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1.
《分离科学与技术》2012,47(9):1286-1294
The adsorption of cephalexin in aqueous solution has been investigated using bentonite and activated carbon as the adsorbents. Batch kinetics and isotherm studies were carried out to evaluate the effect of contact time, adsorbent dosage, pH, particle size, and temperature. Adsorption equilibrium data were well represented by the Langmuir and Freundlich isotherm models. The adsorption intensity was found to be increased as the aqueous phase pH increased, and had a maximum at pH = 6.1. The pseudo-first order, pseudo-second order, and intraparticle diffusion kinetic models were used to describe the kinetic data. The experimental data fitted very well with the pseudo-second-order kinetic model and also followed the simple external and intraparticle model.  相似文献   

2.
以海藻酸纤维作为吸附材料研究了纤维对水溶液中Fe3+的吸附性能,用准一级动力学方程、准二级动力学方程、Elovich方程、粒子扩散方程、双常数方程和指数函数方程数学模型对不同Fe3+浓度、吸附时间的吸附曲线进行分析,研究了其吸附的动力学机理。结果表明:在研究的浓度和条件范围内,准二级动力学模型、Elovich方程和双常数方程的拟合度较好,模拟值与实验值吻合较好,说明海藻酸纤维吸附Fe3+是复杂的非均相扩散的化学吸附过程。粒子扩散方程表明颗粒内扩散不是控制海藻酸纤维吸附Fe3+过程的唯一步骤,而是由膜扩散和颗粒内扩散联合控制。  相似文献   

3.
Adsorption of Methylene Blue (MB) from aqueous solutions on activated carbon prepared from Egyptian rice hulls (ERHA) is studied experimentally. Results obtained indicate that the removal efficiency of Methylene Blue at 25 °C exceeds 99% and that the adsorption process is highly pH-dependent. Results showed that the optimum pH lies between 5 and 9. The amount of Methylene Blue adsorbed form aqueous solution increases with the increase of the initial Methylene Blue concentration and temperature. Smaller adsorbent particle adds to increase the percentage removal of Methylene Blue.The results fit the BET model for adsorption of MB on ERHA, corroborating the assumption of that the adsorbate molecules could be adsorbed in more than one layer thick on the surface of the adsorbent.A comparison of kinetic models at different conditions (pH, Temperature, adsorbent particle size, adsorbent dose and adsorbate concentration) applied to the adsorption of Methylene Blue on the adsorbent was evaluated for the pseudo first-order, the pseudo second-order, Elovich and intraparticle diffusion kinetic models, respectively. Results showed that the pseudo second-order kinetic model correlate the experimental data well.  相似文献   

4.
《分离科学与技术》2012,47(15):2436-2449
In this study, sulphuric acid treated cashew nut shell (STCNS) was used as adsorbent for the removal of lead(II) ions from the aqueous solutions. Adsorption studies were performed by varying the solution pH, contact time, and temperature. Experimental data were analyzed by the model equations such as Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms and it was found that the Freundlich isotherm model fits best with the experimental data at different temperatures studied. The maximum adsorption capacity of lead(II) on STCNS was determined as 408.6, 432, 446.3, and 480.5 mg/g, respectively, at different temperatures (30, 40, 50, and 60°C). The thermodynamic parameters (ΔGo, ΔHo, and ΔSo) were calculated and the thermodynamic properties of lead(II) ions-STCNS system indicate the exothermic process. Adsorption kinetic constants were determined using pseudo-first-order, pseudo-second-order, and the Elovich kinetic models at various temperatures. The adsorption results clearly showed that the adsorption of lead(II) ions onto STCNS followed pseudo-second-order model and the adsorption was both by film diffusion and by intraparticle diffusion. A single-stage batch adsorber was designed using the Freundlich equation.  相似文献   

5.
《Applied Clay Science》2010,48(3-4):362-371
The removal of organophosphate and organophosphonate herbicides from aqueous solution by Ni2Al LDH material was investigated. Batch adsorption studies were conducted to evaluate the effect of various parameters such as contact time and initial herbicides concentrations. The adsorption kinetics was tested for Elovich, intraparticle diffusion, pseudo-second-order, and pseudo-first-order reactions and rate constants of kinetic models were calculated. The equilibrium adsorption data were analysed by Freundlich, Langmuir, and Tempkin using linear regression technique. Langmuir isotherms best fitted the data for adsorption equilibrium for both herbicides. Structural and textural analysis (XRD, FTIR, MEB) of Ni2AlNO3 LDH at different rates of adsorption evidence a mechanism of adsorption via an anion exchange reaction, Glyphosate and Glufosinate being adsorbed, in a 1rst step, at the surface of the cristallites and then intercalated in the interlayer domains.  相似文献   

6.
芝麻叶对亚甲基蓝吸附的动力学与热力学研究   总被引:1,自引:0,他引:1  
刘利娥  刘金盾  韩秀丽  刘洁 《化学工程》2011,39(6):40-43,49
以天然芝麻叶为吸附剂,亚甲基蓝(MB)为吸附质,考察芝麻叶吸附亚甲基蓝的动力学、热力学以及溶液pH值、吸附剂投入量、温度等对吸附的影响.采用准一级、准二级、颗粒内扩散吸附动力模型及Langmuir,Freundlich及Dubinin-Radushkevich(D-R)等温模型分别对吸附动力学和吸附等温线进行分析.结果...  相似文献   

7.
Activated carbons prepared from date pits, an agricultural waste byproduct, have been examined for the adsorption of phenol from aqueous solutions. The activated carbons were prepared using a fluidized bed reactor in two steps; carbonization at 700 °C for 2 hours in N2 atmosphere and activation at 900 °C in CO2 atmosphere. The kinetic data were fitted to the models of intraparticle diffusion, pseudo‐second order, and Lagergren, and followed more closely the pseudo‐second‐order chemisorption model. The isotherm equilibrium data were well fitted by the Freundlich and Langmuir models. The maximum adsorption capacity of activated date pits per Langmuir model was 16 times higher than that of nonactivated date pits. The thermodynamic properties calculated revealed the endothermic nature of the adsorption process. The uptake of phenol increased with increasing initial phenol concentration from10 to 200 ppm and temperature from 25 to 55 °C, and decreased with increasing the solution pH from 4 to 12. The uptake of phenol was not affected by the presence of NaCl salt.  相似文献   

8.
Physical properties of activated carbons prepared from pinewood at different activation times (0.5, 1.5, 2.7, and 4.0 h) in steam at 900 °C were studied. The adsorption equilibria and kinetics of three dyes and three phenols (phenol, 3-chlorophenol, and o-cresol) from aqueous solutions on such carbons were then examined at 30 °C. The adsorption isotherms of phenols could be well fitted by the Freundlich equation, and those of dyes were adequately described by the Langmuir-Freundlich equation. The effect of microporosity of the carbons on adsorption capacity was explored. Four simplified kinetic models including pseudo-first-order equation, pseudo-second-order equation, intraparticle diffusion model, and the Elovich equation were selected to follow the adsorption processes. The adsorption of all six adsorbates could be best described by the Elovich equation. The kinetic parameters of this best-fit model were calculated and discussed.  相似文献   

9.
Various natural adsorbents, which have been in used for removal of pollutants, in general, and phenol, in particular, are mostly directed towards improving the adsorption capacity of the adsorbents by various pretreatments (chemical, thermal or biological), which necessarily lead to increase in the cost as well as in the level of difficulties in regeneration/disposal of the adsorbent. The present studies, on the other hand, are aimed towards evaluating the feasibility of using two common soils as potential low-cost adsorbents for the removal of phenol from its aqueous solution, in their natural forms (i.e., without any pretreatment). Accordingly, experiments were carried out (in batch mode) for optimization of the adsorption parameters (such as pH, contact time, equilibrium time and adsorbent dosage), for varying initial phenol concentrations. The results showed that the maximum phenol adsorption capacity was found at pH ~6, under a constant temperature of 30 ± 2 °C (at 6-hour equilibrium period). Several kinetic models (viz. Lagergren first-order, pseudo-second-order, Elovich and intra-particle diffusion) as well as isotherm models (Langmuir, Freundlich, Redlich and Peterson and Sip) were applied to the experimental data. The pseudo-second-order model was found to be the most suitable model describing the adsorption of phenol by two soils (which indicated this adsorption as a chemisorption process). On analysis of equilibrium isotherms for the adsorption of phenol by two soils, Redlich-Peterson and Sip isotherms were found to be the best representative for phenol-sorption on two selected, soil adsorbents.  相似文献   

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11.
《分离科学与技术》2012,47(2):300-308
The potential use of different activated carbons (ACs) prepared from dates pits and phosphoric acid for the removal of phenol from aqueous solutions was investigated. Date pits were converted into five different types of activated carbons by air and phosphoric acid activation. The specific surface area (BET) of the prepared ACs varied from 794 m2/g, for the phosphoric acid:date pit ratio of 5:1, to 1707 m2/g for a ratio of 2:1. Batch adsorption experiments revealed that the adsorption of phenol varied among all of the prepared ACs, where the 2:1 AC showed the highest uptake. Equilibrium pH studies showed that the phenol removal was pH dependent and the maximum phenol uptake occurred at an equilibrium pH of 3.0. Dynamics studies indicated that the initial uptake of phenol on 2:1 AC at pH 4 was rapid, where 80% of the maximum uptake was achieved during the first 30 minutes; both surface adsorption and intraparticle diffusion were involved in the adsorption process and the data followed the pseudo second-order reaction. The equilibrium adsorption data of phenol on 2:1 AC at solution pH 3 was best described by the Redlich-Peterson, Sips, and Langmuir models.  相似文献   

12.
《中国化学工程学报》2014,22(11-12):1193-1198
The removal of cobalt ion from aqueous solution by Acacia nilotica leaf carbon (HAN), is described. Effect of pH, agitation time and initial concentration on adsorption capacities of HAN was investigated in a batch mode. The adsorption process, which is pH dependent, shows maximum removal of cobalt in the pH range 5 for an initial cobalt concentration of 50 mg·L–1 The experimental data have been analyzed by using the Freundlich, Langmuir, Temkin and Dubinin–Radushkevich isotherm models. The batch sorption kinetics have been tested for a pseudo-first order, pseudo-second order and Elovich kinetic models. The rate constants of adsorption for all these kinetic models have been calculated. Results showed that the intraparticle diffusion and initial sorption of Co(II) into HAN was the main rate limiting step. The adsorption of cobalt ion was confirmed through instrumental analyses such as scanning electron microscope (SEM) and Fourier transform infrared spectroscopy (FTIR). The desorption and recycling ability of HAN were also found. We conclude that HAN can be used for the efficient removal of cobalt from aqueous solution.  相似文献   

13.
The adsorption isotherms and rates of two dyes and humic acid from aqueous solutions onto chitosan‐encapsulated activated carbon (CEAC) beads were measured at 30 °C. Such beads were prepared by mixing different weight percents of cuttlefish‐based chitosan (100%, 80%, 67%, and 55%) and rice‐based activated carbons. It was shown that the isotherms of dyes and humic acid were well fitted by the Freundlich equation. The adsorption capacity and rate could be enhanced when activated carbon was encapsulated with chitosan. Four simplified kinetic models including the pseudo‐first‐order equation, pseudo‐second‐order equation, intraparticle diffusion model, and the Elovich equation were tested to follow the adsorption processes. The adsorption of dyes was best described by the Elovich equation, but that of humic acid was best described by the intraparticle diffusion model. The kinetic parameters of each best‐fit model were calculated and are discussed in this paper. © 2002 Society of Chemical Industry  相似文献   

14.
石英砂负载氧化铁吸附锑的动力学及其吸附机理研究   总被引:1,自引:0,他引:1  
研究了283、293、313K的温度下,石英砂负载氧化铁(IOCS)对锑的吸附动力学。锑在IOCS表面的吸附可分为两个阶段,吸附反应的前120min为快速吸附阶段;120min后,吸附速率明显变慢。温度升高加快了锑在IOCS表面的吸附速率。用Elovich动力学模型、准一级反应模型、准二级反应模型、二级反应模型和粒内扩散动力学模型对试验数据进行回归分析,准二级反应模型能更好地描述锑在IOCS表面的吸附,各吸附模型的模拟优劣顺序为:准二级模型、二级模型、Elovich模型、准一级模型、粒内扩散模型。给出锑在IOCS表面的吸附机理,Sb(OH)3与IOCS表面羟基经两个阶段的反应,最终生成了双齿表面配合物;SbO(OH)和HSbO2与IOCS表面羟基反应生成单齿表面配合物。  相似文献   

15.
《分离科学与技术》2012,47(2):244-255
In this work, the removal of two pharmaceuticals i.e., an antibiotic drug, sulfamethoxazole and an antiparasitary drug, metronidazole onto activated carbon from aqueous solutions were studied. Batch adsorption studies were carried out at different pH, adsorbent concentrations, and temperatures. Adsorption isotherms have been modeled by Freundlich, Langmuir, and Dubinin-Raduskevitch (D-R) equations. The adsorption of these drugs was better represented by the Langmuir equation. The effect of the solution pH on the adsorbed amount of SM and MN was studied by varying the initial pH under constant process parameters at equilibrium conditions. The increase in pH of the solutions caused to decrease adsorption of SM and MN on AC. The kinetics of adsorption in view of three kinetic models, i.e., the first-order Lagergren model, the pseudo-second-order model, and the intraparticle diffusion model was discussed. The pseudo-second-order kinetic model describes the adsorption of both sulfamethoxazole and metronidazole on activated carbon. Rate constants for adsorption and desorption, and surface coverage have been evaluated with the help of another approach of the kinetic scheme. The effect of temperature was also studied at the range between 293 and 313 K. Thermodynamic parameters were calculated. The negative value of enthalpy change (ΔH°) indicated the exothermic nature of the adsorption process, and the negative values of free energy change (ΔG°) were indicative of spontaneity of the adsorption process. In this work adsorption behaviour of SM and MN on activated carbon was also evaluated by the data obtained from column experiments.  相似文献   

16.
《分离科学与技术》2012,47(18):2817-2824
The potential use of papaya seeds as biosorbent for the removal of a large dye molecule, Procion Red, from aqueous solution was investigated. Papaya seeds were characterized by nitrogen adsorption/desorption isotherms and scanning electron microscopy. The results revealed that the papaya seeds exhibit a macro-/mesoporous structure, which is desirable for applications in adsorption processes. The models of Langmuir, Freundlich, and Temkin were employed to fit the equilibrium data, where the Langmuir model showed the most suitable fitting. The maximum adsorption capacity for Procion red dye was found to be 73.26 mg g?1. Pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models were used to analyze the kinetic data obtained at different concentrations of dye. The adsorption process of Procion red dye followed the pseudo-second-order and intraparticle diffusion models. The results indicated that the adsorbent used in this work is adequate for the treatment of large dye molecules containing in aqueous solutions. This work highlights the potential application of papaya seeds in the field of adsorption.  相似文献   

17.
The present study is concerned with the mass transfer and kinetics study of zinc ions removal from aqueous solution using a cation exchange resin packed in a rotating cylindrical basket reactor. The effect of various experimental parameters on the rate of zinc ion removal, such as initial zinc ion concentration, packed bed rotation speed and temperature has been investigated. In addition to find a suitable equilibrium isotherm and kinetic model for the zinc ion removal in a batch reactor. The experimental isotherm data were analyzed using the Langmuir, Freundlich and D–R equations. The equilibrium data fit well in the Langmuir isotherm. The experimental data were analyzed using four sorption kinetic models, pseudo-first and second-order equations, the Elovich and the intraparticle diffusion model equation, to determine the best fit equation for the biosorption of zinc ions onto purolite C-100 MH resin. Results show that the Elovich equation provides the best correlation for the biosorption process.  相似文献   

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利用废弃蛋壳为原料、尿素为添加剂,合成了碳羟基磷灰石(CHAP),用于吸附水中苯酚. 利用红外光谱、扫描电镜、X射线能谱测试技术对CHAP样品表面化学进行了表征,同时考察了环境pH值、吸附时间、苯酚初始浓度及温度对苯酚吸附的影响. 结果表明,在酸性(pH=3~5)和碱性(pH=9~10)条件下,CHAP对苯酚的吸附效果较好,吸附过程符合Langmuir和Freundlich等温式,同时也符合准二级动力学模型.  相似文献   

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