Journal of The Chinese Institute of Chemical Engineers最新文献

Effects of micropore development through varying the KOH/char ratio on the porous, electrochemical, electronic, and adsorptive properties for corncob-derived activated carbons (ACs) prepared by means of the KOH activation method were systematically compared. The pore properties of ACs, including BET surface area, total pore volume, micropore volume ratio, bulk density, and product yield based on the raw material were investigated to gain an understanding for the influence of KOH dosage on the pore development. Element analysis and temperature-programming desorption (TPD) were used to obtain the information of chemical composition and surface oxygen functional groups on ACs in order to propose the reaction mechanism of KOH activation. Based on the pore development, KOH-activated carbons can be classified into two groups: a combination of physical activation and chemical KOH etching at low KOH/char ratios (0.5–2) as well as chemically uniform etching at high KOH/char ratios (≥3.0). From the adsorption study for five organics with molecular weights varying from 129 to 466 g/mol, the specific adsorption capacity of ACs for organics is independent of their specific surface area. The specific capacitance of ACs reached a maximum as the KOH/char ratio was equal to 3, attributed to a compromise between the specific surface area and electronic resistance of ACs.

Effects of culture pH ranging from pH 3.0 to 6.0 on yields of bioactive compounds, antioxidant activity, and free radical scavenging ability of methanolic extracts from mycelia and filtrates of Antrodia camphorata in a submerged culture were investigated. Culture pH significantly affected antioxidant and scavenging free radical activities of both the methanolic extracts of the mycelia and the filtrates. A low culture pH (3.0) favored cell growth, but higher culture pH (5.0) favored antioxidant properties. Antioxidant activities of the methanolic extracts of the mycelia and the filtrates were found to be correlated with total phenolic content, polysaccharide content, and protein/polysaccharide ratios. Antioxidant production was maximum at pH 5.0 at which the total phenolics and polysaccharide/protein ratio in the methanolic extracts of the mycelia were 152.2 mg/g and 0.335, respectively. The total phenolics might be the compounds responsible for the antioxidant activities of the methanolic extracts of the mycelia and the filtrates on lipid peroxidation and scavenging effects of ferrous ions. The maximum polysaccharide content of the methanolic extracts of the filtrates was 55.3 mg/g at pH 5.0. Higher yields of antioxidants were obtained in the submerged culture as compared with that of fruiting bodies. An alternative approach for producing antioxidants of A. camphorata in a submerged culture instead of solid state cultures was demonstrated in this study.

A novel strain, Streptomyces padanus PMS-702, was employed to produce fungichromin (FC, a polyene macrolide antibiotic) in a shake flask cultivation. In comparing the effects of various carbon and nitrogen sources on PMS-702 cultivation, it was found that glucose and soybean meal medium yielded the highest FC within 2 days. Factors such as medium composition, cultivation temperatures, and initial pH were optimized for FC production with response surface methodology (RSM). The optimal cultural condition obtained is as follows: glucose 11.2 g/L, soybean meal 11.2 g/L, CaCO₃ 0.46 g/L, temperature 31.7 °C, and an initial pH 5.5. Under these conditions, FC production reached 112 mg/L, about an increase of 2.86 times, as compared to results under basic conditions.

This paper tests the performance of microporous polyvinylidinefluoride (PVDF) hollow fiber in a gas absorption membrane process (GAM) using the aqueous solutions of piperazine (PZ) and 2-amino-2-methyl-1-propanol (AMP). Experiments were conducted at various gas flow rates, liquid flow rates and absorbent concentrations. Experimental results showed that wetting ratio was about 0.036% when used with the aqueous alkanolamine solutions, while that was 0.39% with aqueous piperazine solutions. The CO₂ absorption rates increased with increasing both liquid and gas flow rates at N_Re < 20. The increase of the PZ concentration showed an increase of absorption rate of CO₂. The CO₂ absorption rate was much enhanced by the addition of PZ promoter. The resistance of membrane was predominated as using a low reactivity absorbent and can be neglected as using absorbent of AMP aqueous solution. The resistance of gas-film diffusion was dominated as using the mixed absorbents of AMP and PZ. An increase of PZ concentration, the resistance of liquid-film diffusion decreased but resistance of gas-film increased. Overall, GAM systems were shown to be an effective technology for absorbing CO₂ from simulated flue gas streams, but the viscosity and solvent–membrane relationship were critical factors that can significantly affect system performance.

The bulk phase of nonionic surfactant C₁₀E₄ solution was monitored by a dynamic light scattering (DLS) system at 20 °C in a narrow range of concentration near the cmc. Two particle aggregations were observed. The DLS data show (i) there exist premicellar multimers (or called sub-micelles) and (ii) micelles coexist with multimers. The C₁₀E₄ sub-micelles have a narrow size distribution with an averaged hydrodynamic diameter (D_h) of 1.35 nm. The D_h of the micelles is around 10.5 nm at 1.0 × 10⁻⁶ mol/mL and increases slightly with C₁₀E₄ concentration. It is illustrated from the DLS data that (i) at C = 0.78–0.82 μmol/mL, monomers and premicellar multimers coexist and (ii) at C = 0.84–0.92 μmol/mL, monomers + submicellar multimers + micelles coexist. At more elevated concentrations, only the signals from the micelles are detected by DLS.

Due to the close boiling points of the mixed diethylbenzene (DEB) isomers, it is rather complicated to separate them by distillation. A new separation technique, distillative freezing (DF), is successfully applied to separate p-DEB from the diethylbenzene isomers in this study. Basically, the DF process operates at a triple point condition, in which the liquid mixture is simultaneously vaporized and solidified due to the three-phase equilibrium. It results in the formation of pure crystals along with the liquid phase and vapor phase of the mixtures. The process can be continued until the liquid phase is completely eliminated and only the pure solid crystals remain in the feed. A model, whereby the DF process is simulated in a series of equilibrium stage operations, is proposed to direct the DF operation. In the model, each stage is operated under an adiabatic condition at a three-phase equilibrium. The experiments show that, in the p-DEB/m-DEB mixtures, p-DEB can be purified from 80% to 99% through several DF operations with the experimental recovery rate of p-DEB in one DF operation ranging from 58% to 77%. The unique feature of this new separation technique is that no filtration and crystal washing is required after the p-DEB crystals are obtained by DF.

The deposition morphology of Brownian/non-Brownian particles within a constricted tube is investigated by applying the Brownian dynamics simulation method in the present paper. Two different geometric structures, the parabolic constricted tube (PCT) and the sinusoidal constricted tube (SCT), are adopted. The effect of various types of the total interaction energy curves of the Derjaguin–Landau–Verwey–Overbeek (DLVO) theory, and of the shadow area cast by those deposited particles, on the particles’ collection efficiencies are also examined. For the PCT structure, under the same interaction energy curve, it is found that the non-Brownian particles always own a higher collection efficiency than that of the Brownian particles. Since the deposition location moves closer to the constriction part of the tube, the collection efficiencies of the Brownian/non-Brownian particles increase with the decrease of flow velocity. The SCT behaves differently, it is found that the collection efficiencies of non-Brownian particles are only slightly higher than those of Brownian particles when SCT is adopted. The steep slope of the tube wall near the constriction part of SCT dominates the whole deposition process of Brownian/non-Brownian particles. In comparison with the available experimental data, it is found that the present method can give a good simulation result.

Granulation of gelatine by the breakup of its laminar jet followed by solidification of the droplets in a solvent has been investigated experimentally. The effects of nozzle size and tank pressure on granulation have been studied. Particles relatively narrow in size distribution were obtained by using small nozzle and low pressure. Particles in two sizes were obtained from nozzles with larger diameters.

The adsorption of gold complexes onto the activated carbon is the basis of modern techniques for gold recovery. The next step is the recovery of adsorbed gold from activated carbon with an efficient eluant. The objective of this study was to investigate an improved process for recovering gold from activated carbon. The process involves contact of gold laden activated carbon with a strong base at ambient temperatures followed by elution with an aqueous solution containing an organic solvent. Results showed that aqueous solutions of organic solvents, preferably aqueous solution of acetone or acetonitrile could be effectively used in the recovery of gold from loaded activated carbon which compared favorably with Zadra and AARL methods.

The hydrogen fuel cell is a promising option as a future energy resource; however, the nature of the gas is such that the conversion process of other fuels to hydrogen on board is necessary. Among the raw fuel resources, methane could be the best candidate as it is plentiful. In this experiment, the possibility of producing hydrogen with less carbon formation from methane by a dielectric barrier discharge (DBD) was investigated. Without the addition of a catalyst, the formation of hydrogen reached between 30% and 35% at methane residence time of 0.22 min and supplied powers in the range of 60–130 W. The hydrogen selectivity increased at higher supplied power, but the process efficiency, defined as a ratio of the produced hydrogen to the supplied power, decreased slightly. In order to boost the hydrogen production with less carbon formation, a mixed oxide catalyst of zinc and chromium was added to the reactor. It was shown that the production of hydrogen was ca. 40% higher than the non-catalytic plasma process.