The effect of free ammonia on volatile fatty acid （VFA） accumulation and process instability was studied using a lab-scale anaerobic digester fed by two typical bio-wastes： fruit and vegetable waste （FVW） and foo...The effect of free ammonia on volatile fatty acid （VFA） accumulation and process instability was studied using a lab-scale anaerobic digester fed by two typical bio-wastes： fruit and vegetable waste （FVW） and food waste （FW） at 35℃ with an organic loading rate （OLR） of 3.0 kg VS/（m3-day）. The inhibitory effects of free ammonia on methanogenesis were observed due to the low C/N ratio of each substrate （15.6 and 17.2, respectively）. A high concentration of free ammonia inhibited methanogenesis resulting in the accumulation of VFAs and a low methane yield. In the inhibited state, acetate accumulated more quickly than propionate and was the main type of accumulated VFA. The co-accumulation of ammonia and VFAs led to an ＂inhibited steady state＂ and the ammonia was the main inhibitory substance that triggered the process perturbation. By statistical significance test and VFA fluctuation ratio analysis, the free ammonia inhibition threshold was identified as 45 mg/L. Moreover, propionate, iso-butyrate and valerate were determined to be the three most sensitive VFA parameters that were subject to ammonia inhibition.展开更多
Ammonia is essential for food and energy.Industrial ammonia synthesis via Haber–Bosch process is energy-intensive and releases large amount of CO2.Increasing research efforts are devoted to "green"ammonia s...Ammonia is essential for food and energy.Industrial ammonia synthesis via Haber–Bosch process is energy-intensive and releases large amount of CO2.Increasing research efforts are devoted to "green"ammonia synthesis.The present article reviews the recent progress in the fields of thermocatalytic, electrocatalytic, photocatalytic and chemical looping processes for dinitrogen reduction towards ammonia formation and discusses the challenges borne for mild-condition synthesis.展开更多
TiO2 nanotube （TINT） electrodes anodized in fluorinated organic solutions were successfully prepared on Ti sheets. Field-emission scanning electron microscopy （FE-SEM） and X-ray diffraction （XRD） were performed ...TiO2 nanotube （TINT） electrodes anodized in fluorinated organic solutions were successfully prepared on Ti sheets. Field-emission scanning electron microscopy （FE-SEM） and X-ray diffraction （XRD） were performed to characterize the TiNT electrodes. The linear voltammetry results under irradiation showed that the TiNT electrode annealed at 450℃ presented the highest photoelectrochemical activity. By combining photocatalytic with electrochemical process, a significantly synergetic effect on ammonia degradation was observed with Na2SO4 as supporting electrolyte at pH 10.7. Furthermore, the photoelectrocatalytic efficiency on the ammonia degradation was greatly enhanced in presence of chloride ions without the limitation ofpH. The degradation rate was improved by 14.8 times reaching 4.98 × 10^-2 min^-1 at pH 10.7 and a faster degradation rate of 6.34 × 10^-2 min^-1 was obtained at pH 3.01. The in situ photoelectrocatalytic generated active chlorine was proposed to be responsible for the improved efficiency. On the other hand, an enhanced degradation of ammonia using TiNT electrode fabricated in fluorinated organic solution was also confirmed compared to TiNT electrode anodized in fluorinated water solution and TiO2 film electrode fabricated by sol-gel method. Finally, the effect of chloride concentration was also discussed.展开更多
基金supported by the Ministry of Science and Technology of China(Nos.2008BADC4B18,2014BAC27B01)
文摘The effect of free ammonia on volatile fatty acid （VFA） accumulation and process instability was studied using a lab-scale anaerobic digester fed by two typical bio-wastes： fruit and vegetable waste （FVW） and food waste （FW） at 35℃ with an organic loading rate （OLR） of 3.0 kg VS/（m3-day）. The inhibitory effects of free ammonia on methanogenesis were observed due to the low C/N ratio of each substrate （15.6 and 17.2, respectively）. A high concentration of free ammonia inhibited methanogenesis resulting in the accumulation of VFAs and a low methane yield. In the inhibited state, acetate accumulated more quickly than propionate and was the main type of accumulated VFA. The co-accumulation of ammonia and VFAs led to an ＂inhibited steady state＂ and the ammonia was the main inhibitory substance that triggered the process perturbation. By statistical significance test and VFA fluctuation ratio analysis, the free ammonia inhibition threshold was identified as 45 mg/L. Moreover, propionate, iso-butyrate and valerate were determined to be the three most sensitive VFA parameters that were subject to ammonia inhibition.
基金the financial supports from the National Natural Science Foundation of China (Grant nos.21633011, 21603220 and 21872137)Sino-Japanese Research Cooperative Program of Ministry of Science and Technology (2016YFE0118300)Youth Innovation Promotion Association CAS (No.2018213)
文摘Ammonia is essential for food and energy.Industrial ammonia synthesis via Haber–Bosch process is energy-intensive and releases large amount of CO2.Increasing research efforts are devoted to "green"ammonia synthesis.The present article reviews the recent progress in the fields of thermocatalytic, electrocatalytic, photocatalytic and chemical looping processes for dinitrogen reduction towards ammonia formation and discusses the challenges borne for mild-condition synthesis.
基金supported by the National Natural Science Foundation of China (Nos. 21277134, 21107103)the State Key Laboratory of Environmental, Criteria and Risk Assessment Chinese Research Academy of Environmental Sciences
文摘TiO2 nanotube （TINT） electrodes anodized in fluorinated organic solutions were successfully prepared on Ti sheets. Field-emission scanning electron microscopy （FE-SEM） and X-ray diffraction （XRD） were performed to characterize the TiNT electrodes. The linear voltammetry results under irradiation showed that the TiNT electrode annealed at 450℃ presented the highest photoelectrochemical activity. By combining photocatalytic with electrochemical process, a significantly synergetic effect on ammonia degradation was observed with Na2SO4 as supporting electrolyte at pH 10.7. Furthermore, the photoelectrocatalytic efficiency on the ammonia degradation was greatly enhanced in presence of chloride ions without the limitation ofpH. The degradation rate was improved by 14.8 times reaching 4.98 × 10^-2 min^-1 at pH 10.7 and a faster degradation rate of 6.34 × 10^-2 min^-1 was obtained at pH 3.01. The in situ photoelectrocatalytic generated active chlorine was proposed to be responsible for the improved efficiency. On the other hand, an enhanced degradation of ammonia using TiNT electrode fabricated in fluorinated organic solution was also confirmed compared to TiNT electrode anodized in fluorinated water solution and TiO2 film electrode fabricated by sol-gel method. Finally, the effect of chloride concentration was also discussed.
