椰壳纤维基高比表面积中孔活性炭的制备

以椰壳纤维为原料,制备高比表面积中孔活性炭.采用正交试验设计实验方案,研究KOH和NaOH复合活化法制备活性炭的实验方案与工艺条件.考察了活化剂配比、炭化温度、活化温度、时间和升温速率对所制活性炭吸附性能的影响.在最佳工艺条件下,所制活性炭的比表面积达到2032m2/g,中孔发达,特别是2nm～4nm的,中孔比例达到28%.活性炭对的碘吸附值为1435mg/g,亚甲基蓝吸附值为495mg/g,产率为49%.     

Removal of organic compounds by alginate gel beads with entrapped activated carbon

The adsorption of alginate gel (AG) beads and AG with activated carbon entrapped (AG–AC) beads prepared using different types of metal ions were investigated by measuring the removal of several organic compounds with different charges and size. AG–AC beads prepared in a CaCl₂ solution adsorbed strongly positively charged compounds as well as electrically neutral and low molecular weight compounds such as p-chlorophenol. However, a high molecular weight humic acid was not adsorbed by AG–AC. The AG–AC selectively adsorbed p-chlorophenol from a humic acid solution. The adsorption capacity obtained from the adsorption isotherm of AC entrapped in AG was compared with that of AC. The AG–AC beads prepared in a solution of FeCl₃ were able to specifically adsorb negatively charged gallic acid. Thus, entrapping AC into AG resulted in the selective adsorption.     

Comparisons of sorbent cost for the removal of Ni2+ from aqueous solution by carbon nanotubes and granular activated carbon

The reversibility of Ni2+ sorption by NaOCl oxidized single-walled carbon nanotubes (SWCNTs), multiwalled carbon nanotubes (MWCNTs) and granular activated carbon (GAC) was investigated to evaluate their repeated availability performance in water treatment. Under the same conditions, the SWCNTs and MWCNTs possess more Ni2+ sorption capacities and show better reversibility of Ni2+ sorption and less weight loss after being repeated sorption/desorption processes than the GAC, suggesting that they are effective Ni2+ sorbents and can be reused through many cycles of water treatment and regeneration. A statistical analysis on the replacement cost of these sorbents revealed that SWCNTs and MWCNTs can be possibly cost-effective Ni2+ sorbents in water treatment regardless of their high unit cost at the present time.     

石油焦系超级活性炭的孔结构控制

采用KOH活化法从大庆石油焦制得超级活性炭，而后对其进行微孔和中孔的调控。中孔调控采用热处理法，所得超级活性炭的中孔率在85％以上，比表面积大于1500m^2／g。同时对热处理后的超级活性炭进行表面硝酸氧化，引入部分含氧官能团。60min酸处理效果明显，羧基的增加量是20min酸处理的9倍。处理后的超级活性炭更适合作催化剂载体。微孔的控制采用化学气相炭沉积法（以苯为碳源），所得超级活性炭的微孔率从51％增加到87％。对CO2和CH4的分离能力从30mg／g提升到47mg／g，具有良好的筛分效果。     

Use of adsorption using granular activated carbon (GAC) for the enhancement of removal of chromium from synthetic wastewater by electrocoagulation

The present work deals with removal of hexavalent chromium from synthetic effluents in a batch stirred electrocoagulation cell with iron-aluminium electrode pair coupled with adsorption using granular activated carbon (GAC). Several working parameters such as pH, current density, adsorbent concentration and operating time were studied in an attempt to achieve higher removal capacity. Results obtained with synthetic wastewater revealed that most effective removal capacities of chromium (VI) could be achieved when the initial pH was near 8. The removal of chromium (VI) during electrocoagulation, is due to the combined effect of chemical precipitation, coprecipitation, sweep coagulation and adsorption. In addition, increasing current density in a range of 6.7-26.7mA/cm2 and operating time from 20 to 100min enhanced the treatment rate to reduce metal ion concentration below admissible legal levels. The addition of GAC as adsorbent resulted in remarkable increase in the removal rate of chromium at lower current densities and operating time, than the conventional electrocoagulation process. The method was found to be highly efficient and relatively fast compared to existing conventional techniques.     

Effects of adsorbent dose, its particle size and initial arsenic concentration on the removal of arsenic, iron and manganese from simulated ground water by Fe3+ impregnated activated carbon

This paper presents the observations of the study on arsenic removal from a contaminated ground water (simulated) by adsorption onto Fe³⁺ impregnated granular activated carbon (GAC-Fe). Fe²⁺, Fe³⁺ and Mn²⁺ have also been considered along with arsenic species in the water sample. Similar study has also been done with untreated granular activated carbon (GAC) for comparison. The effects of adsorbent dose, particle size of adsorbent and initial arsenic concentration on the removal of As(T), As(III), As(V), Fe²⁺, Fe³⁺ and Mn²⁺ have been discussed. Under the experimental conditions, the optimum adsorbent doses for GAC-Fe and GAC have been found to be 8 g/l and 24 g/l, respectively with an agitation time of 15 h. Particle size of the adsorbents (both GAC and GAC-Fe) has shown negligible effect on the removal of arsenic and Fe species. However, for Mn removal the effect of adsorbent particle size is comparatively more. Percentage removal of As(T), As(V) and As(III) increase with the decrease in initial arsenic concentration (As₀). However, the increase in percentage removal of all the arsenic species with decrease in As₀ are less for higher value of As₀ (3000–500 ppb) than those of the lower value of As₀ (500–10 ppb). The % removal of As(T), As(III), As(V), Fe, and Mn were 95%, 92.4%, 97.6%, 99% and 41.2%, respectively when 8 g/l GAC-Fe was used at the As₀ value of 200 ppb. However, for GAC these values were 55.5%, 44%, 71%, 98% and 97%. The pH and temperature of the study were 7 ± 0.1 and 30 ± 1 °C, respectively.     

椰壳类活性炭孔隙结构对苯并噻吩脱附活化能的影响

主要研究活性炭孔隙结构对苯并噻吩脱附活化能及吸附性能的影响.使用ASAP 2010测定了3种椰壳制活性炭SY-6、SY-13和SY-19的BET比表面及其孔隙结构,采用程序升温脱附技术(TPD)测定了苯并噻吩在3种活性炭上的脱附活化能,用静态吸附法进行了苯并噻吩在不同活性炭上的吸附等温线,并讨论了活性炭孔隙结构对苯并噻吩脱附活化能及吸附性能的影响.结果表明,3种活性炭SY-6、SY-13和SY-19的比表面积分别为1106、1070和689m2/g,其平均孔径分别为1.96、2.58和2.16nm.苯并噻吩在SY-6、SY-19和SY-13活性炭上的脱附活化能依次为58.84、53.02和42.57kJ/mol,3种活性炭对苯并噻吩吸附容量的大小依次为SY-6＞SY-19＞SY-13.活性炭平均孔径越小,其表面对苯并噻吩的作用力越大,苯并噻吩在其表面上的脱附活化能越大.Freundlich模型能够较好的来描述苯并噻吩在活性炭上的吸附.     

Fluidisation characteristics of granular activated carbon in drinking water treatment applications

Granular activated carbon (GAC) filtration is an important unit operation in drinking water treatment. GAC filtration is widely used for its filtration and adsorption capabilities as a barrier for undesired organic macro- and micro-pollutants. GAC filtration consists of two successive phases: adsorption and filtration, capturing the impurities from the water in conjunction with a backwash procedure in which the suspended particles are flushed out of the system. Available literature predominantly focusses on adsorption. A less frequently discussed but nevertheless equally crucial aspect of this operation is the backwash procedure of GAC beds. To prevent accumulation of suspended particles and to avoid additional operation costs, optimal backwashing is required. Another factor is sustainability: water utilities are showing increasing interest in exploring new sustainable GAC media. As these have different bed expansion tendencies due to different GAC characteristics with varying geometries, operational developments are needed for prediction models to estimate the expansion degree during backwashing. The prediction of the bed expansion of GAC is complex as the particles are non-spherical, porous and polydisperse. Through a combination of advanced particle laboratory and fluidisation experiments, we demonstrate a new approach which leads to an improved expansion prediction model for the backwashing of GAC filters.     

Surface modification of activated carbon fabric with ozone. Part 2: Thermal analysis with TGA-FTIR and DTA

Two samples of activated carbon fabrics (ACF) with very high surface area (>1300 to >1800 m²/g) fully ozonized in the part 1 of this study were analyzed by thermogravimetric analysis (TGA) coupled both with differential thermal analysis (DTA) and FT-IR spectroscopy (TGA-FTIR). The adsorbed water and the amount of oxygenated functional groups were determined. The ozonized ACF shows an exothermal decomposition at about 181–189°C which may be due at least in part to the decomposition of ozonide and/or peroxide groups. The TGA-FTIR has revealed that the main products released from the thermal decomposition are CO₂ followed by CO. Formic acid was detected only in correspondence to the exothermal transition at 181°C and was taken as a proof of the decomposition of secondary ozonides.     

Surface modification of activated carbon fabric with ozone,part 1: Kinetics and oxidation degree

Two samples of activated carbon fabrics (ACF) with very high surface area (>1300 to >1800 m²/g) were reacted with ozone inside a closed flask under static conditions. The kinetics of ozone decomposition and reaction with the ACF surface was measured in the gas phase using Fourier transform infrared analysis (FT-IR) spectroscopy. The ozone consumption under these conditions was following the pseudofirst-order kinetics law and was accompanied by the production of CO₂ and CO. The ozone-oxidized ACF were studied by FT-IR spectroscopy following the growth of key oxidized functional groups, i.e. phenolic OH, ketone groups intended as carboxyl, lactone, and anhydride, as well as quinone groups as a function of the amount of ozone reacted. The weight uptake of the ACF reacted with ozone was followed gravimetrically. The ACF having >1800 m²/g was able to reach a weight increase of 25% of its original weight due to the formation of oxygenated surface functional groups. Raman spectroscopy was used for the evaluation of defective structures formed in ACF because of ozonization reaction.     

Surface modification of activated carbon fabric with ozone. Part 3: Thermochemical aspects and electron spin resonance

It is shown that the differential scanning calorimetry (DSC) analysis of water desorption from activated carbon fabric (ACF) surfaces having different degrees of oxidation, is a valid alternative to immersion calorimetry in determining the desorption/adsorption energy of an adsorbate on the oxidized ACF surfaces. Processing the DSC endotherm relative to water desorption through the Clausius-Clapeyron equation it is possible to calculate either the water desorption energy from the oxidized ACF surfaces and also the hydrogen bond energy through which the water molecules are bound to the oxidized ACF surface. The DSC analysis of the ozonized ACF has revealed that secondary ozonides and peroxides are formed together with other oxygenated groups on the ACF surface, and were detected through an exothermal transition with two peaks at 118°C and 142°C with the measured decomposition enthalpy directly proportional to the degree of oxidation of the ACF surface. The ESR analysis on pristine ACF has revealed the presence of clustered paramagnetic centers. The reaction of the ACF with ozone greatly enhances the ESR signal since more free radicals are formed on the surface mainly in the form of oxygen-centered peroxide-type.     

Synergy between surface adsorption and photocatalysis during degradation of humic acid on TiO2/activated carbon composites

A photocatalyst comprising nano-sized TiO(2) particles on granular activated carbon (GAC) was prepared by a sol-dipping-gel process. The TiO(2)/GAC composite was characterized by scanning electron microscopy (SEM), X-ray diffractiometry (XRD) and nitrogen sorptometry, and its photocatalytic activity was studied through the degradation of humic acid (HA) in a quartz glass reactor. The factors influencing photocatalysis were investigated and the GAC was found to be an ideal substrate for nano-sized TiO(2) immobilization. A 99.5% removal efficiency for HA from solution was achieved at an initial concentration of 15 mg/L in a period of 3h. It was found that degradation of HA on the TiO(2)/GAC composite was facilitated by the synergistic relationship between surface adsorption characteristics and photocatalytic potential. The fitting of experimental results with the Langmuir-Hinshelwood (L-H) model showed that the reaction rate constant and the adsorption constant values were 0.1124 mg/(L min) and 0.3402 L/mg. The latter is 1.7 times of the calculated value by fitting the adsorption equilibrium data into the Langmuir equation.     

Surface adsorption and wetting properties of amorphous diamond-like carbon thin films for biomedical applications

Diamond-like carbon (DLC) thin films have unique properties for biological and medical applications due to their excellent bio-compatibility, chemical inertness, and superior mechanical properties. It is important to understand the surface properties of DLC thin films for these applications. In this work, we showed that after DLC deposition, NiTi surfaces became much smoother by choosing suitable deposition conditions. Adsorption and wetting properties of DLC films were studied. The adsorption properties of DLC films were unusual in that a hysteresis was found in the adsorption/desorption isotherms, which cannot be interpreted using the conventional theory of capillary condensation in pores. The model proposed in this work for this unusual hysteresis characteristic is that the hysteresis results from the non-wetting property of DLC surfaces in the nano-scale. The nano-sized droplets formed on the DLC surfaces may require significantly higher energy to evaporate than the formation energy. Argon plasma treatment resulted in a small decrease of the contact angles. After oxygen plasma treatment, the wetting contact angles reduced significantly due to the increase of carbon-oxygen sites on the surfaces, suggesting that the low concentration of carbon-oxygen sites on the surfaces of DLC films contributed to the adsorption hysteresis observed in this work.     

The influence of activated carbon surface properties on the adsorption of the herbicide molinate and the bio-regeneration of the adsorbent

In the present study, the effect of the textural and surface chemistry properties of the activated carbon were evaluated in a combined treatment system to remove the herbicide molinate from waters. The process consists of an initial adsorption step followed by the bio-regeneration of the activated carbon through the utilization of a defined bacterial mixed culture (DC), previously described as able to mineralize molinate. Molinate adsorption and partial bio-regeneration was favoured with activated carbons with larger pores, consisting mainly of meso and macropores. In order to study the effect of different surface chemical characteristics while maintaining the original textural properties, a commercial activated carbon was submitted to thermal and nitric acid treatments. The thermal treatment improved the molinate adsorption capacity of activated carbon. However, the bio-regeneration of the nitric acid oxidised activated carbon was slightly higher. With all the activated carbon materials used it was observed that the biological consumption of molinate present in the liquid phase displaced the equilibrium towards the activated carbon partial regeneration.     

石油焦氧化改性制备活性炭及其电容性能研究

采用水热法,利用H2O2对石油焦进行氧化改性,以KOH为活化剂,在碱碳比为3∶1时将改性石油焦制备成活性炭(OAC-3);作为对比,在碱碳比为3∶1、4∶1和5∶1时将未改性石油焦制备成活性炭(AC-3、AC-4和AC-5)。采用XRD、I2吸附、N2吸附和恒流充放电测试,研究氧化改性对石油焦和活性炭结构及性能的影响。研究表明,氧化改性使石油焦石墨微晶的晶面层间距由0.344nm增加到0.351nm,微晶厚度由2.34nm降低到1.86nm,降低了石油焦的活化难度。OAC-3和AC-4的比表面积分别为3066和2929m2/g;在0.2A/g的电流密度下,比电容分别为374.6和338.9F/g;基于OAC-3的超级电容器具有更好的功率特性和更低的内阻。     

用生物测试评价臭氧-生物活性炭净水工艺

设计了一组基于生物标记物的生物测试方法,并用于评价南方某水厂臭氧-生物活性炭中试工艺对水中痕量有机有毒污染物的去除效果.测试方法包括检测类雌激素效应物质的重组基因酵母试验,检测遗传毒性物质的SOS/umu试验和检测芳烃(Ah)受体效应物质的EROD试验.研究表明,仅在水库原水中存在很低浓度水平的间接遗传毒性物质,水处理各工艺出水均为阴性.工艺对类雌激素效应物质和Ah受体效应物质的去除率分别为91.3%和90.6%,主要在臭氧工艺段得到有效去除.采用成组生物标记物方法可以对饮用水中的痕量有机污染物进行毒性筛选或测试,适用于对水处理工艺的风险评价.     

Development of parthenium based activated carbon and its utilization for adsorptive removal of p-cresol from aqueous solution

The activated carbon was prepared from carbonaceous agriculture waste Parthenium hysterophorous by chemical activation using concentrated H2SO4 at 130+/-5 degrees C. The prepared activated carbon was characterized and was found as an effective adsorbent material. In order to test the efficacy of parthenium based activated carbon (PAC), batch experiments were performed to carryout the adsorption studies on PAC for the removal of highly toxic pollutant p-cresol from aqueous solution. The p-cresol adsorption studies were also carried out on commercial grade activated carbon (AC) to facilitate comparison between the adsorption capabilities of PAC and AC. For PAC and AC, the predictive capabilities of two types of kinetic models and six types of adsorption equilibrium isotherm models were examined. The effect of pH of solution, adsorbent dose and initial p-cresol concentration on adsorption behaviour was investigated, as well. The adsorption on PAC and on AC was found to follow pseudo-first order kinetics with rate constant 0.0016 min(-1) and 0.0050 min(-1), respectively. The highest adsorptive capacity of PAC and AC for p-cresol solution was attained at pH 6.0. Further, as an adsorbent PAC was found to be as good as AC for removal of p-cresol upto a concentration of 500 mg/l in aqueous solution. Freundlich, Redlich-Peterson, and Fritz-Schlunder models were found to be appropriate isotherm models for PAC while Toth, Radke-Prausnitz and Fritz-Schlunder were suitable models for AC to remove p-cresol from aqueous solution.     

Kinetic and equilibrium studies on the removal of acid dyes from aqueous solutions by adsorption onto activated carbon cloth

Removal of acid dyes Acid Blue 45, Acid Blue 92, Acid Blue 120 and Acid Blue 129 from aqueous solutions by adsorption onto high area activated carbon cloth (ACC) was investigated. Kinetics of adsorption was followed by in situ UV-spectroscopy and the data were treated according to pseudo-first-order, pseudo-second-order and intraparticle diffusion models. It was found that the adsorption process of these dyes onto ACC follows the pseudo-second-order model. Adsorption isotherms were derived at 25 degrees C on the basis of batch analysis. Isotherm data were treated according to Langmuir and Freundlich models. The fits of experimental data to these equations were examined.     

Equilibrium,kinetic and thermodynamic studies on the adsorption of 2-nitroaniline onto activated carbon prepared from cotton stalk fibre

Activated carbon prepared from cotton stalk fibre has been utilized as an adsorbent for the removal of 2-nitroaniline from aqueous solutions. The influence of adsorbent mass, contact time and temperature on the adsorption was investigated by conducting a series of batch adsorption experiments. The equilibrium data at different temperatures were fitted with the Langmuir, Freundlich, Tempkin, Redlich–Peterson and Langmuir–Freundlich models. The Langmuir–Freundlich isotherm was found to best describe the experimental data. The adsorption amount increased with increasing temperature. The maximum adsorption capacity of 2-nitroaniline was found to be 383 mg/g for initial 2-nitroaniline concentration of 200 mg/L at 45 °C. The kinetic rates were modeled by using the Lagergren-first-order, pseudo-second-order and Elovich models. The pseudo-second-order model was found to explain the adsorption kinetics most effectively. It was also found that the pore diffusion played an important role in the adsorption, and intraparticle diffusion was the rate-limiting step at the first 30 min for the temperatures of 25, 35 and 45 °C. FTIR and ¹³C NMR study revealed that the amino and isocyanate groups present on the surface of the adsorbent were involved in chemical interaction with 2-nitroaniline. The negative change in free energy (ΔG°) and positive change in enthalpy (ΔH°) indicated that the adsorption was a spontaneous and endothermic process.     

表面改性对活性炭孔结构及热电转换性能的影响

为探究表面改性对活性炭孔结构及热电转换性能的影响,使用HNO_3和KOH在不同条件下对活性炭进行表面改性,用N2吸附法和XRD图谱表征活性炭改性前后孔结构和石墨化程度的变化。结果表明,改性后活性炭的比表面积和孔容提高,平均孔径减小,并存在石墨晶体结构。干法改性活性炭的比表面积和总孔容由1 077.880m~2/g和0.763cm~3/g分别增加到1 635.268m~2/g和1.128cm~3/g,并且微孔的孔容增加。改性处理可以去除活性炭中的杂质。分别以改性前后活性炭为材料制备固体电极,KCl为电解液,测试活性炭电极的热电转换性能,发现改性后活性炭具有更高的热电转换性能。