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1.
Removal of Pb2+ and Ni2+ from aqueous solutions by sorption onto natural bentonite was investigated. Experiments were carried out as a function of particle size, the amount of bentonite, pH, concentration of metals, contact time, and temperature. The adsorption patterns of metal ions onto followed the Langmuir, Freundlich, and Dubinin-Radushkevich isotherms. This included adsorption isotherms of single-metal solutions at 303 K by batch experiments. The thermodynamic parameters (DeltaH,DeltaS,DeltaG) for Pb2+ and Ni2+ sorption onto bentonite were also determined from the temperature dependence. The adsorptions were endothermic reactions. The results suggested that natural bentonite is suitable as a sorbent material for recovery and adsorption of metal ions from aqueous solutions.  相似文献   

2.
The cation-exchange capacity of Brazilian natural zeolite, identified as scolecite, was studied with the aim of evaluating its applications in wastewater control. We investigated the process of sorption of chromium(III), nickel(II), cadmium(II), and manganese(II) in synthetic aqueous effluents, including sorption isotherms of single-metal solutions at 298, 313, and 333 K, by batch experiments, and the influence of pH on the process. The results have demonstrated that removal of metals from specific metal solutions is best described by a Freundlich isotherm, in which the values obtained for the Kf constants were in the following order: Cr > Mn > Cd > Ni. A Lagergren pseudo-second-order was the model that best described the sorption mechanism. The retention of metals was shown to be a function of the pH; the maximum binding capacity occurring at pH values around 6.0. Thermodynamic data indicate the spontaneity of the endothermic cation-exchange process. The values of Delta G0 suggest the following selectivity series at 298 K: Ni > Cr > Cd > Mn. The desorption process reaches equilibrium during the first 60 min of binding, suggesting that the mechanism involves specific sites located in the external surface of the scolecite.  相似文献   

3.
We have developed a novel approach to obtain high metal sorption capacity utilizing a membrane containing chitosan and an immobilized reactive dye (i.e. Reactive Yellow-2). The composite membrane was characterized by SEM, FT-IR, swelling test, and elemental analysis. The membrane has uniform small pores distribution and the pore dimensions are between 5 and 10 μm, and the HEMA:chitosan ratio was 50:1. The reactive dye immobilized composite membrane was used in the removal of heavy metal ions [i.e., Pb(II), Hg(II) and Cd(II)] from aqueous medium containing different amounts of these ions (5-600 mg l−1) and at different pH values (2.0-7.0). The maximum adsorption capacities of heavy metal ions onto the composite membrane under non-competitive conditions were 64.3 mmol m−2 for Pb(II), 52.7 mmol m−2 for Hg(II), 39.6 mmol m−2 for Cd(II) and the affinity order was Pb(II) > Hg(II)>Cd(II).  相似文献   

4.
The kinetics of Cd Sorption from aqueous solution on a synthetic calcium hydroxyapatite was investigated at 18, 28 and 75 °C in batch experiments, using also X-ray diffraction, electron microscopy and nuclear microprobe analysis. Cadmium is incorporated into the hydroxyapatite structure via diffusion and substitution for calcium ions, but exchange equilibrium is not achieved even after 12 days of contact at 75 °C and sorption is only partly reversible. Values of diffusion coefficients were estimated from X-ray line broadening and sorption kinetics. The fact that Cd is incorporated into the bulk of the apatite with partial reversibility is important in the context of the safe storage of used sorbent material after decontamination of water polluted by cadmium.  相似文献   

5.
Heavy metals can be immobilized by soils and their distribution among the particulate soil components depends on the identity and amount of the metal, the properties of the soil, and other environmental factors. Cd, Cu and Pb are among the most potentially toxic heavy metals, are present--often together--in numerous polluting spills and in agrochemicals. We evaluated the individual and competitive sorption and retention of Cd, Cu and Pb on 20 soil horizons. As is usual, the isotherms constructed were so irregular, especially the retention isotherms, that it was not possible to classify and compare them in terms of the conventional isotherm shapes. Nor could they be compared using Langmuir or Freundlich parameters, since not all could be fitted with either of these equations. They were therefore characterized and compared in terms of several varieties of distribution coefficient, including a novel adimensional parameter K(r) which on the basis of correlation and principal components analyses was judged to be the most coherent and generally applicable to all experimental conditions (sorption and desorption starting from single- or multi-metal solutions). K(r) proved to be mainly determined by soil pH, effective cation exchange capacity, and Mn oxides content.  相似文献   

6.
Biochar prepared from Triticum aestivum straw (SB) was used to investigate the sorption separation of Cd2+ and Co2+ ions in single and binary systems. The maximum adsorption capacity of SB was higher for Cd2+ ions and the process was strongly pH dependent. Adsorption data in the binary system Cd2+–Co2+ were well described by the extended Langmuir model and the values of affinity parameter b indicate a higher affinity of SB to Cd2+ in comparison with Co2+ ions. The mechanisms for the removal of Cd and Co by biochar were evidenced by the different instrumental analyses as well as by chemical speciation modeling. Elemental mapping of SB revealed spatial distributions of cobalt and cadmium on biochar surfaces. The role of functional groups in metal sorption was confirmed by FTIR. Results demonstrate that SB is a promising heavy metal-immobilizing agent for contaminated soils or water.  相似文献   

7.
Release of heavy metal onto the water and soil as a result of agricultural and industrial activities may pose a serious threat to the environment. In this study, the adsorption behavior of nano hydroxyapatite with respect to Pb2+, Cd2+ and Ni2+ has been studied in order to consider its application to purity metal finishing wastewater. The batch method has been employed, using metal concentrations in solution ranging from 100 to 400 mg/L. The uptake capacity and distribution coefficients (Kd) were determined for the adsorption system as a function of sorbate concentration. The Langmuir, Freundlich, and Dubinin–Kaganer–Radushkevich (DKR) isotherms applied for sorption studies showed that the amount of metal sorbed on nano hydroxyapatite. It was found that the adsorption phenomena depend on charge density and hydrated ion diameter. According to the equilibrium studies, the selectivity sequence can be given as Pb2+ > Cd2+ > Ni2+. These results show that nano hydroxyapatite holds great potential to remove cationic heavy metal species from industrial wastewater.  相似文献   

8.
1-(2-Pyridylazo)-2-Naphthol (PAN) doped sol-gel silica has been investigated for removal of metal ions from aqueous media. In the doped sol-gel silica, the large reagent molecules are entrapped inside the pores while small metal ions can diffuse into the pores where they are complexed by the reagent and retained inside the pores. This new solid sorbent was applied for removal of Cd(II) from aqueous solutions. The kinetics, adsorption isotherm, equilibration time and pH effect on the removal were studied to optimize the conditions to be utilized on a large scale. It was observed that a sol gel loaded with 0.09 mmol PAN/g, had a capacity of 0.044 mmol Cd/g. The desorption of metal ions was carried by 1 M HCl and the sol-gel silica sorbent could be regenerated and reused repeatedly.  相似文献   

9.
The potential of using nano-sized aragonite mollusk shell (nano-Bio-ARA) to remove Cd(2+) from contaminated water was investigated by comparing the sorption kinetics and isotherms with the nano-sized calcite-type mollusk shell (nano-Bio-CAL) and nano-sized geological calcite (nano-Geo-CAL). Nano-Bio-ARA displayed extremely high sorption capacity to Cd(2+) (8.91mmol/g), much higher than nano-Bio/Geo-CAL, and many other natural or engineered materials. The results of thermodynamic experiments indicated that the sorption of Cd(2+) on the nano-ARA was a spontaneous and endothermic process. The coexisting metals in the solution displayed competition effect to the sorption of Cd(2+) on nano-Bio-ARA in the following order: Cu(2+)>Cr(3+)>Pb(2+)>Zn(2+)>Ca(2+). EDTA impeded the sorption of Cd(2+) on nano-Bio-ARA due to its strong chelating capacity to Cd(2+) in the solution. The results demonstrate that nano-Bio-ARA is a potential high-effective material to treat Cd(2+) contaminated water.  相似文献   

10.
Pectin (Pec) and cellulose microfibers (CF) extracted from orange waste were combined to form composite beads with enhanced adsorption capacity. Such beads were extensively tested in the removal of multi-metal ions from water. A factorial design approach was conducted to establish the optimum conditions for adsorption of Cd(II), Cu(II), and Fe(II) on Pec-CF beads. Batch adsorption experiments revealed that removal efficiency of such metal ions falls in the range of 94–58% and it followed the order Fe(II) > Cu(II) > Cd(II). The maximum Cd(II), Cu(II) and Fe(II) adsorption capacities calculated from the Langmuir isotherm were 192.3, 88.5 and 98.0 mg/g, respectively. FTIR analysis suggests that the functional groups on Pec-CF beads (binding sites) favor the adsorption of such metal ions. Desorption and reuse experiments demonstrated the beads could be used for at least five consecutive adsorption/desorption cycles. Our finds suggest the Pec-CF beads can serve as an efficient adsorbent for the removal of multi-metal ions from wastewater.  相似文献   

11.
A new biosorbent for removing toxic metal ions from water/industrial wastewater has been investigated using by-product lignin from paper production. Lignin was extracted from black liquor waste, characterized and utilized for the removal of copper and cadmium from aqueous solutions in single, binary and multi-component systems. Adsorption studies were conducted at different temperatures, lignin particle sizes, pHs and solid to liquid ratios. All the studies were conducted by a batch method to determine equilibrium and kinetic parameters. The Langmuir and Freundlich isotherm models were applied. The Langmuir model fits best the equilibrium isotherm data. The maximum lignin adsorption capacities at 25 degrees C were 87.05 mg/g (1.37 mmol/g) and 137.14 mg/g (1.22 mmol/g) for Cu(II) and Cd(II), respectively. Adsorption of Cu2+ (68.63 mg/g at 10 degrees C and 94.68 mg/g at 40 degrees C) and Cd2+ (59.58 mg/g at 10 degrees C and 175.36 mg/g at 40 degrees C) increased with an increase in temperature. Copper and cadmium adsorption followed pseudo-second order rate kinetics. From kinetic studies, various rate and thermodynamic parameters such as effective diffusion coefficients, activation energy, and activation entropy were evaluated. Adsorption occurs through a particle diffusion mechanism at temperatures 10 and 25 degrees C while at 40 degrees C it occurs through a film diffusion mechanism. The sorption capacity of black liquor lignin is higher than many other adsorbents/carbons/biosorbents utilized for the removal of Cu(II) and Cd(II) from water/wastewater in single and multi-component systems.  相似文献   

12.
Cd2+和Ni2+在粉煤灰上的吸附特性   总被引:2,自引:1,他引:1  
考察了粉煤灰对Cd2+和Ni2+的单组分吸附和双组分吸附性能。结果表明,粉煤灰可有效吸附水溶液中的Cd2+和Ni2+,去除率随pH升高而增加。吸附约60min后趋于平衡。粉煤灰对Ni2+的吸附容量高于Cd2+。单组分吸附平衡符合Freundlich模型和Redlich Peterson (R P)模型。双组分吸附时,Ni2+和Cd2+之间存在明显的竞争吸附效应;随干扰离子浓度升高,竞争吸附效应增强。不同模型拟合结果表明,双组分吸附平衡符合Freundlich竞争吸附模型。脱附实验表明,Cd2+比Ni2+易于脱附;0.1mol/L HCl、0.1mol/L HNO3 和0.05mol/L H2SO4的脱附效果接近,对Cd2+脱附率>60%,对Ni2+脱附率>35%。  相似文献   

13.
Many mine soils are chemically, physically, and biologically unstable and deficient. They are sometimes amended with sewage sludge and ashes but often contain heavy metals that increase the already high mine soils' heavy metal contents. Cd, Cr, Cu, Ni, Pb, and Zn in mutual competition were added to five mine soils (Galicia, Spain). Soil capacities for heavy metal sorption and retention were determined by means of distribution coefficients and selectivity sequences among metals. Influence of soil characteristics on sorption and retention was also examined. Retention selectivity sequences indicate that, in most of the soils, Pb is the preferred retained metal, followed by Cr. The last metals in these sequences are Ni, Cd, and Zn. Soil organic matter content plays a fundamental role in control of Pb sorption. Gibbsite, goethite, and mica influence Cr retention. Soil organic matter, oxides, and chlorite contents are correlated with K(d sigma sp medium). Heavy metals are weakly adsorbed by soils and then desorbed in high amounts. To recover these soils it is necessary to avoid the use of residues or ashes that contain heavy metals due to their low heavy metal retention capacity.  相似文献   

14.
Heavy metal biosorption by bacterial cells   总被引:9,自引:0,他引:9  
Microbial biomass provides available ligand groups on which metal ions bind by different mechanisms. Biosorption of these elements from aqueous solutions represents a remediation technology suitable for the treatment of metal-contaminated effluents. The purpose of the present investigation was the assessment of the capability of Brevibacterium sp. cells to remove bivalent ions, when present alone or in pairs, from aqueous solutions, using immobilized polyacrylamide cells of the microorganism in a flow-through system. The biosorption capacity of Brevibacterium cells was studied for lead, cadmium and copper. The metal cell binding capacity followed the order Cu > Pb > Cd, based on estimated qmax. These values, expressed as mmol metal/g dry weight cells, were 0.54 for Cu, 0.36 for Pb and 0.14 for Cd. Polyacrylamide-gel immobilized cells were effective in Pb, Cu and Cd removal. Lead removal was not affected by the presence of Cd and Cu; lead instead inhibited Cd and Cu removal. The desorption of the metal, by fluxing a chelating solution, restored the metal binding capacity of the cells, thus affording the multiple use of the same biomass in the remediation treatment. Received: 31 July 1997 / Revised: 22 December 1997 / Accepted: 30 December 1997  相似文献   

15.
Microbial biomass provides available ligand groups on which metal ions bind by different mechanisms. Biosorption of these elements from aqueous solutions represents a remediation technology suitable for the treatment of metal-contaminated effluents. The purpose of the present investigation was the assessment of the capability of Brevibacterium sp. cells to remove bivalent ions, when present alone or in pairs, from aqueous solutions, using immobilized polyacrylamide cells of the microorganism in a flow-through system. The biosorption capacity of Brevibacterium cells was studied for lead, cadmium and copper. The metal cell binding capacity followed the order Cu > Pb > Cd, based on estimated qmax. These values, expressed as mmol metal/g dry weight cells, were 0.54 for Cu, 0.36 for Pb and 0.14 for Cd. Polyacrylamide-gel immobilized cells were effective in Pb, Cu and Cd removal. Lead removal was not affected by the presence of Cd and Cu; lead instead inhibited Cd and Cu removal. The desorption of the metal, by fluxing a chelating solution, restored the metal binding capacity of the cells, thus affording the multiple use of the same biomass in the remediation treatment. Received: 31 July 1997 / Revised: 22 December 1997 / Accepted: 30 December 1997  相似文献   

16.
The sorption capacity of high-yield kraft fibers for Cd2+, Co2+, and Ni2+ increased with pH and concentration of the cations in the liquid phase. Within the concentration range for the experiments, which was less than 2 mM, the experimental results fitted the Langmuir, Freundlich, and Sips models with regression coefficient greater than 0.97. Of the three cations investigated, Ni2+ had the highest sorption affinity, followed by Cd2+ and Co2+. The effect of the hydrated radius on the sorption affinity was discussed. Thermodynamically, the sorption was spontaneous and exothermic in the temperature range 283-308 K.  相似文献   

17.
The removal of Cd(II) using polystyrene foam chemically modified with 2,2′-bipyridine has been investigated. The modified polystyrene foam has been characterized by FT-IR spectroscopy, thermogravimetry, elemental analysis and scanning electron microscopy. The solid was employed as a Cd(II) adsorption from aqueous solutions at room temperature. The effects of several variables (pH, shaking speed, agitation time, metal concentration and presence of other ions in the medium) have been studied using batch technique. Flame atomic absorption spectrometry was used to determine the Cd(II) ion concentration in the filtrate after the adsorption process. Maximum sorption 90% was achieved at pH 7 after 30 min of shaking time. Sorbed metal ions have been desorbed with 5 ml of 2 M HNO3 with the detection limit of 16.7 ng ml−1. The Langmuir, Freundlich and D–R isotherm equation were used to describe partitioning behavior of the system at room temperature. Kinetic and thermodynamic behavior of modified polystyrene foam for Cd(II) ion removal was also studied. Br, PO43−, Pb2+, Ni2+ and Cr(VI) suppress the sorption to some extent. The possible sorption mechanism of Cd(II) ions onto modified sorbent is also discussed. Method was utilized to remove Cd(II) ions from aqueous media.  相似文献   

18.
The study describes a sorption of metal ions Pb2+, Cd2+, Zn2+ and Cu2+ on a synthetic mica clintonite. Synthesis of analogues of clintonite was carried out by using inorganic salts as sources of silicon and aluminum in the hydrothermal method. Alkaline conditions were applied to increase the nucleation rate. Powdered clintonite obtained after mechanical grinding was used for the removal of metal ions from the wastewater. The sorption experiments were done under batch process to measure the concentrations of metal ions. Effects of pH, contact time between sorbent and sorbate solution, amount of sorbent and temperature on the sorption of metal ions were studied. The sorption was shown to increase with the pH of the medium. The optimal conditions for sorption of metal ions on synthetic analogues of clintonite were determined.  相似文献   

19.
With increasing industrial development, heavy metal pollution, e.g., cadmium (Cd) pollution, is increasingly serious in soil and water environments. This study investigated the sorption performance of nano-montmorillonite (NMMT) for Cd ions. Adsorption experiments were carried out to examine the effects of the initial metal ion concentration (22.4–224 mg/L), pH (2.5–7.5), contact time (2–180 min) and temperature (15–40 °C). A simulated acid rain solution was prepared to study the desorption of Cd adsorbed on NMMT. After the adsorption or desorption process, the supernatant was analyzed using a flame atomic absorption spectrometry method. The Cd removal rate increased as the pH and contact time increased but decreased as the initial metal ion concentration increased. The maximum adsorption capacity was estimated to be 17.61 mg/g at a Cd2+ concentration of 22.4 mg/L. The sorption process can be described by both the Langmuir and Freundlich models, and the kinetic studies revealed that the pseudo-second-order model fit the experimental data. The Cd desorption rate when exposed to simulated acid rain was less than 1%. NMMT possesses a good adsorption capacity for Cd ions. Additionally, ion exchange was the main adsorption mechanism, but some precipitation or surface adsorption also occurred.  相似文献   

20.
Cd(II) biosorption using Lessonia kelps   总被引:1,自引:0,他引:1  
Lessonia kelps (L. trabeculata and L. nigrescens) have been successfully used for the recovery of Cd(II) from near neutral solutions. The biomass was pre-treated with calcium chloride for stabilization of alginate-based compounds. SEM-EDAX analysis and FT-IR spectrometry analysis were used for identifying the modifications of the biomass. Sorption isotherms were performed at the optimum pH (i.e., pH 6) and the maximum sorption capacity reached up to 1 and 1.5 mmol Cd g(-1) for L. nigrescens (L.n.) and L. trabeculata (L.t.), respectively. The Langmuir equation fits well experimental data. The temperature (in the range 20-40 °C) had a more marked effect on affinity coefficient than on maximum sorption capacity. The influence of particle size, sorbent dosage, metal concentration and temperature was evaluated on uptake kinetics. The kinetic profiles that were modeled using the Crank equation (i.e., the resistance to intraparticle diffusion) were hardly affected by the temperature and the particle size contrary to the sorbent dosage and the metal concentration, which show greater impact. The pseudo-second order rate equation was also tested for the modeling of uptake kinetics.  相似文献   

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