Sorption properties of iron impregnated activated carbon web for removal of methylene blue from aqueous media

In this study, impregnation of iron chloride was carried out on needle punched web of waste acrylic fibers, which was subsequently carbonized under layer of charcoal by physical activation in high temperature furnace to produce iron impregnated activated carbon (FeAC). For comparison purpose, one more sample of activated carbon (AC) was prepared without impregnation of iron chloride. Both the webs were carbonized at 1200 °C with no holding time, and characterization of BET surface area, SEM morphology, EDX elemental analysis, XRD crystalline structure was performed. The FeAC web was used as adsorbent for the removal of methylene blue from aqueous solution. The dye removal percentage was investigated at different experimental parameters like different dye concentrations, adsorbent dosage, stirring speed and different pH. The obtained results were analyzed using linear and non-linear forms of Langmuir and Freundlich isotherms and adsorption kinetics (i.e. pseudo first order and pseudo second order model).     

Applicability of Industrial Sisal Fiber Waste Derived Activated Carbon for the Adsorption of Volatile Organic Compounds (VOCs)

Agricultural waste produced by the industry is a huge threat for the global environment. Utilization of agricultural waste is necessary and there is an urgent need to develop new techniques to solve this important problem. The main objective of this research was to evaluate the applicability of the activated carbon (AC) derived from industrial sisal fiber waste as passive samplers in monitoring toluene by comparing them to industry standard wafer and granular activated carbon (GAC). Carbonization time and ball milling effect on sisal fiber derived AC sample adsorption properties were investigated. Toluene adsorption isotherms were used to predict toluene adsorption capacities. Surface characteristics including surface area and pore volume were used to determine the relationships between them and adsorption capacity. Even though prepared AC samples have mesoporous structure, commercial samples have microporous structure. Surface area from 1245 m²/g to 1297 m²/g and toluene adsorption capacity from 21.4 % to 26.6 % was improved by increasing carbonization time from 1 h to 3 h at 650 °C carbonization temperature and 94.4 ml/min flow rate. Conversely, ball milling technique had negative effect by decreasing the surface area (674 m²/g) and the adsorption capacity of toluene (12.27 %). It is concluded that industrial sisal fiber waste have great potential as a precursor of AC for application in passive monitoring against toluene, particularly the produced mesoporous AC with 3 h carbonization time performs higher adsorption capacity (26.6 %) than commercially available microporous passive sampler (24.1 %) and GAC (22.8 %).     

Effects of carbonization temperatures on characteristics of porosity in coconut shell chars and activated carbons derived from carbonized coconut shell chars

A series of experiments have been conducted to study the effects of different carbonization temperatures (400, 600, 800 and 1000 °C) on characteristics of porosity in carbonized coconut shell char and activated carbon derived from carbonized coconut shell char with different activation times (30, 60, 90 and 120 min) at activation temperature of 900 °C. The results showed that high temperature carbonized coconut shell char and activated carbon samples derived from high temperature carbonized coconut shell chars had higher BET surface area, total volume, micropore volume and yield as compared to those of low temperature carbonized coconut shell char and activated carbon derived from low temperature carbonized coconut shell char. The BET surface area, total volume and micropore volume of activated carbon prepared from char obtained at 1000 °C with activation time of 120 min were 1926 m²/g, 1.26 cm³/g and 0.931 cm³/g, respectively. From the results, it was concluded that we could produce high surface area activated carbons from coconut shells using physical activation (steam activation) by proper selections of carbonization temperature and activation time.     

Evaluation of activated carbon fiber applied in supercapacitor electrodes

This study uses rayon woven fabrics as the raw material for activated carbon fabrics (ACFs), which were manufactured by oxidation, carbonization and activation engineering in a continuous semi-open high-temperature furnace. First, the activated carbon fabrics are prepared under two specific manufacturing conditions with different production rates and flow rates of steam activation at 1000 °C. Then the electrochemical prosperities of the ACFs are evaluated by a three-electrode device. The experimental results show that the BET specific surface area and electrical capacitance are higher with a lower production rate. Moreover, the steam activator higher flow rate under the proposed approach. ACFs with a 2332.1 m²/g specific surface area and 78.7 % mesopore ratio result in a higher electronic conductivity of 430.4 F/g at the low rate charge (5 mV/s) and with 60 % capacitance retention during the high-speed charging-discharging process (100 mV/s).     

Preparations of carbon fibers from precursor pitches synthesized with coal tar or petroleum residue oil

Pitch precursors were synthesized from coal tar(CT) and pyrolysis fuel oil(PFO, petroleum residue oil) at relatively low temperature of 250°C, in the presence of borontrifluoride/diethyletherate complex(BFDE) as a catalyst and nitrobenzene(NB) as a co-catalyst. The softening point, nitrogen content and carbon yield increased with an increase of concentration of NB. The pitch precursors with good spinnability were prepared by removing the volatile components through N₂ blowing. The precursor pitches were spun through a circular nozzle, stabilized at 310°C and finally carbonized at 1000°C. The optically anisotropic structure formed at the absence of NB was changed into isotropic structure, showing a decrease in size of the flow domain. The hollow carbon fiber could be prepared in the process of stabilization. The results proposed that the morphology of carbon materials could be controlled by changing the concentration of catalyst and/or co-catalyst and/or stabilization condition that affect on the mobility of molecules during carbonization.     

Production of carbon fibers modified with ceramic powders for medical applications

Carbon fibers and precursor polyacrylonitrile (PAN) fibres that contain either silica or hydroxyapatite particles, imbedded during the spinning process, were studied in this paper. The modified PAN fibers were thermally stabilized using a multi-stage process in the temperature range between 150 to 280 °C in an oxidative environment. Subsequent carbonization leading to obtain carbon fibers was carried on at 1000 °C in an argon atmosphere. The changes of properties of composite precursor fibers taking place during stabilization and carbonization processes were investigated by the combination of Differential Scanning Calorimetry, Fourier Transform Infrared Spectroscopy, Scanning Electron Microscopy equipped with energy dispersive X-ray spectrometer and ultrasonic methods. Mechanical properties, such as tensile strength, static Young’s modulus, elongation at fracture were analyzed at each stage of thermal stabilization process. Additionally some traditional measurements like fiber diameter and mass were studied. Ceramic powders added to the spinning solution were present also in composites fibers after stabilization and carbonization process. Such modification allows to avoid the post-treatment operations, for example by coating or covering with films, which were usually necessary in order to obtain bioactive character of implants. Modification of carbon fibers using calcium phosphate or silica can lead to the development of a new materials for the manufacturing of implants which can establish direct chemical bonds with bone tissue after implantation.     

Sorption of Yellow 59 on Posidonia oceanica,a non-conventional biosorbent: Comparison with activated carbons

Posidonia oceanica, an endemic marine magnoliophyta found in the Mediterranean Sea, is used as a biosorbent for dye wastewater treatment. The ability of P. oceanica to remove the dye C.I. Acid Yellow 59 from an aqueous solution was compared to that of two commercial activated carbon forms: powdered (PAC) and granular (GAC) activated carbon. The effect of initial pH, mass concentration, contact time and initial dye concentration were investigated for the three sorbents. Equilibrium uptake was found to be pH dependent and maximum uptake was observed at an acid pH (2–3) for all materials. Kinetic studies for initial dye concentration of 20, 50 and 100 mg L^?1 showed that dye uptake followed the pseudo-second order model for all materials and equilibrium was reached in 10, 400 and 600 min for PAC, GAC and P. oceanica, respectively. The equilibrium data tend to fit Freundlich isotherm model for all materials, the best retention of C.I. Acid Yellow 59 was found to be on PAC followed by P. oceanica and then GAC. This comparative study indicates that sorption onto P. oceanica is an effective, cheaper alternative for dye removal.     

Effect of high temperature treatment on electrochemical properties of activated carbon fabric in supercapacitor application

In this study, viscose rayon-based activated fabrics were used as the electrodes of supercapacitors. First, viscose rayon knitted fabrics underwent oxidation, carbonization and activation in a semi-open high-temperature erect furnace to produce activated carbon fabrics (ACFs). They were then treated at temperatures up to 1500 °C for one hour. Electrochemical properties of ACFs were investigated by cycle voltammetry and electrochemical impedance spectroscopy. The ACFs after high temperature treatment has improved conductivity and substantially increased mesopore ratio, yielding higher capacitor retention in rapid charging-discharging processes. It is shown that the ACFs treated at 1500 °C had the highest mesopore ratio of 83 %, specific surface area of 1254 m²/g and average pore diameter of 20.9 Å, resulting in lower resistance of 0.2 Ω-cm. In addition, this ACFs electrode showed the highest capacitance retention of 49 % at high charging speed of 250 mV/s.     

Electrical conductive and structural characterization of electrospun aligned carbon nanofibers membrane

In the paper, the membrane with aligned carbon nanofibers (CNFs) was prepared by electrospinning, stabilization and carbonization. The electrical conductivity of the membrane was examined. The effect of stabilization temperature and drum rotating speed on the conductivity of aligned CNFs membrane was discussed. The study on stabilization temperature showed that 250 °C was optimum parameter for preparing fibrous aligned CNFs membrane with uniform diameter, but 270 °C was benefit to fiber conglutination which could improve the electrical conductivity of the final CNFs membrane. The study on drum rotating speed showed that when drum rotating speed reached 2500 rpm, graphitic structures with parallel graphene sheets could be observed and 1000, 1500 and 2000 rpm CNFs membranes presented desirable conductivity with only 1.3 Ω·cm in the parallel directions and 2.0 Ω·cm in the perpendicular direction.     

Development of Activated carbon from Windmill palm sheath fiber by KOH activation

In this study, activated carbon was prepared from windmill palm sheath fiber (WPF) powder by KOH activation for full utilization of the bioresource. First, the optimal parameters of the activation technology, such as impregnation ratio, temperature, and time, were determined. The pyrolysis process and activation mechanism of KOH were investigated by thermogravimetric analysis (TGA). WPF powder-based activated carbons were then prepared under the optimized condition and characterized by SEM, FTIR, XRD, and nitrogen adsorption techniques. The reaction mechanisms were deduced in two phases. The reaction mechanisms in the first carbonization process were mainly related to substitution, scission, and oxidization reactions of methylene. In the second activation process, KOH and carbon began to react at 350 °C, producing potassium compounds, which further reacted with carbon. Results show that the optimal process for preparing an excellent adsorbent from WPF employs an impregnation ratio of 4:1 at 850 °C for 2.5 h, which can result in a good adsorption property for methylene blue, high BET surface area of 1734.34 m²/g, and total pore volume of 0.96 cm³/g. WPF-based activated carbon demonstrates a remarkable adsorption capacity, and thus WPF has great potential value as a new agricultural resource.     

Thermodynamics of adsorption of laccaic acid onto chitosan and associated dye toxicity studies

The thermodynamics of adsorption of laccaic acid (lac dye) onto chitosan were investigated under acidic condition over various concentrations (20–293 mg/l). Langmuir, Freundlich, and Temkin isotherms were used to analyze the equilibrium data at different temperatures, with the Freundlich isotherm fitting the experimental data significantly better than the other isotherms. The effect of temperature on the adsorption isotherm was studied by carrying out a series of isotherms at 10, 20, 40, and 60 °C. It was found that more dye was strongly adsorbed by chitosan when the temperature of the dye solution increased. Thermodynamic parameters such as free energy change (ΔG°), enthalpy change (ΔH°), and entropy change (ΔS°) were also evaluated. The negative value of ΔG° and positive value of ΔH° indicated that the laccaic acid adsorption process is a spontaneous and an endothermic one. Attenuated total reflectance Fourier transform infrared spectroscopy confirmed the functional groups of chitosan that affected the laccaic acid adsorption. Therefore, laccaic acid molecules could interact with the chitosan via electrostatic forces, hydrogen bonding, and ion-dipole interactions under acidic condition. From the toxicity study, the dye solution with the initial dye concentrations of 40 and 120 mg/l before dye removal showed significant mortality to earthworm Diplocardia communis (P<0.01).     

The impact of heating and cooling on the physico-chemical properties of wheat gluten–water suspensions

The rapid visco analysis (RVA) system was used to measure rheological behaviour in 20% (w/v) gluten-in-water suspensions upon applying temperature profiles. The temperature profiles included a linear temperature increase, a holding step, a cooling step with a linear temperature decrease to 50 °C, and a final holding step at 50 °C. Temperature and duration of the holding phase both affected RVA viscosity and protein extractability. Size-exclusion and reversed-phase HPLC showed that increasing the temperature (up to 95 °C) mainly decreased glutenin extractability. Holding at 95 °C resulted in polymerisation of both gliadin and glutenin. Above 80 °C, the RVA viscosity steadily increased with longer holding times while the gliadin and glutenin extractabilities decreased. Their reduced extractability in 60% ethanol showed that γ-gliadins were more affected after heating than α-gliadins and ω-gliadins. Enrichment of wheat gluten in either gliadin or glutenin showed that both gliadin and glutenin are necessary for the initial viscosity in the RVA profile. The formation of polymers through disulphide bonding caused a viscosity rise in the RVA profile. The amounts of free sulphydryl groups markedly decreased between 70 and 80 °C and when holding the temperature at 95 °C.     

Effect of high temperature treatment on electrochemical properties of carbon nanofiber membrane

In this study, polyacrylonitrile was used as the nanofiber membrane material. Through A two-stage continuous process, namely, oxidation process and carbonization and activation process, an activated nanofiber membrane material was fabricated. Subsequently, the membrane underwent high-temperature heat treatment (1100-1500 °C) to explore the effect of temperature on its properties. Charge/discharge rate was employed to determine the capacitance retention ratio to evaluate the applicability of the fabricated membrane in high-power super capacitor electrodes. The results revealed that in the treated membrane, the lattice size increased from 1.24 nm to between 3.20 and 4.72 nm. In addition, the volume resistivity was reduced from 6 Ω-cm to between 9.70E-2 and 3.85E-2 Ω-cm, substantially improving the electric conductivity. The activated carbon nanofiber membrane treated with high temperature at 1100 °C exhibited the highest capacitance of 704 F/g at a scan rate of 5 mV/s.     

Modeling and differential evolution optimization of PAN carbon fiber production process

In this research, results of an experimental and artificial neural network fuzzy interface system (ANFIS) modeling of operating parameters on tensile strength of the carbon fibers are investigated. To do these experiments, the commercial polyacrylonitrile (PAN) fiber of Polyacryl Iran Corporation (PIC) was used as the precursors. The results show that increasing all of parameters improves tensile strength performance. ANFIS was applied to predict tensile strength of carbon fibers as a function of stabilization temperature at first stage (STFIS), stabilization temperature at second stage (STSS), stabilization temperature at third stage (STTS), stabilization temperature at fourth stage (STFOS), and carbonization temperature (CT). The optimum levels of influential factors, determined for tensile strength are STFIS 200 °C, STSS 225 °C, STTS 240 °C, STFOS 260 °C, CT, and 1400 °C. The modeling results showed that there is an excellent agreement between the experimental data and the predicted values. Furthermore, the fiber process is optimized applying differential evolution (DE) algorithm as an effective and robust optimization method.     

High performance fibers production process using Taguchi experimental design

In this research, results of an experimental interaction effect of operating parameters on tensile strength carbon fibers from a commercial PAN-based precursor are investigated. Ten parameters at two and four levels (L₃₂=2¹×4⁹) were investigated: stabilization temperature at first stage (STFIS), stabilization duration time at first stage (SDTFIS), stabilization temperature at second stage (STSS), stabilization duration time at second stage (SDTSS), stabilization temperature at third stage (STTS), stabilization duration time at third stage (SDTTS), stabilization temperature at fourth stage (STFOS), stabilization duration time at fourth stage (SDTFOS), carbonization temperature (CT), and carbonization duration time (CDT). In this study, Taguchi method was used initially to plan a minimum number of experiments. Statistical analysis, analysis of variance (ANOVA), was also employed to determine the relationship between experimental conditions and yield levels. ANOVA was applied to calculate sum of square, variance, ratio of factor variance to error variance and contribution percentage of each factor on response. The results show that increasing all of parameters improves tensile strength performance. The optimum levels of influential factors, determined for tensile strength are STFIS 200 °C, SDTFIS 120 min, STSS 225 °C, SDTSS 120 min, STTS 240 °C, SDTTS 120 min, STFOS 260 °C, SDTFOS 60 min, CT 1400 °C and CDT 10 min. The results showed that CT and ODTFIS are the most and the less effective factors on response, respectively.     

显脉球须刺蛾多角体病毒的初步研究

从显脉球须刺蛾(Scopelodes venosa Kwangtungensis Hering)幼虫自然罹病死亡虫体中,分离到1株多角体病毒,包涵体呈多角形,有四边、六边、八边等多种形态,大小为600—800×1000—1200nm,多角体会在0.05 mol/L Na_2CO_3+0.1 mol/L NaCl 弱碱溶液中降解,且能释放出短杆状的病毒粒子,其大小为260—300×40—60 nm。室内感染3—4龄幼虫,LC_(50)为4.112×10~3 PIB,回归直线方程为 y=0.549x+2.86     

Effect of temperature and activators on the characteristics of activated carbon fibers prepared from viscose-rayon knitted fabrics

This study used viscose rayon-based knitted fabric, pre-treated by a composite flame retardant, as the precursor. The fabric then underwent oxidation, carbonization and activation in a semi-open high-temperature erect furnace to produce Activated Carbon Fabrics (ACF). The microstructure and chemical properties of the ACF were obtained under carbonization temperatures of 600–1000 °C and by different activation sources. The results showed that the ACF produced was mainly of a microporous structure. When the carbonization temperature was increased, the production rate dropped while both the true density (D_He) and crystallization thickness increased. In addition, ACF prepared using steam, plus water as the activation source, has a larger specific surface area, greater crystallization thickness and a higher true density (D_He).     

Optimization of curing process for polymer-matrix composites based on orthogonal experimental method

In this paper, the orthogonal experimental method was carried out to optimize the curing process of aeronautical composite X850/T800 in autoclave process. Four important curing parameters including curing pressure, heating rate, curing temperature and heat preservation time were taken into account, and sixteen samples were fabricated to study the effects of the four parameters mentioned above on the curing quality by interlaminar properties test and microstructure analysis. The interlaminar properties and the interfacial bonding quality of these samples were studied by the short-beam three points bending test and scanning electron microscopy, respectively. Results revealed that the optimal curing process of X850/T800 composite laminate should be as follows: curing pressure of 0.6 MPa, heating rate of 1.5 °C/min, curing temperature of 160 °C, and heat preservation time of 120 min.     

Preparation of carbon fiber from heavy oil residue through bromination

A pitch precursor for a general purpose carbon fiber was prepared by condensation of pyrolized fuel oil (petroleum residual oil) with bromine under nitrogen blowing. Such a condensation raised the softening point of the pitch from 40°C to 265°C with a yield of 43%. The pitch precursor showed an enhanced aromaticity and enlarged molecular size, which led to a reduction in molecular mobility and optical isotropy. The precursor was spun into fibers of 20 μm diameter at a take-up speed of 700 m/min. The fiber was stepwise stabilized in air and carbonized in Ar gas to obtain an isotropic carbon fiber. The carbon fiber exhibited tensile strengths of 500–800 MPa though the fiber was formed via a crude method. The electric conductivity of the carbon fiber was relatively high, 2.2×10² S/cm, sufficient to be used as electrode materials.     

Impact of redox agents on the physico-chemistry of wheat gluten proteins during hydrothermal treatment

The impact of the oxidants potassium bromate and potassium iodate and the reducing agent dithiothreitol (DTT) on the rheological behaviour of 20% (w/v) gluten-in-water suspensions during thermal treatment was monitored with the rapid visco analyser (RVA). The suspensions were subjected to a linear temperature increase from 40 to 95 °C in 14 min, a holding step of 40 min at 95 °C, a cooling step (7 min) with a linear temperature decrease to 50 °C, and a final holding step at 50 °C (13 min). Potassium iodate (1.18 and 1.77 μmol/g protein) and potassium bromate (1.52 and 15.2 μmol/g protein) decreased RVA viscosities in the holding step and increased sodium dodecyl sulphate (SDS) protein extractabilities suggesting a greater heat resistance and decreased gliadin–glutenin cross-linking. In contrast, in the presence of DTT (1.65 and 3.30 μmol/g protein) RVA viscosity increased at lower temperatures and lowered SDS extractabilities. It is postulated that low concentrations of reducing agent facilitate gliadin–glutenin cross-linking during heating while oxidants hinder gluten polymerization due to decreased levels of free sulphydryl groups and less flexibility of the glutenin chains.