such as pH value, SIF dosage and initial concentration of nitrate were investigated. The removal efficiency of nitrate reached 80% under the conditions of pH of 2.5, nitrate initial con- centration of 45 mg/L and SIF dosage of 100 g/L within 4 h. Results indicated that nitrate removal is inversely related to pH. Low pH value condition favors for the nitrate transformation. Different from the results of others who studied nitrate reduction using iron powder, we found that there was a lag time before nitrate reduction occurs, even at low pH. Finally, the possible mechanism of nitrate reduction by Fe0 is discussed.展开更多
The reduction of hexavalent chromium by scrap iron was investigated in continuous long-term fixed bed system. The effects of pH, empty bed contact time （EBCT）, and initial Cr（VI） concentration on Cr（VI） reductio...The reduction of hexavalent chromium by scrap iron was investigated in continuous long-term fixed bed system. The effects of pH, empty bed contact time （EBCT）, and initial Cr（VI） concentration on Cr（VI） reduction were studied. The results showed that the pH, EBCT, and initial Cr（VI） concentration significantly affected the reduction capacity of scrap iron. The reduction capacity of scrap iron were 4.56, 1.51, and 0.57mg Cr（VI）-g1 Fe0 at pH 3, 5, and 7 （initial Cr（VI） concentration 4 mg.L 1, EBCT 2 min, and temperature 25℃）, 0.51, 1.51, and 2.85 mg Cr（VI）.g-I Fe0 at EBCTs of 0.5, 2.0, and 6.0rain （initial Cr（VI） concentration 4mg.L-1, pH 5, and temperature 25℃）, and 2.99, 1.51, and 1.01 mg Cr（VI）. gl Fe0 at influent concentrations of 1, 4, and 8 mg.L ^-1（EBCT 2 min, pH 5, and temperature 25℃）, respectively. Fe（total） concentration in the column effluent continuously decreased in time, due to a decrease in time of the iron corrosion rate. The fixed bed reactor can be readily used for the treatment of drinking water containing low amounts of Cr（VI） ions, although the hardness and humic acid in water may shorten the lifetime of the reactor, the reduction capacity of scrap iron still achieved 1.98 mg Cr6 ＋- g-~ Fe. Scanning electron micro- scope equipped with energy dispersion spectrometer and X-ray diffraction were conducted to examine the surface species of the scrap iron before and after its use. In addition to iron oxides and hydroxide species, iron-chromium complex was also observed on the reacted scrap iron.展开更多
This study focuses on identifying the factors under which mixed microbial seeds assist bio-chemical denitrification when Scrap Iron Filings(SIF)are used as electron donors and adsorbents in low C/N ratio waters.Batch ...This study focuses on identifying the factors under which mixed microbial seeds assist bio-chemical denitrification when Scrap Iron Filings(SIF)are used as electron donors and adsorbents in low C/N ratio waters.Batch studies were conducted in abiotic and biotic reactors containing fresh and aged SIF under different dissolved oxygen concentrations with NO_(3)^(-)−N and/or PO_(4)^(3−)influent(s)and their nitrate/phosphate removal and by-product formations were studied.Batch reactors were seeded with a homogenized mixed microbial inoculum procured from natural sludges which were enriched over 6 months under denitrifying conditions in the presence of SIF.Results indicated that when influent containing 40 mg/L of NO_(3)^(-)−N was treated with 5 g SIF,79.9%nitrate reduction was observed in 8 days abiotically and 100%removal was accomplished in 20 days when the reactor was seeded.Both abiotic and seeded reactors removed more than 92%PO_(4)^(3−)under high DO conditions in 12 days.Abiotic and biochemical removal of NO_(3)^(-)−N and abiotic removal of PO_(4)^(3−)were higher under independent NO_(3)^(-)−N/PO_(4)^(3−)loading,while 99%PO_(4)^(3−)was removed biochemically under combined NO_(3)^(-)−N and PO_(4)^(3−)loading.This study furthers the understandings of nitrate and phosphate removal in Zero Valent Iron(ZVI)assisted mixed microbial systems to encourage the application of SIF-supported bio-chemical processes in the simultaneous removals of these pollutants.展开更多
The study is aimed at the problem of high content of Cr^(6+),Cr^(3+)and SO_(4)^(2-)is high and low pH value in acid mine drainage(AMD).Moreover,treatment of AMD by sulfate reducing bacteria(SRB)requires the addition o...The study is aimed at the problem of high content of Cr^(6+),Cr^(3+)and SO_(4)^(2-)is high and low pH value in acid mine drainage(AMD).Moreover,treatment of AMD by sulfate reducing bacteria(SRB)requires the addition of carbon source,while the treating effectiveness is not good enough on its own.The sugarcane slag,the corn cob and the sunflower straw were selected as the SRB carbon source cooperating with iron scrap to construct the dynamic columns 1,2 and 3.The mechanism of removing Cr^(6+),Cr^(3+),SO_(4)^(2-)and H+and the regularity of sustained release of carbon source and TFe release was studied in AMD.The removal efficiency of heavy metal ions,the ability of sustained release of carbon source,and the ability of adjusting acid by the three dynamic columns were compared.The result shows that the average removal rates of Cr^(6+),Cr^(3+)and SO_(4)^(2-)in effluent of dynamic column 1,filled by sugarcane slag,iron scrap and SRB,were 96.9%,67.1%and 54.3%.The average release of TFe and chemical oxygen demand(COD)were 4.4 and 287.3 mg/L.Its average pH was 6.98.Compared with the performance of dynamic columns 1,2 and 3,dynamic column 1 performed best in removing Cr^(6+),Cr^(3+)and SO_(4)^(2-)from AMD and controlling the release of COD and TFe,adjusting the pH of the solution.The study is of significance in treatment of AMD by taking for biomass materials as SRB carbon source in cooperation with iron scrap.展开更多
The degradation of five naphthalene derivatives in the simulated wastewater was investigated using the iron-carbon micro-electrolysis method.The optimal initial pH of solution and adsorption of iron-carbon and removal...The degradation of five naphthalene derivatives in the simulated wastewater was investigated using the iron-carbon micro-electrolysis method.The optimal initial pH of solution and adsorption of iron-carbon and removal efficiency of the total organic carbon(TOC)were investigated.The results show that the removal efficiency of the naphthalene derivatives can reach 48.9%?92.6% and the removal efficiency of TOC is 42.8%?78.0% for the simulated wastewater with 200 mg/L naphthalene derivatives at optimal pH of 2.0?2.5 after 120 min treatment.The degradation of five naphthalene derivatives with the micro-electrolysis shows the apparent first-order kinetics and the order of removal efficiency of the naphthalene derivatives is sodium 2-naphthalenesulfonate,2-naphthol,2,7-dihydroxynaphthalene,1-naphthamine,1-naphthol-8-sulfonic acid in turn.It is illustrated that the substituents of the naphthalene ring can affect the removal efficiency of naphthalene due to their electron-withdrawing or electron-donating ability.展开更多
基金Project (No. 20407015) supported by the National Natural Sci-ence Foundation of China
文摘Reduction of nitrate by zero-valent iron is a highly exergonic reaction that has long been known to occur. Use of scrap iron filings (SIF) as the PRB (Permeable Reactive Barrier) material can be used to recycle certain by-products, and identify cheaper replacements for expensive conventional PRB materials, especially pure metallic iron. The feasibility of reductive denitrification of nitrate by SIF was studied by batch experiments. Operational parameters such as pH value, SIF dosage and initial concentration of nitrate were investigated. The removal efficiency of nitrate reached 80% under the conditions of pH of 2.5, nitrate initial con- centration of 45 mg/L and SIF dosage of 100 g/L within 4 h. Results indicated that nitrate removal is inversely related to pH. Low pH value condition favors for the nitrate transformation. Different from the results of others who studied nitrate reduction using iron powder, we found that there was a lag time before nitrate reduction occurs, even at low pH. Finally, the possible mechanism of nitrate reduction by Fe0 is discussed.
文摘The reduction of hexavalent chromium by scrap iron was investigated in continuous long-term fixed bed system. The effects of pH, empty bed contact time （EBCT）, and initial Cr（VI） concentration on Cr（VI） reduction were studied. The results showed that the pH, EBCT, and initial Cr（VI） concentration significantly affected the reduction capacity of scrap iron. The reduction capacity of scrap iron were 4.56, 1.51, and 0.57mg Cr（VI）-g1 Fe0 at pH 3, 5, and 7 （initial Cr（VI） concentration 4 mg.L 1, EBCT 2 min, and temperature 25℃）, 0.51, 1.51, and 2.85 mg Cr（VI）.g-I Fe0 at EBCTs of 0.5, 2.0, and 6.0rain （initial Cr（VI） concentration 4mg.L-1, pH 5, and temperature 25℃）, and 2.99, 1.51, and 1.01 mg Cr（VI）. gl Fe0 at influent concentrations of 1, 4, and 8 mg.L ^-1（EBCT 2 min, pH 5, and temperature 25℃）, respectively. Fe（total） concentration in the column effluent continuously decreased in time, due to a decrease in time of the iron corrosion rate. The fixed bed reactor can be readily used for the treatment of drinking water containing low amounts of Cr（VI） ions, although the hardness and humic acid in water may shorten the lifetime of the reactor, the reduction capacity of scrap iron still achieved 1.98 mg Cr6 ＋- g-~ Fe. Scanning electron micro- scope equipped with energy dispersion spectrometer and X-ray diffraction were conducted to examine the surface species of the scrap iron before and after its use. In addition to iron oxides and hydroxide species, iron-chromium complex was also observed on the reacted scrap iron.
基金We are grateful for the project grants supported by the Major Science and Technology Programs for Water Pollution Control and Management of China(Nos.2012ZX07205-001 and 2017ZX7103-007).
文摘This study focuses on identifying the factors under which mixed microbial seeds assist bio-chemical denitrification when Scrap Iron Filings(SIF)are used as electron donors and adsorbents in low C/N ratio waters.Batch studies were conducted in abiotic and biotic reactors containing fresh and aged SIF under different dissolved oxygen concentrations with NO_(3)^(-)−N and/or PO_(4)^(3−)influent(s)and their nitrate/phosphate removal and by-product formations were studied.Batch reactors were seeded with a homogenized mixed microbial inoculum procured from natural sludges which were enriched over 6 months under denitrifying conditions in the presence of SIF.Results indicated that when influent containing 40 mg/L of NO_(3)^(-)−N was treated with 5 g SIF,79.9%nitrate reduction was observed in 8 days abiotically and 100%removal was accomplished in 20 days when the reactor was seeded.Both abiotic and seeded reactors removed more than 92%PO_(4)^(3−)under high DO conditions in 12 days.Abiotic and biochemical removal of NO_(3)^(-)−N and abiotic removal of PO_(4)^(3−)were higher under independent NO_(3)^(-)−N/PO_(4)^(3−)loading,while 99%PO_(4)^(3−)was removed biochemically under combined NO_(3)^(-)−N and PO_(4)^(3−)loading.This study furthers the understandings of nitrate and phosphate removal in Zero Valent Iron(ZVI)assisted mixed microbial systems to encourage the application of SIF-supported bio-chemical processes in the simultaneous removals of these pollutants.
基金This work was supported by the National Natural Science Foundation of China(41672247,41102157)Liaoning Province’s“Program for Promoting Liaoning Talents”(XLYC1807159)+1 种基金2019 Nature Fund Project Guidance Plan of Liaoning Province(2019-zd-0044)2017 Youth Project of Education Department of Liaoning Province(LJ2017QL035).
文摘The study is aimed at the problem of high content of Cr^(6+),Cr^(3+)and SO_(4)^(2-)is high and low pH value in acid mine drainage(AMD).Moreover,treatment of AMD by sulfate reducing bacteria(SRB)requires the addition of carbon source,while the treating effectiveness is not good enough on its own.The sugarcane slag,the corn cob and the sunflower straw were selected as the SRB carbon source cooperating with iron scrap to construct the dynamic columns 1,2 and 3.The mechanism of removing Cr^(6+),Cr^(3+),SO_(4)^(2-)and H+and the regularity of sustained release of carbon source and TFe release was studied in AMD.The removal efficiency of heavy metal ions,the ability of sustained release of carbon source,and the ability of adjusting acid by the three dynamic columns were compared.The result shows that the average removal rates of Cr^(6+),Cr^(3+)and SO_(4)^(2-)in effluent of dynamic column 1,filled by sugarcane slag,iron scrap and SRB,were 96.9%,67.1%and 54.3%.The average release of TFe and chemical oxygen demand(COD)were 4.4 and 287.3 mg/L.Its average pH was 6.98.Compared with the performance of dynamic columns 1,2 and 3,dynamic column 1 performed best in removing Cr^(6+),Cr^(3+)and SO_(4)^(2-)from AMD and controlling the release of COD and TFe,adjusting the pH of the solution.The study is of significance in treatment of AMD by taking for biomass materials as SRB carbon source in cooperation with iron scrap.
基金Project(05KJD6010110) supported by the Natural Science Foundation of the Education Commission of Jiangsu Province,ChinaProject(2005005) supported by the Science and Technology Foundation of the Environmental Protection Bureau of Jiangsu Province,China
文摘The degradation of five naphthalene derivatives in the simulated wastewater was investigated using the iron-carbon micro-electrolysis method.The optimal initial pH of solution and adsorption of iron-carbon and removal efficiency of the total organic carbon(TOC)were investigated.The results show that the removal efficiency of the naphthalene derivatives can reach 48.9%?92.6% and the removal efficiency of TOC is 42.8%?78.0% for the simulated wastewater with 200 mg/L naphthalene derivatives at optimal pH of 2.0?2.5 after 120 min treatment.The degradation of five naphthalene derivatives with the micro-electrolysis shows the apparent first-order kinetics and the order of removal efficiency of the naphthalene derivatives is sodium 2-naphthalenesulfonate,2-naphthol,2,7-dihydroxynaphthalene,1-naphthamine,1-naphthol-8-sulfonic acid in turn.It is illustrated that the substituents of the naphthalene ring can affect the removal efficiency of naphthalene due to their electron-withdrawing or electron-donating ability.
