Papers by Keyword: Activated Carbon (AC)

Abstract: This paper presents the experimental results given by the operation of a chemical sorption refrigeration system using Expanded Graphite/Activated Carbon/Lithium Chloride (AC/GE/LiCl)-Adsorbent (NH₃ in solution with a 25% concentration). Experimental protocol with the characteristics of the experimental rig developed, working pair specifications and the procedure that has developed in the process is described in detail. Results are presented for different behaviors of the system, where the desorption stage is driven by forced convection. Measurements of the thermal variables of the system show that the adsorption-desorption cycles in the test accomplished, with high and low-pressure zones clearly defined. The cooling effects for the pair material studied have the expected behavior for the mixture proposed.

Abstract: In order to improve capacitance in supercapacitors application, activated carbon (AC) was modified by nitric acid oxidizing treatment. Oxygen-containing functional groups (OCFG) were detected by using FTIR techniques. Cyclic voltammetry and constant current charge-discharge were used to characterize the electrochemical performance of the samples in 6 mol/L KOH solution. FTIR studies showed that chemical modification promoted the formation of OCFG on the surface of AC. It was found that the contribution rate of pseudo-capacitance to the total capacitance increased significantly with the extent of oxidization treatment. When oxidized by 50% HNO3, AC achieved a specific capacitance of 197.26F/g at a current density of 20mA/cm2 corresponding to an increasing rate up to 20%.

Abstract: This paper studied experimental conditions of making higher absorption activated carbon from Jincheng anthracite. The result was obtained by using the orthogonal experiment in which four factors were designated: the carbonization temperature, the carbonization time, the activation time as well as the additive types, with the target of iodine value. The optimized parameters had been found out: the carbonization temperature is 600 °C，the carbonization time is 1.5 h, the activation time is 4 h and the additive is NaNO3 which is better in a weight proportion of 8 %. At last, under the optimized parameters, the better activated carbon products could be gained by acid pickling, which has a higher iodine value 1094.8 mg/g and low ash content 8.73 %.

Abstract: The electric double layer capacitor (EDLC) is considered to be one of the promising systems for electric energy storage. Both the optimization of the micropore structure of the activated carbon electrode and the higher voltage operation of the EDLC are necessary for improving the energy density of the EDLC. Thus, there are already many research examples related to the former. The author focused on the latter to achieve a breakthrough in the energy density. The author will introduce the recent results of the surface modification using nitrogen monoxide and the heat-treatment above 1000°C for the activated carbon electrode.

Abstract: Activated carbons were prepared through chemical activation of lignin from straw pulping precursor using potassium carbonate as the chemical agent. Effects of activated temperature, K₂CO₃ /lignin ratio and the activated time on the yield, Iodine number of activated carbon were investigated. Experimental results indicated that the optimum conditions were as follow: activated temperature 800°C, K₃CO₃ (40% concentration) /lignin ratio 5: l, activated time 50min. These conditions allowed us to obtain a BET surface area of 1104 m2/g, including the external or non-microporous surface of 417 m²/g，Amount of methylene blue adsorption, Iodine number and the yield of activated carbon prepared under optimum conditions were 10.6mL/0.lg,1310 mg/g and 19.75%, respectively.

Abstract: Activated carbons (ACs) were prepared from lignite by microwave heating with KOH as activation agent, the effects of the weight ratio of KOH to coal and microwave heating time on the pore structure of ACs were investigated by N₂ adsorption. The electrochemical characteristics of electrochemical capacitors (ECs) with ACs as electrodes in 3mol/L KOH electrolyte were evaluated by galvanostatic charge/discharge cycling, cyclic voltammetry and electrochemical impedance spectroscopy. The results show that the BET specific surface area and total pore volume of ACs (denoted as AC-R3) can reach 2097m²/g and 1.19cm³/g respectively when the weight ratio of KOH to coal is 3:1 and the microwave heating time is 10 min. The ECs with AC-R3 as electrodes presents a high specific capacitance of 335F/g at a low current density of 50mA/g and still remains 288F/g even at a high current density of 5A/g, it has excellent cycling stability and low leakage current, and the residual specific capacitance is as high as 93.6% after 1000 cycles under the current density of 2.5A/g. The results have demonstrated that the microwave heating with KOH activation is an efficient approach to prepare ACs with high performance for ECs. Keywords: Activated Carbons; Microwave Heating; Electrochemical Capacitors; Electrochemical Characteristics

Abstract: The chemically activated method has been applied to prepare activated carbon from the incinerated medical waste. The preparation process of activated carbon was investigated under various conditions set by several factors, including the type of active agent used, the ratio of active agent and carbonized product, the activation temperature, the dwell time and heating rate. The results demonstrated KOH had shown the best performance as the active agent. The optimal preparation conditions could be described as follows: ratio of KOH and carbonized product 3:1, heating rate 5 °C/min, activation temperature 800 °C with activation time 1 hour. The activated carbon prepared under the optimal preparation conditions showed good adsorption performance. The adsorption capacities for methylene blue and iodine were 24~28 ml/0.1g and 965~1150 mg/g, respectively. BET surface area of activated carbon obtained was as high as 985.1634~1387.4586 m²/g. The activated carbon prepared from medical waste exhibited excellent characteristics of sorbent.

Abstract: In Al-Si-C system, there are many compounds, of which Al₄SiC₄ is useful as high-temperature structure material and the antioxidant in carbon-containing refractory. In this paper, Al₄SiC₄ powders were synthesized by using kaolin grog, aluminum and activated carbon as raw materials. The phase changes of the synthesized samples were examined by X-ray diffraction (XRD), and the microstructure was observed by scanning electron microscope (SEM). The effects of synthesis temperature and the proportion of aluminum on phase compositions of Al-Si-C system were investigated. The results show plate-like Al₄SiC₄ powders can be prepared with optimal ratio of starting materials and synthesis temperature.

Abstract: A composite adsorbent with upper-layer activated carbon (TY) and lower-layer hydrophobic silica gel (HSG) was developed, based on the comprehensive consideration of both adsorption capacity and adsorption heat of activated carbon and hydrophobic silica. For the composite adsorbent, various volumetric ratio of activated carbon to silica gel was designed, and the adsorption capacity and heat effect of the composite adsorbent with different ratio were investigated. The experimental results showed that the optimum ratio was 1:1. Thus, the vapor with high concentration was early adsorbed by the lower-layer hydrophobic silica gel, and then the residual vapor with low concentration was late adsorbed by the upper-layer activated carbon. In this way, incombustibility of silica gel and high adsorption capacity of activated carbon were fully utilized; accordingly the adsorption operation safety was improved and the adsorption capacity of activated carbon was increased owing to that the activated carbon was only used to adsorb the vapor with low concentration.

Abstract: Granular activated carbon is used in adsorption of low concentration ethanol in water, and the saturated carbon is desorbed by microwave irradiation under N2 condition for recovery of the ethanol and regeneration of the activated carbon. Through the study on microwave desorption of ethanol-loaded activated carbon under N2 condition, the following conclusions can be drawn. The highest value of the ethanol concentration appears quicker and higher when the microwave power is stronger. For example, the highest value appears before 80s when the microwave power is 320W; the ethanol-loaded activated carbon can be desorbed nearly completely after 120s when the microwave power is not weaker than 320W; the microwave power has an important effect on the outlet concentration curve of ethanol, and it is an important factor that affects the results of microwave desorption; After three processes of activated carbon adsorption and microwave desorption under N2 condition, the concentration of ethanol can come up to over than 94%～95% from 4%～8%. This paper sets forth the process and principle for microwave desorption of ethanol-loaded activated carbon under N2 condition.