Nitric humic acid was prepared by catalytic oxidation between nitric acid and Guizhou coal, with added catalysts. We investigated catalytic oxidation processes and the factors that affect the reactions. The effects of...Nitric humic acid was prepared by catalytic oxidation between nitric acid and Guizhou coal, with added catalysts. We investigated catalytic oxidation processes and the factors that affect the reactions. The effects of different catalysts, including NiSO4 support on active carbon （AC-NiS04）, NiS04 support on sil- icon dioxide （SiO2-NiSO4）, composites of SO42-1Fe203, Zr-iron and vanadium-iron composite were stud- ied. As well, we investigated nitric humic acid yields and the chemical structure of products by element analysis, FT-IR and E4/E6 （an absorbance ratio at wavelengths of 465 and 665 nm of humic acid alkaline extraction solutions）. The results show that the catalytic oxidation reaction with added catalysts can increase humic acid yields by 18.7%, 16.36% 12.94%, 5.61% and 8.59%, respectively. The highest yield of humic acid, i.e., 36.0%, was obtained with AC-NiSO4 as the catalyst. The amounts of C and H decreased with the amount of nitrogen. The increase in the E4/E6 ratio in catalytic oxidation of （Guizhou） coal shows that small molecular weights and high yields of nitric humic acid can be obtained by catalytic oxidation reactions.展开更多
With this study,we investigated an approach of applying an electrocoagulation method for the removal of humic acid from groundwater. Aluminium electrodes were selected in the experiment. Some major experimental factor...With this study,we investigated an approach of applying an electrocoagulation method for the removal of humic acid from groundwater. Aluminium electrodes were selected in the experiment. Some major experimental factors,such as electrode distance,current densities and pH values were explored. Results suggest that,given a small electrode interval and/or a high current density,a lower pH value leads to an improved removal rate of humic acid. Under acid conditions with a current density 47.6 A/m2,for instance,humic acid concentrations were reduced from 20 mg/L to 0.43 mg/L which resulted in the removal of 97.8% of the humic acid. This encouraging result demonstrated that our electro-coagulation method is effective in the removal of humic acid from groundwater.展开更多
The complexation, precipitation, and migration behavior of uranium in the presence of humic acid (HA) or fulvic acid (FA) were investigated by cation exchange, ultrafiltration and dynamic experiment, respectively. The...The complexation, precipitation, and migration behavior of uranium in the presence of humic acid (HA) or fulvic acid (FA) were investigated by cation exchange, ultrafiltration and dynamic experiment, respectively. The results showed that (i) complex equilibrium between the uranium and humic substances was achieved at approximately 72 h, (ii) the coordination number varied from 1:1 to 1:2 ( U(Ⅵ) : humic acid) as pH increased from 3 to 6; and (iii) , while the complex stability constant decreased when temperature increased, but increased with pH value. We found that the precipitation of uranyl could only be observed in presence of HA, and the precipitation was influenced by conditions, such as pH, uranium concentration, temperature, and the HA concentration. The maximum precipitation proportion up to 60% could be achieved in the condition of 40 mg/L HA solution at pH 6. We further observed that the migration behavior of uranium in soil in the presence of humic acid (HA) or fulvic acid (FA) was different from that in the presence of inorganic colloid, and the effect of humic substances (HS) was limited.展开更多
The adsorption behaviors of uranium on three soil humic acids (HAs), which were extracted from soils of different depths at the same site, were investigated under various experimental conditions. The adsorption result...The adsorption behaviors of uranium on three soil humic acids (HAs), which were extracted from soils of different depths at the same site, were investigated under various experimental conditions. The adsorption results showed that U(Ⅵ) in solutions can be adsorbed by the three soil HAs, with the order of FHA (HA from 5 m depth of soil) >SHA (HA from the surface) >THA (HA from 10 m depth of soil) for adsorption efficiency in each desirable condition, and the adsorption reached equilibrium in about 240 min. Although the maximum adsorption efficiency was achieved at a suitable uranium concentration (10 mg·L-1 U(Ⅵ) for SHA and THA, 20 mg·L-1 U(Ⅵ) for FHA), the adsorption could be described with Langmiur isotherm or Freundlich isotherm equation. The L/S (liquid/solid, mL/g) ratio and pH were important factors influencing the adsorption in our adsorption system besides uranium concentration. The adsorption efficiency decreased with the increase of the L/S ratio and pH at the pH range of 2.0-3.0 for SHA and THA or 2.5-6.0 for FHA. However, no significant difference in adsorption of U(Ⅵ) was observed at the experimental temperature. All the results implied that humic substances have different characteristics in samples even collected at the same site.展开更多
The effect of humic acid(HA) on the diffusion of Re(Ⅶ) was investigated in compacted Gaomiaozi(GMZ)bentonite by the through- and out- diffusion method. The effective diffusion coefficient, D e, and accessible porosit...The effect of humic acid(HA) on the diffusion of Re(Ⅶ) was investigated in compacted Gaomiaozi(GMZ)bentonite by the through- and out- diffusion method. The effective diffusion coefficient, D e, and accessible porosity, εacc, were measured in order to evaluate the impact of humic acid on Re(Ⅶ) diffusion. The D e value was in the range of(5.2–8.3)×10-12m2/s. The diffusion of Re(Ⅶ) was enhanced in the presence of HA, and the D e value increased with the increase of ageing time, indicating that the formation of HA-Re complexes was slow. Moreover, the εacc was in the range of(0.06– 0.16), which is less than the total porosity. It implies that the HA-Re complexes are anions.展开更多
Th/s article deals with the determination of the adsorption properties of metal ions and humic acid in wa- ter on crosslinked chitosan derivatives (carboxymethylchitosan) which were formed using the irradiation techni...Th/s article deals with the determination of the adsorption properties of metal ions and humic acid in wa- ter on crosslinked chitosan derivatives (carboxymethylchitosan) which were formed using the irradiation technique without any additives.The solubility test of these crosslinked materials were investigated in acidic,alkaline media, distilled water,and certain organic solvents.Scanning electron microscopic (SEM) images showed that the crosslinked chitosan derivatives possessed a porous morphological structure.Charged characteristic analyses demon- strated typically pH-dependent properties of the crosslinked materials.The adsorption studies were carried out by the batch method at room temperature.Adsorption of heavy metal ions (such as Cu^(2+),Cd^(2+)) and humic acid onto crosslinked samples was found to be strongly pH-dependent.Adsorption kinetic studies indicated the rapid removal of metal ions,and humic acid from the aqueous solutions.Moreover,isothermal adsorption data revealed that Cu^(2+),Cd^(2+), and humic acid were removed by these crosslinked materials with high efficiency.Adsorption isothermal data were interpreted well by the Langmuir equation.These crosslinked carboxymethylated chitosan derivatives indicate favor- able adsorption of metal ions and humic acid.展开更多
基金sponsored by the Shaanxi Key Scientific and Technological Project, China (No. 2010K07-20)the National Science and Technology Major Project (No. 2011ZX05037-003)
文摘Nitric humic acid was prepared by catalytic oxidation between nitric acid and Guizhou coal, with added catalysts. We investigated catalytic oxidation processes and the factors that affect the reactions. The effects of different catalysts, including NiSO4 support on active carbon （AC-NiS04）, NiS04 support on sil- icon dioxide （SiO2-NiSO4）, composites of SO42-1Fe203, Zr-iron and vanadium-iron composite were stud- ied. As well, we investigated nitric humic acid yields and the chemical structure of products by element analysis, FT-IR and E4/E6 （an absorbance ratio at wavelengths of 465 and 665 nm of humic acid alkaline extraction solutions）. The results show that the catalytic oxidation reaction with added catalysts can increase humic acid yields by 18.7%, 16.36% 12.94%, 5.61% and 8.59%, respectively. The highest yield of humic acid, i.e., 36.0%, was obtained with AC-NiSO4 as the catalyst. The amounts of C and H decreased with the amount of nitrogen. The increase in the E4/E6 ratio in catalytic oxidation of （Guizhou） coal shows that small molecular weights and high yields of nitric humic acid can be obtained by catalytic oxidation reactions.
文摘With this study,we investigated an approach of applying an electrocoagulation method for the removal of humic acid from groundwater. Aluminium electrodes were selected in the experiment. Some major experimental factors,such as electrode distance,current densities and pH values were explored. Results suggest that,given a small electrode interval and/or a high current density,a lower pH value leads to an improved removal rate of humic acid. Under acid conditions with a current density 47.6 A/m2,for instance,humic acid concentrations were reduced from 20 mg/L to 0.43 mg/L which resulted in the removal of 97.8% of the humic acid. This encouraging result demonstrated that our electro-coagulation method is effective in the removal of humic acid from groundwater.
基金Supported by China National Natural Science Foundation(Nos.21071102 and 91126013)Joint Funds of China National Natural Science Foundation and China Academy of Engineering Physics(No.10476015)National Fund of China for Fostering Talents in Basic Science(No.J1210004)
文摘The complexation, precipitation, and migration behavior of uranium in the presence of humic acid (HA) or fulvic acid (FA) were investigated by cation exchange, ultrafiltration and dynamic experiment, respectively. The results showed that (i) complex equilibrium between the uranium and humic substances was achieved at approximately 72 h, (ii) the coordination number varied from 1:1 to 1:2 ( U(Ⅵ) : humic acid) as pH increased from 3 to 6; and (iii) , while the complex stability constant decreased when temperature increased, but increased with pH value. We found that the precipitation of uranyl could only be observed in presence of HA, and the precipitation was influenced by conditions, such as pH, uranium concentration, temperature, and the HA concentration. The maximum precipitation proportion up to 60% could be achieved in the condition of 40 mg/L HA solution at pH 6. We further observed that the migration behavior of uranium in soil in the presence of humic acid (HA) or fulvic acid (FA) was different from that in the presence of inorganic colloid, and the effect of humic substances (HS) was limited.
基金NSFA Joint Fund (China National Natural Science Foundation and the Chinese Academy of Engineering Physics) (10476015)
文摘The adsorption behaviors of uranium on three soil humic acids (HAs), which were extracted from soils of different depths at the same site, were investigated under various experimental conditions. The adsorption results showed that U(Ⅵ) in solutions can be adsorbed by the three soil HAs, with the order of FHA (HA from 5 m depth of soil) >SHA (HA from the surface) >THA (HA from 10 m depth of soil) for adsorption efficiency in each desirable condition, and the adsorption reached equilibrium in about 240 min. Although the maximum adsorption efficiency was achieved at a suitable uranium concentration (10 mg·L-1 U(Ⅵ) for SHA and THA, 20 mg·L-1 U(Ⅵ) for FHA), the adsorption could be described with Langmiur isotherm or Freundlich isotherm equation. The L/S (liquid/solid, mL/g) ratio and pH were important factors influencing the adsorption in our adsorption system besides uranium concentration. The adsorption efficiency decreased with the increase of the L/S ratio and pH at the pH range of 2.0-3.0 for SHA and THA or 2.5-6.0 for FHA. However, no significant difference in adsorption of U(Ⅵ) was observed at the experimental temperature. All the results implied that humic substances have different characteristics in samples even collected at the same site.
基金Supported by National Natural Science Foundation of China(Nos.11275147 and 21207035)Program for Changjiang Scholars and Innovative Research Team in University(No.IRT1280)
文摘The effect of humic acid(HA) on the diffusion of Re(Ⅶ) was investigated in compacted Gaomiaozi(GMZ)bentonite by the through- and out- diffusion method. The effective diffusion coefficient, D e, and accessible porosity, εacc, were measured in order to evaluate the impact of humic acid on Re(Ⅶ) diffusion. The D e value was in the range of(5.2–8.3)×10-12m2/s. The diffusion of Re(Ⅶ) was enhanced in the presence of HA, and the D e value increased with the increase of ageing time, indicating that the formation of HA-Re complexes was slow. Moreover, the εacc was in the range of(0.06– 0.16), which is less than the total porosity. It implies that the HA-Re complexes are anions.
文摘Th/s article deals with the determination of the adsorption properties of metal ions and humic acid in wa- ter on crosslinked chitosan derivatives (carboxymethylchitosan) which were formed using the irradiation technique without any additives.The solubility test of these crosslinked materials were investigated in acidic,alkaline media, distilled water,and certain organic solvents.Scanning electron microscopic (SEM) images showed that the crosslinked chitosan derivatives possessed a porous morphological structure.Charged characteristic analyses demon- strated typically pH-dependent properties of the crosslinked materials.The adsorption studies were carried out by the batch method at room temperature.Adsorption of heavy metal ions (such as Cu^(2+),Cd^(2+)) and humic acid onto crosslinked samples was found to be strongly pH-dependent.Adsorption kinetic studies indicated the rapid removal of metal ions,and humic acid from the aqueous solutions.Moreover,isothermal adsorption data revealed that Cu^(2+),Cd^(2+), and humic acid were removed by these crosslinked materials with high efficiency.Adsorption isothermal data were interpreted well by the Langmuir equation.These crosslinked carboxymethylated chitosan derivatives indicate favor- able adsorption of metal ions and humic acid.
