Electrochemical-nitrate-reduction-reaction(eNitRR)synthesis of ammonia is an effective way to treat ni-trate wastewater and alleviate the pressure of the Haber-Bosch ammonia production industry.How to develop effectiv...Electrochemical-nitrate-reduction-reaction(eNitRR)synthesis of ammonia is an effective way to treat ni-trate wastewater and alleviate the pressure of the Haber-Bosch ammonia production industry.How to develop effective catalysts to electrochemically reduce nitrate to ammonia and purify sewage under com-plex environmental conditions is the focus of current research.Herein,the dopamine polymerization pro-cess and the[(C_(12)H_(8)N_(2))_(2)Cu]^(2+)complex embedding process were run simultaneously in time and space,and ultrafine Cu nanoparticles(Cu/CN)were effectively loaded on nitrogen-doped carbon after heat treat-ment.Using Cu/CN as the catalyst,the ammonia yield rate and Faradaic efficiency of the electrochemical conversion of NO_(3)^(-)to NH_(3)are highly 8984.0μg h^(−1)mg cat.^(−1)and 95.6%,respectively.Even in the face of complex water environments,such as neutral media,acidic media,coexisting ions,and actual nitrate wastewater,nitrate wastewater can be effectively purified to form high value-added ammonia.The strat-egy of simultaneous embedding increases the exposure rate of Cu sites,and the support of CN is also beneficial to reduce the energy barrier of ^(∗)NO_(3)activation.This study rationally designed catalysts that are beneficial to eNitRR,and considered the situation faced by practical applications during the research stage,reducing the performance gap between laboratory exploration and industrial applications.展开更多
High-solids anaerobic digestion of sewage sludge was a promising process, but high solid concentra- tion negatively influenced methane production. The influencing mechanism was systematically analyzed in this study th...High-solids anaerobic digestion of sewage sludge was a promising process, but high solid concentra- tion negatively influenced methane production. The influencing mechanism was systematically analyzed in this study through a series of static anaerobic digestion experiments at total solids （TS） contents of 3%--15%. The results showed that TS 6% was the boundary between low- solids and high-solids anaerobic digestion, and the accumulative methane yield decreased exponentially when TS increased from 6% to 15%. The performance of anaerobic digestion was directly determined by the efficiency of mass transfer, and the relation between methane yield and sludge diffusive coefficients was well described by a power function. Thus, the increasing TS resulted in an exponential increase in sludge viscosity but an exponential decrease in diffusive coefficient. The blocked mass transfer led to the accumulation of volatile fatty acids （VFAs） and free ammonia. Acetic metabolism was the main process, whereas butyric and propionic metabolisms occurred at the initial stage of high-solids anaerobic digestion. The concentration of VFAs reached the maximum at the initial stage, which were still lower than the threshold influencing methanogens. The concen- tration of free ammonia increased gradually, and the methanogenesis was inhibited when free ammonia nitro- gen exceeded 50 mg.L^-1. Consequently, the deterioration of high-solids anaerobic digestion was related to the blocked mass transfer and the resulting ammonia accumu- lation.展开更多
基金supported by the Zhejiang Province Key Research and Development Project(No.2023C01191)the Construction of the Scientific Research Platform of Yunnan Normal University(No.01100205020503202)+1 种基金the“Union University Innovation Team”of Yunnan Normal University(No.01100205020503209)the“Spring City Plan:the High-level Talent Promotion and Training Project of Kunming(No.2022SCP005)”.
文摘Electrochemical-nitrate-reduction-reaction(eNitRR)synthesis of ammonia is an effective way to treat ni-trate wastewater and alleviate the pressure of the Haber-Bosch ammonia production industry.How to develop effective catalysts to electrochemically reduce nitrate to ammonia and purify sewage under com-plex environmental conditions is the focus of current research.Herein,the dopamine polymerization pro-cess and the[(C_(12)H_(8)N_(2))_(2)Cu]^(2+)complex embedding process were run simultaneously in time and space,and ultrafine Cu nanoparticles(Cu/CN)were effectively loaded on nitrogen-doped carbon after heat treat-ment.Using Cu/CN as the catalyst,the ammonia yield rate and Faradaic efficiency of the electrochemical conversion of NO_(3)^(-)to NH_(3)are highly 8984.0μg h^(−1)mg cat.^(−1)and 95.6%,respectively.Even in the face of complex water environments,such as neutral media,acidic media,coexisting ions,and actual nitrate wastewater,nitrate wastewater can be effectively purified to form high value-added ammonia.The strat-egy of simultaneous embedding increases the exposure rate of Cu sites,and the support of CN is also beneficial to reduce the energy barrier of ^(∗)NO_(3)activation.This study rationally designed catalysts that are beneficial to eNitRR,and considered the situation faced by practical applications during the research stage,reducing the performance gap between laboratory exploration and industrial applications.
文摘High-solids anaerobic digestion of sewage sludge was a promising process, but high solid concentra- tion negatively influenced methane production. The influencing mechanism was systematically analyzed in this study through a series of static anaerobic digestion experiments at total solids （TS） contents of 3%--15%. The results showed that TS 6% was the boundary between low- solids and high-solids anaerobic digestion, and the accumulative methane yield decreased exponentially when TS increased from 6% to 15%. The performance of anaerobic digestion was directly determined by the efficiency of mass transfer, and the relation between methane yield and sludge diffusive coefficients was well described by a power function. Thus, the increasing TS resulted in an exponential increase in sludge viscosity but an exponential decrease in diffusive coefficient. The blocked mass transfer led to the accumulation of volatile fatty acids （VFAs） and free ammonia. Acetic metabolism was the main process, whereas butyric and propionic metabolisms occurred at the initial stage of high-solids anaerobic digestion. The concentration of VFAs reached the maximum at the initial stage, which were still lower than the threshold influencing methanogens. The concen- tration of free ammonia increased gradually, and the methanogenesis was inhibited when free ammonia nitro- gen exceeded 50 mg.L^-1. Consequently, the deterioration of high-solids anaerobic digestion was related to the blocked mass transfer and the resulting ammonia accumu- lation.
