Bio based nitrogen doped carbon dots(N-CDs)were obtained from empty fruit bunch carboxymethylcellulose and ethylenediamine(EDA)through one-pot hydrothermal carbonization route.The optimum as-formed NCDs were thoroughl...Bio based nitrogen doped carbon dots(N-CDs)were obtained from empty fruit bunch carboxymethylcellulose and ethylenediamine(EDA)through one-pot hydrothermal carbonization route.The optimum as-formed NCDs were thoroughly characterized via Transmission electron microscopy(TEM),high-resolution TEM(HRTEM),Fourier transform infrared(FTIR),X-ray photoelectron spectra(XPS),UV–vis spectra(UV–Vis)and Fluorescence spectra(PL).Response surface methodology was statistically used to assess three independent variables that have major influence on the fluorescence quantum yield(QY),including temperature(230–270℃),time(2–6 h)and EDA mass(10%–23.3%).Based on analysis of variance(ANOVA)results,synthesis temperature was found to be the most influential factor on the QY,followed by time and EDA mass.Higher temperature,long synthesis time and high amount of EDA were satisfactorily enough for efficient carbonization conversion rate and obtaining highest QY of N-CDs.The obtained quadratic model(R^2=0.9991)shows a good correlation between the experimental data and predicted values.The optimum synthetic parameters are of 270℃temperature,6 h reaction time and 23.3%of EDA mass.The optimized as-made N-CDs exhibited blue photoluminescence with both excitation dependent/independent phenomena and high nitrogen content.The maximum emission intensity was 426 nm at a maximum excitation wavelength of 320 nm,with a QY of up to 22.9%.XPS and FTIR data confirmed the existence of polar containing groups,such as carbonyl,carboxyl,hydroxyl and amino groups over the surface of N-CDs whereas nitrogen species in the form of(pyridinic and graphitic-N)were introduced in the aromatic carbon domains,which imparts the hydrophilic and photostability of N-CDs.Taking into account the low-cost and sustainable production of N-CDs,this method considered a feasible route for converting low quality waste into value-added nanomaterials and utilizing for different functionalization processes and analytical applications.展开更多
Wildfire is crucial in the regulation of nutrient allocation during the succession of boreal forests.However,the allocation strategies of carbon(C),nitrogen(N)and phosphorus(P)between leaves and fine roots in response...Wildfire is crucial in the regulation of nutrient allocation during the succession of boreal forests.However,the allocation strategies of carbon(C),nitrogen(N)and phosphorus(P)between leaves and fine roots in response to wildfire severities remain poorly studied.We aimed to explore the allocation strategies of C,N and P between leaves and fine roots among different fire severities.We selected four wildfire severities(unburned,low,moderate and high severity)after 10 years recovery in the Great Xing’an Mountains,northeast China,and compared C,N and P concentrations in leaves and fine roots of all species among fire severities using stoichiometry theory and allometric growth equations.Compared with unburned treatment,C concentrations in leaves and fine roots increased at low severity,and leaf N concentration was the greatest at high severity,but the lowest fine root N concentration occurred at high severity.Plant nutrient utilization tended to be P-limited at high fire severity according to the mean value of N:P ratio>16.More importantly,C,N and P allocation strategies between fine roots and leaves changed from allometry to isometry with increasing fire severities,which showed more elements allocated to leaves than to fine roots with increasing fire severities.These changes in patterns suggest that the allocation strategies of elements between leaves and fine roots are of imbalance with the wildfire severity.This study deepens our understanding of nutrient dynamics between plant and soil in ecosystem succession.展开更多
Nitrogen removal from ammonium-containing wastewater was conducted using polylactic acid （PLA）/ starch blends as carbon source and carrier for fimctional bacteria. The exclusive and interactive influences of operati...Nitrogen removal from ammonium-containing wastewater was conducted using polylactic acid （PLA）/ starch blends as carbon source and carrier for fimctional bacteria. The exclusive and interactive influences of operating parameters （i.e., temperature, pH, stirring rate, and PLA-to-starch ratio （PLA proportion）） on nitrification （Y1）, denitrification （Y2）, and COD release rates （Y3） were investigated through response surface methodology. Experimental results indicated that nitrogen removal could be successfully achieved in the PLA/starch blends through simultaneous mtnncatlon anti clenltnncatlon. The carbon release rate of the blends was controllable. The sensitivity of Y1, Y2, and Y3 to different operating parameters also differed. The sequence for each response was as follows： for Y1, pH 〉 stirring rate 〉 PLA proportion 〉 temperature; for Y2, PH 〉 PLA proportion 〉.temperature.〉 stirring rate; and for Y3, stirring rate 〉pH 〉 PLA proportion 〉 temperature. In this study, the following optimum conditions were observed： temperature, 32.0℃; pH 7.7; stirring rate, 200.0 r · min^-1 and PLA proportion 0.4. Under these conditions Y1 Y2 and Y3 were 134.0 μg-N·g-blend^-1·h^-1, 160.9μg-N-g-blend^-1·h^-1, and 7.6 × 10^3 μg-O·g-blend^-1·h^-1, respectively. These results suggested that the PLA/starch blends may be an ideal packing material for nitrogen removal.展开更多
基金Universiti Putra Malaysia for funding this project(GP-IPS/2017/9556800).
文摘Bio based nitrogen doped carbon dots(N-CDs)were obtained from empty fruit bunch carboxymethylcellulose and ethylenediamine(EDA)through one-pot hydrothermal carbonization route.The optimum as-formed NCDs were thoroughly characterized via Transmission electron microscopy(TEM),high-resolution TEM(HRTEM),Fourier transform infrared(FTIR),X-ray photoelectron spectra(XPS),UV–vis spectra(UV–Vis)and Fluorescence spectra(PL).Response surface methodology was statistically used to assess three independent variables that have major influence on the fluorescence quantum yield(QY),including temperature(230–270℃),time(2–6 h)and EDA mass(10%–23.3%).Based on analysis of variance(ANOVA)results,synthesis temperature was found to be the most influential factor on the QY,followed by time and EDA mass.Higher temperature,long synthesis time and high amount of EDA were satisfactorily enough for efficient carbonization conversion rate and obtaining highest QY of N-CDs.The obtained quadratic model(R^2=0.9991)shows a good correlation between the experimental data and predicted values.The optimum synthetic parameters are of 270℃temperature,6 h reaction time and 23.3%of EDA mass.The optimized as-made N-CDs exhibited blue photoluminescence with both excitation dependent/independent phenomena and high nitrogen content.The maximum emission intensity was 426 nm at a maximum excitation wavelength of 320 nm,with a QY of up to 22.9%.XPS and FTIR data confirmed the existence of polar containing groups,such as carbonyl,carboxyl,hydroxyl and amino groups over the surface of N-CDs whereas nitrogen species in the form of(pyridinic and graphitic-N)were introduced in the aromatic carbon domains,which imparts the hydrophilic and photostability of N-CDs.Taking into account the low-cost and sustainable production of N-CDs,this method considered a feasible route for converting low quality waste into value-added nanomaterials and utilizing for different functionalization processes and analytical applications.
基金funded by the National Key Research and Development Program of China(2017YFC0504004-1).
文摘Wildfire is crucial in the regulation of nutrient allocation during the succession of boreal forests.However,the allocation strategies of carbon(C),nitrogen(N)and phosphorus(P)between leaves and fine roots in response to wildfire severities remain poorly studied.We aimed to explore the allocation strategies of C,N and P between leaves and fine roots among different fire severities.We selected four wildfire severities(unburned,low,moderate and high severity)after 10 years recovery in the Great Xing’an Mountains,northeast China,and compared C,N and P concentrations in leaves and fine roots of all species among fire severities using stoichiometry theory and allometric growth equations.Compared with unburned treatment,C concentrations in leaves and fine roots increased at low severity,and leaf N concentration was the greatest at high severity,but the lowest fine root N concentration occurred at high severity.Plant nutrient utilization tended to be P-limited at high fire severity according to the mean value of N:P ratio>16.More importantly,C,N and P allocation strategies between fine roots and leaves changed from allometry to isometry with increasing fire severities,which showed more elements allocated to leaves than to fine roots with increasing fire severities.These changes in patterns suggest that the allocation strategies of elements between leaves and fine roots are of imbalance with the wildfire severity.This study deepens our understanding of nutrient dynamics between plant and soil in ecosystem succession.
基金This study was supported by the National Natural Science Foundation of China （Grant No. 41505124） and Fundamental Research Funds for the Central Universities （Grant No. FRF-TP- 15 -044A 1）.
文摘Nitrogen removal from ammonium-containing wastewater was conducted using polylactic acid （PLA）/ starch blends as carbon source and carrier for fimctional bacteria. The exclusive and interactive influences of operating parameters （i.e., temperature, pH, stirring rate, and PLA-to-starch ratio （PLA proportion）） on nitrification （Y1）, denitrification （Y2）, and COD release rates （Y3） were investigated through response surface methodology. Experimental results indicated that nitrogen removal could be successfully achieved in the PLA/starch blends through simultaneous mtnncatlon anti clenltnncatlon. The carbon release rate of the blends was controllable. The sensitivity of Y1, Y2, and Y3 to different operating parameters also differed. The sequence for each response was as follows： for Y1, pH 〉 stirring rate 〉 PLA proportion 〉 temperature; for Y2, PH 〉 PLA proportion 〉.temperature.〉 stirring rate; and for Y3, stirring rate 〉pH 〉 PLA proportion 〉 temperature. In this study, the following optimum conditions were observed： temperature, 32.0℃; pH 7.7; stirring rate, 200.0 r · min^-1 and PLA proportion 0.4. Under these conditions Y1 Y2 and Y3 were 134.0 μg-N·g-blend^-1·h^-1, 160.9μg-N-g-blend^-1·h^-1, and 7.6 × 10^3 μg-O·g-blend^-1·h^-1, respectively. These results suggested that the PLA/starch blends may be an ideal packing material for nitrogen removal.
