Kinetics and thermodynamics of U(Ⅵ) adsorption from aqueous solution by modified corncob

The corncob was microwave-assistedly modified by KMnO₄ and used for adsorption of U(Ⅵ)ions from aqueous solution.The kinetics and thermodynamics of their adsorption were measured using batch experiments.The results show that the kinetics of adsorption follows well the pseudo-second order equation,indicating that the uranium adsorption by the modified corncob is mainly chemisorption. The Langmuir,Freundlich and D-R isothermal adsorption models were used to relate the equilibrium data,finding that Langmuir isotherm of monolayer adsorption is better fitting them,pointing out that the adsorption mainly occurs on surface active sites of modified corncob.The values of apparent activation energy E_a and average adsorption energy E_s support also the suggestion that adsorption of U(Ⅵ) on modified corncob is mainly chemisorption,although some physical adsorption can not be got rid of.The thermodynamic parameters(ΔH,ΔS and ΔG)calculated from the adsorption isotherms at various temperatures indicated that the adsorption of U(Ⅵ)on modified corncob is an endothermic,spontaneous process and more favorable at higher temperature.     

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.     

Relationship between breakthrough curve and adsorption isotherm of Ca(Ⅱ) imprinted chitosan microspheres for metal adsorption

In this work, an equilibrium-dispersion model was successfully established to describe the breakthrough performance of Ca(II) imprinted chitosan (Ca(II)-CS) microspheres packed column for metal adsorption, and the assumptions of Langmuir isotherms and axial dispersion controlled mass transfer process were confirmed. The axial dispersion coefficient in Ca(II)-CS microspheres packed column was found to be almost proportional to the linear velocity and fit for prediction through single breakthrough test. Sensitivity analysis for breakthrough curve indicated the axial dispersion coefficient as well as Langmuir coefficient was sensitive variable for deep removal requirement. The retrieval of the adsorption isotherms of Ca(II)-CS microspheres from breakthrough curve was fulfilled by model ing calibration. A strategy based on the correlation between adsorption isotherms and breakthrough performance was further proposed to simplify the column adsorption design using absorbents with smal/uniform size and fast adsorption kinetics like Ca(II)-CS microspheres to cut down the gap between lab and industry.     

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.     

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。     

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.     

Unravel the potential of zinc oxide nanoparticle-carbonized sawdust matrix for removal of lead(Ⅱ) ions from aqueous solution

Zinc oxide nanoparticles(ZnOnp) are molecular nanoparticles synthesized by a chemical precipitation method from zinc nitrate tetrahydrate and sodium hydroxide.Carbonized sawdust(CSD) was prepared from sawdust obtained from a local wood mill.The matrix of both provides a better material as an adsorbent.The present study applied the functionality of ZnOnp,CSD,and ZnOnp-CSD matrix as adsorbent materials for the removal of Pb(Ⅱ) ions from aqueous solution.The method of batch process was employed to investigate the potential of the adsorbents.The influence of pH,contact time,initial concentration of adsorbate,the dosage of adsorbents,and the temperature of adsorbate-adsorbent mixture on the adsorption capacity were revealed.The adsorption isotherm studies indicate that both Freundlich and Langmuir isotherms were suitable to express the experimental data obtained with theoretical maximum adsorption capacities(q_m) of 70.42,87.72,and 92.59 mg·g~(-1) for the adsorption of Pb(Ⅱ) ions onto ZnOnp,CSD,and ZnOnp-CSD matrix,respectively.The separation factors(R_L) calculated showed that the use of the adsorbents for the removal of Pb(Ⅱ) ions is a feasible process with R_L 1.The thermodynamic parameters obtained revealed that the processes are endothermic,feasible,and spontaneous in nature at 25-50℃.Evaluation of the kinetic model elected that the processes agreed better with pseudo-second order where the values of rate constant(k_2) obtained for the adsorption of Pb(Ⅱ) ions onto ZnOnp,CSD,and ZnOnp-CSD matrix are 0.00149,0.00188,and 0.00315 g·mg~(-1)·min~(-1),respectively.The reusability potential examined for four cycles indicated that the adsorbents have better potential and economic value of reuse and the ZnOnp-CSD matrix indicates improved adsorbent material to remove Pb(Ⅱ) ions from aqueous solution.     

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...     

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     

Synthesis,adsorption and selectivity of inverse emulsion Cd(Ⅱ) imprinted polymers

Inverse emulsion polymerization was employed to synthesize inverse emulsion Cd(II) imprinted polymers(IEII P). The morphology and functional groups of IEIIP were characterized by SEM,FTIR and TG. Static adsorption experiments and competitive adsorption test were used to evaluate the adsorption ability of IEIIP. The adsorption capacity of polymers could reach 86.7 mg·g~(-1) under the optimal adsorption conditions. The pseudo second order kinetic model and Langmuir isotherm model could be used to analyze the experimental data well. The adsorption process of IEIIP was chemical adsorption process and monomolecular type. Thermodynamic parameters showed that the adsorption process was endothermic and could occur spontaneously. The selectivity coefficients k of Cd~(2+)/Pb~(2+), Cd~(2+)/Zn~(2+) and Cd~(2+)/Cu~(2+) were 2.4998, 1.2437 and 4.6882, respectively. The proposed method provides a new thought for removing Cd(II) in water samples.     

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.     

Removal of lead(Pb(Ⅱ))and zinc(Zn(Ⅱ))from aqueous solution using coal fly ash(CFA)as a dual-sites adsorbent

Coal fly ash(CFA)is composed of minerals containing some oxides in crystalline phase(i.e.,quartz and mullite),as well as unburned carbon as mesoporous material,thus enabling CFA to act as a dual-sites adsorbent with unique properties.This work focused on the adsorption of Pb(Ⅱ)and Zn(Ⅱ)from binary system,a mixture containing two metal ion solutions present simultaneously,onto NaOH-modified CFA(MCFA).Several adsorption tests were conducted to evaluate the effect of several parameters,includ-ing pH and contact times.The experiment results indicated that chemical treatment of CFA with NaOH increased pore volume from 0.021 to 0.223 cm3 g-1.In addition,it could also enhance the availability of functional groups on both minerals and unburned carbon,resulting in almost 100％Pb(Ⅱ)and 97％Zn(Ⅱ)adsorbed.The optimum pH for adsorption system was pH=3 and quasi-equilibrium occurred in 240 minutes.Equilibrium data from the experimental results were analyzed using Modified Extended Langmuir(MEL)and Competitive Adsorption Langmuir-Langmuir(CALL)isotherm models.The analysis results showed that the CALL isotherm model could better describe the Pb(Ⅱ)and Zn(Ⅱ)adsorption pro-cess onto MCFA in binary system compared with MEL isotherm model.     

Simple separation method of Zn(Ⅱ) and Cd(Ⅱ) from brine solution of zinc plant residue and synthetic chloride media using solvent extraction

In this work, the possibility of separation of Zn~(2+) and Cd~(2+) metal ions from chloride(brine) solutions was examined. For this purpose, simple solvent extraction(SX) experiments by di-2-ethylhexyl phosphoric acid(D2EHPA)in kerosene as a diluent was performed on synthetic and industrial chloride solution obtained from brine leaching of zinc filter cakes(by-product of zinc hydrometallurgical processing). The optimal conditions for separation were determined. The zinc extraction efficiency was 99% with negligible co-extraction of cadmium.Therefore, a high ΔpH_(0.5) value for Zn(Ⅱ) and Cd(Ⅱ) was achieved. FT-IR and slope analysis indicated that ZnClA·3HA and CdClA·3HA species were probably extracted.     

High-efficiency remediation of cadmium (Cd2+) from aqueous solution using poultry manure– and farmyard manure–derived biochars

Farmyard manure (FYM-BC) and poultry manure (PM-BC) derived biochars were applied as adsorbents to remove Cd²⁺ from water. Results indicated that PM-BC was a more efficient adsorbent than FYM-BC at all experimental conditions. Maximum Cd²⁺ adsorption was observed at pH 4, temperature 318 K and contact time 1 h, regardless of biochar type. The Langmuir model predicted maximum adsorption capacity of 90.09 mg g^?1 for PM-BC. The data fitting to pseudo-second-order model proposed chemisorption of Cd²⁺ onto biochars. Thermodynamics indicated that adsorption was spontaneous and endothermic. Post-adsorption analysis provided evidences of strong chemical interactions between biochars’ functional groups and Cd²⁺ ions.     

Hypercrosslinked functionalized lignosulfonates prepared via Friedel–Crafts alkylation reaction for enhancing Pb(Ⅱ) removal from aqueous

ABSTRACT

Hypercrosslinked functionalized lignosulfonates (CLS) were prepared by Friedel–Crafts alkylation reaction. The structure of CLS without introducing any functional groups and the according adsorption behaviors of Pb(II) were characterized and studied, respectively. Due to increase of specific surface area and abundance exposure of binding sites, the maximum adsorption capacity of CLS was found to be as high as 74.45 mg/g, which was about seven times that of raw lignin. The results provide a new feasible synthesis method for preparing lignin-based materials with porous structures and promising application for the removal of heavy metal ions from wastewater.     

Removal of Cd(Ⅱ) from dilute aqueous solutions by complexation–ultrafiltration using rotating disk membrane and the shear stability of PAA–Cd complex

Removal of cadmium(Ⅱ) ions from dilute aqueous solutions by complexation–ultrafiltration using rotating disk membrane was investigated. Polyacrylic acid sodium(PAAS) was used as complexation agent, as key factors of complexation, pH and the mass ratio of PAAS to Cd~(2+)(P/M) were studied, and the optimum complexation–ultrafiltration conditions were obtained. The effects of rotating speed(n) on the stability of PAA–Cd complex was studied with two kinds of rotating disk, disk Ⅰ(without vane) and disk Ⅱ(with six rectangular vanes) at a certain range of rotating speed. Both of the rejection could reach 99.7% when n was lower than 2370 r·min~(-1) and 1320 r·min~(-1), for disk I and disk Ⅱ, respectively. However, when rotating speed exceeds a certain value,the critical rotating speed(n_c), the rejection of Cd(Ⅱ) decreases greatly. The distribution of form of cadmium on the membrane was established by the membrane partition model, and the critical shear rate(γ_c), the smallest shear rate at which the PAA–Cd complex begins to dissociate, was calculated based on the membrane partition model and mass balance. The critical shear rates(γ_c) of PAA–Cd complex were 5.9 × 10~4 s~(-1), 1.01 × 10~5 s~(-1),and 1.31 × 10~5 s~(-1) at pH = 5.0, 5.5, and 6.0, respectively. In addition, the regeneration of PAAS was achieved by shear induced dissociation and ultrafiltration.     

Nickel(Ⅱ) removal from water using silica-based hybrid adsorbents:Fabrication and adsorption kinetics

A series of novel silica-based hybrid adsorbents were prepared by the crosslinking reaction of N-[3-(trimethoxysilyl)propyl] ethylene diamine(TMSPEDA) with epichlorohydrin(ECH) via a sol–gel process.Fourier transform infrared(FTIR) spectra confirmed that the reaction occurred.TGA curves showed that the thermal stability of these hybrid adsorbents reached as high as 180 °C.As a typical example,the adsorption performance of nickel(II) ions onto an adsorbent(the volume ratio of TMSPEDA and ECH was 4:1) was explored.It was found that the adsorption of nickel(II) ions onto this adsorbent followed the Lagergren pseudo-second-order kinetic model.The investigation of the adsorption mechanism demonstrated that nickel(II) adsorption was chiefly controlled by diffusion–chemisorption,suggesting that more diffusion processes were involved in the adsorption of nickel(II) ions onto this type of adsorbents.Desorption experiment indicates that these hybrid adsorbents can be regenerated.These findings reveal that this type of silica-based hybrid adsorbent is promising in the separation and recovery of nickel(II) ions from Ni-containing wastewater or contaminated water.     

Synthesis of zinc oxide nanoparticles reinforced clay and their applications for removal of Pb (Ⅱ) ions from aqueous media

The aim of the study was to synthesize zinc oxide nanoparticles (ZnONPs) composite with clay by a novel route and then to explore the capability of composite of ZnONPs and silty clay (SC) as adsorbents for Pb (Ⅱ) eradication from aqueous media by batch adsorption method. The effect of different operating factors like temperature, pH, dose and time of contact on the adsorption process were studied to optimize the conditions. Langmuir, Freundlich, Dubinin–Radushkevich (D-R) and Temkin isotherms were applied for the interpretation of the process. The R2 and q values obtained from Langmuir model suggested that the process is best interpreted by this model. The values of adsorption capacity (qm) noted were 12.43 mg·g-1 and 14.54 mg·g-1 on SC and ZnONPs-SC respectively. The kinetic studies exposed that pseudo second order (PSO) kinetics is followed by the processes suggesting that more than one steps are involved to control the rate of reactions. Various thermodynamic variables such as change in free energy (ΔGΘ), change in enthalpy (ΔHΘ) and change in entropy (ΔSΘ) were calculated. Thermodynamic data suggested that Pb (Ⅱ) adsorption on SC and ZnONPs-SC are spontaneous, endothermic and feasible processes.     

Removal efficiency of Pb(II), Zn(II), Cd(II) and Cu(II) from aqueous solution and natural water by ketoenol–pyrazole receptor functionalized silica hybrid adsorbent

In this study, we reported an efficient, alternative, and low-cost adsorbent for the efficient removal of Pb(II), Zn(II), Cd(II) and Cu(II) from water. The new hybrid material has been prepared by immobilizing a conjugated system (2Z)-1-(1,5-dimethyl-1H-pyrazol-3-yl)-3-hydroxybut-2-en-1-one on silica gel previously doped with 3-aminopropyltrimethoxysilane. The formed surface (SiNPz) was perfectly analyzed. Adsorption studies have demonstrated the ability to highlight the surface designed for efficient removal of above toxic metals from aqueous solutions using FAAS. The new material was used for the extraction of metals from natural water and showed efficiency results for toxic heavy metals.