首页 | 本学科首页   官方微博 | 高级检索  
相似文献
 共查询到20条相似文献，搜索用时 625 毫秒
1.
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   

2.
In the present study, Juglans regia shells were used to prepare activated carbon by acid treatment method. J. regia shell-based activated carbon was used for the adsorption of two synthetic dyes namely, a basic dye malachite green and an acid dye amido black 10B. The prepared adsorbent was crushed and sieved to three different mesh sizes 100, 600 and 1,000 μm. The adsorbent was characterized by scanning electron microscopy, surface acidity and zero-point charge. Batch experiments were carried out by varying the parameters like initial aqueous phase pH, adsorbent dosage and initial dye concentration. The equilibrium data were tested with Langmuir, Freundlich, Redlich–Peterson and Sips isotherm at three different temperatures 293, 300 and 313 K and it was found that the Freundlich isotherm best fitted the adsorption of both the dyes. Kinetic data were tested with pseudo first-order model and pseudo second-order model. The mechanism for the adsorption of both the dyes onto the adsorbent was studied by fitting the kinetic data with intraparticle diffusion model and Boyd plot. External mass transfer was found to be the rate-determining step. Based on the ionic nature of the adsorbates, the extent of film diffusion and intraparticle diffusion varied; both being system specific. Thermodynamic parameters were also calculated. Finally, the process parameters of each adsorption system were compared to develop the understanding of the best suitable system.  相似文献   

3.
Adsorption of disperse dyes from aqueous solutions onto calcined alunite has been investigated to assess the possibility of using alunite for removing disperse dyes from aqueous solutions. The effects of particle size, adsorbent mass, initial pH and temperature of the dye solution on the adsorption capacities have been evaluated. Acidic pH was favorable for the adsorption of all dyes: Disperse Blue 56 (DB56), Disperse Red 74 (DR74) and Disperse Yellow 119 (DY119). The experimental data were correlated reasonably well by the Langmuir isotherm and the isotherm parameters (KL and aL) have been calculated. The adsorption capacities were found to be 498, 525 and 500 mg of dye per g of calcined alunite for DB56, DR74 and DY119, respectively. The single-stage batch adsorber design of the adsorption of disperse dyes onto alunite has been studied based on the Langmuir isotherm equation.  相似文献   

4.
This paper presents the first attempt to investigate the potential of Tunisian palygorskite-rich clay (Pal-clay) on the effectiveness of a textile dye “Direct orange 34” (DO34) removal. Important parameters which affect adsorption, such as initial solution pH, contact time, adsorbent mass, initial dye concentration, and temperature, were investigated. The raw Pal-clay was characterized using X-ray diffractometer (XRD), X-ray fluorescence (XRF), Fourier transform infrared spectroscopy (FTIR), cation exchange capacity (CEC), specific surface area (SSA) analysis, and point of zero charge (PZC) determination. The results showed that the Pal-clay has a high selectivity for DO34 and had maximum removal efficiency reaching up to about 91 %. The highest adsorption capacity was obtained at 25 °C and pH of 2. The dye uptake process fitted well to the pseudo-second-order kinetic expression and was best described by the Langmuir and Freundlich isotherms. Intra-particle diffusion studies showed that the adsorption mechanism was not exclusively controlled by the diffusion step and was more likely to be governed by external mass transfer. Thermodynamic parameters such as change in free energy (ΔG°), enthalpy (ΔH°), and entropy (ΔS°) were also calculated. The parameters revealed that the adsorption of dye by the raw clay is spontaneous and exothermic. The results indicate that the Pal-clay has a moderate adsorption capacity towards anionic dye.  相似文献   

5.
Nanofiltration process on dye removal from simulated textile wastewater   总被引：1，自引：1，他引：0  
Dyestuffs removal from industrial wastewater requires special advanced technologies, since dyes are usually difficult to remove by biological methods. In this study nanofiltration process was used for removal of different dyestuffs from solutions. The rate of dye removal by spiral wound nanofiltration membrane in film thin composite MWCO=90 Dalton, was evaluated for four classes of dyes acidic, disperse, reactive and direct in red and blue dyes medium. Dye absorbance was measured by spectrophotometric method (2120 Standard Method 1998). Effects of feed concentration, pressure and total dissolved solids concentration were also studied. Results showed that increasing dye concentration lead to higher color removal up to 98 % and at different pressures for acidic and reactive blue were up to 99.7 %. Different types of dyes had no effect on dye removal and permeate flux. During 2 h. of the operation time, permeate flux decline was increased. Permeate fluxes for different types of red dyes were from 16.6 to 12.6 (L/m2/h.) and for blue dyes were from 16.6 to 10.45 (L/m2/h.). Presence of sodium chloride in dye solutions increased dye rejections nearby 100 %. Chemical oxygen demand removal efficiencies for reactive blue, disperse blue, direct and disperse red dyes were also approximately 100 %.  相似文献   

6.
Metal-complex dyes are widely used in textile industry, but harmful to the environment and human health due to aromatic structure and heavy metal ions. The objective of this work was to evaluate the adsorption potential of bamboo biochar for the removal of metal-complex dye acid black 172 from solutions. Freundlich model was more suitable for the adsorption process of bamboo biochar than Langmuir isotherm, indicating multilayer adsorption of acid black 172 on a heterogeneous bamboo biochar surface. Adsorption kinetics analysis of pseudo-second-order and Weber–Morris models revealed that intraparticle transport was not the only rate-limiting step. The bamboo biochar exhibited a good adsorption performance even at high ionic strength. Analysis based on the artificial neural network indicated that the temperature with a relative importance of 29 % appeared to be the most influential parameter in the adsorption process for dye removal, followed by time, ionic strength, pH and dye concentration.  相似文献   

7.
Contamination of surface water and groundwater by organic pollutants is a serious problem due to their persistence, bioaccumulation and biomagnification through food webs. Since the removal of dyes from wastewater is considered an environmental challenge and government legislation requires textile wastewater to be treated, therefore there is a constant need to have an effective process that can efficiently remove these dyes. The aim of the present study is to evaluate the potentiality of dried Carpobrotus edulis plant as low-cost adsorbent for the removal of the industrial acid blue 113 dye from aqueous solutions using the batch equilibration technique. The effects of different physicochemical parameters such as adsorbent dose, contact time, initial dye concentration, solution pH and temperature on adsorption rate of anionic AB113 dye on microparticles of dried C. edulis plant were investigated. The experimental data were analyzed by using mathematical models to determine the thermodynamic parameters. The negative values of free energy change indicated the spontaneous nature of the adsorption and negative value of enthalpy change suggested the exothermic nature of the adsorption process. These results indicate that dried C. edulis plant as an environmentally friendly adsorbent could be potentially used for the removal of anionic dyes from aqueous solutions.  相似文献   

8.
The adsorption of methyl tert-butyl ether by granular activated carbon was investigated. The experimental data were analyzed using the Freundlich isotherm and the Langmuir isotherm. Although equilibrium data were found to follow Freundlich isotherm model, it were fitted better by the Langmuir model with a maximum adsorption capacity of 204.1 mg/g. The kinetic data obtained at different concentrations were analyzed to predict the constant rate of adsorption using three common kinetic models: pseudo-first-order, pseudo-second-order equation and intraparticle diffusion equation. The pseudo-second-order model was suitable for describing the adsorption kinetics for the removal of methyl tert-butyl ether from aqueous solution onto granular activated carbon. Both the Lagergren first-order rate constant k 1 and pseudo-second-order rate constant k 2 decrease with increasing initial concentrations of methyl tert-butyl ether and the intraparticle diffusion rate constant k p shows the reverse characteristic. Analysis of sorption data using a boyd plot confirmed that external mass transfer is the main rate-limiting step at the initial stage of adsorption. Results illustrate that granular activated carbon is an effective adsorbent for methyl tert-butyl ether and also provide specific guidance into adsorption of methyl tert-butyl ether on granular activated carbon in contaminated groundwater.  相似文献   

9.
Clays, particularly kaolinite, are promising adsorbents for the treatment of textile effluents, but there is a need of better understanding the mechanisms of adsorption, especially in the case of anionic dyes. Thus, the removal of RR120 anionic dye was investigated using Tunisian raw clay (TBK) composed of kaolinite and illite, and a standard kaolinite (KGa-2), and conducting batch experiments by varying different parameters (contact time, ionic strength, concentration, temperature). We investigated the clays’ surface charges by electrophoretic mobility measures and the dye-clay interactions during adsorption, by the streaming-induced potentials (SIP). The results showed that KGa-2 has higher adsorption capacity for RR120 dye than TBK clay, moreover enhanced by increasing the ionic strength and/or lowering the pH of the aqueous. The SIP results showed an increase of negative charges for both clays, reflecting the adsorption of the anionic dye on the positive charges of the amphoteric surfaces of the clays. The SIP magnitudes indicated a higher adsorption rate for KGa-2 in accordance with the kinetic study. The Sips model that described the best adsorption isotherms indicates lateral interactions of the dye molecules, stronger in the case of KGa-2 than TBK. Also, the dye molecules form a thinner layer on KGa-2 surfaces. In addition, the dye molecule’s structure was not altered, as verified by mass spectrometry. The adsorption process was feasible and spontaneous and favored at ambient temperature. Thus, kaolinite-rich clays are effective in the removal of anionic dyes in aqueous solution and potential good adsorbents in wastewater treatment.  相似文献   

10.
Magnesium hydroxide-coated pyrolytic bio-char composite was prepared by chemical precipitation, and the adsorption behavior of anionic dye (directly frozen yellow) onto magnesium hydroxide-coated pyrolytic bio-char was investigated in the batch mode. The Fourier transform infrared spectroscopy, X-ray diffraction spectroscopy and X-ray fluorescence spectroscopy of adsorbents were characterized. Adsorption studies were performed at different pH, salt concentration, contacting time and dye concentration. The pH value of the solution influenced the adsorption capacity significantly, and adsorption is favored of pH 6–8. Salt coexisted in solution increased slightly directly frozen yellow adsorption capacity. The isotherm data were analyzed by Langmuir and Freundlich isotherm model, and Langmuir model was better to predict the equilibrium data. Thermodynamic calculations showed that the adsorption was a spontaneous and endothermic process. Exhausted magnesium hydroxide-coated pyrolytic bio-char was treated by microwave irradiation, and yield of regeneration was 98 % in the case of microwave irradiated time 5 min at 320 W. The magnesium hydroxide-coated pyrolytic bio-char can be reused.  相似文献   

11.
In the present research, coal fly ash, a waste by-product of thermal power plant, has been segregated to obtain hollow and spherical cenospheres which combined with activated carbon in different ratio for effectual remediation of wastewater. Fabricated cenospheres activated carbon (CNAC) composites were characterized by ATR-FTIR, SEM, XRD, BET and CILAS for functionality, surface modification, crystallinity, surface area, pore volume, pore size and particle size analysis, respectively. Batch adsorption has been applied to appraised maximum removal of Disperse Orange 25 (DO) and Disperse Blue 79:1 (DB) dyes at varying solution pH 2 to 12, adsorbent dose 0.1 g cenospheres + 0.1 g AC to 1.0 g cenospheres + 1.0 g AC, dye concentration 10 to 100 mg/L, agitation speed 80 to 240 rpm and contact time 5 to 300 min at three different temperatures (25, 35 and 45 °C). The maximum percentage removal was found to be 79 and 76% for DO and DB dyes, respectively, at optimized condition. Langmuir isotherm showed good interaction with adsorption data, and the obtained maximum equilibrium adsorption capacity was found to be 90.91 mg/g for DO and 83.33 mg/g for DB at 45 °C. Eventually, the negative ?G° (? 7.513 for DO and ? 7.767 for DB) has suggested the feasibility of dyes adsorption on CNAC composites.  相似文献   

12.
《Applied Geochemistry》2002,17(8):1159-1164
Fly ash was modified by hydrothermal treatment with 7 M NaOH. The resultant product displayed an 8-fold increase in surface area. The primary crystalline component of the modified fly ash was identified by X-ray diffraction to be hydroxysodalite (Na6Al6Si6O248H2O). The cation exchange capacity of the modified ash was significantly increased over that of the raw fly ash (188 vs 2 meq g−1). Adsorption experiments showed that the modified fly ash adsorbed a cationic dye (methylene blue) to a much greater extent than an anionic dye (alizarin sulfonate). Saturation adsorption revealed that the capacity of the ash for methylene blue had increased 10-fold during modification when compared to the raw ash. Adsorption is thus ascribed to be a surface effect rather than involving incorporation into the channels of the hydroxysodalite structure.  相似文献   

13.
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   

14.
含氟废水的粉煤灰处理实验研究   总被引：5，自引：0，他引：5  
进行了影响粉煤灰处理含氟废水的各种条件实验，（pH、水灰比、氟浓度、振荡平衡时间），结果表明最佳处理条件是pH值为2．5、水灰比为小于20、氟浓度小于500mg/l、振荡平衡时间大于2．5h，并研究了粉煤灰处理含氟废水的机理，给出了其吸附等温式。  相似文献   

15.
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   

16.
Surfactant-modified natural zeolites (SMNZs) with different coverage types were prepared by loading cetylpyridinium bromide onto the surface of natural zeolites. The resulting SMNZs were characterized and used as adsorbents to remove bisphenol A (BPA) from aqueous solution. The monolayer and bilayer SMNZs were effective for removing BPA from aqueous solution. The BPA adsorption capacity for the monolayer SMNZ increased slightly with increasing pH from 4 to 9, but decreased significantly with increasing pH from 9 to 11. The BPA adsorption capacity for the bilayer SMNZ was relatively high at pH 9–10, but decreased with decreasing pH from 9 to 4 or increasing pH from 10 to 11. The equilibrium adsorption data of BPA on the monolayer and bilayer SMNZs under the experimental condition could be well described by the Langmuir and Freundlich isotherm models. The adsorption kinetics of BPA on the monolayer and bilayer SMNZs followed a pseudo-second-order model. The adsorption of BPA on the monolayer and bilayer SMNZs took place in three different stages: a fast external surface adsorption, a gradual adsorption controlled by both the external mass transfer and the intra-particle diffusion, and a final equilibrium stage. The adsorption of BPA on the monolayer and bilayer SMNZs is spontaneous and exothermic. The mechanisms for BPA adsorption onto the monolayer SMNZ at pH 4–11 include the hydrophobic interaction and hydrogen bonding. The mechanisms for BPA adsorption onto the bilayer SMNZ at pH 4–8 include the organic partitioning and hydrogen bonding. The mechanisms for BPA adsorption onto the bilayer SMNZ at pH 8–11 include the organic partitioning, hydrogen bonding and electrostatic attraction.  相似文献   

17.
不同土层对氟离子的吸附能力不同,在吸附能力较弱的土层建设贮灰场,会导致周边地下水中氟离子质量浓度较高,污染地下水。吉林市来发屯灰场运行多年来,地下水中氟离子质量浓度与背景环境未见明显差异,本文通过对来发屯灰场粉煤灰-粉质粘土和灰场外土层的比较分析,探究吸附机理,结果表明：粉煤灰-粉质粘土对氟离子有较强的吸附能力,能有效防止其对地下水的污染。  相似文献   

18.
Acid mine drainage was reacted with coal fly ash over a 24 h reaction time and species removal trends evaluated. The evolving process water chemistry was modeled by the geochemical code PHREEQC using WATEQ4 database. Mineralogical analysis of the resulting solid residues was done by X-ray diffraction analysis. Selective sequential extraction was used to evaluate the transfer of species from both acid mine drainage and fly ash to less labile mineral phases that precipitated out. The quantity of fly ash, volume of acid mine drainage in the reaction mixture and reaction time dictated whether the final solution at a given contact time will have a dominant acidic or basic character. Inorganic species removal was dependent on the pH regime generated at a specific reaction time. Sulphate concentration was controlled by precipitation of gypsum, barite, celestite and adsorption on iron-oxy-hydroxides at pH > 5.5. Increase of pH in solution with contact time caused the removal of the metal ions mainly by precipitation, co-precipitation and adsorption. PHREEQC predicted precipitation of iron, aluminium, manganese-bearing phases at pH 5.53–9.12. An amorphous fraction was observed to be the most important in retention of the major and minor species at pH > 6.32. The carbonate fraction was observed to be an important retention pathway at pH 4–5 mainly due to initial local pockets of high alkalinity on surfaces of fly ash particles. Boron was observed to have a strong retention in the carbonate fraction.  相似文献   

19.
Adsorption kinetic and equilibrium studies of two reactive dyes, namely, Reactive Red 31 and Reactive Red 2 were conducted. The equilibrium studies were conducted for various operational parameters such as initial dye concentration, pH, agitation speed, adsorbent dosage and temperature. The initial dye concentration was varied from 10 - 60 mg/L, pH from 2–11, agitation speed from 100–140 rpm, adsorbent dosage from 0.5 g to 2.5 g and temperature from 30 °C -50 °C respectively. The activated carbon of particle size 600 μm was developed from preliminary tannery sludge. The dye removal capacity of the two reactive red dyes decreased with increasing pH. The zero point charge for the sludge carbon was 9.0 and 7.0 for the two dyes, respectively. Batch kinetic data investigations on the removal of reactive dyes using tannery sludge activated carbon have been well described by the lagergren plots. It was suggested that the Pseudo second order adsorption mechanism was predominant for the sorption of the reactive dyes onto the tannery sludge based carbon. Thus, the adsorption phenomenon was suggested as a chemical process. The adsorption data fitted well with Langmuir model than the Freundlich model. The maximum adsorption capacity(q0) from Langmuir isotherm were found to have increased in the range of 23.15–39.37 mg/g and 47.62–55.87 mg/g for reactive dyes reactive red 31 and reactive red 2, respectively.  相似文献   

20.
Adsorption characteristics of water hyacinth roots powder for the removal of Indosol Dark-blue GL dye were investigated in batch mode. Operating variables, such as initial solution pH, presence of detergent, adsorbent dosage, initial concentration and contact time, were studied. The results showed that the adsorption of dye increased with increasing the initial concentration and contact time. The adsorption is highly pH dependent and adsorption capacity increased with decrease in pH. Kinetic study revealed that the uptake of Indosol Dark-blue GL was very rapid within the first 15 min and equilibrium time was independent of initial concentration. Batch equilibrium experiments were carried out at different pH and found that equilibrium data fitted well to Langmuir isotherm model. The maximum sorption capacity of the adsorbent was found as 86 mg g?1 at pH 3 which reduced to 64 mg g?1 at pH 5. The presence of detergent reduced the sorption capacity of the adsorbent significantly. Using equilibrium and kinetic data, the forward and backward rate constants were determined from the unified approach model. Desorption study revealed that the dye can be recovered by swing the pH from low to high.  相似文献   

设为首页 | 免责声明 | 关于勤云 | 加入收藏

Copyright©北京勤云科技发展有限公司  京ICP备09084417号