活性炭孔结构对卷烟烟气过滤效率的影响

综述了活性炭孔径分布和比表面积对卷烟烟气过滤效率的影响,介绍了利用气体吸附法表征活性炭孔径分布的方法,并对活性炭滤嘴在低焦油卷烟设计中的应用进行了展望。     

Effects of high relative humidity on the dynamic adsorption of dimethyl methylphosphonate (DMMP) on activated carbon

The effects of high relative humidity (RH) on the breakthrough of the nerve agent simulant dimethyl methylphosphonate (DMMP) vapor in beds of ASC-impregnated, activated carbon were investigated. Maximum concentrations of DMMP at room temperature and RH > 60% were found to be lower by more than an order of magnitude than in dry air. The breakthrough time (t_B) of 1.2 × 10⁻⁴ g l⁻¹ DMMP in pre-humidified beds and humid air of RH = 90% was shortened by a factor of 1.6 relative to adsorption in dry beds and dry air. Analysis of the breakthrough curves according to the Wheeler–Jonas model indicated that the high RH lowered the dynamic adsorption capacity (W_E) but had nearly no effect on the critical bed weight (W_C). The reduction of W_E by humidity correlates with the observed displacement of adsorbed water by DMMP. The use of DMMP for testing filter performance is limited to low and intermediate relative humidities. On the other hand, DMMP in dry air can be used to advantage for testing the capacity of new or used respirator filters and for the detection of filter channeling.     

GOLD ADSORPTION ON ACTIVATED CARBON AND THE EFFECT OF SUSPENDED SOLIDS AND DISSOLVED SILICON DIOXIDE

The use of gold adsorption by activated carbon has recently become widespread on South African gold mines. This has caused a great deal of interest in the kinetics of gold adsorption onto activated carbon. However, almost all previous work has been done using clear solutions. In practice the gold adsorption occurs from a slurry containing fine ground rock particles and possibly a number of other metals in solution as well as organics which may poison the carbon. As the next step in the understanding of the gold adsorption process, this work assesses the impact of a fine solid suspension on the gold adsorption kinetics. This is found to significantly reduce the adsorption rate of gold cyanide (Au(CN)2¯) by G210 activated carbon in completely mixed batch adsorbers. The relative effects of solid particle size and mixing intensity on the adsorption rate are investigated. Batch adsorption rate experiments are performed with clear solutions, and with solutions containing 20% (m/m) fine suspended solid material, agitated at impeller speeds of 200 and 300 r.p.m. with an initial gold cyanide concentration of = 10 p.p.m. Equilibrium isotherms for gold cyanide, gold cyanide/glass particles and dissolved silicon on G210 activated carbon were determined. The batch adsorption kinetics of gold cyanide from clear solutions were successfully modelled using the Homogeneous Surface Diffusion Model of Crittenden & Weber (1978). The adsorption of gold cyanide from clear solutions was found to be characterized by intra-particle diffusion rate control, limited by a finite film mass transfer rate at low gold loadings. When fine suspended solids are present it is shown that blinding of the carbon macropores is the likely cause of the reduced adsorption rate. Although the solids used were artificial in the sense that these would not be present in this form in an industrial operation, it was felt that using solids from an operating mine would introduce complications in addition to the specific effects this paper addresses.     

Effect of adsorbent composition on H2S removal on sewage sludge-based materials enriched with carbonaceous phase

In order to improve the carbonaceous phase content in sewage sludge derived adsorbents, dewatered sludge was physically mixed with polystyrene sulfonic acid-co maleic acid sodium salt with the following ratios of polymer to sludge: 10:90, 30:70, 50:50 and 70:30. The samples, along with the pure precursors, were carbonized at 950 °C and then washed in water to remove the excess of sodium salt/hydroxide. The performance of materials as H₂S adsorbents was tested using a home-developed dynamic breakthrough test. The samples, before and after adsorption process, were characterized by adsorption of nitrogen, potentiometric titration, thermal analysis and SEM. Differences in the performance were linked to the surface properties. It was found that mixing polymer with sludge increases the amount of H₂S adsorbed/oxidized in comparison with the adsorbents obtained from pure precursors (sludge or polymer). Sewage sludge provides the catalytic centers for hydrogen sulfide oxidation whereas a carbonaceous phase contributes to an increase in the dispersion of catalytic centers and provides more “storage space” in its micropores. There is an optimal ratio in the composition of the precursors for which the best performance is achieved. When the content of the polymer is too high, the “buffering capacity” of the sludge-derived phase is not enough to neutralize the suppressing effect of acidic surface groups of a carbonaceous phase.     

氟磺胺草醚废水的处理研究

氟磺胺草醚废水是一种难降解有机废水,其废水中含有大量的二氯甲烷、二甲亚砜、氯苯等物质。采用吸附的方法进行预处理,结果表明,吸附后COD的去除率高达78%,吸附过程主要考察了吸附时间、活性炭种类、活性炭量对吸附效果的影响,通过多组数据控制参数找出最佳运行参数。在最佳状态下进行电解,考察电解时间对废水生化性的影响,找出最佳预处理的条件。     

Adsorption of toluene onto activated carbons exposed to 100 ppb ozone

The effects of 100 ppb ozone exposure on the adsorption of 1 ppm toluene on activated carbon are presented for dry (less than 5% RH) and humid (55% RH) air. In dry air, the 10% toluene breakthrough times of granular carbon beds exposed to ozone for 208 days are 17% less than those of unexposed carbon beds. At 55% RH, the corresponding reduction in toluene breakthrough time is 78%. For a humid environment with 100 ppb ozone, filter life would be reduced by more than half compared to the expected life based on tests in the absence of ozone. This degradation is attributed to changes in carbon surface chemistry, surface area, and pore volume that occur with relatively brief exposure to the ozone.     

Effect of ZnO loading to activated carbon on Pb(II) adsorption from aqueous solution

The effect of zinc oxide loading to granular activated carbon on Pb(II) adsorption from aqueous solution was studied in comparison with zinc oxide particles and oxidized activated carbon. Cu(II), Cd(II) and nitrobenzene were used as reference adsorbates to investigate the adsorption. The BET surface area and point of zero charge (pH_PZC) in the aqueous solution were measured for the adsorbents. The adsorption isotherms were examined to characterize the adsorption of heavy metals and organic molecules. The heavy metal adsorption was improved by both the zinc oxide loading and the oxidation of activated carbon. In contrast, the adsorption of nitrobenzene was considerably reduced by the oxidation, and slightly decreased by the zinc oxide loading. The zinc oxide loading to the activated carbon was found to be effectively used for the Pb(II) adsorption whereas only a part of surface functional groups was used for the zinc oxide particles and the oxidized activated carbon. From the experimental results, the surface functional groups responsible for the Pb(II) adsorption on the zinc oxide loaded activated carbon were considered to be hydroxyl groups that formed on the oxide, while those on the oxidized activated carbon were considered to be carboxylic groups.     

The performance of two adsorption ice making test units using activated carbon and a carbon composite as adsorbents

The available adsorption working pairs applied to adsorption refrigeration system, which utilize activated carbon as adsorbent, are mainly activated carbon-methanol, activated carbon-ammonia, and composite adsorbent-ammonia. The adsorption properties and refrigeration application of these three types of adsorption working pairs are investigated. For the physical adsorbents, consolidated activated carbon showed best heat transfer performance, and activated carbon-methanol showed the best adsorption property because of the large refrigerant amount that can be adsorbed. For the composite adsorbents, the consolidated composite adsorbent with mass ratio of 4:1 between CaCl₂ and activated carbon, showed the highest cooling density when compared to the granular composite adsorbent and to the merely chemical adsorbent. The physical adsorption icemaker that employs consolidated activated carbon-methanol as working pair had the optimum coefficient of refrigeration performance (COP), volume cooling power density (SCP_v) and specific cooling power per kilogram adsorbent (SCP) of 0.125, 9.25 kW/m³ and 32.6 W/kg, respectively. The composite adsorption system that employs the consolidated composite adsorbent had a maximum COP, SCP_v and SCP of 0.35, 52.68 kW/m³ and 493.2 W/kg, respectively, for ice making mode. These results are improved by 1.8, 4.7 and 14 times, respectively, when compared to the results of the physical adsorption icemaker.     

Adsorption of vitamin B12 on ordered mesoporous carbons coated with PMMA

Ordered mesoporous carbons CMK-3 and CMK-1 were prepared from SBA-15 and MCM-48 materials with pore diameters 3.9 nm and 2.7 nm, respectively. When both mesoporous carbons were coated with about 10 wt.% poly(methyl methacrylate) (PMMA), the pore diameters decreased from 3.9 nm to 3.4 nm for CMK-3 and from 2.7 nm to 2.5 nm for CMK-1. These mesoporous carbons containing about 10 wt.% PMMA were studied as adsorbents of Vitamin B 12 (VB12) from water solutions, and their performances were compared with that of pristine CMK-3, CMK-1. Compared with CMK-1, CMK-3 showed higher vitamin B12 adsorption due to a larger mesopore volume, a higher BET surface and a larger pore diameter. After coated with PMMA, both mesoporous carbons showed higher adsorption capacity than pristine materials. The adsorption properties were influenced by the pore structure and surface properties of mesoporous carbons.     

Improving the performance of an active carbon-nitrogen adsorption cryocooler by thermal regeneration

Thermodynamic analysis was done on single and two stage active carbon nitrogen adsorption cryocoolers to study the effect of thermal regeneration on the performance. Heat regeneration within compressors operating in the same temperature range is considered. From the analysis done on 80 K cooler and 117.5 K cooler, it is found that dramatic efficiency improvement is possible with the use of compressor heat regeneration techniques.     

Methane storage in wet activated carbon: Studies on the charging/discharging process

The dynamic behavior of charging/discharging methane onto/from water-preloaded activated carbon was studied at different conditions. It was shown that methane hydrate could form quickly in the porous space of carbon at the condition of 275 K and pressures beginning with 4.12 MPa. The stored methane could be continuously released at a constant flowrate for the whole discharging process. The packing density of 0.6 g cm⁻³ seemed optimal for the wet carbon tested, which yielded 152 V/V of released methane at charging pressure of 8 MPa. The thermal effect observed on the charging/discharging process was low and did not affect the effective storage capacity.     

ADSORPTION OF ORGANIC SOLUTES INTO ACTIVATED CARBONS-BATCH STUDIES

In this paper, a new model is proposed for the adsorption of organic solutes into solids having a bimodal pore size distribution. This model takes into account, the pore and surface diffusion in the macropore and also the adsorption capacities in both macropore and micropore. The model equations are solved numerically (Crank-Nicholson) and in special cases, the asymptotic solutions for micropore uptake control and macropore uptake control are presented. This model is applied to data obtained by Peel, Benedek and Crowe (1981) and is shown to describe the experimental data well. It has been observed that surface diffusion plays a significant role in the adsorption of phenol on activated carbon.     

活性炭纤维对水中亚甲基蓝的吸附脱色研究

研究了活性炭纤维（ACF）对水中亚甲基蓝的吸附脱色试验。温度为15-20℃,滤速为4mL/min时。浓度为10mg/L的亚甲基蓝脱色率达98％以上。活性炭纤维经20次吸附与解吸实验,吸附脱色性能没有明显降低。与颗粒状活性炭（GAC）相比,活性炭纤维吸附脱色亚甲基蓝的速度快,在短时间内,就能达到吸附平衡。     

Adsorption of SO2 on Activated Carbon for Low Gas Concentrations

Adsorption experiments of SO₂ on activated carbon has been carried out for low concentrations (about 100 ppm) at room temperature (15 to 33 °C) with varying humidity in the air. The breakthrough curves show that at high relative humidity or relative higher SO₂ concentration, the load capacity increases with respect to temperature. The humidity of the air is also of benefit to the load capacity of SO₂. When an adsorption process is interrupted and the activated carbon is kept closed for a while, the SO₂ concentration at the exit of a fixed‐bed adsorber is similar to that of the fresh activated carbon and begins at a very low value. It appears that the sorption potential has been refreshed after the storage period. Analysis of desorption experiments by simultaneous thermal analysis combined with mass spectrometry (MS) after loading, shows that the physisorbed SO₂ and H₂O are desorbed at low temperatures. At higher temperatures, the MS peak of SO₂ and H₂O occur at the same time. Compared with desorption immediately after loading, after one day, the desorption peak due to the physisorbed SO₂ disappears. From this, it can be concluded that the refreshment of the loading capacity of the activated carbon after storage is mainly due to a change in the nature of the SO₂ from a physisorbed state to a chemisorbed form. The same mechanism leads to a continuous refreshment of the sorption potential by means of a chemical reaction during the adsorption process.     

Removal of carbon disulfide (CS2) from water via adsorption on active carbon fiber (ACF)

The primary objective of this paper was to demonstrate the suitability of ACF in effectively adsorbing CS₂ from water, and to compare its performance vs. that of GAC. Commercial ACF was modified to increase its specific surface and pore volume. CS₂ removal was studied by adding ACF to water containing CS₂ under varying conditions. The experimental results reveal that ACF is a potential adsorbent for capturing CS₂ under both equilibrium and dynamic adsorption/desorption conditions. The adsorption capacity of ACF was observed to considerably increase with the increase of CS₂ concentration: It was observed that the modified ACF exhibited greater adsorption for CS₂ than the GAC, and the mechanism for this difference was explored; The modified ACF showed a consistent performance within a pH range from 3-9; Under the experimental conditions, an modified ACF sample was adsorbed and desorbed by boiling water repeatedly without exhibiting any appreciable degradation in its adsorption performance.