Study on adsorption performance of Cr(Ⅵ) by modified honeycomb-cinder

利用氢氧化钙对蜂窝煤渣进行改性,并通过粉末X射线衍射光谱（XRD）对改性前后蜂窝煤渣的物质组成进行表征,研究了改性蜂窝煤渣对模拟含铬废水中Cr(Ⅵ)的吸附性能。探讨了吸附剂用量、吸附时间、pH值、振荡速率、温度以及Cr(Ⅵ)初始浓度等对吸附效果的影响。改性蜂窝煤渣吸附处理Cr(Ⅵ)的最佳工艺条件是：吸附剂用量40 g/L,室温下以150 r/min振荡速率吸附处理40 min,当Cr(Ⅵ)初始浓度为30 mg/L时,Cr(Ⅵ)的去除率能达到98.84%。改性蜂窝煤渣对Cr(Ⅵ)具有良好的吸附能力,吸附过程符合二级吸附动力学模型并且可用Langmuir吸附等温线来描述。改性蜂窝煤渣对模拟废水中Cr(Ⅵ)的吸附是煤渣组分和新生分子筛组分共同作用的结果。     

Adsorption behavior of U(Ⅵ) ions from aqueous solution on novel cross-linked magnetic chitosan beads

采用纳米Fe₃O₄作为磁流体包埋、戊二醛和硫脲进行交联壳聚糖,制备磁性交联壳聚糖（TTG-MCTS）。红外光谱（FTIR）和X射线能谱（EDS）分析结果表明,壳聚糖改性后,吸附能力得到提高,铀(Ⅵ)成功地被吸附在TTG-MCTS上。系统研究了溶液pH值、铀(Ⅵ)初始浓度及振荡时间对吸附容量的影响,继而得到最佳工艺条件。吸附过程用Langmuir等温式拟合优于用Freundlich等温式,最大吸附容量为161.3 mg·g^-1。较之拟一级动力学模型,拟二级动力学模型能更好地拟合实验数据。     

Boron separation by adsorption and flotation with Mg–Al-LDHs and SDBS from aqueous solution

Layered double hydroxides(LDHs) have been shown to be effective adsorbents for boron. However, solid–liquid separation is still a problem when separating boron from industrial radioactive waste liquid. In this research, three types of Mg–Al-LDHs including Mg–Al-LDH(NO₃^–), Mg–Al-LDH(Cl^–) and Mg–Al-LDH(SO₄^2–)were applied to adsorb boron, and moreover sodium dodecylbenzenesulfonate(SDBS) was used to float the LDH particles from aqueous solution...     

Removal of diclofenac from aqueous solution with multi-walled carbon nanotubes modified by nitric acid☆

Modified multi-walled carbon nanotubes (MWCNTs) were used as adsorbents for removal of diclofenac. The re-action conditions were examined. Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich isotherm models were applied to determine appropriate equilibrium expression. The results show that the experimental data fit the Freundlich equation well. Thermodynamic parameters show that the adsorption process is spontaneous and exothermic. The kinetic study indicates that the adsorption of diclofenac can be well described with the pseudo-second-order kinetic model and the process is controlled by multiple steps.     

Mechanically activated starch magnetic microspheres for Cd(Ⅱ) adsorption from aqueous solution

Magnetic starch microspheres(AAM-MSM) were synthesized via an inverse emulsion graft copolymerization by using mechanically activated cassava starch(MS) as a crude material, acrylic acid(AA) and acrylamide(AM) as graft copolymer monomers, and methyl methacrylate(MMA) as the dispersing agent and used as an adsorbent for the removal of Cd(II) ions from aqueous solution. Fourier-transform infrared spectroscopy(FT-IR), X-ray photoelectron spectroscopy(XPS), scanning electron microscopy(SEM), and vibrating sample magnetometry(VSM) were used to characterize the AAM-MSM adsorbent. The results indicated that AA, AM, and MMA were grafted to the MS, and the Fe_3 O_4 nanoparticles were encapsulated in the AAM-MSM adsorbent microspheres.The adsorbent exhibited a smooth surface, uniform size, and good sphericity because of the addition of the MMA and provided more adsorption sites for the Cd(II) ions. The maximum adsorption capacity of Cd(II) on the AAM-MSM was 39.98 mg·g~(-1). The adsorbents were superparamagnetic, and the saturation magnetization was 16.7 A·m~2·kg~(-1). Additionally, the adsorption isotherms and kinetics of the adsorption process were further investigated. The process of Cd(II) ions adsorbed onto the AAM-MSM could be described more favorably by the pseudo-second-order kinetic and Langmuir isothermal adsorption models, which suggested that the chemical reaction process dominated the adsorption process for the Cd(II) and chemisorption was the rate-controlling step during the Cd(II) removal process.     

Adsorption of chromium(VI) from aqueous solution by Artist’s Bracket fungi

The objective of this study was to investigate Artist’s Bracket (AB) fungi for the removal of Cr(VI) from aqueous solutions. The effects of pH, adsorbent dosage, temperature, contact time and initial concentration of Cr(VI) were evaluated. The optimal pH value for the removal of Cr(VI) was at pH 2. Moreover, the results showed that the adsorption of Cr(VI) decreased by increasing the initial Cr(VI) concentration and pH. The absorption of Cr(VI) on AB can be described by both Freundlich and Langmuir isotherm models. In addition, both pseudo-first-order and pseudo-second-order kinetic model well described the adsorption of Cr(VI) onto AB.     

Selective adsorption of L-TA/D-TA by β-cyclodextrin derivative modified with l-tryptophan: Isotherm,kinetic and thermodynamics studies

β-Cyclodextrin derivative modified with l-tryptophan (L-Trp-CD) was prepared for recognitive chiral separation of tartaric acid enantiomers from ethanol solution. Kinetic properties were successfully investigated by pseudo-first-order model and pseudo-second-order model. Equilibrium data were described by the Langmuir and Freundlich isotherm models. The thermodynamics parameters (positive values of ΔH° and ΔS°, negative values of ΔG°) indicated that binding system for L-Trp-CD was endothermic, entropy gained and spontaneous. Selective adsorption result of l-tartaric acid (L-TA)/d-tartaric acid (D-TA) by L-Trp-CD indicated that L-Trp-CD has significantly higher adsorption capacity for L-TA compared with D-TA, and the selectivity coefficient is 3.36.     

Static magnetic field-assisted synthesis of Fe_3O_4 nanoparticles and their adsorption of Mn(Ⅱ) in aqueous solution

A facile method for synthesis of the magnetic Fe_3O_4 nanoparticles was introduced.Magnetic nanoparticles were prepared via co-precipitation method with(PMF) and without(AMF) 0.15 T static magnetic field.The effects of magnetic field on the properties of magnetic nanoparticles were studied by XRD,TEM,SEM,VSM and BET.The results showed that the magnetic field in the co-precipitation reaction process did not result in the phase change of the Fe_3O_4 nanoparticles but improved the crystallinity.The morphology of Fe_3O_4 nanoparticles was varied from random spherical particles to rod-like cluster structure.The VSM results indicated that the saturation magnetization value of the Fe_3O_4 nanoparticles was significantly improved by the magnetic field.The BET of Fe_3O_4nanoparticles prepared with the magnetic field was larger than the control by 23.5%.The batch adsorption experiments of Mn(Ⅱ) on the PMF and AMF Fe_3O_4 nanoparticles showed that the Mn(II) equilibrium capacity was increased with the pH value increased.At pH 8,the Mn(Ⅱ) adsorption capacity for the PMF and AMF Fe_3O_4 was reached at 36.81 and 28.36 mg·g~(-1),respectively.The pseudo-second-order model fitted better the kinetic models and the Freundlich model fitted isotherm model well for both PMF and AMF Fe_3O_4.The results suggested that magnetic nanoparticles prepared by the magnetic field presented a fairly good potential as an adsorbent for an efficient removal of Mn(Ⅱ) from aqueous solution.     

Biosorptive removal of arsenite and arsenate from aqueous medium using low-cost adsorbent derived from ‘Pods of green peas’: Exploration of kinetics,thermodynamics and adsorption isotherms

The present work explores the biosorption characteristics of pods of green peas (PGP) for arsenite [As(III)] and arsenate [As(V)] removal from aqueous medium. Optimization of adsorption parameters like contact time, arsenic concentration, temperature, biosorbent dose and pH through batch mode of experiments was studied. Among the different isotherm models, Langmuir for As(III) and Temkin for As(V) provided the best fit for the obtained data of arsenic sorption onto PGP. D-R mean free energy (E) indicates the process is physisorption. Thermodynamics studies were found to be endothermic, feasible and spontaneous. Kinetically, adsorption follows the pseudo-second-order kinetics in sorption of As(III) and As(V) both. The desorption studies of exhausted PGP show 81% of As(III) and 72% of As(V) could be leached out. Reusability of biosorbent up to 7th cycles of incessant operation supports their commercial importance with very little effects of common ions on sorption capacity.     

Removal of chromium (Ⅵ) from aqueous solutions using quaternized chitosan microspheres

In this study, quaternized chitosan microspheres(QCMS) were prepared and its Cr(VI) removal potential was investigated. Batch experiments were conducted to examine kinetics, adsorption isotherm, p H effect,and thermodynamic parameters. Equilibrium was attained within 50 min and maximum removal of 97.34%was achieved under the optimum conditions at p H 5. Adsorption data for Cr(VI) uptake by the QCMS were analyzed according to Langmuir, Freundlich, and Temkin adsorption models. The maximum uptake of Cr(VI)was 39.1 mg·g~(-1). Thermodynamic parameters for the adsorption system were determinated at 293 K, 303 K,313 K and 323 K.(ΔH° = 16.08 k J·mol~(-1);ΔG° =- 5.84 to- 8.08 k J·mol~(-1)and ΔS° = 74.81 J·K~(-1)·mol~(-1)).So the positive values of both ΔH° and ΔS° suggest an endothermic reaction and increase in randomness at the solid–liquid interface during the adsorption. ΔG° values obtained were negative indicating a spontaneous adsorption process. The kinetic process was described by a pseudo-second-order rate equation very well. The results of the present study indicated that the QCMS could be considered as a potential adsorbent for Cr(VI) in aqueous solutions.     

Direct extraction of Mo(Ⅵ) from sulfate solution by synergistic extractants in the rotation column

Direct extraction of molybdenum from sulfate solution with synergistic extractants(mixture of D_2EHPA and TBP)was studied in the rotation column. The influence of extractant concentration and initial pH of aqueous phase was studied in the bench scale experiments. The outcomes demonstrated that the synergistic solvent extraction enhances the constancy of the extracted complexes for transfer into the organic phase. In the continuous experiments, the effect of different operating parameters such as speed of agitation, inlet solvent flow rate and inlet aqueous flow rate on the holdup, mean drop size, drop size distribution, slip and characteristic velocities and extraction percentage were examined. Modified correlations were proposed for prediction of hydrodynamic parameters with consideration of reaction extraction condition in the rotation column. Furthermore, these correlations were compared with the experimental data. According to the results, the direct extraction of Mo(Ⅵ) from aqueous solution and sulfuric media with extraction efficiency of 90.4% was obtained at higher rotor speed(240 r·min~(–1) rpm) in this column.     

Equilibrium adsorption studies on removal of diclofenac sodium from aqueous solution using sawdust–polyaniline (SD–PAn) composites

In this work, equilibrium adsorption studies were carried out for the removal of antiinflamatory drug diclofenac sodium (DS) from aqueous solutions using sawdust–polyaniline(SD-PAn) composite as a potential sorbent at 20, 30, and 40°C. The composite sorbent was characterized by FTIR and SEM analysis. The particles exhibited porous and rough surface. The equilibrium uptake data was interpreted by the Langmuir, the Freundlic, the Temkin, and the Dubinin–Redushkevich (D -R) isotherm models. The maximum adsorption capacity was found to decrease with increase in temperature, thus indicating exothermic nature of the adsorption process. The thermodynamic parameters were evaluated using Langmuir, Flory–Huggins, Frumkin, and modified-Frumkin models. The negative values of ΔG_ads⁰ and ΔH⁰ indicated spontaneous and exothermic nature of the adsorption process, respectively. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci 125:1382–1390, 2012     

Adsorption of Hg(Ⅱ) from aqueous solution using thiourea functionalized chelating fiber

A fast and selective adsorbent for Hg(II) from aqueous solutions using thiourea(TU) functionalized polypropylene fiber grafted acrylic acid(PP-g-AA),PP-g-AA-TU fibers,was characterized by Fourier transform infrared spectroscopy and X-ray photoelectron spectroscopy.The adsorption behavior of the functionalized chelating fibers for Hg(II) was investigated by static adsorption experiments,and the effects of some essential factors on adsorption of Hg(II) were examined,such as pH,initial concentration,adsorption time,coexisting cations,and temperature.The results showed that the adsorptive equilibrium could be achieved in 10 min,and the equilibrium adsorption quantity of PP-g-AA-TU fibers was 20 times that of PP-g-AA fibers.The PP-g-AA-TU fibers showed a very high adsorption rate and a good selectivity for Hg(II) over a wide range of p H.The adsorption isotherm can be well described with Langmuir model,with the maximum adsorption capacity for Hg(II) up to52.04 mg·g~(-1)and the removal of Hg(II) more than 97%.The kinetic data indicate that the adsorption process is best-fitted into the pseudo-second-order model.     

Effects of ultrasound on adsorption and desorption of chromium(Ⅵ) on activated carbon

研究了超声波对活性炭吸附/脱附Cr(Ⅵ)的影响,结果表明：有无超声波作用下,活性炭对Cr(Ⅵ)的吸附率均随pH值的升高而减小,相对于无超声作用体系,超声作用下的相平衡向吸附量减小的方向移动,且pH值越大,其减小的幅度越大;当Cr(Ⅵ)初始浓度由20 mg·L^-1增至110 mg·L^-1时,超声波作用下的Cr(Ⅵ)去除率由99.9%降至79.8%,平衡吸附量则由3.3 mg·g^-1增至15.0 mg·g^-1,与无超声波作用下的效果接近,但无超声波作用时的吸附率持续上升至平衡,而超声波作用下的吸附率先快速增加至近平衡,再出现小幅下降后又缓慢增至平衡。脱附实验发现,无论有无超声作用,活性炭表面Cr(Ⅵ)在蒸馏水中的脱附率均很小;添加NaOH可显著改善脱附效果,脱附率随NaOH用量的增加而增加,且超声场中NaOH对脱附的促进作用显著高于非超声场中的效果。     

Sorption of dissolved organics from aqueous solution by polystyrene resins—II. External and internal mass transfer

External and internal mass transfer were characterized for the sorption of 2,4-dichlorophenol and p-nitrophenol on polystyrene resins. An evaluation method is presented which estimated the external mass-transfer coefficient, κ_L, from the concentration uptake in an integral fixed-bed reactor. The experimental κ_L values are compared with values predicted using four different empirical correlations. The effect of axial dispersion on the values of κ_L was shown to be small under the given conditions.To quantify the intraparticle mass transfer, an effective diffusion coefficient, D_eff, was estimated using the pore diffusion model interpretation of data from a differential column reactor within a recirculated batch system. The D_eff values depend on both resin structure and solute properties. Values of D_eff between 0.3 × 10⁻⁹ and 1.8 × 10⁻⁹ m²/s were observed for macroporous resins, which exceed values that are characteristic of pore diffusion, and a value of 0.6 × 10⁻¹¹ m²/s was estimated for a microporous resin.     

Sorption of dissolved organics from aqueous solution by polystyrene resins—I. Resin characterization and sorption equilibrium

The results of sorption equilibrium studies indicate that adsorption is only one of the three mechanisms involved in removing organics from aqueous solution by polystyrene resins. The other two mechanisms are associated with the resin's capability to incorporate organics into their polymer matrix while swelling. To describe the overall sorption behaviour, it is not sufficient to characterize the resin structure by estimating pore size distribution and internal surface area of the dry polymers. The amount of swelling in different organic solvents must also be evaluated as an important structural parameter of polystyrene resins. The role of the different mechanisms depends on both the resin structure and the physical and chemical properties of the solute. The solute's affinity for the polystyrene surface can be correlated with the solute's benzene-water partition coefficient. A heuristic model is presented which relates the sorption capacity to both the resin and solute properties.     

Adsorption of γ-picoline onto acid-activated bentonite from aqueous solution

The adsorption of γ-picoline onto acid-activated bentonite was investigated. The adsorption reached a maximum at pH = 7. Pseudo-first-order, pseudo-second-order, the Elovich equation, and intraparticle diffusion models were used to analyze the kinetic data obtained at different concentrations. The pseudo-second-order model was best applicable to describe the adsorption of γ-picoline on acid-activated bentonite. The Langmuir model provided good correlation with the experimental data. The adsorption of γ-picoline was endothermic with ∆H° = 29 J/mol.     

Kinetics study on reactive extraction of hydroxy-(2-methyl-phenyl)-acetic acid enantiomers from organic solution by HP-β-CD

Kinetics data is important for the reliable scale-up of a lab-scale process and for selection, design and operation of related equipment. This paper reports on the kinetics study for reactive extraction of hydroxy-(2-methyl-phenyl)-acetic acid (HA) enantiomers by hydroxypropyl-β-cyclodextrin (HP-β-CD) from the organic phase to the aqueous phase. The theory of extraction with chemical reaction was used. The effects of agitation speed, interfacial area, pH value of aqueous phase, initial concentration of HA enantiomers and initial concentration of extractant on the specific rate of extraction were investigated. The reactions have been found to be first order in HA and second order in HP-β-CD with the forward rate constants of 4.873 × 10⁻⁴ m⁶/(mol² s) for R-HA and 4.343 × 10⁻⁴ m⁶/(mol² s) for S-HA, respectively.     

Insights into the adsorption performance and mechanism of Cr(Ⅵ) onto porous nanocomposite prepared from gossans and modified coal interface:Steric,energetic,and thermodynamic parameters interpretations

Herein,iron oxide/hydroxides deposits(gossans) were utilized,for the first time,in the fabrication of magnetite nanoparticles(MNPs) to load modified coal(MC).The as-synthesized MNPs@MC composite was characterized via different techniques and utilized for the Cr(Ⅵ) remediation.Experimental studies supported by theoretical treatment were applied to offer a new overview of the Cr(Ⅵ) adsorption geometry and mechanism at 25-45℃.Experimental results suggested that the Cr(Ⅵ) uptake was mainly governed ...