The removal of organic matter and iron oxides could increase and decrease soil CEC in tropical and subtropical regions, but the quantitative information is insufficient so far about the change of soil CEC, the influen...The removal of organic matter and iron oxides could increase and decrease soil CEC in tropical and subtropical regions, but the quantitative information is insufficient so far about the change of soil CEC, the influence factors and their contribution. In this study, the subhorizon soils of 24 soil series in the tropical and subtropical China were used, pH, particle size composition, organic matter, iron oxides of these samples were measured, and also CECs were measured and compared for the original soils and after the removal of organic matter and iron oxides. The results showed that, compared with CEC of the original soil, the eliminating organic matter increased soil CEC significantly by 2.28% - 56.50% with a mean of 24.02%, but the further obliterating iron oxides decreased soil CEC significantly by 0.75% - 20.30% with a mean of 7.73%. CEC after the removal of organic matter and iron oxides had positive correlation with iron oxides (p < 0.01) and negative correlation with sand content (p < 0.01 and p < 0.05). CEC after organic matter eliminated was mainly decided by iron oxides (51.68%), followed by silt content (22.19%);while CEC after iron oxides obliterated was mainly determined by iron oxides (50.55%). The increase of CEC after organic matter eliminated was co-affected by the contents of clays, slits, iron oxides and pH (22.00% - 27.34%), while the decrease of CEC after iron oxides obliterated further was dominated by the content of organic matter (66.92%). More other soil parameters should be considered for higher predicting accuracy in the regression model of soil CEC after the removal of organic matter and iron oxides, and the recommended optimal models obtained in this study were as follows: for soil CEC after organic matter eliminated, CEC = 1.665 <span style="white-space:nowrap;">−</span> 0.546pH <span style="white-space:nowrap;">−</span> 0.024OM + 0.053Fe<sub>x</sub>O<sub>y</sub> <span style="white-space:nowrap;">−</span> 0.001Silt + 0.007Clay + 0.972CEC<sub>original</sub> (R<sup>2</sup> was 0.923, RSME was 1.55 cmol(+)<span style="white-space:nowrap;"><span style="white-space:nowrap;">∙</span></span>kg<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup>, p < 0.01), while for soil CEC after iron oxides further obliterated, CEC = 1.665 <span style="white-space:nowrap;">−</span> 0.546pH <span style="white-space:nowrap;">−</span> 0.024OM + 0.053Fe<sub>x</sub>O<sub>y</sub> <span style="white-space:nowrap;">−</span> 0.001Silt + 0.007Clay + 0.972CEC<sub>original</sub> (R<sup>2</sup> was 0.923, RMSE was 1.55 cmol(+)<span style="white-space:nowrap;"><span style="white-space:nowrap;">∙</span></span>kg<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup>, p < 0.01). Further research is needed in the future as for exploring internal functional mechanism in view of soil electrochemistry and mineralogy.展开更多
Clay CEC is one of identification indexes of the LAC-ferric horizon which is the diagnostic horizon of ferrosols in Chinese Soil Taxonomy, and it is defined as soil CEC × 1000/clay content, rather than the measur...Clay CEC is one of identification indexes of the LAC-ferric horizon which is the diagnostic horizon of ferrosols in Chinese Soil Taxonomy, and it is defined as soil CEC × 1000/clay content, rather than the measured CEC of the extracted clays;however, such a calculation method would definitely lead to an overestimation of clay CEC because it doesn’t remove the contribution to soil CEC from other soil parameters. In this study, the physiochemical data of the subhorizons from 82 soil series in the tropical and subtropical regions in south China were used, clay CEC was calculated according to the current formula and measured after clays being extracted, the measured and calculated clay CEC were compared, the influencing factors were analyzed for their difference, and the new algorithms were established for clay CEC. The results showed that the measured clay CEC was 21.86% - 99.53% with a mean of 66.88% of the calculated one (significantly lower at p < 0.01), and their difference was significantly correlated with the contents of clays, sand and OM, and mainly decided by the contents of clays and Fe<sub>2</sub>O<sub>3</sub> (the contribution was 52.51% and 25.36%, respectively). By comparison of established regression models of clay CEC with other soil parameters, two new algorithms were recommended for clay CEC as follows: 1) Clay CEC = 10.32 <span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span> 0.14pH <span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span> 0.05OM <span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span> 0.11Fe<sub>2</sub>O<sub>3</sub> + 0.01Silt <span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span> 0.01Clay + 1.17CEC<sub>soil</sub>, R<sup>2</sup> = 0.705, P < 0.01;2) Clay CEC = <span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>3.40 + 0.01Sand + 0.02Silt + 1.05CEC<sub>soil</sub>, R<sup>2</sup> = 0.589, P < 0.01).展开更多
Cation exchange capacity (CEC) is one of the most important properties of soils. The NH<sub>4</sub>OAc (pH = 7.0) exchange method is usually recommended to determine CEC (CEC<sub>1</sub>) of al...Cation exchange capacity (CEC) is one of the most important properties of soils. The NH<sub>4</sub>OAc (pH = 7.0) exchange method is usually recommended to determine CEC (CEC<sub>1</sub>) of all soils with different pH values, particularly for studies on soil taxonomy. But comparatively the BaCl<sub>2</sub>-MgSO<sub>4</sub> forced-exchange method is more authentic in determining CEC (CEC<sub>2</sub>) of tropical and subtropical highly-weathered acid soils. But so far little is known about the difference between CEC<sub>1</sub> and CEC<sub>2</sub>. In this study, the physiochemical data of 114 acid B horizon soils from 112 soil series of tropical and subtropical China were used, CEC<sub>1</sub> and CEC<sub>2</sub> were determined and compared, the influencing factors were analyzed for the difference between CEC<sub>1</sub> and CEC<sub>2</sub>, and then a regression model was established between CEC<sub>1</sub> and CEC<sub>2</sub>. The results showed that CEC<sub>2</sub> was significantly lower than CEC<sub>1</sub> (p < 0.01), CEC<sub>2</sub> was 14.76% - 63.31% with a mean of 36.32% of CEC<sub>1</sub>. In view of the contribution to CEC from other properties, CEC<sub>2</sub> was mainly determined by pH (45.92%), followed by silt (21.05%), free Fe<sub>2</sub>O<sub>3</sub> (17.35%) and clay contents (12.76%), CEC<sub>1</sub> was mainly decided by free Fe<sub>2</sub>O<sub>3</sub> content (40.38%), followed by pH (28.39%) and silt content (27.29%;and the difference between CEC<sub>1</sub> and CEC<sub>2</sub> was mainly affected by free Fe<sub>2</sub>O<sub>3</sub> (50.92%), followed by silt content (26.46%) and pH (21.80%). The acceptable optimal regression model between CEC<sub>2</sub> and CEC<sub>1</sub> was established as CEC<sub>2</sub> = 2.3114 × CEC<sub>1</sub><sup>1.1496</sup> (R<sup>2</sup> = 0.410, P < 0.001, RMSE = 0.15). For the studies on soil taxonomy, the BaCl<sub>2</sub>-MgSO<sub>4</sub> forced-exchange method is recommended in determining CEC of the highly-weathered acid soils in the tropical and subtropical regions.展开更多
Highly efficient and robust electrocatalysts have been in urgent demand for oxygen evolution reaction(OER).For this purpose,high-cost carbon materials,such as graphene and carbon nanotubes,have been used as supports t...Highly efficient and robust electrocatalysts have been in urgent demand for oxygen evolution reaction(OER).For this purpose,high-cost carbon materials,such as graphene and carbon nanotubes,have been used as supports to metal oxides to enhance their catalytic activity.We report here a new Co_(3)O_(4)-based catalyst with nitrogen-doped porous carbon material as the support,prepared by pyrolysis of porous polyurea(PU) with Co(NO_(3))_(2)immobilized on its surface.To this end,PU was first synthesized,without any additive,through a very simple one-step precipitation polymerization of toluene diisocyanate in a binary mixture of H2O-acetone at room temperature.By immersing PU in an aqueous solution of Co(NO_(3))_(2)at room temperature,a cobalt coordinated polymer composite,Co(NO_(3))_(2)/PU,was obtained,which was heated at 500℃ in air for 2 h to get a hybrid,Co_(3)O_(4)/NC,consisting of Co_(3)O_(4)nanocrystals and sp2-hybridized N-doped carbon.Using this Co_(3)O_(4)/NC as a catalyst in OER,a current density of10 mA·cm^(-2)was readily achieved with a low overpotential of 293 mV with a Tafel slope of87 mV·dec^(-1),a high catalytic activity.This high performance was well retained after 1000 recycled uses,demonstrating its good durability.This work provides therefore a facile yet simple pathway to fabrication of a new transition metal oxides-based N-doped carbon catalyst for OER with high performance.展开更多
Filtration control is important to ensure safe and high efficient drilling.The aim of the current research is to explore the feasibility of using basil seed powders(BSPs)to reduce filtration loss in water-based drilli...Filtration control is important to ensure safe and high efficient drilling.The aim of the current research is to explore the feasibility of using basil seed powders(BSPs)to reduce filtration loss in water-based drilling fluid.The effect of BSP concentration,thermal aging temperature,inorganic salts(NaCl and CaCl_(2))on the filtration properties of bentonite/basil suspensions was investigated.The filtration control mechanism of BSP was probed via water absorbency test,zeta potential measurement,particle size distribution measurement,and filter cake morphologies observation by scanning electron microscope.The incorporation of BSPs into the bentonite suspension generated acceptable rheology below 1.0 w/v%.The BSPs exhibited effective filtration control after thermal aging at 120C,but less efficiency at 150C.After thermal aging at 120℃,the bentonite suspension containing 1.0 w/v%BSPs could resist NaCl and CaCl_(2) pollution of 5.0 w/v%and 0.3 w/v%respectively.Besides general filtration control behaviors,the exceptional water retaining capability formed by numerous nanoscale 3D networks in the basil seed gum and considerable insoluble small particles in BSPs might further contribute to the filtration control.The excellent filtration properties bring basil seed a suitable and green candidate for the establishment of high-performance drilling fluids.展开更多
文摘The removal of organic matter and iron oxides could increase and decrease soil CEC in tropical and subtropical regions, but the quantitative information is insufficient so far about the change of soil CEC, the influence factors and their contribution. In this study, the subhorizon soils of 24 soil series in the tropical and subtropical China were used, pH, particle size composition, organic matter, iron oxides of these samples were measured, and also CECs were measured and compared for the original soils and after the removal of organic matter and iron oxides. The results showed that, compared with CEC of the original soil, the eliminating organic matter increased soil CEC significantly by 2.28% - 56.50% with a mean of 24.02%, but the further obliterating iron oxides decreased soil CEC significantly by 0.75% - 20.30% with a mean of 7.73%. CEC after the removal of organic matter and iron oxides had positive correlation with iron oxides (p < 0.01) and negative correlation with sand content (p < 0.01 and p < 0.05). CEC after organic matter eliminated was mainly decided by iron oxides (51.68%), followed by silt content (22.19%);while CEC after iron oxides obliterated was mainly determined by iron oxides (50.55%). The increase of CEC after organic matter eliminated was co-affected by the contents of clays, slits, iron oxides and pH (22.00% - 27.34%), while the decrease of CEC after iron oxides obliterated further was dominated by the content of organic matter (66.92%). More other soil parameters should be considered for higher predicting accuracy in the regression model of soil CEC after the removal of organic matter and iron oxides, and the recommended optimal models obtained in this study were as follows: for soil CEC after organic matter eliminated, CEC = 1.665 <span style="white-space:nowrap;">−</span> 0.546pH <span style="white-space:nowrap;">−</span> 0.024OM + 0.053Fe<sub>x</sub>O<sub>y</sub> <span style="white-space:nowrap;">−</span> 0.001Silt + 0.007Clay + 0.972CEC<sub>original</sub> (R<sup>2</sup> was 0.923, RSME was 1.55 cmol(+)<span style="white-space:nowrap;"><span style="white-space:nowrap;">∙</span></span>kg<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup>, p < 0.01), while for soil CEC after iron oxides further obliterated, CEC = 1.665 <span style="white-space:nowrap;">−</span> 0.546pH <span style="white-space:nowrap;">−</span> 0.024OM + 0.053Fe<sub>x</sub>O<sub>y</sub> <span style="white-space:nowrap;">−</span> 0.001Silt + 0.007Clay + 0.972CEC<sub>original</sub> (R<sup>2</sup> was 0.923, RMSE was 1.55 cmol(+)<span style="white-space:nowrap;"><span style="white-space:nowrap;">∙</span></span>kg<sup><span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>1</sup>, p < 0.01). Further research is needed in the future as for exploring internal functional mechanism in view of soil electrochemistry and mineralogy.
文摘Clay CEC is one of identification indexes of the LAC-ferric horizon which is the diagnostic horizon of ferrosols in Chinese Soil Taxonomy, and it is defined as soil CEC × 1000/clay content, rather than the measured CEC of the extracted clays;however, such a calculation method would definitely lead to an overestimation of clay CEC because it doesn’t remove the contribution to soil CEC from other soil parameters. In this study, the physiochemical data of the subhorizons from 82 soil series in the tropical and subtropical regions in south China were used, clay CEC was calculated according to the current formula and measured after clays being extracted, the measured and calculated clay CEC were compared, the influencing factors were analyzed for their difference, and the new algorithms were established for clay CEC. The results showed that the measured clay CEC was 21.86% - 99.53% with a mean of 66.88% of the calculated one (significantly lower at p < 0.01), and their difference was significantly correlated with the contents of clays, sand and OM, and mainly decided by the contents of clays and Fe<sub>2</sub>O<sub>3</sub> (the contribution was 52.51% and 25.36%, respectively). By comparison of established regression models of clay CEC with other soil parameters, two new algorithms were recommended for clay CEC as follows: 1) Clay CEC = 10.32 <span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span> 0.14pH <span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span> 0.05OM <span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span> 0.11Fe<sub>2</sub>O<sub>3</sub> + 0.01Silt <span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span> 0.01Clay + 1.17CEC<sub>soil</sub>, R<sup>2</sup> = 0.705, P < 0.01;2) Clay CEC = <span style="white-space:nowrap;"><span style="white-space:nowrap;">−</span></span>3.40 + 0.01Sand + 0.02Silt + 1.05CEC<sub>soil</sub>, R<sup>2</sup> = 0.589, P < 0.01).
文摘Cation exchange capacity (CEC) is one of the most important properties of soils. The NH<sub>4</sub>OAc (pH = 7.0) exchange method is usually recommended to determine CEC (CEC<sub>1</sub>) of all soils with different pH values, particularly for studies on soil taxonomy. But comparatively the BaCl<sub>2</sub>-MgSO<sub>4</sub> forced-exchange method is more authentic in determining CEC (CEC<sub>2</sub>) of tropical and subtropical highly-weathered acid soils. But so far little is known about the difference between CEC<sub>1</sub> and CEC<sub>2</sub>. In this study, the physiochemical data of 114 acid B horizon soils from 112 soil series of tropical and subtropical China were used, CEC<sub>1</sub> and CEC<sub>2</sub> were determined and compared, the influencing factors were analyzed for the difference between CEC<sub>1</sub> and CEC<sub>2</sub>, and then a regression model was established between CEC<sub>1</sub> and CEC<sub>2</sub>. The results showed that CEC<sub>2</sub> was significantly lower than CEC<sub>1</sub> (p < 0.01), CEC<sub>2</sub> was 14.76% - 63.31% with a mean of 36.32% of CEC<sub>1</sub>. In view of the contribution to CEC from other properties, CEC<sub>2</sub> was mainly determined by pH (45.92%), followed by silt (21.05%), free Fe<sub>2</sub>O<sub>3</sub> (17.35%) and clay contents (12.76%), CEC<sub>1</sub> was mainly decided by free Fe<sub>2</sub>O<sub>3</sub> content (40.38%), followed by pH (28.39%) and silt content (27.29%;and the difference between CEC<sub>1</sub> and CEC<sub>2</sub> was mainly affected by free Fe<sub>2</sub>O<sub>3</sub> (50.92%), followed by silt content (26.46%) and pH (21.80%). The acceptable optimal regression model between CEC<sub>2</sub> and CEC<sub>1</sub> was established as CEC<sub>2</sub> = 2.3114 × CEC<sub>1</sub><sup>1.1496</sup> (R<sup>2</sup> = 0.410, P < 0.001, RMSE = 0.15). For the studies on soil taxonomy, the BaCl<sub>2</sub>-MgSO<sub>4</sub> forced-exchange method is recommended in determining CEC of the highly-weathered acid soils in the tropical and subtropical regions.
基金financially supported by the Natural Science Foundation of Shandong Province,China(grant numbers ZR2021MB112,ZR2019MB031,ZR2020QB065)Natural Science Foundation of Guangdong Province,China(grant number2020A1515110374)Science and Technology Bureau of Jinan City,Shandong Province,China(2021GXRC105)。
文摘Highly efficient and robust electrocatalysts have been in urgent demand for oxygen evolution reaction(OER).For this purpose,high-cost carbon materials,such as graphene and carbon nanotubes,have been used as supports to metal oxides to enhance their catalytic activity.We report here a new Co_(3)O_(4)-based catalyst with nitrogen-doped porous carbon material as the support,prepared by pyrolysis of porous polyurea(PU) with Co(NO_(3))_(2)immobilized on its surface.To this end,PU was first synthesized,without any additive,through a very simple one-step precipitation polymerization of toluene diisocyanate in a binary mixture of H2O-acetone at room temperature.By immersing PU in an aqueous solution of Co(NO_(3))_(2)at room temperature,a cobalt coordinated polymer composite,Co(NO_(3))_(2)/PU,was obtained,which was heated at 500℃ in air for 2 h to get a hybrid,Co_(3)O_(4)/NC,consisting of Co_(3)O_(4)nanocrystals and sp2-hybridized N-doped carbon.Using this Co_(3)O_(4)/NC as a catalyst in OER,a current density of10 mA·cm^(-2)was readily achieved with a low overpotential of 293 mV with a Tafel slope of87 mV·dec^(-1),a high catalytic activity.This high performance was well retained after 1000 recycled uses,demonstrating its good durability.This work provides therefore a facile yet simple pathway to fabrication of a new transition metal oxides-based N-doped carbon catalyst for OER with high performance.
基金This research was supported by CNPC Innovation Foundation(2020D-5007-0310),Natural Science Foundation of China(No.51974354)the Fundamental Research Funds for the Central Universities(No.18CX02099A).
文摘Filtration control is important to ensure safe and high efficient drilling.The aim of the current research is to explore the feasibility of using basil seed powders(BSPs)to reduce filtration loss in water-based drilling fluid.The effect of BSP concentration,thermal aging temperature,inorganic salts(NaCl and CaCl_(2))on the filtration properties of bentonite/basil suspensions was investigated.The filtration control mechanism of BSP was probed via water absorbency test,zeta potential measurement,particle size distribution measurement,and filter cake morphologies observation by scanning electron microscope.The incorporation of BSPs into the bentonite suspension generated acceptable rheology below 1.0 w/v%.The BSPs exhibited effective filtration control after thermal aging at 120C,but less efficiency at 150C.After thermal aging at 120℃,the bentonite suspension containing 1.0 w/v%BSPs could resist NaCl and CaCl_(2) pollution of 5.0 w/v%and 0.3 w/v%respectively.Besides general filtration control behaviors,the exceptional water retaining capability formed by numerous nanoscale 3D networks in the basil seed gum and considerable insoluble small particles in BSPs might further contribute to the filtration control.The excellent filtration properties bring basil seed a suitable and green candidate for the establishment of high-performance drilling fluids.