颗粒活性炭的特性参数与吸附性能的关系试验

采用活性炭进行饮用水的深度处理,选择适合原水水质的活性炭至关重要,通过6种不同颗粒活性炭特性参数的测试,对饮用水有机物的吸附试验以及吸附等温线的测定,结果表明:针对颗粒活性炭的筛选,碘值,亚甲蓝值,吸附等温线的KF及斜率1/n值均不能单独作为评价筛选活性炭优劣的指标,而应综合考虑颗粒活性炭的孔径分布与原水中有机物的相对分子质量分布相匹配等。研究还表明:碘值,亚甲蓝值,吸附等温线的KF存在一定的相关性,从颗粒活性炭的特性参数和吸附性能参数可以推测活性炭滤柱试验吸附效果。颗粒活性炭用于饮用水深度处理,能去除水中相对分子质量小的有机物,处理的水量为颗粒活性炭体积的4800倍时,对CODMn的去除率为15%左右。     

An inverse method to estimate adsorption kinetics of light hydrocarbons on activated carbon

An inverse algorithm to estimate the adsorption kinetics inside the spherical particles in a constant molar flow (CMF) gas adsorber reservoir by measuring the bulk pressure is developed. The formulation includes Knudsen diffusion, surface diffusion, slip and viscous flows. To obtain an efficient algorithm, the conjugate gradient method (CGM) for optimization procedure and the incremental differential quadrature method (IDQM) for solving the governing equations are adopted. The results show that the Knudsen diffusion, surface diffusion, slip and viscous flows effects depend on the type of adsorbate and adsorbent gases. It is shown that the effective diffusivity is not constant and goes through a minimum at an intermediate pressure. Also, it is found that the Knudsen diffusion and the viscous flow are the dominant parts of the mass transfer process at low and high pressure, respectively, and despite the viscous flow, the Knudsen diffusion is highly sensitive to temperature change.     

Hydrogen adsorption characteristics of activated carbon

Hydrogen adsorption on activated carbons was investigated in the present works up to 100 bars at 298 K. Coconut-shell was activated by potassium hydroxide, resulting in activated carbons with different porosities. All of prepared activated carbons are microporous and show the same adsorption properties. The complete reversibility and fast kinetics of hydrogen adsorption show that most of adsorbed quantity is due to physical adsorption. A linear relationship between hydrogen adsorption capacity and pressure is obtained for the all samples regardless of their porosities. Hydrogen adsorption capacities are linear function of porosities such as specific surface area, micropore surface area, total pore volume, and micropore volume. The maximum hydrogen adsorption capacity of 0.85 wt.% at 100 bars, 298 K is obtained in these materials.     

Multicomponent adsorption equilibria of phenols on activated carbon

Multicomponent adsorption equilibria of phenols on activated carbon were predicted by the ideal adsorbed solution (IAS) theory and results were compared with those calculated from two different Freundlich-type isotherms. Although some deviations between measured and calculated results are observed, the IAS theory permits rapid and relatively accurate predictions of adsorption equilibria for two-and three-component systems comparing with other isotherms. The results obtained show that the IAS theory is quite suitable for the extended application to multicomponent adsorption systems.     

The adsorption of bile salts on activated carbon

Activated carbon (AC) has been shown to be effective in reducing serum cholesterol and triglycerides. The mechanism for this action is proposed to be a result of the removal of bile salts in the gut. In this paper, the adsorption of cholate, glycocholate, taurocholate, chenodeoxycholate and deoxycholate on AC is studied in vitro. The results indicate that AC has a high capacity for bile salts, completely removing them from solutions of up to 5 mM and at a rate consistent with physiological activity. Of the 2 types of AC tested, one was shown to exhibit greater capacity and selectivity over the other. A negligible effect was seen with variation of pH through the range 7–9. Desorption occurs in the presence of bile salt-free buffer, but to a minimal extent. Based on these data, the adsorption of bile salts by AC appears to be a likely mechanism for AC-induced reduction of serum lipids.     

活性炭吸附氯气的性能研究

对活性炭的氯气吸附性能进行了研究。研究表明,活性炭在0.332 MPa、0℃时,对氯气的吸附量(质量分数)可达到40.7%;经过脱附后,可进行多次吸附和脱附,且吸附量没有下降。     

The adsorption of methane-ethane mixtures on activated carbon

The single component adsorption of methane and ethane and also the adsorption of binary mixtures of methane and ethane have been studied in a small fixed isothermal bed containing activated carbon. Results indicate that an empirical Langmuir isotherm fits the experimental data for single components. An extended form of the empirical Langmuir isotherm, in which the parameters are obtained from single component data, satisfactorily describes the adsorption of binary mixtures. The potential theory of Polanyi is also helpful in extending the experimental data. Breakthrough curves of both components from a diluted feed of methane and ethane could be predicted with good precision for the two activated carbons studied. Furthermore, the concentration waves of the components were sufficiently spaced to suggest that these carbons may be of use as a separating agent for methane-ethane mixtures.     

Influence of solvent type on dibenzothiophene adsorption onto activated carbon fiber and granular coconut-shell activated carbon

The adsorption behavior of dibenzothiophene (DBT) on an activated carbon fiber (ACF) and a granular coconut-shell activated carbon (GCSAC) in the solvents n-hexane, n-decane, toluene, and mixture of n-decane and toluene was investigated. The DBT adsorption onto both samples was more active in n-hexane than in n-decane. The lowest DBT adsorption was observed in toluene. Regardless of the type of activated carbons and solvents, all the isotherms fit the Freundlich equation better than the Langmuir equation. At low equilibrium concentrations of <2 mass ppm-S, GCSAC displayed greater capacity for DBT adsorption than did ACF in all the tested solvents. The adsorption kinetics of ACF and GCSAC in all the tested solvents were governed by a pseudo-second-order model.     

Binary vapor adsorption by activated carbon

The adsorption of binary vapor mixtures has been investigated on BPL grade activated carbon. Vapor mixtures include $\text{CNCl}\text{H}{}_2\text{O}$, $\text{HCN}\text{H}{}_2\text{O}$ and $\text{HCN}\text{CNCl}$. Preadsorption of one vapor generally lowers the adsorption of the second vapor below its single vapor isotherm value. Adsorption of CNCl after pre-adsorbing HCN is greater than the adsorption of HCN after pre-adsorbing CNCl. correlating with the higher affinity coefficient observed for CNCl. The adsorption of H₂O vapor is reduced to very low levels by pre-adsorbing HCN or CNCl.     

Electrochemical enhancement of adsorption capacity of activated carbon fibers and their surface physicochemical characterizations

The adsorption of activated carbon fibers (ACFs) and their surface characteristics were investigated before and after electrochemical polarization. The adsorption kinetics of m-cresol showed the dependence on polarized potential, and the adsorption rate constant increased by 77.1%, from 6.38 × 10⁻³ min⁻¹ at open-circuit (OC) to 1.13 × 10⁻² min⁻¹ at polarization of 600 mV. The adsorption isotherms at different potentials were in good agreement with Langmuir isotherm model, and the maximum adsorption capacity increased from 2.28 mmol g⁻¹ at OC to 3.67 mmol g⁻¹ at polarized potential of 600 mV. These indicated that electrochemical polarization could effectively improve the adsorption rate and capacity of ACFs. The surface characteristics of ACFs before and after electrochemical polarization were evaluated by N₂ adsorption-desorption isotherms, scanning electron microscope (SEM), zeta potential and Fourier transform infrared spectroscopy (FTIR). The results showed that the BET specific surface area and pore size increased as the potential rose. However, the surface chemical properties of ACFs hardly changed under electrochemical polarization of less than 600 mV. This study was beneficial to understand the mechanism of electrochemically enhanced adsorption.     

Hexavalent chromium adsorption on superparamagnetic multi-wall carbon nanotubes and activated carbon composites

Hexavalent chromium (Cr(VI)) adsorption from aqueous solutions on magnetically modified multi-wall carbon nanotubes (M-MWCNT) and activated carbon (M-AC) was investigated. M-MWCNT and M-AC were prepared by co-precipitation method with Fe²⁺:Fe³⁺ salts as precursors. The magnetic adsorbents were characterized by X-ray diffraction (XRD), thermogravimetric analysis (TGA) and scanning electron microscope (SEM). The effects of amount of adsorbents, contact time, initial pH, temperature and the initial concentration of Cr(VI) solution were determined. The adsorption equilibrium, kinetics, thermodynamics and desorption of Cr(VI) were investigated. Equilibrium data fitted well with the Langmuir isotherm for both of the adsorbents. The theoretical adsorption capacities are 14.28 mg/g of M-MWCNT and 2.84 mg/g of M-AC. Cr(VI) adsorption kinetics was modeled with pseudo-second order model, intra-particle diffusion model and Bangham model. Thermodynamic parameters were calculated and ΔG°, ΔH° and ΔS° indicate that the adsorption of Cr(VI) onto M-MWCNT and M-AC was exothermic and spontaneous in nature. Results revealed that M-MWCNT is an easily separated effective adsorbent for Cr(VI) adsorption from aqueous solution.     

污泥活性炭制备及其吸附性能研究

以城市污水处理厂剩余污泥作为原料,采用化学活化法(Zn Cl2作为活化剂)和微波辐照制备污泥活性炭,研究其对亚甲基蓝的吸附效果和吸附等温过程。结果表明,当p H值3、投加量1 g/L、吸附时间120 min和温度35℃时,亚甲基蓝的吸附率都在98%以上。等温吸附过程很好的符合Langmuir模型。     

室温图案化聚甲基丙烯酸甲酯及在导电高分子中的应用

通过软印刷技术,利用界面作用力的差异,将聚甲基丙烯酸甲酯(PMMA)图案从软模板表面转移到基底表面。转移过程中具有高效(5 s)、室温及无需施加外压的特点。转移时间对PMMA的形貌高度无明显影响,改变旋涂速度和PMMA溶液浓度可以调节PMMA图案的高度。同时,通过氧等离子体刻蚀去除PMMA图案残留层,以此诱导聚吡咯(PPy)原位沉积图案化。     

Kinetics and equilibrium of dissolved oxygen adsorption on activated carbon

The macroscopic adsorption behavior of dissolved oxygen on a coconut shell-derived granular activated carbon has been studied in batch mode at 301 and 313 K for initial dissolved oxygen concentrations of 10-30 mg/l and oxygen/carbon ratios of 2-180 mg/g. BET (Brunauer, Emmett, and Teller) surface area, micropore volume, and pore size distribution were determined from N₂ isotherm data for fresh and used samples of carbon. The surface groups were characterized using Boehm titrations, potentiometric titrations, and FTIR study. The material is characterized by its high specific surface area , microporocity (micropore volume ), its basic character ( total basic groups) and its high iron content (15,480 ppm Fe). BET n-layer isotherm describes adsorption equilibrium suggesting cooperative adsorption and important adsorbate-adsorbate interactions. Kinetic data suggest a process dependent on surface coverage. At low coverage a Fickian, intraparticle diffusion rate model assuming a local equilibrium isotherm (oxygen dissociation reaction) adequately describes the process. The calculated diffusion coefficients (D) vary between and for initial oxygen concentration of 10 and 20 mg/l, respectively. Sensitivity analysis shows that the oxygen dissociation equilibrium constant determines the equilibrium concentration, whereas the diffusion coefficient controls the kinetic rate of the adsorption process having no effect at the final equilibrium concentration. A combined kinetic mass transfer model with concentration-dependent diffusion (parabolic form) has been developed and successfully applied on the dissolved oxygen adsorption system at high surface coverage. For equilibrium uptake of the estimated mean mass transfer coefficient and adsorption rate constant are and , respectively.     

The relation between the adsorption characteristics of polar organic compounds (alcohols and acids) and their orientation polarization on activated carbon

The high temperature adsorption of n-alcohols (methanol, ethanol, propanol and butanol) and the aliphatic acids (formic, acetic, propionic and buteric) was studied on steam activated carbon using micro Chromatographic technique. In the light of the theory of polarization, it was found that the adsorption of these polar alcohols depends on their orientation polarization. A relation was found between the high temperature adsorption characteristics and the orientation polarization of the alcohols and the aliphatic acids on activated carbon.     

Electrochemically enhanced adsorption of aniline on activated carbon fibers

For adsorptive separation processes, the adsorption rate and capacity are two important factors affecting the costs. This study describes the anodic polarization of activated carbon fibers (ACFs), which can enhance the adsorption rate and capacity of aniline. The electrosorption kinetics and the affecting factors (bias potential, electrolyte, and pH) of isotherms for aniline on ACFs were investigated. The adsorption/electrosorption of aniline on ACFs follow pseudo-first-order adsorption kinetics, and the adsorption rate improves with increasing bias potential. The electrosorption isotherms, which exhibit a variety of responses depending on bias potential, electrolyte and pH, follow the two classical models of Langmuir and Freundlich. With electrosorption of aniline from aqueous solution, a two-fold enhancement of adsorption capacity is achievable. The initial and saturated ACFs were characterized using scanning electron micrograph (SEM) and Fourier transform infrared spectroscopy (FT-IR). The SEM micrographs show that the surface of ACFs is not oxidized, which is also verified by cyclic voltammetry results. The FT-IR spectroscopy suggests that the interaction between aniline and ACFs is main weak physisorption instead of chemisorption. These experimental results suggest that the electrochemical polarization of ACFs can effectively improve the adsorption rate and capacity of aniline, which may be due to the enhanced affinity between aniline and ACFs instead of the oxidation on the surface of ACFs or in the solution.