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.     

Desorption Kinetics of A N,N-Dimethylformamide Vapor from Granular Activated Carbon and Hydrophobic Zeolite

Abstract

Such thermodynamic properties as enthalpy, free energy, and entropy of adsorption have been computed for N,N-dimethylformamide (DMF) vapor on two commercial adsorbents: coconut shell Type PCB of activated carbon and Type DAY of hydrophobic zeolite. The computation is based on the Langmuir adsorption isotherms obtained at 293, 303, and 313 K as reported by Tsai et al. The laden adsorbents were regenerated with hot inert nitrogen gas and studied by thermal gravimetric analysis at three different heating rates. The apparent activation energies (E _des) of thermal desorption were determined by using the Friedman method. The zeolite DAY has an adsorption potential higher than that of activated carbon PCB as indicated by the more negative value of the adsorption enthalpy of DMF vapor. The average value of E _des of zeolite DAY is larger than that of activated carbon PCB.     

Effect of Preparation Conditions on the Property Cu/AC Adsorbents for Phosphine Adsorption

Copper-based activated carbon adsorbents (Cu/AC) were prepared and used to investigate the effects of various copper precursors, impregnation solution concentration, and calcination temperature on phosphine (PH₃) adsorption removal from yellow phosphorus tail gas. N₂ adsorption isotherm and X-ray Diffraction (XRD) were used for characterizing the Cu/AC adsorbents. It can be seen that the Cu(N)/AC adsorbent prepared from the Cu(NO₃)₂ precursor has higher PH₃ breakthrough adsorption capacity than other three adsorbent because the surface copper status of it is mainly CuO. Fresh activated carbon requires an optimal impregnation solution concentration (0.05 mol/L) to reach this optimal PH₃ breakthrough adsorption capacity (78.62 mg/g). The result shows that the surface chemical characteristics (Cu content) of activated carbon is more important than the physical ones (specific surface or pore volume) for the PH₃ adsorption performance. When the calcination temperature is 350°C, the Cu(N)/AC adsorbent has the biggest PH₃ breakthrough adsorbed amount of 112.38 mg/g. The present study confirmed that the Cu/AC adsorbents would be one of the candidates for PH₃ adsorption removal from yellow phosphorus tail gas.     

Evaluation of pressure-temperature swing adsorption for sulfur hexafluoride (SF<Subscript>6</Subscript>) recovery from SF<Subscript>6</Subscript> and N<Subscript>2</Subscript> gas mixture

The separation/concentration of SF₆, a strong greenhouse gas, of 1.3% in N₂ was investigated using pressure-temperature swing adsorption (PTSA) with activated carbon. To screen an effective adsorbent to be used for PTSA, adsorption isotherms on the selected adsorbents were obtained. Among the studied adsorbents, AC-1, a coconut-shell based commercial activated carbon, showed the largest adsorption amount of 3.5 mmol-SF₆/g-carbon at 303.65 K and 3 atm and the highest selectivity among the adsorbents tested. Its adsorption isotherm was well fit into Langmuir-Freundlich model. Before feasibility test of PTSA, a series of experiments were performed to investigate the effect of operating parameters including adsorption pressure, feed flow rate, desorption temperature and evacuation time on the PTSA performance using the 3-step PTSA cycle (pressurization, adsorption and regeneration-recovery). As the adsorption pressure, desorption temperature and evacuation time were increased, respectively, purity and recovery increased. Increasing the feed flow rate resulted in low purity and recovery. The maximum purity of 19.5% and recovery of 50.1% were obtained with adsorption pressure of 2.5 atm, desorption temperature of 200 °C and evacuation of 1 hour.     

Low-cost metal oxide activated carbon prepared and modified by microwave heating method for hydrogen storage

Novel microporous activated carbon (MAC) with high surface area and pore volume has been synthesized by microwave heating. Iron oxide nanoparticles were loaded into MAC by using Fe(NO₃)₃·9H₂O followed by microwave irradiation for up to five minutes. The surface modified microporous activated carbon was characterized by BET, XRD, SEM and thermogravimetric examinations. Adsorption data of H₂ on the unmodified and modified MACs were collected with PCT method for a pressure range up to 120 bar at 303 K. Greater hydrogen adsorption was observed on the carbon adsorbents doped with 1.45 wt% of iron oxide nanoparticle loaded due to the joint properties of hydrogen adsorption on the carbon surface and the spill-over of hydrogen molecules into carbon structures.     

煤层气在活性炭和炭分子筛上变压吸附分离

变压吸附分离是有效的气体分离提纯方法,采用合适的吸附剂可对煤层气(CH4/N2混合气体)进行高效分离,节约能耗。在单床吸附装置上测量了CH4/N2混合气体在3种活性炭和4种炭分子筛吸附柱上的穿透曲线,并进行实验研究再生条件对吸附剂分离性能的影响。实验结果表明,7种吸附剂均对CH4/N2混合气具有一定程度的分离能力,且高温真空再生后吸附效果更好;但仍需开发出更有效的吸附剂。     

Preparation of powdered activated carbon from rice husk and its methane adsorption properties

Success of adsorbed natural gas (ANG) storage process is mainly based on the characteristics of the adsorbent, so various synthesized adsorbents were analyzed for methane adsorption on a thermodynamic basis. Activated carbon from rice husk (AC-RH) was synthesized and its methane adsorption capacities were compared with phenol based activated carbons (AC-PH₂O and AC-PKOH). The adsorption experiments were conducted by volumetric method under various constant temperatures (293.15, 303.15, 313.15 and 323.15 K) and pressure up to 3.5MPa. Maximum methane adsorption was observed in AC-RH as its surface area is higher than the other two adsorbents. The experimental data were correlated well with Langmuir-Fruendlich isotherms. In addition, isosteric heat of adsorption was calculated by using Clausius-Clapeyron equation.     

Comparative study of methylene blue dye adsorption onto activated carbon,graphene oxide,and carbon nanotubes

Three different carbonaceous materials, activated carbon, graphene oxide, and multi-walled carbon nanotubes, were modified by nitric acid and used as adsorbents for the removal of methylene blue dye from aqueous solution. The adsorbents were characterized by N₂ adsorption/desorption isotherms, infrared spectroscopy, particle size, and zeta potential measurements. Batch adsorption experiments were carried out to study the effect of solution pH and contact time on dye adsorption properties. The kinetic studies showed that the adsorption data followed a pseudo second-order kinetic model. The isotherm analysis indicated that the adsorption data can be represented by Langmuir isotherm model. The remarkably strong adsorption capacity normalized by the BET surface area of graphene oxide and carbon nanotubes can be attributed to π–π electron donor acceptor interaction and electrostatic attraction.     

Various carbon-based MgAl2O4 adsorbents and their removal efficiency of CR dye and antibiotics in aqueous media: High selective adsorption capacity,performance prediction and mechanism insight

Various carbon -based MgAl₂O₄ (MAO) adsorbents were synthesized by a simple ultrasound irradiation technology with the activated carbon (AC), carbon quantum dots (CQDs), C₃N₄ (CN) and graphene oxide (GO) as carbon sources. The optimum synthesis conditions for the carbon -based MAO adsorbents were determined by the study of the addition of different types of carbon and different mass ratios of m_{Various carbon}: m_MAO = 2.5%, 5.0%, 7.5% and 10%. The carbon -based MAO adsorbents were used for the adsorption of Congo red (CR) dye, tetracycline hydrochloride (TCH), oxytetracycline hydrochloride (OCH), ciprofloxacin (CIP), naproxen sodium (NPS) and tetrabromobisphenol A (TBBPA) and the seven factors affecting the adsorption behavior were discussed, including the type of carbon, AC content, initial dye concentration (C_CR), adsorbent dosage (C_{carbon -based MAO adsorbents}), adsorption time (A_t), pH value and reaction temperature (T). The corresponding adsorption isotherm models such as Langmuir, Tempkin, Koble-Corrigan, Toth and Freundlich models and thermodynamics of carbon -based MAO adsorbents for the adsorption of CR dye were also studied. When pH = 7.8, C_CR = 200 mg/L, A_t = 90 min, T = 287 K and C_{AC 5.0 wt%-MAO} = 1 g/L, the removal rate of CR dye reaches 89.7%. The back propagation (BP) neural network model was used to predict the adsorption percentage of carbon-based MAO adsorbents, which was consistent with the experimental results. The high adsorption capacity of AC 5.0 wt%-MAO adsorbents for the adsorption of CR dye can be assigned to the synergistic effects of electrostatic interaction, intermolecular force, n-π interaction and hydrogen bonding, while for the adsorption of TCH, OCH and CIP can be ascribed to the electrostatic interaction. This study demonstrated a huge potential of carbon -based MAO adsorbents as an eco-friendly adsorbent for the adsorption of dyes and drugs.     

不同碳基材料对Cr(Ⅵ)的吸附动力学研究

以传统活性炭(木质炭、煤质炭)与碳纳米管为碳基吸附剂,研究不同碳基吸附剂对Cr(Ⅵ)的吸附效果,并对其吸附动力学进行研究。结果表明,传统活性炭对Cr(Ⅵ)的吸附性能优于碳纳米管,木质、煤质活性炭和碳纳米管对Cr(Ⅵ)的理论最大吸附量分别为158.23、152.44、48.69 mg/g;传统活性炭和碳纳米管对Cr(Ⅵ)的吸附过程均符合准二级动力学方程;传统活性炭和碳纳米管对Cr(Ⅵ)的吸附属于物理吸附。     

Removal of sulfur compounds in FCC raw C4 using activated carbon impregnated with CuCl and PdCl2

Fluid catalytic cracking (FCC) is one of the most important refinery processes for economical efficiency that produces commercial fuels with acceptable concentrations of sulfur. Several activated carbon (AC) based adsorbents were studied to develop a more efficient adsorbent for removal of mercaptanes and sulfides during the FCC C4 refinery process. The adsorbents were prepared by impregnating AC with CuCl and PdCl₂. To evaluate the degree of metal halide impregnation into the AC support, each adsorbent was characterized by N₂ adsorption, elemental analysis (EA) and XRF. Three types of ACs were used to investigate the effect of the structural properties such as surface area, total pore volume and pore size distribution. From this analysis, an AC micro pore size of 0.7 nm was found to be the most effective support material for FCC C₄ removal of sulfur compounds. The experimental adsorption isotherms were compared with Langmuir and Freundlich models and were found to fit the Freundlich model much better than the Langmuir model. The sulfur removal performance of the prepared adsorbents was tested using the breakthrough experiments. The sulfur adsorption capacities of adsorbents decreased in the following order: AC impregnated PdCl₂, AC impregnated CuCl and non-impregnated AC (NIAC). The saturated adsorbents were regenerated by toluene treatment and reactivated at 130 °C under a vacuum.     

Optimization of Activated Carbon Sulfurization to Reach Adsorbent with the Highest Capacity for Mercury Adsorption

This work deals with the use of elemental sulfur immobilized on the activated carbon surface, as an active phase to enhance the sorbent's mercury adsorption capacity. The sulfurization procedure was optimized, and the influence of two factors (temperature and initial ratio of sulfur to carbon), on the final properties and mercury adsorption capacities of the adsorbents was investigated. The sulfurized adsorbents were characterized using CHNS/O elemental analysis, surface area and porosimetry, FT-IR spectroscopy, SEM-EDS, and pH_pzc measurement. A series of batch studies were also conducted to delineate the effect of contact time, initial pH, solution temperature, and initial mercury concentration on the adsorption capacity of the adsorbents. Furthermore, attempts were made to desorb mercury from the metal loaded adsorbents using various concentrations of KCl, KBr and KI solutions.     

Adsorption characteristics of bamboo activated carbon

Dye is difficult to remove from aqueous solution with common adsorbents due to its large molecular size. Mesoporous bamboo activated carbon is utilized in the adsorption of Black 5, Red E and phenol. The adsorption performance of the carbon is experimentally examined along with the characterization of the adsorbent. The comparison of adsorption capacity of the bamboo activated carbon with that of coconut activated carbon and carbon cryogel indicates that the large volume of mesopore in the carbon helps the expansion of adsorption capacity. Microscopic observation, the measurement of pore characteristics and fitting to the adsorption isotherms are conducted in the characterization of the bamboo activated carbon.     

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.     

直接合成法制备载银稻壳活性炭及其对苯并噻吩的吸附

分别采用直接合成法和浸渍法制备了载银稻壳活性炭脱硫吸附剂,通过N2吸附-脱附、TEM及XRD测试手段对其进行表征,通过静态吸附实验研究了载银稻壳活性炭对苯并噻吩的吸附性能。结果表明,直接合成法在活化稻壳制得活性炭的同时将银颗粒均匀地负载在活性炭的表面;与浸渍法相比,直接合成法上的活性组分分散更均匀,粒径更小,且NO3-在稻壳活化过程中也起到了增加活性炭比表面积、孔体积和孔径的作用。通过对比实验证明了直接合成法制备的载银活性炭对模拟汽油中的苯并噻吩具有较高的吸附容量,30℃时,模拟汽油中的硫含量为542.6 ppm,吸附剂的硫吸附容量达到了15.58 mg/g。     

Adsorption Equilibrium and Fixed Bed Adsorption of Aniline onto Polymeric Resin and Activated Carbons

The adsorption of aniline on several adsorbents including resin Sepabeads SP206 and activated carbons Jacobi and Norit, has been studied. The influence of temperature in the adsorption capacity was obtained by batch method. Langmuir and Bi-Langmuir were the best models to represent the equilibrium sorption isotherm of aniline in the resin and the activated carbons, respectively. Higher adsorption capacity was obtained for both activated carbons than that for resin, being the maximum adsorption capacity three times higher. Nevertheless, the aniline adsorption capacity onto resin is much more influenced by the temperature.

The dynamic behavior of aniline onto Sepabeads SP206 resin and activated carbon Jacobi was also studied. Breakthroughs and reverse breakthroughs were carried out in a laboratory-scale column to study the adsorbent regeneration. A Linear Driving Force (LDF) model was used to predict the experiments for the two adsorbents. The results demonstrated that Sepabeads SP206 resin can be easily regenerated by using water, while around 50% of aniline remains adsorbed in the activated carbon. Furthermore, after 4 cycles of adsorption-desorption, only around 60% of aniline can be recovered from the activated carbon Jacobi; this behavior can be explained by the aniline that is chemically adsorbed into the activated carbon.     

不同孔径活性炭吸附挥发性有机物的分子模拟

借助Materials Studio软件建立了0.902nm、1.997nm、3.000nm、4.000nm孔径的活性炭狭缝孔模型,采用巨正则蒙特卡洛模拟（Grand Canonical Monte Carlo）的模拟方法计算了其对挥发性有机物（VOCs,如异己烷、苯、甲苯、丙酮和甲醇）的吸附数据,考察了活性炭孔径的变化对VOCs吸附性能的影响,并对实际应用进行指导。模拟结果显示：活性炭对VOCs的吸附受孔径和吸附能的共同影响,在293.15K、各物质饱和蒸气压p₀下,随着孔径的增大,吸附质吸附剂之间的亲和力呈下降趋势。活性炭孔径由0.902nm增加到4.000nm对异己烷、苯、甲苯的饱和吸附量逐渐增大,而4.000nm孔径活性炭对丙酮饱和吸附量小于3.000nm孔径活性炭,3.000nm、4.000nm孔径活性炭对甲醇饱和吸附量小于1.997nm孔径活性炭。在工业废气VOCs吸附回收中选择0.902～1.997nm孔径活性炭能够达到最佳效果。     

吸附制冷用复合吸附剂的吸附性能

固体吸附式制冷因具有环保和节能两大优势,成为国内外竞相开发的热点,尤其是将其用于新型空调系统和太阳能应用产品方面的开发研究备受关注．但从实用化研究成果来看,还远不满足工业化条件,其主要原因之一是受吸附制冷工质对（吸附剂-制冷剂）的性能制约．目前,国内外关于吸附制冷工质对的研究报道比较多,所采用的吸附（工）质仍然以水、甲醇、乙醇和氨为主,对于吸附剂的研究进展比较快,已从当初单一组分吸附剂的选用发展到目前多组分、复合吸附剂的研制．研制性能优良的吸附剂被认为是推动固体吸附式制冷工业化的关键之一．     

Adsorption of H2, CO2, CH4, CO,N2 and H2O in Activated Carbon and Zeolite for Hydrogen Production

Abstract

The design of a layered pressure swing adsorption unit to treat a specified off-gas stream is based on the properties of the adsorbent materials. In this work we provide adsorption equilibrium and kinetics of the pure gases in a SMR off-gas: H₂O, CO₂, CH₄, CO, N₂, and H₂ on two different adsorbents: activated carbon and zeolite. Data were measured gravimetrically at 303–343 K and 0–7 bar. Water adsorption was only measured in the activated carbon at 303 K and kinetics was evaluated by measuring a breakthrough curve with high relative humidity.     

Comparative study of the textural characteristics of oil palm shell activated carbon produced by chemical and physical activation for methane adsorption

The objective of this study is to relate textural and surface characteristics of microporous activated carbon to their methane adsorption capacity. Oil palm shell was used as a raw material for the preparation of pore size controlled activated carbon adsorbents. The chemical treatment was followed by further physical activation with CO₂. Samples were treated with CO₂ flow at 850 °C by varying activation time to achieve different burn-off activated carbon. H₃PO₄ chemically activated samples under CO₂ blanket showed higher activation rates, surface area and micropore volume compared to other activation methods, though this sample did not present high methane adsorption. Moreover, it was shown that using small proportion of ZnCl₂ and H₃PO₄ creates an initial narrow microporosity. Further physical activation grantees better development of pore structure. In terms of pore size distribution the combined preparation method resulted in a better and more homogenous pore size distribution than the conventional physical activation method. Controlling the pore size of activated carbon by this combined activation technique can be utilized for tuning the pore size distribution. It was concluded that the high surface area and micropore volume of activated carbons do not unequivocally determine methane capacities.