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1.
The ability of magnetically modified activated sludge affected by thermal treatment to remove water-soluble organic dyes was examined. Twelve different dyes were tested. Based on the results of the initial sorption study, four dyes (namely aniline blue, Nile blue, Bismarck brown Y and safranin O) were chosen for further experiments due to their promising binding onto magnetic activated sludge. Significant factors influencing adsorption efficiency such as dependence of contact time, initial pH or temperature were studied in detail. The adsorption process was very fast; more than 88 % of dye content (55 mg/L) was adsorbed within 15 min under experimental conditions used. The equilibrium adsorption data were analyzed by Freundlich, Langmuir and Sips adsorption isotherm models, and the fitting of each isotherm model to experimental data was assessed on the basis of error functions. The maximum adsorption capacities of magnetic activated sludge were 768.2, 246.9, 515.1 and 326.8 mg/g for aniline blue, Bismarck brown Y, Nile blue and safranin O, respectively. The kinetic studies indicated that adsorption of all selected dyes could be well described by the pseudo-second-order kinetic model, and the thermodynamic data suggested the spontaneous and endothermic process.  相似文献   

2.
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   

3.
污灌土壤对铅的吸附和解吸特性   总被引：1，自引：0，他引：1  
为了解污灌土壤对铅的吸附-解吸机制,进行不同条件下的吸附-解吸试验。结果表明：污灌土壤对铅的吸附量随铅初始浓度的增大,呈现先强烈吸附再缓和的过程。Langmuir模式对污灌土壤等温吸附铅的拟合效果最好,其饱和吸附量为7.84 mg/g。亚砷酸盐的存在会阻碍污灌土壤对Pb2+的吸附,亚砷酸盐加入前后污灌土壤对铅的吸附率从99.9％～100％下降到97.8％～99.0％。加亚砷酸盐条件下污灌土壤对铅的等温吸附模式以Freundlich模式的拟合效果最好。污灌土壤对吸附态铅的解吸量随解吸振荡时间的延长而不断增加,且解吸率随时间增加总体趋于降低。Elovich方程和幂函数方程均能很好地拟合污灌土壤对铅的解吸动力学过程,尤其是Elovich方程的拟合效果最为显著。  相似文献   

4.
This work aimed to investigate the adsorption characteristics, both kinetically and thermodynamically, of Cu(II) and Pb(II) removal from aqueous solutions onto mixed-waste activated carbon, as well as to study the competitive behavior found in mixed heavy metal solution systems. This study shows that activated carbon prepared from mixed waste is an effective adsorbent for the removal of Cu(II) and Pb(II) from aqueous solutions, with the aim of detoxifying industrial effluents before their safe disposal onto water surfaces. The adsorption process was characterized in terms of kinetic and thermodynamic studies. In addition, the influence of presence of Cu(II) and Pb(II) in a competitive system was investigated. The results showed that the maximum adsorption capacities were gained at a pH of 6 with a contact time of 180 min, a metal solution concentration of 300 ppm, and an adsorbent dose of 0.3 g/L. The adsorption process was found to follow a pseudo-first-order kinetic model. Thermodynamic parameters such as ΔG o, ΔH o, and ΔS o showed that the sorption process was spontaneous and endothermic in nature. A competitive study demonstrated the applicability of mixed-waste activated carbon to adsorb Cu(II) and Pb(II) from a solution of mixed metals. In addition, the adsorption capacity was found to be as effective as other adsorbents reported in the literature. The developed adsorptive removal procedure was applied for treatment of real wastewater samples and showed high removal efficiency.  相似文献   

5.
Sorption and desorption behavior of lead on a Chinese kaolin   总被引：1，自引：0，他引：1  
The sorption and desorption of Pb on kaolin from Suzhou, China were investigated. The sorption experiment was conducted in a 0.01 M NaNO3 aqueous solution with respect to the effects of initial Pb concentration, pH, solid/solution ratio, and temperature. Langmuir and Freundlich models well described equilibrium isotherms of Pb sorption. Less than 5% of Pb sorbed was desorbed with 0.01 M NaNO3 extraction, suggesting a dominant specific sorption of Pb. As the initial pH increased, the sorption of Pb on the kaolin increased. More than 60% of Pb was sorbed at pH 2.69 far below the point of zero net charge of the kaolin at 4.2, indicating a mechanism of Pb inner-sphere complex or by chemisorption. Lead sorption decreased with increasing temperature, indicating a process of exothermic sorption.  相似文献   

6.
Beidellite, a low-cost, locally available and natural mineral was used as an adsorbent for the removal of lead and cadmium ions from aqueous solutions in batch experiments. The kinetics of adsorption process was tested for the pseudo first-order, pseudo second-order reaction and intra-particle diffusion models. The rate constants of adsorption for all these kinetic models were calculated. Comparison amongst the models showed that the sorption kinetics was best described by the pseudo second-order model. Langmuir and Freundlich isotherm models were applied to the experimental equilibrium data for different temperatures. The adsorption capacities (Q°) of beidellite for lead and cadmium ions were calculated from the Langmuir isotherm. It was found that adsorption capacity was in the range of 83.3–86.9 for lead and 42–45.6 mg/g for cadmium at different temperatures. Thermodynamic studies showed that the metal uptake reaction by beidellite was endothermic in nature. Binary metal adsorption studies were also conducted to investigate the interactions and competitive effects in binary adsorption process. Based on the optimum parameters found, beidellite can be used as adsorbent for metal removal processes.  相似文献   

7.
王焰新 《地学前缘》2001,8(2):301-307
经济、有效、易获得的生物质和地质材料 (及二者的废弃物 )可用来取代传统的活性炭或离子交换树脂用于去除废水中的重金属。已经公开发表的低成本吸附剂主要可分为两类 :(1)生物质 (包括林业和农业的废弃物 ) :树皮 /富含丹宁酸的物质 ,木质素 ,几丁质 /甲壳质 ,死的生物体 ,苔藓 ,海草 /海藻 /褐藻酸 ,废弃的茶叶 ,稻壳 ,羊毛 ,棉花等 ;(2 )地质材料 (包括矿物利用后的工业废弃物 ) :沸石 ,粘土 ,泥炭 ,有铁氧化物包壳的砂 ,粉煤灰等。其中 ,对于重金属具有强吸附能力的吸附剂有甲壳质、沸石和木质素 ,例如 ,它们对一些重金属的最大吸附能力分别为 :甲壳质对Cd ,Hg ,Pb分别为 5 5 8,112 3 ,796mg/g ,沸石对Pb为 15 5 4mg/g ,木质素对Pb为 15 87mg/g。地质材料的环境利用值得引起地学界和环境工程界更广泛的重视。基于地质材料和水岩相互作用机理的环境污染控制技术有望成为 2 1世纪重要的环保替代技术。由于缺少连续的可比性强的成本信息 ,要比较不同的生物质和地质材料的成本和吸附性能仍较困难。尽管已对低成本吸附剂领域进行了很多研究 ,但要更好地了解低成本吸附剂的作用机理及其实用性 ,仍需要做大量的室内和现场工作。  相似文献   

8.
A total of 422 bacterial isolates were obtained from the lead (Pb) ore in north-eastern Iran. The Pb tolerances of these strains were studied using microbroth serial dilution approach and 35 strains could grow up to 3250 ppm Pb concentration. Of these strains, 10 of them represented qualitatively high levels of Pb adsorption and were selected for quantitative studies. Strain AS2 which is phylogenetically related to genus Bacillus showed the highest level of Pb remediation. The effects of different factors, including pH, initial Pb concentration, temperature and inoculum size, were studied on the remediation process. Pb remediation capacity was reached at 74.5 mg/g (99.5 % of initial Pb) at pH 4.5, temperature 30 °C, inoculum size 1.0 % (v/v) and an initial Pb concentration of 500 ppm after 24 h. Pb desorption capacity of strain was 66 %. The novel isolate could remove 98 % of Pb from the contaminated industrial wastes after 24 h. Pb uptaking to the cell surface was proven using scanning electron microscopic micrograph and energy-dispersive X-ray spectroscopy analysis. Most Pb removal efficiency was observed in the active cell culture as compared to the inactive cell and extracellular polymeric substances. The novel strain represents a good candidate for removal of environmental anthropogenic Pb pollutions.  相似文献   

9.
A 210Pb radiotracer was used to monitor Pb solid-aqueousphase partitioning in sorption experiments at ambient temperature, pH = 8.2, and atmospheric PCO2 in 0.15 M NaNO3 solutions. A 24 h isotherm is linear up to Pb concentrations of 4 × 10-6 M, above which an increase in slope suggests precipitation. The effect of Pb concentration, calcite loading, and ionic strength on Pb sorption with time was monitored. Sorption kinetics are rapid, followed by a slower sorption step.At a constant calcite loading500 mg L-1,fractional sorptiondecreases with increasing initialPb concentration. The reverse isobserved for surface coverage, with0.6, 5.6 and 40.2% of availableCa2+sites occupied at10-8,10-7 and10-6 MPb after 96 h. At a constant Pb concentration of10-6 M,fractional sorption increases with increasing particleloading, however surface coverage decrease with72.5 and 22.1%Ca2+sites occupied at 100 and200 mg L-1calcite after 96 h.The adsorption coefficient (Kd) is approximately 103,increases with initial Pb concentration, but remains unaffected by variable calcite loading. Absence of an ionic strength effect on Pb sorption is interpreted as the dominance of inner-sphere complexation. For desorption experiments conducted over a range of initial sorption times, an average desorption index > 0.8 but < 1 indicates that sorption is largely reversible, but is accompanied by slight incorporation. Solid-solution formation increases with time, as observed by slower initial desorption rates for samples with longer sorption times. These findings indicate that Pb may be effectively sequestered by calcite; however re-release via desorption is likely as Pb does not become significantly incorporated into the mineral structure.  相似文献   

10.
Conditional surface binding constants and complexation capacities for Zn, Pb, Cd, and Cu were determined from surface titration experiments of heterogeneous natural aquatic particulate matter of different origin and composition. Metals and particles were evaluated in naturally occurring concentration ranges in river water.The adsorption of trace metals can be adequately described with a single conditional binding constant over a wide range of metal : particle ratios. Binding constants for aquatic particles at pH 8.0 are remarkably independent from particle composition and are specific for each metal: log Kads Zn = 8.39, log Kads Pb = 9.67, log Kads Cd = 8.61, log ads Cu = 9.84. From competition experiments with Ca and Pb we extracted a sorption coefficient for Ca of log Kads Ca = 2.5 (pH 8.0). Maximum surface binding capacities for all metal ions were found for particles containing high fractions of Mn-oxides which are associated with large specific surface areas. Generally, we found sorption capacities to decrease in the sequence Cu Pb, Zn > Cd.The experiments suggest that the conditional surface binding constants and complexation capacities are applicable to model trace metal adsorption in the concentration ranges of natural waters under conditions similar to the experiments. Results also imply that the chemical nature of particle surface sites is rather uniform in the intermediate concentration range or that the array of binding sites averages out differences in sorption strength over the prevailing concentration range of metal ions, respectively.  相似文献   

11.
Activated carbon produced from fluted pumpkin (Telfairia occidentalis) seed shell was utilized for the removal of lead (II) ion from simulated wastewater. Adsorption tests were carried out in series of batch adsorption experiments. Several kinetic models (Bhattacharya-Venkobacher, Elovich, pseudo first and second order, intra-particle and film diffusion) were tasted for conformity to the experimental data obtained. The Langmuir and Freundlich adsorption models were also used to test the data. The amount of lead (II) ion adsorbed at equilibrium from a 200 mg/L solute concentration was 14.286 mg/g. The experimental data conform very well to the pseudo-second order equation where equilibrium adsorption capacities increased with increasing initial lead (II) concentration. The rate of the adsorption process was controlled by the film (boundary layer) diffusion as the film diffusion co-efficient values obtained from data analysis were of the order of 10 6cm2/s. From the plots, the linear regression coefficient (R2) of the Langmuir model was higher than that of the Freundlich: the adsorption isotherm obeyed the Langmuir model better than the Freundlich model.  相似文献   

12.
An iron (III)-impregnated sorbent was prepared from sugarcane bagasse and ferric chloride solution via carbonization/activation in a muffle furnace at 500?°C for 4?h. The adsorption removal of chromium (VI) from aqueous solution by the iron (III)-impregnated sorbent was then studied in a batch system. With increasing initial chromium (VI) concentration from 25 to 130?mg/L at an adsorbent dose of 300?mg/50?mL, the amount of adsorbed chromium (VI) increased from 4.15 to 12.20?mg/g at 20?°C, from 4.16 to 12.50?mg/g at 30?°C, and from 4.16 to 13.72?mg/g at 40?°C. The dynamical data fit very well with the pseudo-second-order kinetic model, and the calculated adsorption capacities of 4.16, 8.37, and 13.37?mg/g were equal to the actual values of the experiments at the initial chromium (VI) concentrations of 25, 50, and 100?mg/L, respectively. The Langmuir isotherm could yield better fits than the Freundlich isotherm. The calculated isotherm parameters confirmed the favorable adsorption of chromium (VI) on the iron (III)-impregnated sorbent.  相似文献   

13.
Sorption of radionuclides onto stable colloids can significantly enhance their transport in groundwater. Batch adsorption studies were performed to evaluate the influence of various experimental parameters like initial pH, contact time, temperature and concentration of Na+ and Ca2+ ions on the sorption of Cs on clay. The sorption process is dependent on pH of the solution with distribution coefficient (K d) found to increase with increase in pH. The kinetic experiments were carried out at different temperatures, and the results have shown that the sorption process fits well into a pseudo-second-order mechanism with apparent activation energy of 45.7?kJ/mol. The rate constant was found to decrease with increase in temperature. The thermodynamic parameters such as ?G 0, ?H 0 and ?S 0 were calculated. The negative value of ?H 0 indicates that the reaction is exothermic. The negative values obtained for ?G 0 indicated that the sorption of cesium on clay was spontaneous at all studied concentrations. The distribution coefficient was found to decrease with increasing concentration of Na+ and Ca2+ ions. The cesium sorption data were fitted to Freundlich, Langmuir, Temkin and Dubinin–Radushkevich (D–R) isotherms. The values of Langmuir separation factor (R L) indicate a favorable Cs adsorption. The values of mean free energy of sorption (E) at various temperatures ranged from 10.5 to 11.1?kJ/mol, which indicates that the sorption process follows chemisorption.  相似文献   

14.
The potential use of the immobilized microalgae (in Ca-alginate) of Chlamydomonas reinhardtii to remove Hg(II), Cd(II) and Pb(II) ions from aqueous solutions was evaluated using bare Ca-alginate bead as a control system. Ca-alginate beads containing immobilized microalgae were incubated for the uniform growth at 22 °C for 5 days. Effects of pH, temperature, initial concentration of metal ions and biosorbent dosages on the adsorption of Hg(II), Cd(II) and Pb(II) ions were studied. Adsorption of Hg(II), Cd(II) and Pb(II) ions on the immobilized microalgae showed highest values at around pH 5.0 to 6.0. The adsorption equilibrium was represented with Langmuir and Freundlich adsorption isotherms. The adsorption of these ions on the immobilized microalgae followed second-order kinetics and equilibrium was established in about 60 min. The temperature change in the range of 5–40 °C did not affect the adsorption capacities of the immobilized microalgae. The immobilized-algal systems can be regenerated using 2 M NaCl for Hg(II), Cd(II) and Pb(II) ions.  相似文献   

15.
In the present experimental study, solid waste was used as an adsorbent and the effectiveness of the adsorbent was increased by novel treatment methods. Red mud, acid-treated activated red mud and iron oxide-coated acid-treated activated red mud were used for the removal of lead (II). The structural and functional groups were identified to confirm the removal of lead (II) by powder X-ray diffraction and Fourier transform infrared spectroscopy analyses. The enhancement of surface area was confirmed by Brunauer–Emmett–Teller analysis. Batch adsorption experiment was also conducted, and various parameters such as the effect of adsorbent dosage, pH, contact time and initial ion concentration were analyzed and reported. Adsorption equilibrium data were investigated using Langmuir, Freundlich and Dubinin–Radushkevich isotherm models with three parameters, and the rate of reaction was examined through kinetic models. The results indicate that in particular a novel modified form of red mud, namely iron oxide-coated acid-treated activated red mud was well fitted in lead (II) removal compared with reported adsorbents. The Langmuir isotherm shows that the maximum adsorption of adsorbate per gram was greater than other adsorbents (27.02 mg/g). In Freundlich isotherm, the Freundlich constant n values lie between 1 and 10 indicate the favorable adsorption. The calculated n values for normal red mud, acid-treated activated red mud and iron oxide-coated acid-treated activated red mud were found to be 1.9, 2.1 and 2.0 respectively. The correlation coefficient value was higher and the rate of reaction follows the pseudo-second-order kinetic model.  相似文献   

16.
利用13X沸石分子筛净化含Pb~(2+)废水的实验研究   总被引：11，自引：0，他引：11  
马鸿文  肖万  陶红 《现代地质》2003,17(2):157-162
采用静态间歇法 ,实验研究了含Pb2 +废水的 pH值及吸附时间对 13X沸石分子筛吸附Pb2 +性能的影响 ,得出了最佳去除效果的优化条件为 :废水的 pH值接近中性 ,吸附时间 10min。通过吸附实验 ,确定了在Pb2 +初始浓度为 2 0mg/L的条件下 ,13X沸石对Pb2 +的吸附量为 2 1 4 2mg/g ,即每克沸石净化含Pb2 +废水的最大体积量约为 75 0mL。解析实验表明 ,加入沉淀剂 ,浓缩洗脱液中的Pb2 +即以PbS的形式生成沉淀 ,为回收金属铅提供了可能 ;13X沸石在循环使用 5次的条件下 ,对废水中Pb2 +的吸附率仍高达 98% ,重复使用性能良好。经处理后的净化水中Pb2 +的浓度小于 0 4mg/L ,显著低于国家废水排放标准GB8978 88的指标 ( 1 0mg/L)。 13X沸石对Pb2 +的主要吸附形式是离子交换和表面络合反应。  相似文献   

17.
In this work, the effectiveness of native and chemically modified rice bran to remove heavy metal Pb(II) ions from aqueous solution was examined. Chemical modifications with some simple and low-cost chemicals resulted in enhancement of the adsorption capacities and had faster kinetics than native rice bran. Experiments were conducted in shake flasks to monitor the upshot of parameters over a range of pH, initial Pb(II) concentrations and contact times using a batch model study. The sorption capacities q (mg g?1) increased in the following order: NaOH (147.78), Ca(OH)2 (139.08), Al(OH)3 (127.24), esterification (124.28), NaHCO3 (118.08), methylation (118.88), Na2CO3 (117.12) and native (80.24). The utmost uptake capacity q (mg g?1) was shown by NaOH-pretreated rice bran. The results showed that, using NaOH-modified rice bran, the chief removal of Pb(II) was 74.54 % at pH 5, primary Pb(II) concentration 100 mg L?1 and contact time 240 min. Equilibrium isotherms for the Pb(II) adsorption were analyzed by Langmuir and Freundlich isotherm models. The Langmuir isotherm model, showing Pb(II) sorption as accessible through the high value of the correlation coefficient (R 2 = 0.993), showed a q max value of 416.61 mg g?1. The kinetic model illustrated adsorption rates well, depicted by a second order, which gives an indication concerning the rate-limiting step. Thermodynamic evaluation of the metal ion ?G o was carried out and led to the observation that the adsorption reaction is spontaneous and endothermic in nature. NaOH chemically modified rice bran was a superb biosorbent for exclusion of Pb(II) and proved to be excellent for industrial applications.  相似文献   

18.
矿物材料与环境污染治理—以粘土矿物和沸石为例   总被引：9，自引：0，他引：9  
矿物的性能，矿区地质测试和吸附能力实验表明，粘土矿物和沸石等矿物材料对于Cr,Cd,Pb,Hg,As等有害元素具有很强的吸附能力，是理想的低成本吸附剂，在废水处理中可用来取代活性炭或离子交换树脂来去除重金属等有害元素。  相似文献   

19.
The present work discusses the mineralogy, saturated adsorption of ammonium and adsorption of heavy metal ions （Cu^2＋, Pb^2＋ and Zn^2＋） on industrial vermiculite samples from the Yuli Mine in Xinjiang Autonomous Region. The saturated adsorption capacity of ammonium and the affection factors of adsorption of Cu^2＋, Pb^2＋ and Zn^2＋ are discussed on the basis of the mineralogical characteristics of the industrial vermiculite samples. The saturated adsorption capacities of ammonium are between 56.02 and 98.42 mmol/100g. The time of adsorption equilibrium is about 30-60 min, and the pH values and concentration of the ion solution significantly affect the adsorption capacities of the heavy metal ions. The adsorption capabilities of the heavy metal ions on industrial vermiculite are almost the same in the low ion concentration solutions, characterized by a sequence of Zn^2＋〉Pb^2＋〉Cu^2＋ for adsorption capacity in solutions with relatively high ion concentration. The results have practical significance for the application of the industrial vermiculite to treating wastewater containing ammonium or heavy metal ions.  相似文献   

20.
As, Hg and Pb are examples of heavy metals which are present in different types of industrial effluents responsible for environmental pollution. Their removal is traditionally made by chemical precipitation, ion-exchange and so on. However, this is expensive and not completely feasible to reduce their concentrations to the levels as low as required by the environmental legislation. Biosorption is a process in which solids of natural origin are employed for binding the heavy metal. It is a promising alternative method to treat industrial effluents, mainly because of its low cost and high metal binding capacity. The kinetics was studied for biosorption experiments using coconut fiber for As (III), Hg (II) and Pb (II) ions adsorption. The specific surface area and surface charge density of the coconut fiber are 1.186×1025 (m2/g) and 5.39 ×1024 (meq/m2), respectively. The maximum adsorption capacity was found to be the highest for Pb (II) followed by Hg (II) and As (III). The modification of the adsorbent by thiolation affected the adsorption capacity. Equilibrium sorption was reached for the metal ions at about 60 min. The equilibrium constant and free energy of the adsorption at 30 °C were calculated. The mechanism of sorption was found to obey the particle-diffusion model. The kinetic studies showed that the sorption rates could be described by both pseudo first-order and pseudo second-order models. The pseudo second-order model showed a better fit with a rate constant value of 1.16 × 10?4/min. for all three metal ions. Therefore, the results of this study show that coconut fiber, both modified and unmodified, is an efficient adsorbent for the removal of toxic and valuable metals from industrial effluents.  相似文献   

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