微波加热化学活化法制备高比表面活性炭

以中间相炭微球为原料,KOH为活化剂,采用微波加热化学活化法在不同条件下制备出高比表面积活性炭,考察了活化前后中间相炭微球的结构变化与不同活化条件对炭微球性能的影响.研究表明:活化后中间相炭微球的石墨微晶结构被破坏,所制得的活性炭是无定形组织.活性炭比表面积和孔容随着KOH/MCMB的增大先增大后减小.KOH/MCMB较小时,比表面积和孔容随活化时间的延长达到最大值后不再发生变化,在KOH/MCMB较大时,比表面积和孔容随活化时间的延长先增大后减小.     

Influence of pretreatment and activation conditions in the preparation of activated carbons from anthracite

The influence of pretreatment and activation conditions on anthracite activation was investigated. Separation of low ash coals by using dense media was conducted to obtain appropriate raw materials for activation. Activated carbons were produced from crushed and granule coals by physical activation (steam or CO₂) and physical activation with chemical pretreatment in mild and strong conditions. Microporous activated carbons having a surface area of 900 m₂/g were produced by steam activation from granules with 60% burn-off for 3 hrs of activation. Chemical pretreatment at the strong condition increased the surface area by 30% as compared with non-treated activated carbons. Chemical pretreatment, in general, affected activation degree, so pore volume increased by 20% and burn-off increased remarkably at the identical activation conditions. CO₂ activation was proven to be an effective method for producing microporous activated carbons having an average pore diameter of 20 å.     

Steam and KOH activation of biochar: Experimental and modeling studies

Biochar was used as a precursor of activated carbon using physical (steam) and chemical (potassium hydroxide) activation processes. The effects of operating conditions for each activation method on the BET surface area of the product and reaction yield were investigated using central composite design (CCD). For both activation processes, quadratic models were developed, by Design-Expert software, for BET surface area and reaction yield. The optimum operating conditions were calculated by the models to produce physically and chemically activated carbons with large surface area and product yield. The optimum BET surface area and product yield of physical activation are, respectively, 643 m²/g and 56.9 wt%, and of chemically activated carbon are, respectively, 783 m²/g and 75.3 wt%, which showed good agreement with the experimental values. Average pore diameters of physically and chemically activated carbons were in the ranges of 13–26 Å and 13–15 Å, respectively.     

Enhanced mercury adsorption in activated carbons from biomass materials and waste tires

Agricultural residues and waste tires constitute an important source of precursors for activated carbon production. Activated carbons offer a potential tool for mercury emissions control. In this work, pine and oak wood, olive seed and tire wastes have been used for the preparation of activated carbons, in order to be examined for their mercury removal capacity. In the case of activated carbons produced from pine/oak woods and tire wastes, a two stage physical activation procedure was applied. Activated carbons derived from olive seeds were prepared by chemical activation using KOH. Pore structure of the samples was characterized by N₂ and CO₂ adsorption, while TPD-IR experiments were performed in order to determine surface oxygen groups. Hg° adsorption experiments were realized in a bench-scale adsorption unit consisting of a fixed-bed reactor. The influence of activation technique and conditions on the resulted activated carbon properties was examined. The effects of pore structure and surface chemistry of activated carbons were also investigated. Activated carbons produced from olive seeds with chemical activation possessed the highest BET surface area with well-developed micropore structure, and the highest Hg° adsorptive capacity. Oxygen surface functional groups (mainly lactones) seem to be involved in Hg° adsorption mechanism.     

The preparation of activated carbon from macadamia nutshell by chemical activation

Different structured activated carbons were prepared from macadamia nutshell by chemical activation with potassium hydroxide and zinc chloride. The influence of process variables on the carbons' pore structure was studied in order to optimise these parameters. The results were also compared with those previously obtained on the chemical activation of coal. The most important parameter in chemical activation with both chemical agents was found to be the impregnation ratio. Carbonization temperature is the second important variable which had significant effect on pore volume evolution. Under the experimental circumstances studied, the optimum conditions in preparation of carbons with high surface area and pore volumes with both chemical agents are identified.     

Role of microporosity and surface functionality of activated carbon in methylene blue dye removal from water

Activated carbons have been prepared from jute stick by both chemical and physical activation methods using zinc chloride and steam, respectively. They were characterized by evaluating surface area, iodine number, pore size distribution, and concentration of surface functional groups. The chemically activated carbon largely featured micropore structure, while the physically activated carbon mainly featured macropore structure. The specific surface area of chemically and physically activated carbons was 2,325 and 723 m ² /g, while the iodine number was 2,105 and 815mg/g, respectively. The concentration of surface functional groups was determined by Boehm titration method, which suggested that different types of surface functional groups are randomly distributed on chemical activated carbons, while it is limited for physical activated carbon. The microporosity along with surface functional groups provided a unique property to chemically activated carbon to adsorb Methylene Blue dye to a large extent. The adsorption of dye was also affected by the adsorption parameters such as adsorption time, temperature and pH. Comparatively, higher temperature and pH significantly facilitated dye adsorption on chemically activated carbon.     

复合活化剂制备稻壳活性炭影响因素及特性

以稻壳为原料,ZnCl₂-CuCl₂为复合活化剂,制备稻壳活性炭,并以BET比表面积和吸附性能为指标,通过正交试验对制备的工艺条件进行优化,并对制得的稻壳活性炭采用氮气吸附等温线、X射线衍射仪(XRD)表征。结果表明,稻壳可以被制得大比表面积活性炭。影响活性炭比表面积和吸附性能最重要的因素是氯化锌浓度和活化温度,最佳制备工艺条件是氯化锌浓度5 mol/L,氯化铜浓度 0.4 mol/L,活化温度500 ℃,活化时间2 h。该条件下制得的稻壳活性炭比表面积为1 924 m²/g,碘吸附值为1 041 mg/g,亚甲基蓝吸附值为 188 mg/g。     

Role of activated carbon structural properties and surface chemistry in mercury adsorption

In this work the performance of activated carbons prepared from raw and demineralised lignite for gas-phase Hg° removal was evaluated. A two-stage activation procedure was used for the production of the activated samples. In order to study the effect of mineral matter on pore structure development and surface functionality of the activated carbons, a demineralisation procedure involving a three-stage acid treatment of coals, was used, prior to activation. Hg° adsorption tests were realized in laboratory-scale unit consisted of a fixed-bed reactor charged with the tested activated samples. The examined adsorbent properties that may affect removal capacity were the pore structure, the surface chemistry and the presence of sulphur on the surface of activated carbons. The obtained results revealed that activated carbons produced from demineralised lignite posses a high-developed micropore structure with increased total pore volume and BET surface area. These samples exhibit enhanced Hg° adsorptive capacity. In all cases, mercury removal efficiency increased by sulphur addition. Finally, the starting material properties and activation conditions affect the concentration and the type of the oxygen groups on activated carbon surface, that have been determined with TPD-MS experiments.     

Synthesis of activated carbons by chemical activation of new anthracene oil-based pitches and their optimization by response surface methodology

This paper deals with the synthesis of new anthracene oil-based activated carbons by chemical activation with KOH. It focuses on the optimization of the processing conditions involved by means of surface response methodology. A factorial design (2³+3) in one block with four degrees of freedom was used to optimize the process, based on the responses BET surface area, total pore volume, mesopore volume, micropore volume and mol ratio CO:CO₂. The variables measured include KOH to pitch ratio (1:1, 3:1 and 5:1), activation temperature (700 up to 1000 °C) and pitch characteristics. The activation of anthracene oil-based pitch led to activated carbons with BET surface area values of 2880 m² g⁻¹. The factorial design expresses every response factor as a mathematical equation using the experimental variables. The most critical factor for each experiment design response has been identified from the analysis of variance (ANOVA). These mathematical models were also used to obtain the optimum processing conditions for the production of activated carbon with controlled properties. The experimental processing of the optimized activated carbons gave rise to a sample with BET, total pore volume, mesopore volume, micropore volume values which were in good agreement with those predicted by statistical analysis.     

Preparation of activated carbons by utilizing solid wastes from palm oil processing mills

Feasibility of producing activated carbons by utilizing solid wastes (extracted flesh fibre and seed shell) from palm oil processing mills was investigated. The effects of activation conditions (CO₂ flow rate, activation temperature and retention time) on the characteristics of the activated carbons, i.e. density, porosity, BET surface area, pore size distribution and surface chemistry were studied. In this study, the optimum conditions for activation were an activation temperature of 800 °C and a retention time of 30 min for fiber or 50 min for shell, which gave the maximum BET surface area. Pore size distribution revealed that the shell-based activated carbons were predominantly microporous whilst fiber activated carbon had predominant mesopores and macropores, suggesting the application of shell and fiber activated carbon as adsorbents for gas-phase and liquid-phase adsorption, respectively. This was confirmed by further gas- and liquid-phase adsorption tests.     

Efficient CO2 Capture by Ultra‐high Microporous Activated Carbon Made from Natural Coal

Efficient CO₂ capture capabilities of activated carbons prepared from natural coal are presented. The preparation method involved simple chemical activation using wet impregnation or dry physical mixing of the raw sample with activating agents like KOH or NaOH. The activated materials were characterized for their structural and textural properties by different analysis techniques. The activated samples exhibited well‐developed porosity, large surface area, and high pore volumes and had other active elements like oxygenated functional groups. These groups modified the surface energy of the resultant samples. The superior performance of the activated carbons was attributed to several factors, including large surface area, presence of narrow micropores, and oxygenated functional groups on the surface.     

Effects of chemical modification of petroleum cokes on the properties of the resulting activated carbon

Activated carbons have been prepared from petroleum cokes by the combination of a chemical treatment with HClO₄ or H₂O₂ and a chemical activation with KOH at a constant KOH/coke ratio of 3/1. The influence of different chemical treatments on the properties of the activated carbon precursors and final carbons activated with KOH was invested by using XRD, FTIR, and BET techniques. XRD results indicated that the value of interplanar distance d₀₀₂ increased by chemical treatment and the disappearance of the peak corresponding to 0 0 2 faces correlated to high specific surface area. FTIR studies showed that chemical modification promoted the formation of surface oxygen functionalities. Significant effects on BET surface area, pore texture and iodine adsorption capacity were evidenced. The results show that chemical modification prior to activation dramatically increased the BET surface area and total pore volume of the resulting activated carbon. Modified petroleum coke based activated carbon with chemical activation had higher specific surface area (2336 m²/g) and better iodine adsorption value (1998 mg/g).     

Phosphoric and boric acid activation of pine sawdust

Chemical activation of pine sawdust using aqueous solutions of phosphoric and boric acid was studied. Thermogravimetric analyses of the impregnated lignocellulosic precursor as well as their reactivities are presented. The role of the activating agents in the thermal decomposition of the precursor and their effects on the development of porosity in activated carbons is discussed. The use of boric acid as activating agent and a final heat treatment temperature (HTT) of 600 °C produced some porosity and activated carbons with a surface area of 600 m² g^?1. With a HTT of 450 °C, molecular sieve‐like materials were produced. In contrast, phosphoric acid activation produced activated carbons with high surface areas. The amount of phosphoric acid retained in the precursor was, as expected, a function of the initial concentration as well as the impregnation time and temperature. The fact that the activated carbon porosity increases with the phosphoric acid content per gram of precursor was confirmed. The use of 6 M phosphoric acid solution and HTT of 450 °C produced the activated carbon with the highest surface area, about 1600 m² g^?1. The high degree of microporosity which developed in phosphoric acid‐activated carbons is related to the low reactivity during the thermal treatment of chemical activation. The presence of up to 10% oxygen during HTT with phosphoric acid activation caused only small textural changes. Copyright © 2003 Society of Chemical Industry     

活性炭表面化学改性技术的研究进展与展望

活性炭表面官能团和杂原子的数量与种类是影响活性炭吸附性能的重要因素。国内外研究表明,通过对活性炭进行表面改性可以显著改善活性炭对特定物质的吸附性能。文章简要介绍了活性炭的物理和化学性质,并从活性炭材料的表面化学性质方面论述了近年来国内外在活性炭材料改性方面的研究进展,最后提出了活性炭表面改性技术的发展方向和趋势。     

Activated Carbon by Potassium Carbonate Activation from Pine Sawdust (Pinus montezumae Lamb.)

Activated carbon (AC) was gained from Pinus montezumae (PM) wood sawdust and chemical activation with K₂CO₃ was used for obtaining activated carbons. Variations in reaction conditions such as temperature, impregnation ratio (IR), and activation time were carried out to study their influence on the specific surface area (SSA) and average pore volume (APV) in AC. Materials were analyzed by means of Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM), and X-ray diffraction (XRD) to determine the functional groups, pore structure, and morphology of pine sawdust and activated carbons. Activated carbons were amorphous in nature with some crystalline regions.     

Spherical carbons: Synthesis,characterization and activation processes

Spherical carbons have been prepared through hydrothermal treatment of three carbohydrates (glucose, saccharose and cellulose). Preparation variables such as treatment time, treatment temperature and concentration of carbohydrate have been analyzed to obtain spherical carbons. These spherical carbons can be prepared with particle sizes larger than 10 μm, especially from saccharose, and have subsequently been activated using different activation processes (H₃PO₄, NaOH, KOH or physical activation with CO₂) to develop their textural properties. All these spherical carbons maintained their spherical morphology after the activation process, except when KOH/carbon ratios higher than 4/1 were used, which caused partial destruction of the spheres. The spherical activated carbons develop interesting textural properties with the four activating agents employed, reaching surface areas up to 3100 m²/g. Comparison of spherical activated carbons obtained with the different activating agents, taking into account the yields obtained after the activation process, shows that phosphoric acid activation produces spherical activated carbons with higher developed surface areas. Also, the spherical activated carbons present different oxygen groups’ content depending on the activating agent employed (higher surface oxygen groups content for chemical activation than for physical activation).     

Vanadium(V) Removal by Adsorption onto Activated Carbon Derived from Starch Industry Waste Sludge

This study examines the adsorption potential of activated carbons for vanadium (V) removal from aqueous solution. Activated carbons were produced via chemical activation of waste treatment sludge from the starch industry. Specific surface area and pore sizes of waste sludge samples were determined through chemical activation and pyrolysis. Experimental data indicated that sludge samples had micropore structure and specific surface area of up to 1196 m²/g. First-order and second-order models were applied to determine adsorption kinetics. Freundlich, Langmuir, and Dubinin–Radushkevich isotherms were used to analyze equilibrium data of adsorption. Equilibrium adsorption data showed the best fit to the Freundlich isotherm. Adsorption of vanadium (V) follows second-order kinetic models. Maximum adsorption was observed at pH 4.0. Langmuir adsorption capacity was found to be 37.17 mg/g. The results of the study indicated that activated carbon obtained from industrial sewage sludge was effective in removing vanadium from aqueous solutions, which creates a significant advantage for treatment of industrial wastewaters and management of solid wastes.     

Removal of Cu (II) from water pollutant with Tunisian activated lignin prepared by phosphoric acid activation

Activated lignin with a relative high BET surface area and a well-developed porosity has been prepared from Tunisian deposit lignin, by H₃PO₄ activation at various process conditions. Physical and chemical properties of activated carbons produced, implying BET surface area, Boehm titration, Fourier Transform Infrared Spectroscopy (FTIR) and thermogravimetric analysis (TGA), were investigated. It was found that the maximum surface area reached at the carbonization temperature of 500 °C in H₃PO₄ activation, and that the activated lignin prepared from lignin acidic activation, showed a surface area of 463 m²/g. The potential application of these carbons for the removal of heavy metal contaminant, has been investigated by measuring their adsorption capacities for Cu (II) as representative of main local toxic contaminant found in industrial wastewaters. The results obtained compare well and even favourably with those reported in literature for other unconventional materials.     

Process optimization of K2C2O4-activated carbon from kenaf core using Box–Behnken design

Potassium oxalate was evaluated as a new activating agent for preparation of kenaf core-based activated carbons. The preparation conditions were optimized through Box–Behnken design (BBD) to maximize I₂ and methylene blue (MB) adsorption values. Two quadratic models were developed to correlate the preparation variables namely activation temperature, impregnation ratio and activation time for both responses. The activated carbon produced at the optimum combination of process parameters showed 1161 mg/g and 330 mg/g of I₂ and MB uptakes, which were in excellent agreement with the predicted values from the models. Porosity parameters and scanning electron microscopy were used to investigate the obtained optimal sample. The results reveal that K₂C₂O₄ could be recommended as a promising effective activating agent for producing activated carbons from kenaf core with high surface area and potentially desirable dye removal capacity.     

Preparation and characterisation of demineralised tyre derived activated carbon

The effect of demineralisation and activation conditions on the physical and chemical properties of activated carbon adsorbents produced from waste tyre char has been investigated. Experimental data showed that hydrochloric acid treatment prior to the activation is able to remove certain mineral contents such as zinc, calcium, sodium and others from the tyre char. The removal of some of the components which have catalytic effect on the activation increase the yield of the activated carbon and at the same time lower the ash content of the tyre activated carbon. The tyre demineralised activated carbons are generally mesoporous with a surface area up to 960 m²/g and therefore are comparable to commercial products. The adsorption of phenol onto the tyre activated carbon was also tested and the Redlich–Peterson equilibrium isotherm model gave the best-fit to experimental data for the phenol using the non-linear error functions.