褐煤活性炭吸附苯酚的研究

The feasibility and adsorption effect of lignite activated carbon for phenol removal from aqueous solutions were evaluated and investigated. A series of tests were performed to look into the influence of various experimental parameters such as contact time, initial phenol concentration, temperature, and pH value on the adsorption of phenol by lignite activated carbon. The experimental data were fitted well with the pseudo-second-order kinetic model. The adsorption is an endothermic process and conforms to Freundlich thermodynamic model. The results indicate that the lignite activated carbon is suitable to be used as an adsorbent material for adsorption of phenol from aqueous solutions.     

KOH activated lignin based nanostructured carbon exhibiting high hydrogen electrosorption

Carbon materials capable of efficient hydrogen electrosorption at ambient conditions can be used for negative electrode material in chemical power sources, competitive for metallic hydride alloys. This paper describes physical, chemical and electrochemical properties of active carbon (LAC) produced from lignin processed by standard carbonization and KOH activation at temperature of 950 °C. Microporous carbon with BET surface of 1946 m²/g obtained in such conditions has a complex porous structure with a considerable number of supermicropores and small mesopores (ca. 50%). As a result, efficient hydrogen electrosorption of 510 mA h/g (1.89 wt% in meaning of energy storage) is obtained and favorable discharge characteristics at current densities up to 1 A/g.     

Enhancement of electrosorption capacity of activated carbon fibers by grafting with carbon nanofibers

The composite films of activated carbon fibers (ACFs) and carbon nanofibers (CNFs) are prepared via chemical vapor deposition of CNFs onto ACFs in different times from 0.5 to 2 h and their electrosorption behaviors in NaCl solution are investigated. The morphology, structure, porous and electrochemical properties are characterized by scanning electron microscopy, transmission electron microscopy, Raman spectroscopy, N₂ adsorption at 77 K, contact angle goniometer and electrochemical workstation, respectively. The results show that CNFs have been hierarchically grown on the surface of ACFs and the as grown ACF/CNF composite films have less defects, higher specific capacitances, more suitable mesoporous structure and more hydrophilic surface than the pristine ACFs, which is beneficial to their electrosorption performance. The ACFs/CNFs with CNFs deposited in 1 h exhibit an optimized NaCl removal ratio of 80%, 55% higher than that of ACFs and the NaCl electrosorption follows a Langmuir isotherm with a maximum electrosorption capacity of 17.19 mg/g.     

活性炭纤维电吸附去除四环素的研究

为了提高活性炭纤维(ACF)对有机污染物的吸附去除率,将活性炭纤维固定在形稳性阳极电极(DSA)上,借助电场提高其吸附率.以四环素为目标污染物,考察了外加电压、四环素初始浓度、活性炭纤维量、时间以及初始pH条件对电吸附效果的影响.结果表明,在60min的反应时间内,当外加电压为1000mV时活性炭纤维对四环素的去除率最...     

Fundamentals of electrosorption on activated carbon for wastewater treatment of industrial effluents

The potential of electroadsorption/desorption on activated carbon for waste water treatment of industrial effluents is studied. Adsorption isotherms of hydrophobic differently charged model substances on activated carbon were measured in order to obtain specific information about the influence of the charge (+1,–1 and 0) on the adsorbability of comparable, aromatic species and the influence of the bed potential on the adsorption equilibria. In all these cases the adsorption equilibria show a dependence on applied potential in electrolyte of approximately 1m ionic strength. With electrosorption from aqueous solution, a fivefold enhancement of the concentration in one potential controlled adsorption/desorption cycle is achievable. The use of the solvent methanol instead of water for desorption allows for a concentration enhancement by a factor of hundred in the desorptive step. The adsorption capacity of the activated carbon changes only slightly with cycle number. Two cell designs for the performance of potential controlled adsorption/desorption cycles on the large scale are discussed.     

Adsorption and electrosorption of mercury(II) acetate onto activated charcoal cloth from aqueous solution

The adsorption of mercury(II) acetate from aqueous solution onto an activated charcoal cloth (ACC) has been studied using shaking and flow-through techniques. It was found that the adsorption capacities of the ACC shaken in mercury(II) acetate solution could reach 2 × 10⁻³ mol g⁻¹ at pH 5.5. The flow-through experiments gave lower adsorption results because of a decreased concentration gradient and limitations due to film diffusion. The latter could be overcome by increasing the flow-rate. Application of an electrical potential to the ACC during flow-through experiments, increased the uptake of mercury(II). This was most marked when the applied polarity was negative, −1 volt, with respect to a Calomel reference electrode. Then the diffusion coefficient reached a constant value and the cloth continued to remove mercury(II) out of the solutions passing through it.     

活性炭改性及对废水中苯酚的吸附研究

采用醋酸和高温热处理改性活性炭,用于吸附废水中的苯酚,探究pH、温度、苯酚浓度、时间对吸附性能的影响。结果表明,吸附苯酚溶液的优化条件为:吸附剂为经65%醋酸改性后700℃煅烧的改性活性炭,其用量为0.5 mg/L,苯酚浓度100 mg/L,pH=3,吸附温度40℃,时间80 min。在此条件下,苯酚的吸附量达112.36 mg/g。在25℃下,静态和动态实验表明,活性炭对苯酚的吸附更满足Freundlich吸附模型和准二级动力学方程。     

Increased chemisorption onto activated carbon after ball-milling

Activated carbon has been milled for up to 1000 h in a laboratory-scale tumbling ball mill under a vacuum. Thermogravimetric (TG) analysis of the powder in argon showed an increasing mass loss with milling time indicating the presence of chemisorbed gas. TG Fourier transform infrared spectrometry showed the gas was a mixture of water, CO₂ and an unidentified gas (probably oxygen). BET surface area measurements showed a decreasing surface area with milling time, however, this was shown to be massively in error for the longer milling times due to the presence of the chemisorbed gas. The area occupied by the chemisorbed gas increased from 40 to 80% of the true surface area which was almost constant at 1258±27 m² g⁻¹ for all three powders. These results show that extremely large errors may be made when using BET analysis to determine the surface area of powders, especially those where the surface activity is substantially increased during processing.     

Adsorption of phenol and 1-naphthol onto XC-72 carbon

XC-72 carbon (XC-72) was characterized by SEM, XPS, N₂ adsorption-desorption, particle size distribution analysis and potentiometric acid-base titration. The adsorption of phenol and 1-naphthol on XC-72 was studied as a function of contact time, pH, adsorbent content and temperature. The kinetic adsorption data were described well by the pseudo-second-order model. The adsorption isotherms of phenol were described well by Freundlich model, while the adsorption isotherms of 1-naphthol were fitted well by Langmuir model. The results demonstrated that XC-72 had much higher adsorption capacity for 1-naphthol than for phenol. The adsorption thermodynamic data were calculated from the temperature-dependent adsorption isotherms at T=293, 313 and 333 K, and the results indicated that the adsorption of phenol was an exothermic process, whereas the adsorption of 1-naphthol was an endothermic process. XC-72 is a suitable material for the preconcentration of phenol and 1-naphthol from large volumes of aqueous solutions.     

Mechanism of lithium electrosorption by activated carbons

Sorption of Li⁺ ions from diluted aqueous medium has been investigated on activated carbons. The pure chemical sorption is controlled by pH of the solution as well as by the nature and concentration of surface groups, showing cation-exchanger properties of the carbon substrate. Lithium sorption is enhanced by applying a cathodic polarization to the activated carbon, and reversing voltage allows a full desorption of trapped lithium. In the selected conditions of investigation, the electrostatic attraction is not responsible of ions sorption as demonstrated by the low values of capacitance measured at constant potential or current. Our experiments proved that local high pH values at the carbon cathode, due to reduction of water, are the cause for increasing the dissociation of surface groups and consequently the amount of adsorbed lithium ions. On the other hand, with positive polarization, water is oxidized at the carbon surface, and proton exchange favors the release of lithium ions to the solution.     

Behavior of phenol adsorption on thermal modified activated carbon

Adsorption process is acknowledged as an effective option for phenolic wastewater treatment. In this work, the activated carbon(AC) samples after thermal modification were prepared by using muffle furnace. The phenol adsorption kinetics and equilibrium measurements were carried out under static conditions at temperature ranging from 25 to 55 °C. The test results show that the thermal modification can enhance phenol adsorption on AC samples. The porous structure and surface chemistry analyses indicate that the decay in pore morphology and decrease of total oxygen-containing functional groups are found for the thermal modified AC samples. Thus, it can be further inferred that the decrease of total oxygen-containing functional groups on the modified AC samples is the main reason for the enhanced phenol adsorption capacity. For both the raw sample and the optimum modified AC sample at 900 °C, the pseudo-second order kinetics and Langmuir models are found to fit the experimental data very well. The maximum phenol adsorption capacity of the optimum modified AC sample can reach144.93 mg·g-1which is higher than that of the raw sample, i.e. 119.53 mg·g-1. Adsorption thermodynamics analysis confirms that the phenol adsorption on the optimum modified AC sample is an exothermic process and mainly via physical adsorption.     

活性炭纤维吸附废水中酚的研究

通过静态和动态试验对活性炭纤维吸附废水中的酚进行了研究,测定了吸附等温线,考察了活性炭纤维的用量、苯酚浓度,以及过柱流速对吸附的影响.结果表明,活性炭纤维对苯酚的动态吸附容量为256 mg/g随着活性炭纤维用量的增加,处理水稳定时间延长;苯酚浓度越高,穿透时间越短;过柱流速越大,穿透时间越短;吸附饱和后的活性炭纤维再生后,吸附容量几乎不变.     

活性炭对苯酚的吸附研究

进行了活性炭处理含苯酚废水的应用研究,考察了影响苯酚吸附效果的因素。确定了处理水中苯酚的最佳条件:吸附平衡时间为30 min;最佳pH值为6左右;苯酚初始浓度为10 mg/L;投炭量为20～25 mg/L;苯酚的吸附率高达97.4%;温度对苯酚吸附率的影响不明显。研究了活性炭对苯酚的吸附动力学特性,分别用伪一级动力学方程、伪二级动力学方程、修正伪一级动力学方程和颗粒内扩散模型进行拟合,对于不同浓度的苯酚废水都只有伪二级动力学方程拟合程度比较高,伪二级动力学方程更为真实地反映苯酚在活性炭上的吸附机理。     

活性炭纤维对电镀废水中镍的电吸附性能研究

研究了活性炭纤维电极电吸附法对模拟电镀废水中Ni2+的去除效果及其影响因素,确定了最佳电极电位、板间距、活性炭纤维表面积、溶液初始浓度,并作出相应的吸附平衡分析。实验结果表明:在施加电极电位为1.0 V,活性炭纤维表面积为50 cm2,电极板间距为30 mm,Ni2+初始质量浓度为20 mg/L条件下,达到平衡后,Ni2+的去除率可达88.15%。     

Adsorption of phenol onto activated carbons having different textural and surface properties

Adsorption of phenol in aqueous phase onto activated carbons (ACs) having different textural and surface properties has been considered. Six types of ACs were used: three were commercial, and three were obtained from Kraft lignin chemically activated with sodium hydroxide, potassium hydroxide or ortho-phosphoric acid. The apparent surface areas of the commercial ACs varied from 620 to 1320 m²/g, while ACs made from lignin presented surface areas as high as 1300 m²/g and 2900 m²/g when prepared with H₃PO₄ and alkaline hydroxides, respectively; moreover, the highest proportion of microporosity was found for ACs derived from lignin. A kinetic study was carried out, showing that the phenol adsorption data may be correctly adjusted, for all the ACs tested, by an equation corresponding to a pseudo second-order chemical reaction. Freundlich, Langmuir and Tempkin equations were tested for modelling the adsorption isotherms at equilibrium, and it was concluded that Langmuir model fitted adequately the experimental data. However, Tempkin model fitted even better the adsorption data obtained with ACs derived from lignin activated with alkaline hydroxides, which are characterized by the highest number of surface groups. Remarkably high phenol adsorption capacities were found for the ACs prepared by activation of Kraft lignin with NaOH and KOH: 238 and 213 mg/g of AC, respectively. Finally, the adsorption of phenol was found to depend not only on the micropore volume, but also on the total amount of carbonyl and basic groups and on the ratio of acid to basic groups.     

Comparison of catalytic ozonation of phenol by activated carbon and manganese-supported activated carbon prepared from brewing yeast

Activated carbon (AC) was prepared using brewing yeast as precursor by chemical activation and manganese was supported on activated carbon (Mn/AC) by adsorption-activation method. The characterizations of prepared AC and Mn/AC and their performance as ozonation catalysts was tested. The results indicated that the crystalline phase of supported manganese was MnO. The total BET surface areas of prepared AC and Mn/AC were found to be 1603.0 m²/g and 598.9 m²/g, with total pore volumes of 1.43 and 0.49 cm³/g, respectively. The average pore diameters of AC and Mn/AC were found to be 3.5 nm and 3.3 nm. Adsorption capacities of phenol onto the produced AC and Mn/AC were determined by batch test, at 25 °C and pH 7. Langmuir and Freundlich isotherm models were used to fit the isotherm experimental data, and the Langmuir isotherm model fitted these two adsorption systems well. The maximum uptakes of phenol by AC and Mn/AC were estimated to be 513.5 mg/g and 128.2 mg/g. The presence of AC prepared from brewing yeast was advantageous for TOC reduction of phenol solution compared with single ozonation, and the greatest TOC removal efficiency was obtained in the presence of Mn/AC. All ozonation reactions followed the pseudofirst-order kinetics model well, the degradation rate of phenol was enhanced in the presence of catalysts, and the more pronounced degradation rate was achieved in O₃/Mn/AC system. The rate constants were determined to be 2.16×10⁻² min⁻¹ for O₃ alone, 5.70×10⁻² min⁻¹ for O₃/AC and 6.82×10⁻² min⁻¹ for O₃/Mn/AC.     

Adsorption of Imazamox herbicide onto Filtrasorb 400 activated carbon

Imazamox is an imidazolinone herbicide, a new class of pesticides, which can exist as cationic, anionic or neutral species in water. The adsorption isotherms of Imazamox onto Filtrasorb 400 (F400) activated carbon were determined varying the pH and the ionic strength of the aqueous medium. The results show that ionic strength has no significant effect on Imazamox uptake, contrary to pH, and that F400 has a high affinity for Imazamox. Moreover, it is found that Imazamox adsorbs onto F400 as its neutral form. The best fit of the experimental points is obtained with the Langmuir–Freundlich model, consistent with surface site heterogeneity. Finally, calculating Langmuir–Freundlich isotherms for various constant pH values, it is shown that the two plateaus observed in the experimental isotherms obtained at free pH are due to the variation of the pH along the isotherms.     

Adsorption of saccharides from aqueous solution onto activated carbon

The Freundlich's adsorption constants of 13 saccharides and 4 polyhydric alcohols from aqueous solutions onto an activated carbon have been determined and correlated with various physical constants. A good linear relationship is obtained between the adsorption constants and the physical constant such as molecular refraction or parachor. Further, the adsorption isotherms of saccharides can be predicted from the carbon atom number and the oxygen atom number in the molecular formula.