不同类型黏土矿物吸附作用对镁同位素分馏的影响

明确表生过程中Mg同位素分馏行为是示踪全球Mg循环和大陆风化过程的基础。黏土矿物吸附–解吸附是影响Mg同位素分馏的重要机制,然而这一过程中Mg同位素的分馏行为存在较大争议,尤其是黏土矿物类型和其他阳离子的影响还未有效评估。本研究选择高岭石、伊利石和蒙脱石3种典型的黏土矿物,在解吸附矿物初始吸附的Mg元素之后,加入不同含量的MgCl_(2)溶液和含有其他阳离子的河水中进行吸附–解吸附实验,并测试吸附前、后溶液和吸附组分中的元素含量和Mg同位素组成。结果表明,在相同含量的MgCl_(2)溶液中,蒙脱石对Mg的吸附能力明显高于伊利石和高岭石,这是由于蒙脱石存在层间域吸附。当吸附达到饱和状态时,黏土矿物对Mg的吸附量将不受溶液中Mg含量影响。当有其他阳离子(Na^(+)、K^(+)、Ca^(2+)等)存在时,交换作用会明显降低蒙脱石对Mg的吸附能力,但对高岭石和伊利石影响不大,这是因为交换作用主要发生在层间域。此外,在吸附–解吸附过程中,Mg同位素的分馏不明显(Δ^(26)Mg≈0),主要是由于黏土矿物吸附过程中受平衡分馏影响。

Solvent impregnated resin prepared using ionic liquid Cyphos IL 104 for Cr(VI) removal

Ionic liquid (IL) trihexyl (tetradecyl) phosphonium bis 2,4,4-trimethylpentylphosphinate (Cyphos IL 104) was impregnated on XAD-7 resin. The solvent impreganated resin (SIR) was prepared and applied in Cr(VI) removal. The morphology and the thermal stability of the resins were explored. The effects of equilibrium time and initial pH value on Cr(VI) adsorption were investigated. Adsorption isotherm, separation and desorption of the SIR, and selectivity of SIR were also explored. The results show that Cyphos IL 104 exists in the inner XAD-7 resin, and the optimum pH value range of the SIR for Cr(VI) extraction is 0 to 2. When NaOH used as desorption solution, the Cr(VI) can be effectively desorbed from the SIR.

Effective adsorption of sulfate ions with poly(m-phenylenediamine) in aqueous solution and its adsorption mechanism

Sulfate adsorption by poly（m-phenylenediamine）s（PmPDs） with various oxidation states synthesized through chemically oxidative polymerization was investigated.Series of sorption experiments were conducted,and the adsorption mechanism and the relationship between oxidation state and adsorption performance were studied with the characterization of Fourier transform infrared spectroscopy（FTIR）,X-ray photoelectron spectroscopy（XPS）,pH tracking and energy calculation.The results show that the adsorption performance in acidic solution is improved with the decrease of oxidation state of poly（m-phenylenediamine）（PmPD）.The rate constant is as high as 425.5 mg/（g·min） in the short equilibrium time of 30 min.The estimated highest adsorptivity of sulfate ions is 95.1%.According to the Langmuir equation,the adsorbance is 108.5 mg/g.The sulfate desorption efficiency is about 95% and the accumulative adsorbance is up to 487.95 mg/g in 5 cycles.

Adsorption Kinetics of NH_4^+ by Purple Soils with Different pH Values

Ammonium adsorption and desorption properties by purple soils with dif- ferent pH were studied. The results showed that the adsorption and desorption amounts of NH4＋ by purple soils increased with the increase of NH4＋ concentration, regardless of soil pH values; the largest adsorption and desorption amounts of NH4＋ by purple soil at pH 6.0 were 10.3 and 7.96 mg/g, respectively; the largest adsorp- tion and desorption amounts of NH4＋ by purple soil at pH 7.2 were 12.8 and 4.62 mg/g, respectively; the largest adsorption and desorption amounts of NH4＋ by purple soil at pH 8.0 were 13.5 and 2.23 mg/g, respectively. The isothermal adsorption ki- netics of NH4＋ by purple soils fits the Freundlich equation best （R〉0.95）. This study shows that the adsorption of NH4＋ by purple soils with different pH values is multi- molecular layer uneven surface adsorption.

Adsorption and desorption behaviors of ssDNA molecules on mica surface by surface forces apparatus

An approach for studying the adsorption and desorption behaviors of single-stranded DNA（ ssDNA） molecules on the mica surface by the surface forces apparatus（ SFA） is reported,which can be used to characterize the precise thickness,configuration and mechanical properties of ssDNA layers on the mica surface at a certain buffer solution. The formation of ss DNA layers is first studied by tuning the ssDNA concentrations, and the experimental results indicate that the ss DNA concentration of 100 ng / μL is ideal for forming a ssDNA monolayer structure on the mica surface, and the hardwall value measured to be 1.04 nm under this circumstance is regarded as the thickness of the ssDNA monolayer confined on mica. The desorption behavior of ssDNA molecules from the mica surface is further studied by observing and comparing different shapes of the force-distance curves under certain conditions. It is found that the desorption of ss DNA molecules from the mica surface occurs as the monovalent salts are added into the gap buffer. It is inferred that the competition effect between monovalent and divalent salts can induce the release of ssDNA from substrate.The results also reveal that 10 mmol / L monovalent salts（ Na~＋）is sufficient for the desorption of ssDNA from mica. This work provides an applicable method to study the binding mechanism of ss DNA molecules on inorganic substrates.

Effect of Organic Manure on Phosphorus Adsorption－Desorption and Availability in Paddy Soil Derived from Red Earth

A field test with the traditional rotation of paddy rice/upland crop (wheat) was carried out on a paddysoil derived from red earth to elucidate the effect of organic manure on the phosphorus adsorption-desorptionby soil and its P availability Soil samples were taken from different treatments at rice harvesting stage andanalysed. The isothermal adsorption of P by the samples fitted very well with Langmuir equation, and hence,the parameters in the equation, i.e., maximum adsoaption (qm), constant related to bonding energy (k) andtheir product (k x qm) could be used as a comprehensive index to characterize the potential P adsorptivityof the soil.Organo-inorganic fertilization and organic manuring conld decrease qm and k, while mineral P appli-cation had little effect on them. The isothermal desorption of P was significantly correlated with initiallyadded and isothermally adsorbed P. Part of P added was fixed, which represented the P fixation capacityof soil, and organic manuring could obviously lower the P fixation. The content of soil available P had asignificant negative correlation with qm, k and fixed P. It is concluded that organic manure could increase theP availability of paddy soil derived from red earth by decreasing qm, k, maximum buffering capacity (MBC=k x qm) and fixation capacity.

Temperature Effect on Boron Adsorption-Desorption Kinetics in Soils

The effect of temperature on the properties of boron adsorption-desorption in brown-red soil, yellowbrown soil and calcareous alluvial soil of Hubei Province was investigated with the mobile displacement technique. The experimental data of B adsorption-desorption amounts and reaction t line at 25 and 40℃ were fitted by the zero-order, first-order and parabolic diffusion kinetic equations. The adsorption process was in conformity with the parabolic diffusion law at both the temperatures, and the values of rate constant of the parabolic diffusion equation in B adsorption were 0.138, 0.124 and 0.105 mg kg-1 min-1/2 at 25℃, and 0.147, 0.146 and 0.135 mg kg-1 min-1/2 at 40℃ for the brown-red soil, yellow-brown soil, and calcareous alluvial soil, respectively. The relationship between amount of B desorption and reaction time could be well described by the first-order kinetic equation, and the corresponding values of rate constant were 0.0422, 0.0563 and 0.0384 min-1 at 25℃, and 0.0408, 0.042 3 and 0.0401 min-1 at 40℃ for the brown-red soil, the yellow-brown soil and the calcareous alluvial soil, respectively. Therefore, the desorption process of B might be related to the amount of B adsorbed in soil. The higher the temperature, the lower the amount of B adsorption for the same soil in the same reaction time. The values of the apparent activation energy of B adsorption in the three soils calculated with the rate constants of parabolic diffusion equation were 3.27, 8.44 and 12.99 kJ mol-1, respectively, based on the experimental data of B adsorption amounts and reaction time at 25 and 40℃.

Freeze-thaw Effects on Sorption/Desorption of Dissolved Organic Carbon in Wetland Soils

The effects of freeze-thaw cycles on sorption/desorption of dissolved organic carbon （DOC） in two wetland soils and one reclaimed wetland soil were investigated. DOC concentrations added were 0-600 mg/L. Laboratory incubations of sorption/desorption of DOC had been carried out at -15℃ for 10 h, and then at ＋5℃ for 13 h. Soil samples were refrozen and thawed subsequently for 5 cycles. Initial Mass model was used to describe sorption behavior of DOC. The results indicate that freeze-thaw cycles can significantly increase the sorption capacity of DOC and reduce the desorption capacity of DOC in the three soils. The freeze-thaw effects on desorpfion of DOC in soils increase with the increasing freeze-thaw cycles. The conversion of natural wetlands to soybean farmland can decrease the sorption capacity and increase the desorption capacity of DOC in soils. Global warming and reclamation may increase DOC release, and subsequently increase the loss of carbon and the emission of greenhouse gas.

Zinc adsorption and desorption characteristics in root cell wall involving zinc hyperaccumulation in Sedum alfredii Hance

Radiotracer techniques were employed to characterize 65Zn adsorption and desorption in root-cell-wall of hyperac-cumulating ecotype (HE) and non-hyperaccumulating ecotype (NHE) species of Sedum alfredii Hance. The results indicated that at the end of a 30 min short time radioisotope loading period, comparable amounts of 65Zn were accumulated in the roots of the two ecotypes Sedum alfredii, whereas 2.1-fold more 65Zn remains in NHE root after 45-min desorption. At the end of 60 min uptake period, no difference of 65Zn accumulation was observed in undesorbed root-cell-wall of Sedum alfredii. However, 3.0-fold more 65Zn accumulated in desorbed root-cell-wall of NHE. Zn2+ binding in root-cell-wall preparations of NHE was greater than that in HE under high Zn2+ concentration. All these results suggested that root-cell-wall of the two ecotypes Sedum alfredii had the same ability to adsorb Zn2+, whereas the desorption characteristics were different, and with most of 65Zn binding on root of HE being available for loading into the xylem, as a result, more 65Zn was translocated to the shoot.

Adsorption and Desorption of Exogenous Rare Earth Elements in Soils:Ⅰ. Rate and Forms of Rare Earth Elements Sorbed

Adsorption and desorption of exogenous rare earth elements (REE) in soils were studied.Results showed that soils had strong adsorbability for REE and the rate of adsorption of REE was over 95% of the added REE in these tests.The characteristics of adsorption isotherms corresponded well with the both Freundlich and Temkin equations,but deviated from the Langmuir equation.The adsorption of REE tended to increase with the rising of soil pH.A sequential extraction method used for studing the desorption and distribution of REE sorbed in soils are also discussed.

Effects of Organic Anions on Phosphate Adsorption and Desorption from Variable-Charge Clay Minerals and Soil

Effects of citrate and tartrate on phosphate adsorption and desorption from kaolinite, goethite, amorphous Al-oxide and Ultisol were studied. P adsorption was significantly decreased as the concentration of the organic anions increased from 10-5 to 10-1 M. At 0.1 M and pH 7.0, tartrate decreased P adsorption by 27.6% - 50.6% and citrate by 37.9 - 80.4%, depending on the kinds of adsorbent. Little Al and/ or Fe were detected in the equilibrium solutions, even at the highest concentration of the organic anions. Effects of the organic anions on phosphate adsorption follow essentially the competitive adsorption mechanism.The selectivity coefficients for competitive adsorption can be used to compare the effectiveness of different organic anions in reducing P adsorption under given conditions.Phosphate desorption was increased by 3 to 100 times in the presence of 0.001 M citrate or tartrate compared to that in 0.02 M KC1 solution alone. However, for all the soil and clay minerals studied the amount of P desorbed by citrate or tartrate was generally lower than or close to that of isotopically exchangeable P. The effect of organic anions on phosphate desorption arises primarily from ligand exchange.

Adsorption and desorption behavior of silver ions onto valonia tannin resin

Valonia tannin （VT） was gelated through polymerization with formaldehyde to prepare an adsorbent, which was found effective to remove Ag＋ from aqueous solution. The adsorption-desorption behaviors of valonia tannin resin （VTR） were investigated under various initial Ag＋ concentrations, solution temperatures, pH values etc. The applicability of empirical kinetic models was also studied. The pseudo-second-order model studies revealed the Ag＋ sorption was very rapid. VT and VTR were characterized using FTIR and SEM before and after adsorption. The Ag＋ biosorption on VTR increased with a rise in initial concentration of Ag＋ and with a decrease in temperature. Desorption experiments were conducted at low pH values and the solutions of H2SO4, HNO3 and HCl were used for desorption. The VTR shows high adsorption capacity to Ag＋ in a wide pH range of 2.0-7.0, and a maximum adsorption capacity of 97.08 mg/g was obtained at pH 5.0 and 296 K when the initial concentration of Ag＋ was 100.0 mg/L. Ag＋ ion desorption could reach 99.6% using 1 mol/L HCl＋1% thiourea （NH2CSNH2） solution. By utilizing such characteristics of VTR, it is expected that it can be applied to recovering Ag＋ efficiently and simply with low cost.

Biosorption and desorption of Cd^(2+) from wastewater by dehydrated shreds of Cladophora fascicularis

The adsorption and desorption of algae Cladophora fascicularis and their relation with initial Cd2+ concentration, initial pH, and co-existing ions were studied. Adsorption equilibrium and biosorption kinetics were established from batch experiments. The adsorption equilibrium was adequately described by the Langmuir isotherm, and biosorption kinetics was in pseudo-second order model. The experiment on co-existing ions showed that the biosorption capacity of biomass decreased with an increasing concentration of competing ions. Desorption experiments indicated that EDTA was efficient desorbent for recovery from Cd2+. With high capacities of metal biosorption and desorption, the biomass of Cladophora fascicularis is promising as a cost-effective biosorbent for the removal of Cd2+ from wastewater.

Characteristics of Phosphorous Adsorption and Desorption by Organo-Mineral Colloidal Complexes of Purple Paddy Soils

The kinetic characteristics of P adsorption and desorption by organo-mineral colloidal complexes (OMC)were studied using acid, calcareous and neutral purple paddy soils taken from Chongqing and Sichuan, China.The results showed that the P adsorption capacity of the organo-mineral colloidal complexes differed with the soil types, being higher for the acid and calcareous purple soils than for the neutral purple soils. Partial removal of the organic matter increased the adsorption capacity of the colloidal complexes. A very significant positive correlation was found between the amounts of P desorbed from OMC and the P saturation degrees.The P adsorption reaction was quick at the early stage and slowed later. The raise of temperature increased P adsorption capacity and P adsorption rate of the colloidal complexes. The adsorption processes could be described by the Elovich equation.

Purification of chlorogenic acid in Flos Lonicerae with system of polar ordered resins

A system of polar ordered resins was established for purification of chlorogenic acid in Flos Lonicerae. It was composed of three reversed phase resins, AB-8, DM-130 and NKA-9, representative for their gradually increased polarity and selectivity. A method of RP-HPLC was used for determination of chlorogenic acid. And the performance of adsorption and desorption for chlorogenic acid with the system of polar ordered resins was studied. Furthermore, the effects of concentration, pH and flow rate of the adsorbate on adsorption ability were researched. It is indicated that the optimum parameters for chlorogenic acid are as follows: pH 3.5 with a flow rate of 2.5 BVh, the concentration of extract solution at 0.50, 0.40, 0.30 gL respectively for the adsorptive operation twice, and 6.93, 8.66, 10.39 molL ethanol used as gradient eluants. The purity of resulted product of chlorogenic acid arrives 70.20% with yield of 89.79%. With simple procedures, low costs and high purity product, the method of system of polar ordered resins followed by sequential reversed phase separations can be used to refine the chlorogenic acid in the extraction of Flos Lonicerae.

Adsorption of Phosphate on Variable Charge Soils

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.

Effect of Initial Concentration on Adsorption-Desorption Characteristics and Desorption Hysteresis of Hexachlorobenzene in Soils

Adsorption and desorption are important processes that influence the transport, transformation, and bioavailability of hexachlorobenzene (HCB) in soils. To examine the adsorption-desorption characteristics of HCB, equilibrium batch experiments were carried out using two soils (red soil and paddy soil) with different initial HCB concentrations (0.25, 0.50, 0.75, 1.00, 1.50, 2.50, 3.50, and 5.00 mg L-1 ) by using 0.01 mol L-1 calcium chloride as the background solution. The successive desorption experiments (48, 96, 144, 192, and 240 h) were conducted after each adsorption equilibrium experiment. The results revealed that adsorption and desorption isotherms of HCB on two soils were nonlinear, which can be best described by the Freundlich equation with the square of the correlation coefficient (r 2 ) ranging from 0.97 to 0.99. Desorption of HCB from the two soils exhibited hysteresis at all HCB concentrations because the Freundlich desorption coefficients were always higher than the Freundlich adsorption coefficients. The hysteretic effect was enhanced with increasing initial HCB concentration, and positive hysteresis was observed at different concentrations.

Effects of Phosphate Adsorption on Adsorption-Desorption and Availability of Cu and Zn Ions in Ultisols and Alfisols

Surface charge, secondary adsorption- desorption and form distribution of Cu2+ and Zn2+ in Ultisols and Alfisols having adsorbed phosphate were studied by potentiometric titration, adsorption equilibrium and sequential extraction method, respectively. The soil surface negative charges increased whereas the amount of positive charges decreased with increase of P adsorbed. The soil secondary adsorption capacity for Cu2+ and Zn2+ was positively significantly correlated with the amount of P adsorbed by the soils, which could be described by the Langmuir equation. The amounts of Cu2+ and Zn2+ desorption from soils were decreased after P adsorption by the soils and the relationship between them was linear. After the soils adsorbed P, form distribution of Cu2+ and Zn2+ in soils changed remarforbly.

Separation of Proteins by Electrophoretic Affinity Chromatography

A new kind of electrophoretic affinity chromatography (EAC) for bioseparation was proposed. Separation by EAC was conducted in a multicompartment electrolyzer in which the affinity gel media were packed in one of the central compartments. The presence of an electric field accelerated the migration of proteins inside the gel matrix during adsorption and desorption processes. This led to the increase of the overall speed of separation. The present study was focused on the effect of the strength of the electric field on adsorption and desorption processes.

Arsenic Removal from Pinctada martensii Enzymatic Hydrolysate by Using Zr(Ⅳ)-Loaded Chelating Resin

The present study investigated the removal of inorganic arsenic from Pinctada martensii enzymatic hydrolysate through unmodified resin （D296） and Zr（IV）-loaded chelating resin （Zr-D401）. By loading Zr to macroporous chelating resin D401, the as exchange adsorption active sites are generated. This transforms D401 from a material that does not have the arsenic adsorption capacity into a material that has excellent arsenic exchange adsorption capacity. The static adsorption experiments were conducted to investigate the optimal removal condition for D296 and Zr-D401. The experimental results show that： the optimum condition for D296 is that T= 25℃, pH= 5, resin additive amount= 1 g （50 mL）-1, and contact time = 10 h, the corresponding arsenic removal rate being 65.7%, and protein loss being 2.33%; the optimum condition for Zr-D401 is that T=25 ℃, pH = 8, resin additive amount= 1 g （50 mL）-1, and contact time=10 h, the corresponding arsenic removal rate being 70.3%, and protein loss being 4.65%. These results show that both of the two resins are effective in arsenic removal for preserving useful substance. Our research provides scientific evidence and advances in the processing technology for heavy metal removal in shellfish.