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1.
BACKGROUND: A study of the removal of arsenic from a sample of actual groundwater using crosslinked xanthated chitosan is described. RESULTS: Removal of As(III) and As(V) was studied at pH 7.5 under equilibrium and dynamic conditions. The equilibrium data were fitted to Langmuir and Freundlich adsorption models and the various model parameters evaluated. The monolayer adsorption capacity from the Langmuir model for xanthated chitosan flakes (XCF) (As(V) 20.0 ± 0.56 mg g?1; As(III) 33.0 ± 0.32 mg g?1) were lower than obtained for xanthated chitosan granules (XCB) (As(V) 36.0 ± 0.52 mg g?1; As(III) 48.0 ± 0.45 mg g?1). Adsorption of As (V) was unaffected by the presence of other anions while in the case of As(III) the presence of sulfate and silicate caused a 26.5–50.9% decrease in adsorption. A sample (940 bed volumes) of a groundwater spiked with 200 µg L?1 As(V) treated with XCF in column experiments reduced the arsenic concentration to < 10 µg L?1. The adsorbent was also successfully applied for the removal of total inorganic arsenic down to < 10 µg L?1 from real samples of arsenic‐contaminated groundwater. CONCLUSION: Xanthated chitosan was an efficient adsorbent for the removal of both forms of arsenic from groundwater under near neutral conditions. The presence of sulfur and the amino groups resulted in increased adsorption capacity of the sorbent. Copyright © 2012 Society of Chemical Industry  相似文献   

2.
Shujuan Zhang  Xiao-yan Li 《Carbon》2010,48(1):60-412
To enhance As(V) removal, an activated carbon fiber (ACF) based adsorbent was fabricated by impregnation of nano-sized magnetite to the surface of ACF with chitosan as the coating support. The As(V) adsorption capacity of the modified ACF (MACF) was approximately eight times of that of the raw ACF (RACF). Even at As(V) concentrations lower than 10 μg L−1, the MACF exhibited a considerably high adsorption capacity to As(V), whereas the RACF was ineffective even at an As(V) concentration ten times higher to 10 μg L−1. The MACF was able to reduce As(V) concentration below its maximum contaminant level regulated by the US EPA for drinking water in a wide pH range without formation of the more poisonous As(III). Kinetic experiments indicated that the diffusion of As(V) within the pores of the MACF was more rapid than that of the RACF and that the surface reaction was the dominant step in the adsorption of As(V) onto the MACF. Compared with the RACF, the MACF had a wider applicable pH range from 2 to 8 for the As(V) uptake. Besides enhanced As(V) uptake, the MACF maintained its high adsorption capability to organic contaminants, such as phenol and humic acid.  相似文献   

3.
In this study, Ce3+-based cryogel with methacryloyl antipyrine (MAAP) and 2-hydroxyethyl methacrylic acid (HEMA) [p(HEMA-MAAP-Ce3+] was prepared. MAAP-Ce3+ complex was characterized by UV–near infrared and energy-dispersive X-ray spectroscopy. Cryogel was characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, and swelling test. Pore size of the cryogel was found to be about 30–50?µm. The effects of flow rate, pH, temperature, and initial enzyme concentration have been investigated. Maximum adsorption capacity was found to be 57.84?mg?g?1 cryogel at pH 6.0. After seven times of adsorption–desorption cycles of same cryogel, it was observed that there is negligible decrease in the adsorption capacity.  相似文献   

4.
Activated carbon prepared from Eichhornia was used for the adsorptive removal of Pb(II) from aqueous solution. As the raw material for the preparation of the activated carbon is an aquatic weed, the production of this carbon is expected to be economically feasible. Parameters such as agitation time, metal ion concentration, adsorbent dose and pH were studied. Adsorption equilibrium was reached in 100 min for a solution containing 15 mgdm?3 and 125 min for solutions containing 20 and 25 mgdm?3 Pb(II), respectively. Adsorption parameters were determined using both Langmuir and Freundlich isotherm models. The adsorption capacity was 16.61 mgg?1 at pH 3.0 for particle sizes of 125–180 µm. Pb(II) removal increased as the pH increased from 2 to 4 and remained constant up to pH 10.0. Desorption studies were also carried out with dilute hydrochloric acid to recover both carbon and Pb(II). Quantitative desorption of Pb(II) from carbon indicates that adsorption of metal ion is by ion exchange. © 2002 Society of Chemical Industry  相似文献   

5.
《分离科学与技术》2012,47(14):2909-2932
Abstract

Physical and chemical characterization of granular ferric hydroxide (GFH) [e.g., scanning electron micrographs (SEM), X‐ray diffraction (XRD) analysis, Brunauer‐Emmett‐Teller (BET) and Langmuir surface area measurements, pore size distribution, pH titration, and zeta potential measurements] were conducted to determine its performance as an adsorbent for trace arsenic(V) removal. Speciation diagrams for arsenate and phosphate were produced for the present system. The equilibrium adsorption isotherms were measured over initial arsenate concentrations ranging from 100–750 µg/L and the pH range of 4–9. The adsorption of arsenate was found to decrease as the pH of the solution was increased, thus giving the optimal adsorption of arsenate onto GFH at pH 4. Adherence to the Langmuir isotherm was found at all pHs for the arsenate adsorption. The competitive effect of phosphate on the uptake of arsenate at pH 4 by GFH was investigated, outlining the greater affinity of GFH for arsenate adsorption compared to phosphate. The kinetic performance of GFH was assessed and the results were analyzed by applying a particle diffusion model.  相似文献   

6.
The present work has focused on the removal of arsenic (III) using two effective adsorbents such as red mud treated with HCl and coated with Fe2O3. Adsorption of As (III) was performed by the function of pH, adsorbent dose, contact time, initial ion concentration, and the appropriate conditions for adsorption were determined. The characterization studies of the adsorbent were analyzed using X-ray diffraction, X-ray fluorescence, Brauner–Emmett–Teller, scanning electron microscope, and FTIR spectroscopy. The result of the studies shows that the adsorbent is suitable for the effective removal of As (III) ions. Batch adsorption process showed that the maximum adsorption occurred at Fe2O3-coated red mud. The equilibrium data were well fitted to the nonlinear Langmuir isotherm model and the maximum adsorption capacity (qm) of Fe2O3-coated red mud was found to be 21.85?mg?g?1 which indicates that Fe2O3-coated red mud had more adsorption capacity. In the Freundlich isotherm, the experimentally obtained n value of Fe2O3-coated red mud was 2.393 which indicates the favorable adsorption of As (III) on the adsorbent. Dubinin–Radushkevich isotherm confirms that the adsorption process is physical in nature. Furthermore, the adsorption kinetic studies followed the pseudo-first-order model. All the results concluded that Fe2O3-coated red mud can be considered as a cost-effective and potential adsorbent for As (III) removal.  相似文献   

7.
Abstract

This work aims to evaluate the Cr(VI) removal efficiency and adsorption capacity of the raw coconut fiber from synthetic aqueous solutions through the operational parameters as well as to represent the mechanisms of removal by kinetic and isotherm models. The experimental study was conducted in batch system and the optimum conditions for the adsorption of this metal by the biomass were according to: pH 2, contact time of 270?min, and 10?g/L of adsorbent dosage concentration. The removal efficiency obtained for Cr(VI) solutions was 99.2% at concentrations of 25–50?mg/L. For the highest concentrations, the removal decreased from 96.3% to 74.4%, when Cr(VI) solutions ranged from 100?mg/L to 250?mg/L, respectively. The adsorption kinetics was applied and showed a good agreement for pseudo-second-order and Elovich models, which point out a chemisorption. For the adsorption capacity at equilibrium conditions, the best fit was for the Redlich–Peterson isotherm indicating favorable adsorption and monolayer coverage.  相似文献   

8.
Mesoporous-activated carbon was prepared from fallen coconut (Cocos nucifera) leaf, an agricultural waste through a microwave-induced H3PO4 activation process. The characterization of the coconut leaf–activated carbon (CAC) was evaluated through the iodine number, ash content, bulk density, and moisture content. Fourier transform infrared spectroscopy, scanning electron microscope, Brunauer–Emmett–Teller (BET) surface area, X-ray diffraction, and pHPZC. CAC has a mesopore content of 84% with an average pore size of 36.5?Å and a large BET surface area of 632?m2/g. The uptake properties of the CAC with methylene blue was evaluated at different CAC dosage levels (0.2–10?g/L), initial pH (3–10), methylene blue concentration (50–350?mg/L), and time (0–360?min) using batch mode operation. The kinetic profiles were described by the pseudo-second-order kinetics. The equilibrium data were well fitted to the Langmuir model with a maximum monolayer adsorption capacity of 250?mg/g at 30°C. Thermodynamic functions indicate a spontaneous and exothermic nature of the adsorption process. This study indicates that coconut leaves are a promising renewable precursor that can be utilized to develop an efficient mesoporous-activated carbon.  相似文献   

9.
《分离科学与技术》2012,47(15):2412-2425
Red mud, a waste tailing from alumina production, was activated with calcination and acid treatment for simultaneous removal of F? and As from water solution. After activation, the specific area and Si-O-M and Al-O-H functional groups of the activated red mud (ARM) greatly increased. Results showed that the adsorption equilibrium time for F?, As(V), and As(III) was 18, 12, and 48 h, respectively. Kinetic data revealed that adsorption kinetics well followed the pseudo-second order model for F?, As(V), and As(III). The presence of As(V)/As(III) improved the adsorption rate of F?. With the co-existence of F? and As, F? adsorption was independent of initial solution pH between 4.0 and 10.0, and As adsorption between 2.0 and 10.0. Adsorption of F?, As(V), and As(III) was better described by the Langmuir model than the Freundlich model, indicating that adsorption was in the form of a monolayer. Fluoride had a significant effect on As(V) adsorption, while the less affected As(III) adsorption. The presence of 1.0 mg/L As(III)/As(V) had no significant influence on F? adsorption. ARM had high adsorption capacity for F?, As(V), and As(III), which resulted from the increases in the specific area and Si-O-M and Al-O-H functional groups. Results demonstrated that ARM is a potential adsorbent for simultaneous removal of F? and As from contaminated groundwater.  相似文献   

10.
Abstract

Zero-valent iron nanoparticles (NZVI-NPs) possess significantly high surface area and volume ratio, and this unique surface characteristic has enhanced reactivity to their adsorption potential. In this work, a bio-matter (Olive leaves extract) is deployed as a nature-inspired reducing agent for the synthesis of NZVI-NPs. The particle size of NZVI-NPs has been determined using particle sizer. The NZVI-NPs are characterized using analytical and morphological techniques such as ultraviolet???visible spectroscopy (UV???vis), energy dispersive X-ray spectroscopy (EDS), X-ray diffraction spectroscopy (XRD), scanning electron microscope (SEM), Brunauer–Emmett–Teller (BET), and Fourier transform infrared (FTIR) spectroscopy. The average crystalline size of NZVI-NPs are around 30–60?nm while maximum adsorption is at 225?nm. XRD spectrum shows two distinctive diffraction peaks at 25.40° and 42.50° corresponding to lattice plane value indexed at (200) and (222) planes of faced centered cubic (FCC). At optimized experimental conditions, NZVI-NPs show 97% removal efficiency of Ni+2 ions from aqueous solution. The equilibrium time has been found to be 55?min and the monolayer maximum adsorption capacity is 139.5?mg/g. Kinetically, Ni+2 ions adsorption has been modelled using various physical isotherms and the data best fitted Freundlich isotherm model and pseudo-first-order kinetic; revealing a maximum adsorption capacity of 139.5?mg/g at 25?±?3?°C and pH of 6.5. Desorption tests affirm the possibility of recovering reasonable amount of NZVI-NPs after used. The specific surface area of the NZVI-NPs sample measured by BET analysis is 21.9967 m2/g indicating a high adsorption capacity.  相似文献   

11.
Zirconium pillared clay (PILC) was prepared using montmorillonite as the base clay. Adsorption of tannic acid (tannin) was studied by a batch equilibrium technique, as a function of adsorbate concentration, temperature, pH, agitation speed, particle size of the adsorbent and ionic strength. The process of uptake is governed by diffusion controlled first‐order reversible rate kinetics. The higher uptake for the pH range 4.0–6.0 was attributed to external hydrogen bonding between phenolic‐OH groups of tannin molecules and the hydrogen bonding sites on the clay. The removal of tannin by adsorption was found to be >99.0% depending on the initial concentration in the pH range of 4.0–6.0. The process involves both film and pore diffusion to different extents. The effects of solute concentration, temperature, agitation speed and particle size on the diffusion rate were investigated. Tannin uptake was found to increase with ionic strength due to the compression of diffuse double layers. The applicability of Langmuir and Freundlich isotherm models has been tested. The maximum adsorption capacity of PILC was found to be 45.8 µmol g?1 of clay and the affinity constant is 2.9 × 10?2 dm3 µmol?1 at 30 °C. Thermodynamic parameters such as ΔG °,ΔH ° and ΔS ° were calculated to predict the nature of adsorption. The isosteric enthalpies of adsorption were also determined and found to decrease with increasing surface coverage. Regeneration with hot water (60 °C) has been investigated for several cycles with a view to recovering the adsorbed tannin and also restoring the sorbent to its original state. Copyright © 2001 Society of Chemical Industry  相似文献   

12.
《中国化学工程学报》2014,22(11-12):1340-1346
Although common calcium-containing minerals such as calcite and gypsum may fix arsenic, the interaction between modified calcic minerals and arsenic has seldom been reported. The uptake behavior of As(III)/As(V) from aqueous solutions by calcium sulfate whisker (CSW, dihydrate or anhydrite) synthesized through a cooling recrystallization method was explored. A series of batch experiments were conducted to examine the effect of pH, reaction time, whisker dosage, and initial As concentration. X-ray diffraction (XRD) and scanning electron microscopy (SEM) were used to characterize the samples prepared. The results showed that pH of the aqueous solution was an important parameter for As(III)/As(V) uptake, and an excellent removal efficiency could be achieved under strongly alkaline condition. The data from batch experiments for reaction of As(V) with calcium sulfate dihydrate whisker (CSDW) and calcium sulfate anhydrous whisker (CSAW) were well described with extended Langmuir EXT1 model, from which theoretic maximum adsorption capacity of 46.57 mg As(V)·(g CSDW) 1 and 39.18 mg As(V)·(g CSAW) 1 were obtained. Some calcium arsenate solids products, such as CaAsO3(OH) (weilite, syn), Ca3(AsO4)2 (calcium arsenate), CaO–As2O5, Ca–As–O, Ca5(AsO4)3OH·xH2O (calcium arsenate hydroxide hydrate), and CaH(AsO4)·2H2O (hydrogen calcium arsenic oxide hydrate), were detected at pH = 12.5 through XRD analysis. This indicates that the interaction mechanism between As(V) and CSW is a complex adsorption process combined with surface dissolution and chemical precipitation.  相似文献   

13.
Fe (III)-loaded chitosan (CS) hollow fibers (CS-Fe (III) HF) were successfully prepared according to the dry-wet spinning technique. The CS-Fe (III) HFs were characterized by X-ray diffraction (XRD), scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray photoelectron spectroscopy (XPS) and thermal gravimetric analysis (TGA). Removal of pentavalent arsenic was studied through biosorption on CS-Fe (III) HF adsorptive membranes. The response surface methodology (RSM) was applied to investigate the influence of the main operating parameters such as contact time, pH, initial As (V) concentration and HFs dosage on the adsorption capacity of As (V). From the Pareto analysis, pH, [As (V)]o, [CS-Fe (III) HF membranes] and squared effect of [As(V)]o were found to produce the largest effect on biosorption of As (V). Kinetic studies showed that the pseudo-second-order kinetic model provides the best correlation to the experimental results. Equilibrium data fitted well with the Langmuir model with maximum adsorption capacity of 3,703 μg g?1. A laboratory scale glass membrane module consisting of three CS-Fe(III) HFs has also been prepared and tested for biosorption of As (V) at a real scale. Permeability of As (V) ions through the CS-Fe (III) HF membranes was 0.145 μmol m?2 h?1 bar ?1.  相似文献   

14.
ABSTRACT

Hydrous titanium dioxide was impregnated on the surface of zeolite to obtain a kind of hydrous TiO2/zeolite (HTiO2/ZFA) adsorbent using the hydrothermal method. HTiO2/ZFA was characterised by scanning electron microscopy combined with energy-dispersive spectrometer, X-ray diffraction, Fourier transform infrared, particle size distribution; and the pH of zero point charge measurement and its performance for Cu(II) adsorption were investigated. It was shown that Ti was not inserted into the skeleton of ZFA and hydrous TiO2 loaded on the surface was amorphous. The pHzpc of HTiO2/ZFA decreased to pH 5.5 from pH 6.5 of ZFA. Cu(II) adsorption was favoured in a pH range of 3.0–6.0, and 90% copper could be removed in first 30?min for 60?mg?L–1 Cu(II) solution. The Langmuir isotherm model could well describe the adsorption isotherm data and the maximal Cu(II) adsorption capacity reached 251.9?mg?g–1. Moreover, the HTiO2/ZFA could be desorbed by HCl solution for further use, which implied an effective application in wastewater treatment.  相似文献   

15.
《分离科学与技术》2012,47(9):1557-1569
Abstract

The effectiveness of pretreating a spent catalyst with an iron-salt solution to improve its As(V) removal capacity was studied. Various factors, such as types and concentrations of iron salt, pH. and initial As(V) concentration were investigated for their effects on the improvement of As(V) removal capacity. A significant increase in As(V) removal capacity can be achieved by iron-coated spent catalyst. Adsorption density of As(V) decreased with increasing pH. Langmuir adsorption isotherm was utilized to describe the adsorption reaction. Results from IR analysis and zeta potential measurement indicate that As(Y) is specifically adsorbed onto iron-coated spent catalyst. This study shows that spent catalyst can be converted to a useful adsorbent for As(V) removal.  相似文献   

16.
In this study, a sol–gel process was used to prepare hybrid nanocomposite consisting of octa(maleimidophenyl) silsesquioxane-silica/titania (maleimide–POSS (polyhedral oligomeric silsesquioxanes)–SiO2/TiO2) to use in methylene blue (MB) adsorption and as an antibacterial agent. The structure, surface, and morphological characteristics were confirmed through Fourier transform infrared spectroscopy, X-ray diffraction, X-ray photoelectron spectroscopy, and transmission electron microscopy. The optical and thermal stabilities were studied by conducting UV–visible and thermogravimetric analysis–differential scanning electron calorimetry analysis. The experimental results showed a maximum dye adsorption capacity of 92% achieved using 0.5?g of hybrid nanocomposite after 2.5?h at pH 9. We also investigated the effect that the adsorbent dosage, pH, and contact time had on the removal efficiency of the MB dye in aqueous solution. The recycling experiment showed a good adsorption capacity of the MB dye, even after five repeated cycles. Furthermore, the hybrid nanocomposite was tested against pathogenic bacteria, such as Bacillus cereus, Lactobacillus, Escherichia coli, and Pseudomonas aeruginosa. The nanocomposite was observed to be highly sensitive to E. coli, B. cereus, and P. aeruginosa, as confirmed by the size of the zone inhibition.  相似文献   

17.
Fe2O3–TiO2 porous ceramic (Fe/TiPC) beads with photo-catalytic performances and high adsorption capacities were prepared by a simple high temperature solid reaction and were applied for arsenic removal from drinking water. The microstructure and morphology of Fe/TiPC were characterized by X-ray diffraction and scanning electron microscopy. More than 90% removal ratio for As (III) and As (V) were respectively achieved by Fe/TiPC within 2 h under UV irradiation. The Langmuir capacity values of Fe/TiPC for As (III) and As (V) were 13.86 and 15.73 mg/g, respectively. In addition, Fe/TiPC could be reused for up to five times without significant reduction in the photocatalytic sensitivity and adsorption capacity aspects. Good catalytic oxidation performances and high adsorption capacities as well as a sample preparation for Fe/TiPC suggest that the composites may have practical prospects for the As (III) and As (V) removal from contaminated water.  相似文献   

18.
The aim of this present work is to investigate the adsorption capacity, kinetics and mechanism of arsenite ion removal onto beta-Cyclodextrin–Chitosan–Fe3O4 nanocomposite (β-CD–CS–Fe3O4 nanocomposite) from aqueous solutions. Iron oxide nanoparticles (Fe3O4) were synthesized using the co-precipitation method and the nanocomposite was successfully prepared via the solution-blending method. The analysis to determine arsenite ion adsorption was carried out using ICP-MS by varying pH, contact time and arsenite concentration parameters. The sorption of arsenite was found to be dependent on pH, time and arsenite initial concentrations. The adsorption equilibrium was reached in the first 20 min with the maximum uptake of 96%. Adsorption data were fitted well to the Langmuir isotherm describing a monolayer adsorption mechanism and pseudo-second-order models for kinetic study. It was established that the β-CD–CS polymer blend grafted with Fe3O4 nanoparticles enhanced the adsorption capacity because of the complexation abilities of the multiple OH and NH2 groups in the polymer backbone with metal ions. Subsequently, the mechanism of adsorption was investigated by studying the physicochemical properties of the adsorbent and the adsorbed species using the FTIR, TGA, DSC, XRD, SEM and TEM techniques. The characterizations before and after incorporations of the β-CD–CS composite with Fe3O4 nanoparticles showed well-improved properties for better adsorption of arsenite (As(III)) ions.  相似文献   

19.
The adsorption of Cr (VI) from aqueous solution onto nanoparticles hematite (α-Fe2O3) of different morphologies synthesized by acid hydrolysis, transformation of ferrihydrite, sol gel methods has been investigated. The hematite particle sizes were in the range 15.69-85.84 nm and exhibiting different morphologies such as hexagonal, plate-like, nano-cubes, sub-rounded and spherical. The maximum adsorption capacity of Cr (VI) was found to be in the range 6.33–200 mgg?1 for all hematite samples. The kinetics of sorption was rapid, reaching equilibrium at 45–240 minutes. Sorption kinetics and equilibria followed pseudo-second order and Langmuir adsorption isotherm models. The rate constants were in the range 0.996–2.37×10?2 g/mg/min for all samples. The maximum adsorption was attained at pH 3.0, while adsorption decreased as the pH increased from pH 3.0 to 10.0. The study revealed that the hematite with plate-like morphology has the highest adsorption capacity. The sorption process has been found to be feasible following a chemisorption process, and adsorption of Cr (VI) onto hematite nanoparticles was by inner sphere surface complexation due to low desorption efficiency in the range 9.54–53.4%. However, the result of ionic strength revealed that the reaction was by outer sphere complexation. This study showed that morphologies play a vital role in the adsorption capacities of samples of hematite in the removal of Cr (VI) from aqueous solution.  相似文献   

20.
《分离科学与技术》2012,47(6):776-785
Biosorption of As(V) was carried out using Paecilomyces variotii biomass in batch and column mode experiments. Various pretreatments like autoclaving (APV), iron doping (FePV), and PVP K25 doping (PVPPV) of biomass were carried out to increase and compare the adsorption efficiency of As(V) onto the biomass. At maximum concentration of 2.5 mg/L of As(V), the removal was observed to be 58.4, 51.29, and 47.7% with FePV, PVPPV, and APV biomass respectively. PVPPV required comparatively less time (135 min) to attain equilibrium when compared to other adsorbents (165 min). FePV showed higher As(V) adsorption capacity (Qo) of 1.563 mg/L in batch mode. The batch mode data were analysed using Langmuir and Freundlich isotherms and first order and pseudo second-order kinetic models. The maximum removal was observed at pH 2 with FePV. In column mode experiments, the change in the flow rate and the bed volume affected the adsorption capacity of the adsorbent. FePV showed maximum adsorption of As(V) in column mode experiments also. The desorption experiments revealed that the adsorbents could be reused so that it can be a cost-effective adsorbent for As(V) removal from drinking water.  相似文献   

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