Characterization of metal adsorption kinetic properties in batch and fixed-bed reactors

Copper adsorption kinetic properties in batch and fixed-bed reactors were studied in this paper. The isothermal adsorption experiments showed that the copper adsorption capacity of a granular activated carbon (Filtrasorb 200) increased when ionic strength was higher. The presence of EDTA diminished the adsorption. An intraparticle diffusion model and a fixed-bed model were successfully used to describe the batch kinetic and fixed-bed operation behaviors. The kinetics became faster when the solution pH was not controlled, implying that the surface precipitation caused some metal uptake. The external mass transfer coefficient, the diffusivity and the dispersion coefficient were obtained from the modeling. It was found that both external mass transfer and dispersion coefficients increased when the flow rate was higher. Finally effects of kinetic parameters on simulation of fixed-bed operation were conducted.     

活性炭孔隙结构在其甲苯吸附中的作用

选用4种商用活性炭(AC),利用氮气绝热吸附、扫描电子显微镜(SEM)和傅立叶变换红外光谱(FTIR)测试了活性炭的物化性质。以甲苯为吸附质,在温度为298.15 K下进行了静态和动态吸附实验,研究了活性炭孔结构对其吸附性能、吸附行为、表面覆盖率和吸附能的影响。结果表明:活性炭的比表面积和孔容是其吸附性能主要影响因素,孔径在0.8～2.4 nm之间的孔容和甲苯吸附量之间存在较好的线性关系,且线性斜率随甲苯浓度增加而变大。甲苯吸附行为符合Langmuir吸附等温模型和准一阶动力学方程式。活性炭孔结构是甲苯吸附速率的主要制约因素。在甲苯快速吸附阶段,微孔为吸附速率主要制约因素,在甲苯颗粒内扩散阶段,微孔和表面孔为吸附速率的主要制约因素,在吸附末尾阶段,中孔和大孔为吸附速率的主要制约因素。4种活性积炭对甲苯的吸附能随其比表面变大而变大。     

超声前处理强化活性炭吸附活性艳红X-3B染料废水

探究了超声前处理活性艳红X-3B染料废水强化活性炭吸附降解性能及不同超声参数的影响规律,包括超声功率和超声时间。研究结果表明,超声前处理活性艳红X-3B染料废水可通过空化效应使有机大分子裂解为小分子易于被活性炭吸附,同时可强化其到活性炭微孔中传输,提高了活性炭吸附降解性能,最佳超声功率为320 W。浓度越高,所需超声时间越长,当超声达到一定时间后,继续超声不会影响染料分子的吸附。超声前处理虽然不会改变吸附平衡时间,但可有效增加活性炭处理活性艳红X-3B染料废水的饱和吸附量。     

Immobilization of polyphenol oxidase onto mesoporous activated carbons -- isotherm and kinetic studies

Investigations were carried out in batch modes for studying the immobilization behavior of polyphenol oxidase (PPO) on two different mesoporous activated carbon matrices, MAC400 and MAC200. The PPO was immobilized onto MAC400 and MAC200 at various enzyme activities 5 x 10(4), 10 x 10(4), 20 x 10(4), 30 x 10(4)Ul(-1), at pH 5-8, and at temperature ranging from 10 to 40 degrees C. The intensity of immobilization of PPO increased with increase in temperature and initial activities, while it decreased with increase in pH. Immobilization onto MAC400 followed the Langmuir model while Langmuir and Freundlich models could fit MAC200 data. Non-linear pseudo first order, pseudo second order and intraparticle diffusion models were evaluated to understand the mechanism of immobilization. The free and immobilized enzyme kinetic parameters (K(m) and V(max)) were determined by Michaelis-Menten enzyme kinetics. The K(m) values for free enzyme, PPO immobilized in MAC400 and in MAC200 were 0.49, 0.41 and 0.65 mM, respectively. The immobilization of PPO in carbon matrices was confirmed using FT-IR spectroscopy and scanning electron microscopy.     

孔结构和表面化学性质对活性炭吸附性能的影响

测定了室温下3种活性炭(GAC-C、GAC-P和GAC-T)对CO2、CH4和N2的吸附性能,并对颗粒活性炭孔结构和表面化学性质进行了表征,探讨了孔结构和表面化学性质对活性炭吸附性能的影响。结果表明:由于吸附机理、孔结构、表面含氧官能团和分子极性的差异,CO2、CH4和N2在活性炭上的饱和吸附量和吸附常数的关系为CO2>CH4>N2;CH4和N2的饱和吸附量主要受活性炭微孔孔容的影响,N2和CO2饱和吸附量的差异分别是由0.572～2.0 nm的微孔和0.4～6 nm的孔引起的;CH4吸附常数主要受较大中孔和大孔影响,N2吸附常数与微孔密切相关,大孔对CO2的吸附常数影响最大。     

Enhanced mercuric chloride adsorption onto sulfur-modified activated carbons derived from waste tires

A number of activated carbons derived from waste tires were further impregnated by gaseous elemental sulfur at temperatures of 400 and 650 degrees C, with a carbon and sulfur mass ratio of 1:3. The capabilities of sulfur diffusing into the micropores of the activated carbons were significantly different between 400 and 650 degrees C, resulting in obvious dissimilarities in the sulfur content of the activated carbons. The sulfur-impregnated activated carbons were examined for the adsorptive capacity of gas-phase mercuric chloride (HgC1) by thermogravimetric analysis (TGA). The analytical precision of TGA was up to 10(-6) g at the inlet HgCl2 concentrations of 100, 300, and 500 microg/m3, for an adsorption time of 3 hr and an adsorption temperature of 150 degrees C, simulating the flue gas emitted from municipal solid waste (MSW) incinerators. Experimental results showed that sulfur modification can slightly reduce the specific surface area of activated carbons. High-surface-area activated carbons after sulfur modification had abundant mesopores and micropores, whereas low-surface-area activated carbons had abundant macropores and mesopores. Sulfur molecules were evenly distributed on the surface of the inner pores after sulfur modification, and the sulfur content of the activated carbons increased from 2-2.5% to 5-11%. After sulfur modification, the adsorptive capacity of HgCl2 for high-surface-area sulfurized activated carbons reached 1.557 mg/g (22 times higher than the virgin activated carbons). The injection of activated carbons was followed by fabric filtration, which is commonly used to remove HgCl2 from MSW incinerators. The residence time of activated carbons collected in the fabric filter is commonly about 1 hr, but the time required to achieve equilibrium is less than 10 min. Consequently, it is worthwhile to compare the adsorption rates of HgCl2 in the time intervals of < 10 and 10-60 min.     

Removal of Disperse Red dye by bamboo-based activated carbon: optimisation, kinetics and equilibrium

This research involved the use of response surface methodology (RSM) to investigate the adsorption of Disperse Red 167 dye onto the bamboo-based activated carbon activated with H₃PO₄ (PBAC) in a batch process. F400, a commercially available activated carbon, was used in parallel for comparison. Analysis of variance showed that input variables such as the contact time, temperature, adsorbent dosage and the interaction between the temperature and the contact time had a significant effect on the dye removal for both adsorbents. RSM results show that the optimal contact time, temperature, initial dye concentration and adsorbent dosage for both adsorbents were found to be 15.4 h, 50 °C, 50.0 mg L^?1 and 12.0 g L^?1, respectively. Under these optimal conditions, the removal efficiencies reached 90.23 % and 92.13 % for PBAC and F400, respectively, with a desirability of 0.937. The validation of the experimental results confirmed the prediction of the models derived from RSM. The adsorption followed a nonlinear pseudo-first-order model and agreed well with the Freundlich and Temkin isotherm as judged by the levels of the AICc and the Akaike weight. Furthermore, the thermodynamics analysis indicated that, for both adsorbents, the adsorption was a physical process that was spontaneous, entropy-increasing and endothermic.     

Adsorption kinetics of herbicide paraquat from aqueous solution onto activated bleaching earth

In the present study, the activated bleaching earth was used as adsorbent for the herbicide paraquat adsorption in a batch adsorber. The rate of adsorption has been investigated under the controlled process parameters like agitation speed, initial paraquat concentration, adsorbent dosage and temperature. A batch kinetic model, based on the assumption of a pseudo-second order mechanism, has been tested to predict the rate constant of adsorption, equilibrium adsorption capacity, time of half-adsorption, and equilibrium concentration by the fittings of the experimental data. The results of the kinetic studies show that the adsorption process can be well described with the pseudo-second order equation. Based on the isotherm data obtained from the fittings of the adsorption kinetics, Freundlich model appears to fit the adsorption better than Langmuir model. In addition, the effective diffusion coefficient has also been estimated based on the restrictive diffusion model.     

Physicochemical characteristics of carbonaceous adsorbent for dioxin-like polychlorinated biphenyl adsorption

It has been known that dioxin-like polychlorinated biphenyls (DL-PCBs) are present in almost all types of environments worldwide. Activated carbon treatment has been expected for the removal of DL-PCBs because it is a simple and low-cost removal technology. In the present study, the physicochemical properties of activated carbon were investigated to identify the characteristics of 16 different types of activated carbon on adsorption properties for DL-PCBs. To accomplish this, micropore volume, and pore diameter were calculated by t-plot analysis and the mesopore volume was analyzed by the Barrett-Joyner-Halenda (BJH) method. In addition, the Brunauer-Emmett-Teller (BET) surface area, pH, metal elements, and surface acid functional groups were analyzed. Then, adsorption experiments using DL-PCB in hexane solution were conducted, and the relationship between adsorption and physicochemical properties of activated carbon was investigated. The results showed that activated carbons having a surface area of 700-1200 m² g⁻¹ and micropores with diameters of about 0.7-0.8 nm exhibited high activity for the adsorption of PCBs. The results also clearly showed that the mesopore volume of activated carbon influenced the adsorption rate and the equilibrium adsorption.     

Preparation of activated carbon from dried pods of Prosopis cineraria with zinc chloride activation for the removal of phenol

Utilization of agrowaste materials for the production of activated carbon, as an excellent adsorbent with large surface area, is well established industrially, for dephenolation of wastewater. In the present work, dried pods of Prosopis cineraria—a novel and low-cost agrowaste material—were used to prepare activated carbons by zinc chloride activation. Batch adsorption experiments were carried out to study the effects of various physicochemical parameters such as initial phenol concentration, adsorbent dose, initial solution pH, and temperature. Pseudo-first-order second-order and diffusion kinetic models were used to identify the possible mechanisms of such adsorption process. The Langmuir and Freundlich equations were used to analyze the adsorption equilibrium. Maximum removal efficiency of 86 % was obtained with 25 mg?L^?1 of initial phenol concentration. The favorable pH for maximum phenol adsorption was 4.0. Freundlich equation represented the adsorption equilibrium data more ideally than the Langmuir. The maximum adsorption capacity obtained was 78.32 mg?g^?1 at a temperature of 30 °C and 25 mg?L^?1 initial phenol concentration. The adsorption was spontaneous and endothermic. The pseudo-second-order model, an indication of chemisorption mechanism, fitted the experimental data better than the pseudo-first-order Lagergren model. Regeneration of spent activated carbon was carried out using Pseudomonas putida MTCC 2252 as the phenol-degrading microorganism. Maximum regeneration up to 57.5 % was recorded, when loaded phenol concentration was 25 mg?L^?1. The data obtained in this study would be useful in designing and fabricating an efficient treatment plant for phenol-rich effluents.     

Kinetics and isotherm analysis of Tropaeoline 000 adsorption onto unsaturated polyester resin (UPR): a non-carbon adsorbent

The presence of dyes in water is undesirable due to the toxicological impact of their entrance into the food chain. Owing to the recalcitrant nature of dyes to biological oxidation, a tertiary treatment like adsorption is required. In the present study, unsaturated polyester resin (UPR) has been used as a sorbent in the treatment of dye-contaminated water. Different concentrations of Tropaeoline 000 containing water were treated with UPR. The preliminary investigations were carried out by batch adsorption to examine the effects of pH, adsorbate concentration, adsorbent dosage, contact time, and temperature. A plausible mechanism for the ongoing adsorption process and thermodynamic parameters have also been obtained from Langmuir and Freundlich adsorption isotherm models. Thermodynamic parameter showed that the sorption process of Tropaeoline 000 onto activated carbon (AC) and UPR were feasible, spontaneous, and endothermic under studied conditions. The estimated values for (ΔG) are ?10.48?×?10³ and ?6.098?×?10³ kJ mol^?1 over AC and UPR at 303 K (30 °C), indicating towards a spontaneous process. The adsorption process followed pseudo-first-order model. The mass transfer property of the sorption process was studied using Lagergren pseudo-first-order kinetic models. The values of % removal and k _ad for dye systems were calculated at different temperatures (303–323 K). The mechanism of the adsorption process was determined from the intraparticle diffusion model.     

Activated carbon from industrial solid waste as an adsorbent for the removal of Rhodamine-B from aqueous solution: kinetic and equilibrium studies

The activated carbon was prepared using industrial solid waste called sago waste and physico-chemical properties of carbon were carried out to explore adsorption process. The effectiveness of carbon prepared from sago waste in adsorbing Rhodamine-B from aqueous solution has been studied as a function of agitation time, adsorbent dosage, initial dye concentration, pH and desorption. Adsorption equilibrium studies were carried out in order to optimize the experimental conditions. The adsorption of Rhodamine-B onto carbon followed second order kinetic model. Adsorption data were modeled using both Langmuir and Freundlich classical adsorption isotherms. The adsorption capacity Q0 was 16.12 mg g(-1) at initial pH 5.7 for the particle size 125-250 microm. The equilibrium time was found to be 150 min for 10, 20 mg l(-1) and 210 min for 30, 40 mg l(-1) dye concentrations, respectively. A maximum removal of 91% was obtained at natural pH 5.7 for an adsorbent dose of 100mg/50 ml of 10 mg l(-1) dye concentration and 100% removal was obtained when the pH was increased to 7 for an adsorbent dose of 275 mg/50 ml of 20 mg l(-1) dye concentration. Desorption studies were carried out in water medium by varying the pH from 2 to 10. Desorption studies were performed with dilute HCl and show that ion exchange is predominant dye adsorption mechanism. This adsorbent was found to be both effective and economically viable.     

Fixed bed adsorption of acid dyes onto activated carbon

The context of the study here is the adsorption of acid dyes from wastewater arising from a nylon carpet printing plant which currently receives no treatment. Since nylon is a particularly difficult fibre to dye, acid dyes are required for successful coloration. However, their presence, in high concentrations, in aqueous effluent arising from the plant can create major problems with respect to disposal. A treatment method based on adsorption onto granular activated carbon (GAC F400) in a fixed column configuration is described and breakthrough data of the dyes determined. The breakthrough data were correlated using a model based on liquid and pore diffusion with a good fit of experimental results obtained. Trends in the effective diffusivity used in the model correlated with other authors. A slight decrease in effective diffusivity was found with decrease in particle size and was attributed to interactions between the relatively large molecular sized dye and the microspore structure found in granular activated carbon.     

黑曲霉死菌与活性炭对直接耐晒翠蓝FBL的吸附性能

采用批式实验,系统考察了黑曲霉死菌和活性炭的粉剂投加量,染料初始浓度,pH和反应时间对酞菁染料FBL脱色效果的影响;并采用扫描电镜图像,分析吸附剂的结构变化。结果表明,对于FBL染料的吸附处理,黑曲霉死菌粉剂与活性炭粉剂适宜的吸附条件为:酸性至弱碱性pH下,投加量为8 g/L;黑曲霉死菌粉剂比活性炭粉剂的吸附速度快、脱色性能高、抗染料浓度负荷冲击能力强。扫描电镜图像分析显示,黑曲霉死菌粉剂所具有的多层纤维结构为吸附染料分子提供较大的比表面。     

浸渍-碱性微波法载磁活性炭粉对壬基酚的吸附

利用浸渍-碱性微波法制备载磁粉末活性炭,通过等温吸附实验和动力学吸附实验,研究对比了其与原料活性炭、浸渍载铁活性炭对壬基酚的吸附性能。采用氮气吸附仪、FTIR、XRD、国标(GB/T12496.19-1999)邻菲啰啉分光度法及VSM,分别对3种样品进行了物相结构、表面官能团、铁含量及磁性能的分析,并探讨了吸附机理。结果表明,浸渍-碱性微波法载磁活性炭的总孔容及孔隙率均有较大提高;其吸附等温线符合Freundich方程,吸附动力学过程符合准二级动力学方程与孔道内扩散模型,相关系数R2均大于0.900。原活性炭经一定浓度的铁盐溶液浸渍后,铁含量由2%提高到8%。在碱性、N2气氛条件下微波后,铁系物主要存在形式为零价铁和Fe3O4,制得的载磁活性炭饱和磁化强度为1.12 emu/g。     

双氯芬酸的吸附去除过程与机制

研究了非甾体抗炎药双氯芬酸的吸附去除过程与机制。对吸附处理效果较好的活性炭与纳米羟基氧化铁（α-FeOOH）进行了比表面积、Zeta电位等表面特性的表征,研究比较了双氯芬酸在活性炭与α—FeOOH2种材料上的吸附去除效果与吸附机制。结果表明,在相同的实验条件下,活性炭与α-FeOOH对双氯芬酸吸附去除率可分别达到97．9％和84．3％;双氯芬酸在活性炭上的吸附主要是由于活性炭较大的比表面积与疏水分配作用,在α-FeOOH上的吸附主要是由于静电引力作用;活性炭与α-FeOOH对双氯芬酸的吸附去除效果均随pH的升高而降低;在pH=6时,活性炭与α-FeOOH对双氯芬酸钠的吸附等温线均符合Langmuir方程,单位饱和吸附量分别为109．98mg／g和58．96mg／g;活性炭对双氯芬酸具有更强的吸附能力。     

Application of zeolite-activated carbon macrocomposite for the adsorption of Acid Orange 7: isotherm, kinetic and thermodynamic studies

In this study, the adsorption behavior of azo dye Acid Orange 7 (AO7) from aqueous solution onto macrocomposite (MC) was investigated under various experimental conditions. The adsorbent, MC, which consists of a mixture of zeolite and activated carbon, was found to be effective in removing AO7. The MC were characterized by scanning electron microscopy (SEM), energy dispersive X-ray, point of zero charge, and Brunauer–Emmett–Teller surface area analysis. A series of experiments were performed via batch adsorption technique to examine the effect of the process variables, namely, contact time, initial dye concentration, and solution pH. The dye equilibrium adsorption was investigated, and the equilibrium data were fitted to Langmuir, Freundlich, and Tempkin isotherm models. The Langmuir isotherm model fits the equilibrium data better than the Freundlich isotherm model. For the kinetic study, pseudo-first-order, pseudo-second-order, and intraparticle diffusion model were used to fit the experimental data. The adsorption kinetic was found to be well described by the pseudo-second-order model. Thermodynamic analysis indicated that the adsorption process is a spontaneous and endothermic process. The SEM, Fourier transform infrared spectroscopy, ultraviolet–visible spectral and high performance liquid chromatography analysis were carried out before and after the adsorption process. For the phytotoxicity test, treated AO7 was found to be less toxic. Thus, the study indicated that MC has good potential use as an adsorbent for the removal of azo dye from aqueous solution.     

吸附-氧化法应急处理饮用水源突发苯酚污染的研究

以黄浦江上游水源地突发苯酚污染为背景,重点考察了粉末活性炭（PAC）吸附、高锰酸钾（KMnO4）氧化及两者联用技术的除酚效能。结果表明,活性炭及氧化剂种类的选择是影响处理效果的重要因素,微孔发达、比表面积巨大的竹炭对苯酚的去除效果明显优于煤质炭、椰壳炭和木质炭;KMnO4对苯酚的氧化能力强于次氯酸钠和高铁酸钾。增大PAC和KMnO4的投加量,可有效提高对苯酚的去除率;PAC吸附-KMnO4氧化联用技术可大大提高除酚效能,投加50mg／LPAC,2mg／LKMnO4可将初始浓度为250／μg／L和500／μg／L的含酚原水分别处理至18μg／L和66／μg／L,是应对高浓度苯酚突发污染的有效应急措施。     

Evaluation of adsorption characteristics of an anionic azo dye Brilliant Yellow onto hen feathers in aqueous solutions

Purpose and aim

Removal of an anionic azo dye Brilliant Yellow has been carried out from its aqueous solutions by using hen feathers as potential adsorbent.

Materials and methods

Hen feathers procured from local poultry were cut, washed, and activated. Detailed chemical and physical analysis of hen feathers and its characterization through scanning electron microscopy, X-ray diffraction, and infrared measurements have been made. Procured dye has been adsorbed over under batch measurements and adsorption process is monitored using UV spectrophotometer.

Results

Optimum parameters for the adsorption of Brilliant Yellow over hen feathers have been determined by studying the effect of pH, temperature, concentration of dye, and amount of adsorbent. On the basis of Langmuir adsorption, isotherms feasibility of the ongoing adsorption has been ascertained and thermodynamic parameters have been calculated. Attempts have also been made to verify Freundlich, Tempkin, and Dubinin?CRadushkevich adsorption isotherm models. It is found that during adsorption, uniform distribution of binding energy takes place due to interaction of the dye molecules and the ongoing adsorption process is chemisorptions. The kinetic measurements indicate dominance of pseudo-second-order process during the adsorption. The mathematical treatment on the kinetic data reveals the rate-determining step to be governed through particle diffusion at 8?×?10^?5?M and involvement of film diffusion mechanism at higher concentration at temperatures at all the temperatures.

Conclusions

The developed process is highly efficient and it can be firmly concluded that hen feather exhibits excellent adsorption capacity towards hazardous azo dye Brilliant Yellow.     

三氯乙酸与其他有机物在活性炭上的竞争吸附

通过等温吸附实验,考察了三氯乙酸(TCAA)与十二烷基苯磺酸钠(DBS)、腐殖酸(HA)在活性炭(GAC)上的竞争吸附现象。结果表明,GAC对TCAA的吸附符合Langmuir模型,对DBS和HA的吸附均符合Freudlich模型;在GAC上,DBS和HA对TCAA构成竞争吸附,大分子HA阻塞GAC的微孔,使得TCAA与DBS难以进入微孔;GAC对3种物质的吸附能力由大到小依次为DBS、TCAA和HA;离子型表面活性剂DBS憎水性一端与TCAA竞争吸附位,亲水性一端与TCAA形成吸附,使GAC总饱和吸附量有所加大。