Influence Of Activation Time Research Articles

Effect of activation time on sulfur-doped porous carbon for efficient degradation of organic pollutants with persulfate

Metal-free catalysis by using carbonaceous materials has propelled to the forefront in investigation of persulfate (PS) activation for green degradation of aqueous organic pollutants. Herein, sulfur-doped porous carbons (S-AC) were feasibly produced by chemical activation of Poly (phenylene sulphide) with KOH as activator. The influences of activation time on the porous structure, sulfur doping level, and chemical functionality of the as-prepared carbons were investigated by various characterization means. The S-AC samples were employed as metal-free catalysts to activate PS for phenol removal. Experiments results demonstrated that sulfur doping enhanced the catalytic activity of S-AC, and the S-AC-2 sample prepared by carbonization activation of 2 h was demonstrated to be a promising alternative to common metal oxides and other advanced carbon-based materials. Moreover, the S-AC-2/PS system could efficiently degrade various organics, which can be a green material for wastewater treatment and environmental remediation. In addition, the effects of various reaction parameters on phenol removal were discussed. It was found that S-AC-2 still presented an outstanding performance in a wide pH range. Furthermore, the PS activation mechanism over S-AC-2 was investigated by a series of classical radical quenching tests, EPR and Linear Sweep Voltammetry.

Improved extraction of cobalt and lithium by reductive acid from spent lithium-ion batteries via mechanical activation process

Cobalt (Co) and lithium (Li) were extracted from pure LiCoO2 powders and actual cathode material powders from the spent lithium-ion batteries (LIBs) after l-ascorbic acid dissolution via a mechanical activation process. The influences of activation time and rotation speed on the leaching were discussed. The mechanism of the improved leaching yield was proposed based on the characterization analysis including X-ray diffraction, scanning electron microscope, BET-specific surface area and particle size analyzer. The reduced particle size, increased specific surface area of activated samples, destroyed crystal structure and amorphous state of LiCoO2 contributed to the improved leaching efficiencies of Co and Li. With the activated process, about 99% Co and 100% Li were extracted from actual spent LIBs after 60-min grinding at 500 rpm with mild conditions. This effective process would be of great importance for recovering valuable metals from the spent LIBs at room temperature.

Comparative study on microstructure and surface properties of keratin- and lignocellulosic-based activated carbons

The paper probed the preparation of activated carbon by potassium silicate (K2SiO3) activation from keratin waste (cowhair waste, CW) and lignocellulosic materials (Cyperus alternifolius, CA) and the comparisons of physicochemical properties of the resulting carbons. These impregnation conditions were as follows: one impregnated at room temperature for 12h then dipped at high temperature for 30min; the other was only impregnated at room temperature for 12h, producing four activated carbons CWAC-1, CWAC-2, CAAC-1, and CAAC-2. The influence of activation time, K2SiO3/precursor weight ratio, and the pre-process on properties of activated carbons was discussed. The CWAC-1 produced at 700°C with the K2SiO3/precursor weight ratio of 2:1 possessed the Brunauer–Emmet–Teller (BET) surface area of 1965m2/g and total pore volume of 1.345cm3/g, while CAAC-1 prepared at the same conditions attained the BET surface area of 1710m2/g and total pore volume of 0.949cm3/g. The surface area and total pore volume of CAAC increased with the impregnation ratio. Moreover, CWAC-1, CWAC-2, CAAC-1, and CAAC-2 exhibited high portion of micropores, illustrating the role of K2SiO3. The analysis with a Fourier transform infrared spectrometer indicates that CWAC has more functional groups than CAAC, as well as CWAC-1 and CWAC-2 which possess similar functional groups.

Influence of activation time on the microstructure and antibacterial activity of Nanosilver-containing activated carbon fibers prepared from liquefied wood

Liquefied wood-based carbon fibers activated for different periods of time were modified by silver to produce nanosilver-containing activated carbon fibers (WACF/Ag). The microstructure and antibacterial activities of WACF and WACF/Ag were studied in this work. The results showed that WACF activated for longer periods of time had richer porosity and higher content active carbon-hydrogen bonds. More silver nanoparticles were found on WACF activated for longer periods of time. After loading silver on WACF, the relative contents of element carbon and graphitic carbon on fibers decreased, whereas those of elements oxygen and carbon bonded to oxygen-containing functions increased. With an increase in activation time, the changing ratios for elements oxygen and nitrogen gradually increased, while those for most of carboncontaining functions decreased. Meanwhile, as the activation time increased, the increasing silver particles were distributed on the surface and in pores of WACF, leading to the increasing micropores and mesopores of fibers were blocked by silver nanoparticles. The antibacterial activity of WACF/Ag was strengthened by increasing the activation time of WACF.

Optimization of preparation conditions for activated carbons from date stones using response surface methodology

The optimal conditions for preparation of activated carbons from date stones by ferric chloride activation (FAC) and commonly used zinc chloride activation (ZAC) were investigated. The influence of activation time, activation temperature, and impregnation ratio on the yield and phenol (Ph) uptake of such carbons were studied. Based on Box–Wilson central composite design, two second order polynomial models were developed to correlate the process variables to the two responses. From the analysis of variance the significant variables on each response were identified. For FAC, an optimum condition of 76min activation time, 707°C activation temperature, and 1.6 impregnation ratio gave 97.96mg/g Ph uptake and 47.24% yield, while for ZAC, 86.11mg/g Ph uptake and 39.16% yield were obtained at 30min activation time, 717°C activation temperature, and 0.5 impregnation ratio. The Langmuir isotherm was used to correlate equilibrium data of Ph adsorption, showing maximum Ph uptake of 170.97 and 161.54mg/g for FAC and ZAC, respectively. Also, the characteristics of both carbons were determined and found to have surface areas of 780.06 and 1045.61m2/g, respectively.

Experimental Study on Biopsy Sampling Using New Flexible Cryoprobes: Influence of Activation Time, Probe Size, Tissue Consistency, and Contact Pressure of the Probe on the Size of the Biopsy Specimen

Cryoextraction is a procedure for recanalization of obstructed airways caused by exophytic growing tumors. Biopsy samples obtained with this method can be used for histological diagnosis. The objective of this study was to evaluate the parameters influencing the size of cryobiopsies in an in vitro animal model. New flexible cryoprobes with different diameters were used to extract biopsies from lung tissue. These biopsies were compared with forceps biopsy (gold standard) in terms of the biopsy size. Tissue dependency of the biopsy size was analyzed by comparing biopsies taken from the lung, the liver, and gastric mucosa. The effect of contact pressure exerted by the tip of the cryoprobe on the tissue was analyzed on liver tissue separately. Biopsy size was estimated by measuring the weight and the diameter. Weight and diameter of cryobiopsies correlated positively with longer activation times and larger diameters of the cryoprobe. The weight of the biopsies was tissue dependent: lung < liver < stomach. Only little tissue dependency was found for the biopsy diameter. The biopsy size increased when the probe was pressed on the tissue during cooling. Cryobiopsies can be taken from different tissue types with flexible cryoprobes. The size of the samples depends on tissue type, probe diameter, application time, and pressure exerted by the probe on the tissue. Even the cryoprobe with the smallest diameter can provide larger biopsies than a forceps biopsy in lung. It can be expected that the same parameters influence the sample size of biopsies in vivo.

Overcoming the barrier to graphitization in a polymer-derived nanoporous carbon

A new pathway to synthesize a carbon with both nanoporosity and pre-graphitic structures has been discovered by annealing at 2000 °C a CO 2 activated, non-graphitizing, nanoporous carbon originally derived from polyfurfuryl alcohol. The activation process with CO 2 overcomes the barrier to graphitization normally present in this carbon even when treated at high temperature. Gas adsorption analysis, skeletal density measurements, X-ray diffraction, and transmission electron microscopy are utilized to probe the structure of both the non-activated and the activated carbons at 800, 1200, 1800, and 2000 °C. The influence of activation time is also examined. Prior to activation the nanopore walls are comprised of several layers of disordered graphenes. Activation eliminates the barrier to graphitization by reducing the number of layers below the limit of detection and by removing carbon material highly susceptible to oxidation. Annealing at 2000 °C of the carbon activated to 84% burnoff induces the formation of pre-graphitic domains amongst the nanoporous carbon. The (0 0 2) bands corresponding to 2 θ = 24.3°, 26°, and 26.5° are identified and assigned to amorphous, turbostratic, and graphitic morphologies. A pore volume of 0.50 cm 3 g −1 localized in pores below 2 nm in size is preserved after annealing.

Kinetic model for the isothermal activation of bentonite by sulfuric acid

The activation mechanism of typical bentonite powder with sulfuric acid was studied from variations in their surface area during the reaction. The surface area of activated samples at different activation temperatures and times were measured by methylene blue adsorption to quantify the effect of acid. The influence of activation time was investigated by isothermal experiments, performed at different temperatures. The specific surface area–time data were analyzed by using a modified kinetic model and the values of kinetic parameters were calculated. Also, the influence of acid concentrations on kinetic parameters was evaluated. The validity of proposed model to describe the bentonite activation kinetic was substantiated by computation of reaction time to achieve maximum value of specific surface area in other temperatures.

The Influence of Activation Time on the Contraction Force of Myocardial Tissue: a Simulation Study

The Influence of Activation Time on the Contraction Force of Myocardial Tissue: a Simulation Study

04/02679 Influence of activation time on characteristics ofactivated coke: Zhang, S. et al. Zhongguo Kuangye Daxue Xuebao, 2003, 32, (3), 289–292.(In Chinese)

04/02679 Influence of activation time on characteristics ofactivated coke: Zhang, S. et al. Zhongguo Kuangye Daxue Xuebao, 2003, 32, (3), 289–292.(In Chinese)

Preparation and characterization of activated carbons from rice husks and shells of palm fruits

Activated carbons from palm fruit shells (PFS) and rice husks (RH) were prepared using physical and chemical activation processes, respectively. The influence of activation time and temperature (in the case of PFS) and impregnation ratio and carbonization temperature (in the case of RH) on the properties of the resultant carbons were studied. In the case of PFS carbons, there were an increase in adsorption capacity and surface areas with increase in activation time and temperature. The surface area ranged between 292 and 642 m2g-1 at temperature range of between 1000 and 1200 K. In the case of RH carbons, surface areas and adsportion capacity also increased with increase in impregnation ratio and carbonization temperature. However, at temperatures above 1100 K there was a decrease in both surface area and adsorption capacity. The surface areas ranged between 146 m2g-1 and 526 m2g-1 at a temperature range of 1000 to 1100 K for the later carbons. Tanz. J. Sci. Vol. 28(2) 2002: 131-142

Influence of activation time on the properties of polyacrylonitrile‐based activated carbon hollow fiber

AbstractActivated carbon hollow fiber (ACHF) was prepared from polyacrylonitrile (PAN) hollow fiber through carbonization in nitrogen and activation with carbon dioxide. The effect of the activation time on the pore size distribution and the surface structure of the resulted ACHF was investigated. The results show that increasing the activation time at 800°C can increase the number of pores and reduce the crystal size, the tensile strength, the modulus, and the elongation. © 1995 John Wiley &amp; Sons, Inc.