To address the environmental and health hazards of nitrate(NO_(3)^(-))in water,a denitrification advanced reduction process(ARP)using only formic acid(HCOOH)activated by ultraviolet(UV)light was proposed.The efficienc...To address the environmental and health hazards of nitrate(NO_(3)^(-))in water,a denitrification advanced reduction process(ARP)using only formic acid(HCOOH)activated by ultraviolet(UV)light was proposed.The efficiency,influencing factors,mechanism,and kinetics of the reduction were investigated through component analysis and radical detection.Results show that,after 90 min of UV illumination,the reduction and gas conversion ratios of 50 mg/L NO_(3)^(-)-N reach 99.9%and 99.8%,respectively,under 9 mM of C_(0)(HCOOH),pH=3.0,and N_(2) aeration.Meanwhile,96.7%of HCOOH is consumed and converted into gas.The NO_(3)^(-)-N conversion process includes the transformation to NO_(2)^(-)-N,followed by a further reduction to gas and a direct conversion into gas,introducing small amounts of nitrite and ammonia.The carbon dioxide anion radical(·CO_(2)^(-))from HCOOH/HCOO^(-)is the principal cause of NO_(3)^(-)-N reduction by UV/HCOOH/N 2 ARP.In contrast,·CO_(2)^(-)production is caused by the hydroxyl radical(·OH).The NO_(3)^(-)-N reduction efficiency is enhanced by the increase in the light intensity,considerably affected by the initial pH,and less affected by inorganic anions,including Cl^(-),H_(2)PO_(4)^(-),and HCO_(3)^(-)/CO_(3)^(2-).The initial HCOOH concentration and light intensity are the main factors that influence the NO_(3)^(-)-N reduction rate.展开更多
We studied the decomposition of two haloacetic acids (HAAs),dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA),in water by single oxidants ozone (O3) and ultraviolet radiation (UV) and the advanced oxidation p...We studied the decomposition of two haloacetic acids (HAAs),dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA),in water by single oxidants ozone (O3) and ultraviolet radiation (UV) and the advanced oxidation processes (AOPs) constituted by the combinations of O3/UV,H2O2/UV,O3 /H2O2,and O3/H2O2/UV. The concentrations of HAAs were analyzed at specified time intervals to track their decomposition. Except for O3 and UV,the four combined oxidation processes remarkably enhance the decomposition of DCAA and TCAA owing to the generated very reactive hydroxyl radicals. The fastest decomposition process is O3/H2O2/UV,closely followed by O3/UV. DCAA is much easier to decompose than TCAA. The kinetics of HAA decomposition by O3/UV can be described well by a pseudo first-order reaction model under a constant initial dissolved O3 concentration and fixed UV radiation. Humic acids and HCO3-in the reaction system both decrease the decomposition rate constants for DCAA and TCAA. The amount of H2O2 accumulates in the presence of humic acids in the O3/UV process.展开更多
基金The National Major Science and Technology Project(No.2017ZX07202-004-005)。
文摘To address the environmental and health hazards of nitrate(NO_(3)^(-))in water,a denitrification advanced reduction process(ARP)using only formic acid(HCOOH)activated by ultraviolet(UV)light was proposed.The efficiency,influencing factors,mechanism,and kinetics of the reduction were investigated through component analysis and radical detection.Results show that,after 90 min of UV illumination,the reduction and gas conversion ratios of 50 mg/L NO_(3)^(-)-N reach 99.9%and 99.8%,respectively,under 9 mM of C_(0)(HCOOH),pH=3.0,and N_(2) aeration.Meanwhile,96.7%of HCOOH is consumed and converted into gas.The NO_(3)^(-)-N conversion process includes the transformation to NO_(2)^(-)-N,followed by a further reduction to gas and a direct conversion into gas,introducing small amounts of nitrite and ammonia.The carbon dioxide anion radical(·CO_(2)^(-))from HCOOH/HCOO^(-)is the principal cause of NO_(3)^(-)-N reduction by UV/HCOOH/N 2 ARP.In contrast,·CO_(2)^(-)production is caused by the hydroxyl radical(·OH).The NO_(3)^(-)-N reduction efficiency is enhanced by the increase in the light intensity,considerably affected by the initial pH,and less affected by inorganic anions,including Cl^(-),H_(2)PO_(4)^(-),and HCO_(3)^(-)/CO_(3)^(2-).The initial HCOOH concentration and light intensity are the main factors that influence the NO_(3)^(-)-N reduction rate.
基金Natural Science Foundation of Chongqing under Grant No. CSTC2008BB7299.
文摘We studied the decomposition of two haloacetic acids (HAAs),dichloroacetic acid (DCAA) and trichloroacetic acid (TCAA),in water by single oxidants ozone (O3) and ultraviolet radiation (UV) and the advanced oxidation processes (AOPs) constituted by the combinations of O3/UV,H2O2/UV,O3 /H2O2,and O3/H2O2/UV. The concentrations of HAAs were analyzed at specified time intervals to track their decomposition. Except for O3 and UV,the four combined oxidation processes remarkably enhance the decomposition of DCAA and TCAA owing to the generated very reactive hydroxyl radicals. The fastest decomposition process is O3/H2O2/UV,closely followed by O3/UV. DCAA is much easier to decompose than TCAA. The kinetics of HAA decomposition by O3/UV can be described well by a pseudo first-order reaction model under a constant initial dissolved O3 concentration and fixed UV radiation. Humic acids and HCO3-in the reaction system both decrease the decomposition rate constants for DCAA and TCAA. The amount of H2O2 accumulates in the presence of humic acids in the O3/UV process.
