Impact of Cr(Ⅲ)complexation with organic acid on its adsorption in silts and fine sands

Trivalent chromium(Cr(Ⅲ))can form stable soluble complexes with organic components,altering its adsorption properties in the water-soil environment.This increases the risk of Cr(Ⅲ)migrating to deeper soils and transforming into toxic Cr(VI)due to the presence of manganese oxides in sediments.In this study,Citric Acid(CA)was selected as a representative organic ligand to prepare and characterize Cr(III)-CA complexes.The characteristics,mechanisms and environmental factors influencing the adsorption of Cr(Ⅲ)-CA on porous media(silts and fine sands)were investigated in the study.The results show that Cr(Ⅲ)coordinates with CA at a 1:1 molar ratio,forming stable and soluble Cr(Ⅲ)-CA complexes.Compared to Cr(III)ions,the equilibrium adsorption capacity of Cr(Ⅲ)-CA is an order of magnitude lower in silts and fine sands.The adsorption of Cr(Ⅲ)-CA in silts and fine sands is dominated by chemical adsorption of monolayers,following the pseudo-second-order kinetic equation and the Langmuir isotherm adsorption model.Varying contents of clay minerals and iron-aluminum oxides prove to be the main causes of differences in adsorption capacity of Cr(Ⅲ)-CA in silts and fine sands.Changes in solution pH affect the adsorption rate and capacity of Cr(Ⅲ)-CA by altering its ionic form.The adsorption process is irreversible and only minimally influenced by ionic strength,suggesting that inner-sphere complexation serves as the dominant Cr(Ⅲ)-CA adsorption mechanism.

Synthesis and adsorption properties for Au(Ⅲ) of alkoxycarbonyl thiourea resin

A novel alkoxycarbonyl thiourea resin(ATR)was synthesized by monomer polymerization of oxydiethane-2,1-diyl dicarbonisothiocyanatidate and polyethylene polyamine,and characterized by FT-IR.The adsorption properties of ATR were investigated by batch test.The adsorption capacities for Au(Ⅲ),Ag(Ⅰ),Cu(Ⅱ),Zn(Ⅱ),Fe(Ⅲ),Ca(Ⅱ)and Mg(Ⅱ)are 4.65,4.40,0.40,0.90,0.86,0.0080 and 0.016 mmol/g,respectively,when the adsorption condition is as follows:contact time 24 h,temperature 30℃,initial concentration of Au(Ⅲ)5.08 mmol/L and that of other metals 0.10 mol/L,and concentration of acid 1.0 mol/L.The adsorption capacity for Au(Ⅲ)increases with the increase of contact time,temperature and initial concentration of Au(Ⅲ).The capacity after five adsorption-desorption cycles remains 90%that of the first time,and the separation factors of ATR for binary metal ion solutions are larger than 995,indicating that ATR is of good regeneration property and selectivity.XPS results show that the functional atoms of ATR supply electrons for Au and coordinate with Au during the adsorption.

有机膦酸改性碳纳米管/硫化铋复合材料的设计合成及其对Au(Ⅲ)的吸附性能研究

本研究设计合成新型高效重金属吸附材料有机膦酸羧酸改性多壁碳纳米管/硫化铋(PBTCA-MWCNTs/Bi_(2)S_(3)),对材料进行了傅里叶红外光谱(FT-IR)、扫描电镜(SEM)、能谱(EDX)和X射线光电子能谱(XPS)等表征,并研究其对重金属离子的吸附性能。结果发现:PBTCA-MWCNTs/Bi_(2)S_(3)有优良的Au(Ⅲ)吸附性能;Langmuir模型拟合结果显示,材料在25℃时吸附容量达到1655.50 mg·g^(-1)。对该材料吸附热力学、吸附动力学和吸附选择性等方面的研究为Au(Ⅲ)回收提供了有效的技术支持。

Adsorption behavior and mechanism of Bi(Ⅲ) ions on rutile-water interface in the presence of nonyl hydroxamic acid

The adsorption behavior and mechanism of Bi（Ⅲ） ions on the rutile-water interface were investigated through micro-flotation, Zeta potential measurement, adsorption amount measurement and X-ray photoelectron spectroscopy（XPS）. According to the results of micro-flotation, Bi（Ⅲ） ions could largely improve the rutile flotation recovery（from 62% to 91%）, and they could increase the activating sites and reduce the competitive adsorption between nonyl hydroxamic acid negative ions and OH-ions, which determined that Bi（Ⅲ） ions were capable of activating rutile flotation. The adsorption of Bi（Ⅲ） ions onto the rutile surface led to the shift of Zeta potential into the positive direction, which was good for the adsorption of nonyl hydroxamic acid anions. In addition, the results of XPS indicated that the chemical environment around Ti atom had not changed before and after the adsorption of Bi（Ⅲ） ions. Based on the adsorption mechanism of Bi（Ⅲ） ions, it was deduced that firstly Bi（Ⅲ） ions occupied the vacancies of the original Ca^2＋, Mg^2＋ and Fe^2＋ ions on the rutile surface; secondly Bi（Ⅲ） ions covered on the rutile surface in the form of hydroxides.

多胺桥联聚倍半硅氧烷/壳聚糖蛇-笼型复合材料的制备及其对Au(Ⅲ)的吸附性能研究

本研究以3-氯丙基三甲氧基硅烷(CPTS)、乙二胺(EDA)和二乙烯三胺(DETA)为原料,制备两种单体B-DETA-m和B-EDA-m,然后将桥联单体与不同比例壳聚糖(CTS)反应,合成了EDA/CTS和DETA/桥联聚倍半硅氧烷(BPS)两个系列蛇-笼型复合材料。对复合材料进行了红外光谱、比表面积及孔隙度分析、扫描电镜等表征,考察了复合材料对Au(Ⅲ)的吸附性能。结果表明,CTS的加入能够有效提高材料的吸附性能,其中拥有较丰富孔隙度和较大比表面积的EDA/CTS-30和DETA/CTS-30对Au(Ⅲ)吸附能力最强。本研究为含CTS和BPS的新型吸附剂、色谱柱等材料的研发提供了理论依据,可应用于污水处理,对后续环境治理研究具有积极意义。

Recovery of rare earth element ytterbium(Ⅲ) by dried powdered biomass of spirulina: Adsorption isotherm, kinetic and thermodynamic study

The adsorption characteristics and mechanisms of spirulina powder were investigated when it was used as adsorbent to recover ytterbium(Ⅲ) from wastewater solution. Surface structure and element valence of the adsorbent were analyzed by SEM and XPS for the exploring of its adsorption mechanism for ytterbium(Ⅲ). The adsorption characteristics of ytterbium(Ⅲ) on spirulina powder was analyzed through assessing adsorption isotherm, kinetics and thermodynamic models. The adsorption isotherm data were best explained by Langmuir model, and the adsorption capacity of spirulina powder for ytterbium(Ⅲ) was 72.46 mg/g when adsorption temperature was 318 K. The kinetic experiment results showed that the pseudo-second order kinetic model can better simulate the adsorption process of spirulina powder to ytterbium(Ⅲ), indicating that the rate-controlling step was chemical adsorption. Spirulina can be an efficient and economical ytterbium(Ⅲ) recycling material, because it showed good adsorption stability and reusability from the adsorption-desorption cycle experiment results.

A Periodic Density Functional Study on Adsorption Properties of Methoxy on Au(111) Surface

Adsorption of CH3O at four sites （top, bridge, hcp, fcc） on Au（111） surface has been investigated by density functional theory method at the generalized gradient approximation level. We have performed calculations on adsorption energies, structures, Mulliken charges and vibrational frequencies of CH3O on Au（111） surface with full-geometry optimization. The predicted results are compared with the available experimental observation. The calculated CH3O adsorption structure and stretching vibrational frequencies agree well with experimental ones, and precise determinations of adsorption sites are carded out. The most favorite adsorption on Au（111） occurs at the bridge site, and O-C axis is tilted to the surface. However, on hollow sites （hcp, fcc） the species is adsorbed in an upright geometry （pseudo-C3v local symmetry）.

Kinetic and thermodynamic studies of adsorption of gallium(Ⅲ) on nano-TiO_2

Nano-TiO2 was employed for the adsorption of gallium from aqueous solution in batch equilibrium experiments to investigate its adsorption properties. It was found that the adsorption efficiency of Ga（Ⅲ） was more than 96% at pH 3.0. The adsorption capacities and rates of Ga（Ⅲ） onto nano-TiO2 were evaluated as a function of solution concentration and temperature. The results were analyzed using the Langmuir adsorption isotherms. Adsorption isothermal data could be well interpreted by the Langmuir model. The mean energy of adsorption, 15.81 kJ.mol^-1, was calculated from the D-R adsorption isotherm. The kinetic experimental data properly correlate with the pseudo-second-order kinetic model. The thermodynamic parameters for the process of adsorption have been estimated. The △H and △G values of gallium（Ⅲ） adsorption on nano-TiO2 showed an endothermic and spontaneous nature of adsorption.

Adsorption of D113 Resin for Dysprosium(Ⅲ)

The adsorption behavior and mechanism of D ll 3 resin for Dy（lII） was investigated by using the method of resin adsorption. Experimental results show that the optimum medium pH of adsorption of D 113 resin for Dy^3- is pH=6.00 in the HAc-NaAc medium. The static adsorption capacity of D113 resin for Dy3. is 292.7 mg·g^-1. The optimum eluant is 0.5 mol,L-~ HC1. The adsorption rate constant is k298=6.8× 10-6s^-1. The apparent activation energy of D113 resin for Dy（Ⅲ） is 14.79 kJ·mol^-1. The adsorption behavior of D113 resin for Dy（Ⅲ） obeys the Freundlich isotherm. The adsorption parameters of thermodynamic are AH=14.48 kJ·mol^-1,△S=54.69 J·mol^-1,K^-1, △G= 1.82 kJ·mol^-1.The adsorption mechanism of Dll3 resin for Dy^3- was confirmed by chemical analysis and IR spectra.

A new liquid membrane diffusion model for characterizing the adsorption kinetics of europium by using a continuous measurement of adsorption platform

To explore the kinetic adsorption under continuous and nonequilibrium states, an integration of continuous measurement and adsorption platform kinetics method was proposed, which was initially called the ICM-AP kinetics method, and a corresponding kinetic adsorption experimental method was developed. Adsorption experiments of europium(Eu) on Ca-bentonite,Na-bentonite, and the D231 cation exchange resin were performed using the ICM-AP kinetics method and continuous measurements. Because the kinetic experimental results observed in this study were different from those of traditional batch adsorption data, pseudo-first-order or pseudo-second-order kinetic models were unsuitable for fitting the experimental data.Hence, a liquid membrane diffusion(LMD) model was developed based on the assumption of simultaneous adsorption/desorption to discuss the mechanism of kinetic adsorption. The kinetic adsorption mechanism was also studied by using XPS.The results indicated that the proposed adsorption model can fit the experimental data more suitably, and the adsorption/desorption behaviors of Eu on bentonite and the D231 resin were simultaneously observed, suggesting that the adsorption kinetics of Eu(Ⅲ) was mainly dominated by hydrated Eu(Ⅲ) ions on the liquid membrane.

Cr(Ⅲ) adsorption by sugarcane pulp residue and biochar

A batch experiment was conducted to investigate the adsorption of trivalent chromium （Cr（Ⅲ）） from aqueous solutions by sugarcane pulp residue （SPR） and biochar. The results show that Cr（Ⅲ） adsorption by SPR and biochar is highly pH-dependent and Cr（Ⅲ） adsorption amount increases with the increase of pH. The adsorption kinetics of Cr（Ⅲ） fits well with the pseudo-second-order model. The maximum Cr（Ⅲ） adsorption capacities of 15.85 mg/g and 3.43 mg/g for biochar and SPR were calculated by Langmuir model. This indicates that biochar has a larger ability for Cr（Ⅲ） adsorption than SPR. The free energy change value （AG） reveals a spontaneous sorption process of Cr（Ⅲ） onto SPR and non-spontaneous sorption process onto biochar. The entropy change （AS） and enthalpy change （AH） are found to be 66.27 J/（mol＇K） and 17.13 kJ/mol for SPR and 91.59 J/（mol-K） and 30.875 kJ/mol for biochar which further reflect an affinity of Cr（Ⅲ） onto SPR and biochar. It is suggested that biochar has potential to be an efficient adsorbent in the removal of Cr（Ⅲ） from industrial wastewater.

Removal of Cr(Ⅲ) and Cr(Ⅵ) from aqueous solution by adsorption on sugarcane pulp residue

Sugarcane pulp residue （SPR）, a waste from sugar-refinery, which possesses a large surface area, can be used for removing chromium （Cr（Ⅲ） and Cr（Ⅵ）） from wastewater. In this work, the kinetics, isotherms of Cr（Ⅲ） and Cr（V[） adsorption and their removal by SPR were investigated. The results show that the removal percentages of Cr（Ⅵ） and Cr（Ⅲ） increase with increasing SPR dosage and temperature and decrease with increasing SPR particle size and the initial concentration of chromium ions. However, the influence of pH value on the Cr（Ⅵ） removal differs from that of the Cr（Ⅲ） removal. The Cr（Ⅵ） removal percentage decreases with increasing pH values, while the Cr（Ⅲ） removal percentage increases with increasing pH value. The adsorption kinetics of Cr（Ⅵ） and Cr（Ⅲ） well fits with pseudo-second-order model. Langmuir adsorption isotherm can well describe the adsorption phenomena of chromium ions with the maximum adsorption capacity of 0.567 mg/g for Cr（Ⅵ） and 3.446 mg/g for Cr（Ⅲ）. Moreover, SPR reveals higher adsorption capacity for Cr（Ⅲ） than that for Cr（Ⅵ）, which implies that SPR has more potential application for Cr（Ⅲ）-containing wastewater treatment than that for Cr（Ⅵ）-containing wastewater treatment.

Adsorption and Hydrogenation Process of p-Chloronitrobenzene on Au_(20)Cluster:a DFT Study

We have systematically investigated the adsorption and hydrogenation process of p-chloronitrobenzene on Au20 cluster using density functional theory-DFT） calculations.The adsorption of two types of all species,vertical adsorption and parallel adsorption,is compared,revealing that former model is more stable than the latter,and all of the species prefer to adsorb at the vertex site.After adsorption,electrons transferred from Au20 cluster to the p-chloronitrobenzene molecule.Almost all hydrogenation processes are exothermic,and the C–Cl bond scissions are considered as the rate-limiting step for both Paths A-p-CNB→p-CAN→AN） and B-p-CNB→NB→AN） with the energy barriers of 2.62 and 2.95 e V,respectively.These suggest that the C–Cl bond scission is not easy to occur on Au20 cluster due to the high energy barrier,especially the path B.The p-chloroaniline is the main hydrogenation product catalyzed by Au20.

Fabrication and adsorption property of novel adsorbent for potential application to wastewater with Fe(Ⅲ) ions

The spherical macroporous cellulose(SMC) was fabricated using medical absorbent cotton as raw material and nano CaCO3 as porogenic agents.And then,the phenylglycine was grafted onto the SMC to obtain the novel spherical macroporous cellulose derivative adsorbent(PSMC).FT-IR and scanning electron microscope(SEM) were employed to characterize the adsorbents and Fe3+ ions served as model solute to evaluate the adsorption property of the adsorbents.The experimental results show that the amount of porogenic agents and the value of pH have obvious influence on adsorption capacity of the adsorbents.The data of adsorption kinetic and isotherm display that the adsorbents possess excellent equilibrium adsorption capacity(348.94 mg/g) and have a bright prospect and considerable potential in the treatment of Fe3+ ions in wastewater.

Adsorption behaviour of Eu(Ⅲ) on natural bamboo fibres: effects of pH, humic acid, contact time, and temperature

To study the adsorption properties of organic functional groups in plant fibres and identify a highly efficient and affordable adsorbent for radioactive wastewater treatment,natural bamboo fibre(NBF)samples were prepared,and the adsorption properties of Eu(Ⅲ)on NBFs were studied under given experimental conditions.The effects of the pH,solid-to-liquid ratio,background ions,humic acid,contact time,and temperature on the adsorption behaviour of Eu(Ⅲ)on NBFs were investigated.Adsorption was greatly influenced by pH,and the adsorption curves presented two inflection points at pH≈7 and pH≈11.Moreover,while the ionic strength presented a negative effect at pH<7,the high ionic strength favoured adsorption at pH>7.During adsorption on NBFs,the–OH,C–H,O–H,C–O,and C=O were the main adsorption groups.Hydrolysis occurring on the NBF surface caused the adsorption process to become increasingly difficult at pH>7.The maximum adsorption capacity of NBFs was 147.6 mg/g at 308 K,and the adsorption could be described using the pseudo-second-order kinetic model.The adsorption of Eu(Ⅲ)on NBFs was a spontaneous and endothermic process according to the thermodynamic parameters of the process,and the adsorption thermodynamics could be well described using the Freundlich adsorption model.Therefore,NBFs were determined to be an efficient,inexpensive,and easily disposable sewage treatment material.

First-principles Study on Adsorption of Au Atom on Hydroxylated SiO_2 Surface

Adsorption of single gold （Au） atom at three kinds of sites （hollow, bridge and top） on the hydroxylated β-cristobalite SiO2 （1 1 1） surface was studied using the first-principles calculations with general gradient approximation （GGA）. The results of adsorption energies and density of electronic states （DOS） suggest that the hollow and bridge sites have the basically equal capability of binding Au, while the ability of the Top site is weaker. Two new energy levels emerge after the adsorption at all sites; in DOS of the Hollow configuration, one locates at -0.15 eV, composed of Au 5d and O 2p electronic states, another just crosses through the Fermi level, consisting of Au 6s, H 1s and O 2p. In addition, Mulliken population analyses indicate that electron transfer takes place between the Au atom and the surface H and O atoms in the Hollow and Bridge configurations, which can be used to interpret the adsorption of Au onto the positions. However, neither H nor O chemically bonds with Au atom.

Impedance Characterization of Adsorption Process of Calmodulin on Au Substrate and its Combination with Ca^(2+)

In this paper, the adsorption process of calmodulin (CaM) on Au substrate was first investigated with electrochemical impedance spectroscopy (EIS) method. The result reveals that the adsorption of the protein-calmodulin contains two steps, i.e., one short quick step followed by a slow one. The complexation of calmodulin with Ca2+ was also first probed using EIS technique, in which the complexation of CaM with Ca2+ could be reflected by the change of apparent membrane capacitance(Capp) clearly. In all above measurements, a redox couple Fe(CN)63-/ Fe(CN)64- was used as probing-pin to reflect all the changes occurring in the above process. Our work suggests that some biological processes of CaM could be studied using EIS method conveniently.

Adsorption of Rare Earth Ion La(Ⅲ) on Yunnan Bowl Tea Surface from Aqueous Solution

The adsorption characteristics of rare earth ion La(Ⅲ) on Yunnan bowl tea surface from aqueous solution and effects of various surfactants on the adsorption were studied. It was found that Yunnan bowl tea can adsorb strongly La(Ⅲ) and pH may affect drastically the adsorption amount of La(Ⅲ). The adsorption law of La(Ⅲ) on Yunnan bowl tea surface follows the Langmuir equation. The maximum adsorption amount of La(Ⅲ) can reach 15 mg·g (-1). A comprehensive adsorption model is suggested according to the experimental results.

PREPARATION AND CHARACTERIZATION OF NOVEL CHITOSAN DERIVATIVES:ADSORPTION EQUILIBRIUM OF IRON(Ⅲ) ION

The adsorption of Fe(Ⅲ)ions from aqueous solution by chitosan alpha-ketoglutaric acid(KCTS)and hydroxamated chitosan alpha-ketoglutaric acid(HKCTS)was studied in a batch adsorption system.Experiments were carried out as function of pH,temperature,agitation rate and concentration of Fe(Ⅲ)ions.The Langmuir and Freundlich adsorption models were applied to describe the equilibrium isotherms and isotherm constants were determined.The Langmuir model agrees very well with experimental data.The pseudo-first-order a...

Effects of Non-specific and Specific Solvation on Adsorption of BPTI on Au Surface： Insight from Molecular Dynamics Simulation

Proteins adsorption at solid surfaces are of paramount important for many natural processes. However, the role of specific water in influencing the adsorption process has not been well understood. We used molecular dynamics simulation to study the adsorption of BPTI on Au surface in three water environments （dielectric constant model, partial and full solvation models）. The result shows that a fast and strong adsorption can occur in the dielectric environment, which leads to significant structure changes, as confirmed by great deviation from the crystal structure, largely spreading along the Au surface, rapid lose in all secondary structures and the great number of atoms in contact with the surface. Compared to the dielectric model, slower adsorption and fewer changes in the calculated properties above are observed in the partial solvation system since the specific water layer weakens the adsorption effects. However, in the partial solvation system, the adsorption of polar Au surface causes a significant decrease in the specific hydration around the protein, which still results in large structure changes similar to the dielectric system, but with much less adsorption extent. Enough water molecules in the full solvation system could allow the protein to rotate, and to large extent preserve the protein native structure, thus leading to the slowest and weakest adsorption. On the whole, the effects of non-specific and specific solvation on the protein structure and adsorption dynamics are significantly different, highlighting the importance of the specific water molecule in the protein adsorption.