Zn adsorption by pure oxides or in the presence of a high concentration of inner electrolyte has been extensively studied. But, in studies on Zn adsorption in the complicated soil system, especially in variable charge...Zn adsorption by pure oxides or in the presence of a high concentration of inner electrolyte has been extensively studied. But, in studies on Zn adsorption in the complicated soil system, especially in variable charge soils, profound knowledge about the adsorption mechanism still lacks. In this paper, taking Zn ion adsorption by two typical variable charge soils as the object of the study, author discusses the relation between Zn adsorption and pH and possible adsorption mechanisms. The results showed that in the low pH range where the amount of Zn adsorbed did not exceed 50% of Zn added, the specific adsorption was the dominant mechanism. The species of Zn specifically adsorbed was free Zn2+ ion. In the middle and high pH ranges, the mechanisms of specific and electrostatic adsorptions, co-existed, accounting for about 70% and 30% , respectively. Noteworthily, in the high pH range, the hydroxyl Zn ion (ZnOH +) from Zn2+ hydrolysis probably was a preferable species for specific adsorption.展开更多
The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsor...The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsorption on Al-oxide-typed surfaces between pH 3.5 to pH 5.5 as suspension pH changed from 2 to 9, but the adsorption amount of phosphate decreased continually as pH rose on Fe-oxide typed surfaces. The adsorption amount of phosphate and the maximum phosphate adsorption pH decreased in the order of yellow-red soil > lateritic red soil > red soil > paddy soil, which was coincided with the content order of amorphous Al oxide. The removement of organic matter and Fe oxide made the maximum phosphate adsorption pH rise from 4.0 to 5.0 and 4.5, respectively. The desorption curves with pH of four soils showed that phosphate desorbed least at pH 5. Generally the desorption was contrary to the adsorption with pH changing. There was a good accordance between adsorption or desorption and the concentration of Al in the suspension. The possible mechanisms of phosphate adsorption are discussed.展开更多
Chemical forms of the phosphate adsorbed on goethite surfaces and characteristics of the coordinategroups which exchange with P on goethite surfaces in solutions with different pll values were investigated.Results sho...Chemical forms of the phosphate adsorbed on goethite surfaces and characteristics of the coordinategroups which exchange with P on goethite surfaces in solutions with different pll values were investigated.Results showed that the chemical forms of P on goethite surfaces changed from the dominance of monodentatecorrdination to that of bidentate one with increasing pH of the solution. By influencing types of phosphateions in solutions, pH affected the chemical forms of P on goethite surfaces. The amount of OH￣- displacedby phosphate on goethite surfaces was the most at pH 7.0, the second at pH 9.0, and the least at pH 4.5.展开更多
A self-made constant pH automated titration instrument was used to study thekinetics of hydroxyl release during selenite reacting with variable charge soils. The rate ofhydroxyl release was very rapid at the first sev...A self-made constant pH automated titration instrument was used to study thekinetics of hydroxyl release during selenite reacting with variable charge soils. The rate ofhydroxyl release was very rapid at the first several minutes, then gradually slowed down, and atlast did not change any more. The experimental data was well fitted by the Langmuir kineticequation, arid with increasing selenite concentration or decreasing solution pH, the reaction lastedlonger, the maximum of hydroxyl release (x_m) increased, and the binding constant (k) decreased.The time of hydroxyl release with Xuwen latosol was much longer than that with Jinxian red soil.展开更多
A synthetic activated carbon was manufactured from date-palm stones using zinc chloride, cadmium chloride and sodium chloride at different temperatures and atmospheres. Specific surface area, RC and pH were measured a...A synthetic activated carbon was manufactured from date-palm stones using zinc chloride, cadmium chloride and sodium chloride at different temperatures and atmospheres. Specific surface area, RC and pH were measured and the activated carbon was used to absorb the orange II dye. Adsorption equilibrium was also studied, and it was found that the adsorption process on the synthetic activated carbon fit very well with the Langmuir isotherm model and less fit with Freundlich isotherm model. The specific surface area was highly affected by increasing temperature of combustion while the atmosphere of combustion had a little effects on surface area. The results showed that the atmosphere and temperature had no such effect on RC values. However, the RC of zinc chloride samples gave the highest values compared to that of cadmium chloride or sodium chlorides. The values of pH indicated an acid medium for cadmium chloride to alkali medium for sodium chloride, while the samples of zinc chloride showed a neutral medium.展开更多
The effects of Ca(2+) and Al(3+)ions on flocculating process of kaolin using plogycrylamide as flocculant was studied. Mechanism of the effects was investigated and discussed through molecularorbit(MO) theory , soluti...The effects of Ca(2+) and Al(3+)ions on flocculating process of kaolin using plogycrylamide as flocculant was studied. Mechanism of the effects was investigated and discussed through molecularorbit(MO) theory , solution chemistry calculation and electronic probe examination in this article.展开更多
Modified humic acid (MHA) binder based on lignite humic substances is a novel sort of promising organic binder for iron ore pellets.Humic acid (HA) is one of the main ingredients of MHA binder.Pure HA was firstly isol...Modified humic acid (MHA) binder based on lignite humic substances is a novel sort of promising organic binder for iron ore pellets.Humic acid (HA) is one of the main ingredients of MHA binder.Pure HA was firstly isolated from lignite and then adsorption of HA onto magnetite particle surface was investigated.The final results indicate that the adsorption of HA onto magnetite surface accords with Langmuir model well,and it is evidently influenced by the initial HA concentration and solution pH value.Adsorption depends on chemical interaction at pH values above the PZC (the pH where the Zeta potentials of minerals are zero) of magnetite,while electrostatic attraction and chemical interaction both contribute to the adsorption at pH values below the PZC.展开更多
In this paper,we studied the pH dependent plasmon-driven surface-catalysis(PDSC) reactions of p,p'-dimercaptoazobenzene(DMAB) produced from para-aminothiophenol(PATP) and 4-nitrobenzenethiol(4NBT) both theoretical...In this paper,we studied the pH dependent plasmon-driven surface-catalysis(PDSC) reactions of p,p'-dimercaptoazobenzene(DMAB) produced from para-aminothiophenol(PATP) and 4-nitrobenzenethiol(4NBT) both theoretically and experimentally.The surface enhanced Raman spectrum(SERS) of DMAB produced from PATP and 4NBT on Ag films in solutions with various pH values has been measured.The simulation and experimental results indicated that the pH dependence of PATP appeared in acidic environment and came from the amino group NH2.Furthermore,the ratio of intensity of Raman peak caused by PATP and DMAB indicated that this acidic sensor had higher pH sensitivity when it was excited by photons of higher energy.展开更多
文摘Zn adsorption by pure oxides or in the presence of a high concentration of inner electrolyte has been extensively studied. But, in studies on Zn adsorption in the complicated soil system, especially in variable charge soils, profound knowledge about the adsorption mechanism still lacks. In this paper, taking Zn ion adsorption by two typical variable charge soils as the object of the study, author discusses the relation between Zn adsorption and pH and possible adsorption mechanisms. The results showed that in the low pH range where the amount of Zn adsorbed did not exceed 50% of Zn added, the specific adsorption was the dominant mechanism. The species of Zn specifically adsorbed was free Zn2+ ion. In the middle and high pH ranges, the mechanisms of specific and electrostatic adsorptions, co-existed, accounting for about 70% and 30% , respectively. Noteworthily, in the high pH range, the hydroxyl Zn ion (ZnOH +) from Zn2+ hydrolysis probably was a preferable species for specific adsorption.
文摘The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsorption on Al-oxide-typed surfaces between pH 3.5 to pH 5.5 as suspension pH changed from 2 to 9, but the adsorption amount of phosphate decreased continually as pH rose on Fe-oxide typed surfaces. The adsorption amount of phosphate and the maximum phosphate adsorption pH decreased in the order of yellow-red soil > lateritic red soil > red soil > paddy soil, which was coincided with the content order of amorphous Al oxide. The removement of organic matter and Fe oxide made the maximum phosphate adsorption pH rise from 4.0 to 5.0 and 4.5, respectively. The desorption curves with pH of four soils showed that phosphate desorbed least at pH 5. Generally the desorption was contrary to the adsorption with pH changing. There was a good accordance between adsorption or desorption and the concentration of Al in the suspension. The possible mechanisms of phosphate adsorption are discussed.
文摘Chemical forms of the phosphate adsorbed on goethite surfaces and characteristics of the coordinategroups which exchange with P on goethite surfaces in solutions with different pll values were investigated.Results showed that the chemical forms of P on goethite surfaces changed from the dominance of monodentatecorrdination to that of bidentate one with increasing pH of the solution. By influencing types of phosphateions in solutions, pH affected the chemical forms of P on goethite surfaces. The amount of OH￣- displacedby phosphate on goethite surfaces was the most at pH 7.0, the second at pH 9.0, and the least at pH 4.5.
基金Project supported by the National Natural Science Foundation of China (Nos. 49971046 and 49831005).
文摘A self-made constant pH automated titration instrument was used to study thekinetics of hydroxyl release during selenite reacting with variable charge soils. The rate ofhydroxyl release was very rapid at the first several minutes, then gradually slowed down, and atlast did not change any more. The experimental data was well fitted by the Langmuir kineticequation, arid with increasing selenite concentration or decreasing solution pH, the reaction lastedlonger, the maximum of hydroxyl release (x_m) increased, and the binding constant (k) decreased.The time of hydroxyl release with Xuwen latosol was much longer than that with Jinxian red soil.
文摘A synthetic activated carbon was manufactured from date-palm stones using zinc chloride, cadmium chloride and sodium chloride at different temperatures and atmospheres. Specific surface area, RC and pH were measured and the activated carbon was used to absorb the orange II dye. Adsorption equilibrium was also studied, and it was found that the adsorption process on the synthetic activated carbon fit very well with the Langmuir isotherm model and less fit with Freundlich isotherm model. The specific surface area was highly affected by increasing temperature of combustion while the atmosphere of combustion had a little effects on surface area. The results showed that the atmosphere and temperature had no such effect on RC values. However, the RC of zinc chloride samples gave the highest values compared to that of cadmium chloride or sodium chlorides. The values of pH indicated an acid medium for cadmium chloride to alkali medium for sodium chloride, while the samples of zinc chloride showed a neutral medium.
文摘The effects of Ca(2+) and Al(3+)ions on flocculating process of kaolin using plogycrylamide as flocculant was studied. Mechanism of the effects was investigated and discussed through molecularorbit(MO) theory , solution chemistry calculation and electronic probe examination in this article.
基金Project(50804059) supported by the National Natural Science Foundation of ChinaProject(50725416) supported by the National Natural Science Funds for Distinguished Young Scholars of China
文摘Modified humic acid (MHA) binder based on lignite humic substances is a novel sort of promising organic binder for iron ore pellets.Humic acid (HA) is one of the main ingredients of MHA binder.Pure HA was firstly isolated from lignite and then adsorption of HA onto magnetite particle surface was investigated.The final results indicate that the adsorption of HA onto magnetite surface accords with Langmuir model well,and it is evidently influenced by the initial HA concentration and solution pH value.Adsorption depends on chemical interaction at pH values above the PZC (the pH where the Zeta potentials of minerals are zero) of magnetite,while electrostatic attraction and chemical interaction both contribute to the adsorption at pH values below the PZC.
基金supported by the Fundamental Research Funds for the Central Universities(CDJZR11300003)National Basic Research Program of China(973 Program,2012CB626801)+2 种基金National Natural Science Foundation of China(11274057)Fundamental Research Funds for the Central Universities(DC12010117)Program for Liaoning Excellent Talents in University(LJQ2012112)
文摘In this paper,we studied the pH dependent plasmon-driven surface-catalysis(PDSC) reactions of p,p'-dimercaptoazobenzene(DMAB) produced from para-aminothiophenol(PATP) and 4-nitrobenzenethiol(4NBT) both theoretically and experimentally.The surface enhanced Raman spectrum(SERS) of DMAB produced from PATP and 4NBT on Ag films in solutions with various pH values has been measured.The simulation and experimental results indicated that the pH dependence of PATP appeared in acidic environment and came from the amino group NH2.Furthermore,the ratio of intensity of Raman peak caused by PATP and DMAB indicated that this acidic sensor had higher pH sensitivity when it was excited by photons of higher energy.
