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1.
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Two strains of green microalgae C.reinhardti and C.pyrenoidosa were examined for their biosorption of Mn2+,Fe2+,Co2+,Ni2+,Cu2+,Zn2+,and Cd2+from aqueous multi-metal solutions.A wide range of biosorption capacities can be observed due to different strains of microalgae and different species of trace metals.This characteristic was ascribed to the distinct components and structures of algal cell walls and the different physicochemical properties of trace metals,such as atomic weight and ion density.C.pyrenoidosa showed higher uptake capacities than C.reinhardti and both of them had a preference for the uptake of cadmium over others in the trace metal solution,suggesting they can be a good biomaterial for biosorption of cadmium.Live microalgal cells displayed a more complex sorption process than dead microalgal cells because of cell assimilation.  相似文献   

3.
Removal of dyes by low-cost adsorbents is an effective method in wastewater treatment. Iranian natural clays were determined to be effective adsorbents for removal of a basic dye (methylene blue) from aqueous solutions in batch processes. Characterizations of the clays were carried out by X-ray diffraction, Brunauer–Emmett–Teller surface area analysis and field-emission scanning electron microscopy. Effects of the operational parameters such as adsorbent dosage, initial dye concentration, solution pH and temperature were investigated on the adsorption performance. Adsorption isotherms like Langmuir, Freundlich and Temkin were used to analyze the adsorption equilibrium data and Langmuir isotherm was the best fit. Adsorption kinetics was investigated by pseudo-first-order, pseudo-second-order and intraparticle diffusion models and the results showed that the adsorption system conforms well to the pseudo-second-order model. The thermodynamic parameters of adsorption (ΔS°, ΔH° and ΔG°) were obtained and showed that the adsorption processes were exothermic.  相似文献   

4.
In this research, spent coffee grains were modified with citric acid solutions (0.1 and 0.6 M) to increase the quantity of carboxylic groups improving its metal adsorption capacity. Added functional groups on modified and non-modified spent coffee grains were identified and quantified by attenuated total reflection Fourier transform infrared analyses and potentiometric titrations, respectively. These adsorbents were used for the removal of lead (II) and copper (II) from aqueous solutions at 30 °C and different pH in batch systems. In addition, adsorption–desorption experiments were conducted to evaluate the possibility of re-using the modified adsorbent. Potentiometric titrations data reveal that the quantity of carboxylic groups was increased from 0.47 to 2.2 mmol/g when spent coffee grains were modified with 0.1 and 0.6 M citric acid. Spent coffee grains treated with 0.6 M citric acid, achieved a maximum adsorption capacity of 0.77 and 1.53 mmol/g for lead (II) and copper (II), respectively, whereas non-modified spent coffee grains only reached 0.24 and 0.19 mmol/g for lead (II) and copper (II), respectively. Desorption of lead (II) and copper (II) achieved around 70 % using 0.1 N HCl for non-modified and modified spent coffee grains with 0.6 M citric acid. It is suggested that lead (II) and copper (II) species were adsorbed mainly on the carboxylic groups of modified spent coffee grains and these metals may be exchanged for hydrogen and calcium (II) ions during adsorption on non-modified spent coffee grains. Finally, the adsorption equilibrium was reached after 400 min for modified spent coffee grains with 0.6 M citric acid. Modified spent coffee grains are a promising option for removing metal cations from aqueous solutions due to its low cost and high adsorption capacity (about 10 times higher than the activated carbons).  相似文献   

5.
Silver nanoparticles (Ag NPs) were synthesized in situ, using a one-step green methodology with Camellia sinensis (green tea) aqueous extract as reducing agent, and supported on a carbonaceous material (Ag-CM), originated from the pyrolysis of sewage sludge. UV–Vis spectroscopy, X-ray diffraction, scanning electron microscopy, transmission electron microscopy and Brunauer–Emmet–Teller were used to characterize the nanocomposite. Ag-CM composite exhibited very good catalytic activity in the degradation process of methylene blue (MB) dye in aqueous solution without using sunlight or UV radiation. Batch kinetic and isothermal experiments, using 30 mg/L MB solution, showed that Ag-CM composite removed near to 91 % of MB in 9 h, whereas the carbonaceous material alone removed only 60 % in 30 h. Experimental data were adjusted to different kinetic and isotherms models, where both materials fit the second-order and Langmuir–Freundlich models, respectively; therefore, a chemisorption mechanism probably occurs in these heterogeneous materials.  相似文献   

6.
The biosorption of ammoniacal nitrogen (N-NH4 +) from aqueous solutions by dead biomass of brown seaweed Cystoseira indica and Jatropha oil cake (JOC), which is generated in the process of biodiesel recovery from its seeds, was studied under diverse experimental conditions. The N-NH4 + biosorption was strictly pH dependent, and maximum uptake capacity of C. indica (15.21 mg/g) and JOC (13.59 mg/g) was observed at initial pH 7 and 3, respectively. For each biosorbent–N-NH4 + system, kinetic models were applied to the experimental data to examine the mechanisms of sorption and potential rate-controlling steps. The generalized rate model and pseudo-second-order kinetic models described the biosorption kinetics accurately, and the sorption process was found to be controlled by pore and surface diffusion for these biosorbents. Results of four-stage batch biosorber design analysis revealed that the required time for the 99 % efficiency removal of 40 mg/L N-NH4 + from 500 L of aqueous solution were 76 and 96 min for C. indica and JOC, respectively. The Fourier transform infrared spectroscopy analysis before and after biosorption of ammonium onto C. indica and JOC revealed involvement of carboxylic and hydroxyl functional groups.  相似文献   

7.
The adsorption capacity of raw and sodium hydroxide-treated pine cone powder in the removal of methylene blue (MB) from aqueous solution was investigated in a batch system. It was found that the base modified pine cone exhibits large adsorption capacity compared with raw pine cone. The extent of adsorption capacity was increased with the increase in NaOH concentration. Overall, the extent of MB dye adsorption increased with increase in initial dye concentration, contact time, and solution pH but decreased with increase in salt concentration and temperature for both the systems. Surface characteristics of pine cone and base modified pine cone were investigated using Fourier transform infrared spectrophotometer and scanning electron microscope. Equilibrium data were best described by both Langmuir isotherm and Freundlich adsorption isotherm. The maximum monolayer adsorption capacity was found to be 129.87 mg g?1 at solution pH of 9.02 for an initial dye concentration of 10 ppm by raw pine cone. The base modified pine cone showed the higher monolayer adsorption capacity of 142.25 mg g?1 compared with raw pine cone biomass. The value of separation factor, R L, from Langmuir equation and Freundlich constant, n, both give an indication of favourable adsorption. The various kinetic models, such as pseudo-first-order model, pseudo-second-order model, intraparticle diffusion model, double-exponential model, and liquid film diffusion model, were used to describe the kinetic and mechanism of adsorption process. Overall, kinetic studies showed that the dye adsorption process followed pseudo-second-order kinetics based on other models. The different kinetic parameters, including rate constant, half-adsorption time and diffusion coefficient, were determined at different physicochemical conditions. A single-stage bath adsorber design for the MB adsorption onto pine cone and modified pine cone has been presented based on the Langmuir isotherm model equation. Thermodynamic parameters, such as standard Gibbs free energy (ΔG 0), standard enthalpy (ΔH 0) and standard entropy (ΔS 0), were also calculated.  相似文献   

8.
This work describes the synthesis of poly(acrylic acid) microgels and fabrication of magnetic cobalt nanoparticles in the prepared microgels. Cobalt nanoparticles were fabricated by loading the cobalt (II) ions in microgels from aqueous solution and their subsequent reduction with sodium borohydride (NaBH4). Bare and composite microgels were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy and transmission electron microscopy. The catalytic properties of the prepared microgel composites were investigated by using them as catalyst for the reduction of 4-nitrophenol and methylene blue. The effect of temperature and catalyst dose on the rate of reduction of these toxic pollutants was investigated. The reusability of prepared catalysts was also studied for the five consecutive cycles, and an increase in catalytic activity was observed after every cycle. The prepared bare and magnetic microgels were found as very effective adsorbent for the removal of methylene blue from aqueous medium. Very rapid adsorption rate was found for the removal of methylene as its 100 mg was adsorbed on per gram of dried hydrogels in about 25 min. The effects of different parameters like amount of adsorbate and concentration of adsorbent on the adsorption process were studied. Langmuir, Freundlich and Temkin adsorption isotherms were applied, and it was found that adsorption of MB follows Freundlich model better than others. Furthermore, pseudo-first-order and pseudo-second-order kinetic models were also applied and adsorption of MB was found to abide by pseudo-second-order kinetics.  相似文献   

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Adsorption of hexavalent chromium from aqueous solutions by wheat bran   总被引:1,自引:6,他引:1  
In this research, adsorption of chromium (VI) ions on wheat bran has been studied through using batch adsorption techniques. The main objectives of this study are to 1) investigate the chromium adsorption from aqueous solution by wheat bran, 2) study the influence of contact time, pH, adsorbent dose and initial chromium concentration on adsorption process performance and 3) determine appropriate adsorption isotherm and kinetics parameters of chromium (VI) adsorption on wheat bran. The results of this study showed that adsorption of chromium by wheat bran reached to equilibrium after 60 min and after that a little change of chromium removal efficiency was observed. Higher chromium adsorption was observed at lower pHs, and maximum chromium removal (87.8 %) obtained at pH of 2. The adsorption of chromium by wheat bran decreased at the higher initial chromium concentration and lower adsorbent doses. The obtained results showed that the adsorption of chromium (VI) by wheat bran follows Langmuir isotherm equation with a correlation coefficient equal to 0.997. In addition, the kinetics of the adsorption process follows the pseudo second-order kinetics model with a rate constant value of 0.131 g/mg.min The results indicate that wheat bran can be employed as a low cost alternative to commercial adsorbents in the removal of chromium (VI) from water and wastewater.  相似文献   

11.
Hexavalent chromium has been proved to be the reason of several health hazards. This study aimed at evaluating the application of pomegranate seeds powder for chromium adsorption (VI) from aqueous solution. Chromium adsorption percentage (VI) increased with increasing the adsorbent dosage. Chromium adsorption capacity (VI), at pH = 2 and 10 mg/L initial metal concentration, decreased from 3.313 to 1.6 mg/g through increasing dosage of adsorbent from 0.2 to 0.6 g/100 ml. The adsorption rate increased through increase in chromium initial concentration (VI). However, there was a removal percentage reduction of chromium (VI). Chromium adsorption kinetics by different models (pseudo-first-order, modified pseudo-first-order, pseudo-second-order, Elovich, intraparticle diffusion, Boyd kinetic) was investigated as well. Studies on adsorption kinetic indicated that the experimental data were matched by pseudo-second-order model (R 2 = 0.999) better. Obtained results demonstrated the pomegranate seeds can be used as an effective biomaterial and biosorbent for hexavalent chromium adsorption from aqueous solutions.  相似文献   

12.
In this research, a new low cost and abundant biosorbent; Agave americna (L.) fibres has been investigated in order to remove metal dye (Alpacide yellow) from aqueous solutions. In order to optimize the biosorption process, the effect of pH, temperature, contact time and initial solution concentration was investigated in batch system. The results indicated that acidic pH=2 was favourable for metal dye removal. The increase of temperature increases the velocity of the biosorption reaction. The biosorption kinetics of alpacide yellow were closer to the pseudo-second order than to the first order model for all concentrations and temperature. The calculated thermodynamic parameters such as dGG°, dGH° and dGS° indicated a spontaneous and endothermic biosorption process of metal dye onto Agave americana fibres. The equilibrium data were analysed using the Langmuir and Freundlich isotherms and showed a good fit with Langmuir model at lower temperatures and with Freundlich model at 50 °C.  相似文献   

13.
用一种新的合成方法在水相中合成了钛磁铁矿(Fe3-xTixO4),并用XRD和FTIR对已合成的Fe3-xTixO4进行了表征。结果表明:合成的Fe3-xTixO4为立方晶系尖晶石结构,样品中的钛离子都已经进入Fe3-xTixO4晶格中,且Fe3-xTixO4表面羟基量随着钛掺杂量的增加而增加。随后,以亚甲基蓝为模拟染料污染物,考察了Fe3-xTixO4的吸附性能。实验表明:钛掺杂能够显著促进Fe3-xTixO4对亚甲基蓝的吸附,吸附反应在0.5h内就能达到吸附平衡。  相似文献   

14.
Peat of Brunei Darussalam shows a great potential for the removal of methylene blue (MB) and malachite green (MG) dyes from aqueous solution. Carefully controlled batch experiments performed by changing one parameter at a time indicate that the optimum time periods of agitation and settling required for maximum removal of MB are 2.0 and 1.0 h, respectively, while these values for MG are 4.0 and 1.0 h, respectively. The optimum pH is determined to be the ambient value, and under the optimum conditions, 90 % removal of both dyes was determined under laboratory conditions. The equilibrium adsorption data analyzed for various isotherm models suggest that the Sips and Redlich–Peterson (R–P) models are valid for MB and MG, respectively. Further, thermodynamic studies show that the adsorption of both dyes on peat is spontaneous and endothermic. The adsorption capacities (q max) of MB and MG dyes on peat are 0.45 and 0.31 mmol g?1, respectively. Characterization of the surfaces of peat before and after treatment of dyes by SEM and FTIR provides conclusive evidence of adsorption of both dyes. Kinetics studies indicate that the adsorption of both MB and MG dyes is favored toward the pseudo-second-order model, with a little contribution of MG to the pseudo-first-order model. These results suggest that peat is a potential low-cost adsorbent for the removal of MB and MG dyes.  相似文献   

15.
In this study, the removal of free cyanide from aqueous solutions by activated carbon was investigated. Effects of metal impregnation (Cu and Ag), aeration, and concentrations of adsorbent and cyanide on the rate and extent of the removal of cyanide were studied. The results have shown that the capacity of activated carbon for the removal of cyanide can be significantly improved (up to 6.3-fold) via impregnation of activated carbon with metals such as copper and silver. Silver-impregnated activated carbon was found to be the most effective at the reduction of cyanide level in solution. This appeared to be coupled with its comparatively high metal content after impregnation process where silver (5.07%) could be more readily loaded on activated carbon than copper (0.43%). Kinetics and equilibrium data for cyanide removal by plain and metal-impregnated activated carbons were determined to be consistent with the pseudo second-order kinetics and the Langmuir adsorption isotherms, respectively. Aeration (0.27 l/min) was found to exert a profound effect on the process leading to a 5.5–49.1% enhancement in the performances of plain and metal-impregnated activated carbons. This enhancement could be attributed to the increase in the availability of active sites on activated carbon for adsorption and the catalytic oxidising activity of activated carbon in the presence of oxygen. Practical limiting capacity of plain, copper- and silver-impregnated activated carbons for the removal of cyanide were experimentally determined to be 19.7, 22.4 and 29.6 mg/g, respectively.  相似文献   

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The kinetics of Co(II) ions adsorption on thermally activated dolomite was studied with respect to the calcination temperature of natural dolomite. The sorption of Co(II) onto all samples is reasonably fast: The first 30–35 min accounts for approximately 70–80 % of Co(II) removal from feed solutions. In order to select the main rate-determining step in the overall uptake mechanism, a series of experiments were performed and data obtained were interpreted in terms of film diffusion control, intraparticle diffusion, pseudo-first-order and pseudo-second-order models. From the modeling of kinetic data, it can be concluded that adsorption of Co(II) ions from aqueous solution by heat-treated dolomite is a complex phenomenon and occurs in a mixed diffusion mode—the kinetic data are well described by the pseudo-second-order equation. The possible multistage sorption mechanism involving film diffusion and intraparticle diffusion control steps as well as chemical interaction between Co(II) ions and calcined dolomite is proposed.  相似文献   

18.
Copper is a major problem in industrial wastewater streams, seriously affecting the quality of potential drinking water. Several approaches, including continuous membrane processes or batch-wise application of adsorbents, are in use to tackle this problem. Unfortunately, these processes suffer from their particular drawbacks, such as low permeance or disposal of saturated adsorbents. However, a combination of these processes could constitute a step towards a more efficient copper removal solution. Here, we present a nanopaper ion-exchanger prepared from cellulose nanofibrils produced from fibre sludge, a paper industry waste stream, for the efficient, continuous removal of copper from aqueous solutions. This nanopaper ion-exchanger comprises phosphorylated cellulose nanofibrils that were processed into nanopapers by papermaking. The performance of these phosphorylated nanopaper membranes was determined with respect to their rejection of copper and permeance. It was shown that this new type of nanopaper is capable of rejecting copper ions during a filtration process by adsorption. Results suggest that functional groups on the surface of the nanopapers contribute to the adsorption of copper ions to a greater extent than phosphate groups within the bulk of the nanopaper. Moreover, we demonstrated that those nanopaper ion-exchangers could be regenerated and reused and that in the presence of calcium ions, the adsorption capacity for copper was only slightly reduced.  相似文献   

19.
Sugar beet pulp is an abundant, renewable and low-cost precursor for production of activated carbon. In the present study, sugar beet pulp based activated carbon was prepared by using phosphoric acid as activating agent for adsorption of methylene blue. The conditions of preparation process had a significant influence on the adsorption of methylene blue, and the optimal preparation conditions were obtained as follows: liquid-to-solid ratio of 5, temperature of 450 °C and phosphoric acid concentration of 3 mol/L. The properties of sugar beet pulp based activated carbon were characterized by nitrogen adsorption isotherm. The adsorption increases as the increase of contact time, adsorption temperature and pH, and initial concentration of methylene blue. Batch kinetic studies showed that an equilibrium time of 100 min was needed for the adsorption, and the adsorbance of methylene blue is 244.76 mg/g at equilibration. Kinetic models, Weber’s pore diffusion model and Boyd’s equation were applied to the experimental data to study the mechanism of adsorption and the controlled step. The results showed that the adsorption kinetics followed the pseudo-second-order type kinetic model, intraparticle diffusion was not the rate-limiting mechanism and adsorption process was controlled by film diffusion.  相似文献   

20.
Doklady Earth Sciences - Data on the species and strain specificity of micromycetes in the processes of toxic elements extraction from multicomponent solutions are obtained as results of modal...  相似文献   

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