Recycling of carbon fibre reinforced polymeric waste for the production of activated carbon fibres

Composite waste composed of carbon fibres and polybenzoxazines resin has been pyrolysed in a fixed bed reactor at temperatures of 350, 400, 450, 500 and 700 °C. Solid residues of between 70 and 83.6 wt%, liquid yields 14 and 24.6 wt% and gas yields 0.7 and 3.8 wt% were obtained depending on pyrolysis temperature. The derived pyrolysis liquids contained aniline in high concentration together with oxygenated and nitrogenated aromatic compounds. The pyrolysis gases consisted mainly of CO₂, CO, CH₄, H₂ and other hydrocarbons. The carbon fibres used in the composite waste were separated from the char of the solid residue via oxidation of the char at two different temperatures and investigated for their mechanical strength properties. The carbon fibres recovered from the sample pyrolysed at 500 °C and oxidised at 500 °C exhibited mechanical properties which were 90% of that of the original virgin carbon fibres. Steam activation of the recovered carbon fibres was carried out at 850 °C at different times of activation. The effect of activation time on BET surface area, activated carbon fibres yield, porosity and the morphological structure of activated carbon fibres was evaluated. A maximum BET surface area of over 800 m² g⁻¹ was obtained for the activated carbon fibres produced at 850 °C for 5 h of activation. Nitrogen adsorption-desorption isotherms showed that the adsorption capacity increased as the activation time increased up to 5 h of activation and then after that decreased.     

Spectroscopy analyses of hybrid unsaturated polyester composite reinforced by Alfa,wool, and thermo-binder fibres

Alfa’s fibres surfaces were modified chemically by the presence of wool and [poly(ester terephthalate) (PET)–polyethylene (PE)] thermo-binder fibres. Indeed, vibrational analyses based on Fourier transform infrared spectroscopy and Raman measurements have confirmed the existence of chemical interactions between these fibres. These analyses have shown that the hydrophilic character of Alfa fibres could be decreased either by hydrogen bonds between water molecules and wool fibres or by the crystallinity of PET constituents in PET-PE thermo-binder fibres which might confer its hydrophobic character to Alfa’s fibres surfaces. As a result, the compatibility between the Alfa fibres and the unsaturated polyester matrix was enhanced, which allowed adhesion mechanism based on chemical bonds formed by secondary bonding. Such adhesion mechanism was also proven by the ¹³C Cross-Polarization Magic Angle Spinning Nuclear Magnetic Resonance spectroscopy results.     

How slug flow can improve ultrafiltration flux in organic hollow fibres

The study deals with the use of a gas-liquid two-phase flow to reduce particle membrane fouling in organic hollow fibres by injecting air directly into the feed stream. A theoretical approach of slug flow in fibres demonstrates that the slugs created inside the fibres induce high wall shear stresses. Moreover, the membrane surface is alternately submitted to positive and negative shear stresses. This succession of stresses is expected to prevent filtered particles from settling on the membrane surface and then enhance the ultrafiltration mass transfer. Experiments were carried out with clay suspensions in hollow fibre membrane. A range of various air velocities and particle concentrations was examined and the effect of a steady gas flow was compared to that of an intermittent one. As expected, the injecting air process leads to an increase of the permeate flux by up to 110% for U_g=1 m s⁻¹ (flux multiplied by 2.1), for all the various concentrations studied. Furthermore, even at a low air velocity a significant enhancement can be achieved (+60% for U_g=0.1 m s⁻¹, flux multiplied by 1.6). An intermittent gas flow seems to be less effective than a steady one in similar experimental conditions.     

Synthesis and characterization of microcrystalline cellulose powder from corn husk fibres using bio-chemical route

In the present study low cost microcrystalline cellulose (MCC) powder was prepared from cornhusk fibres, extracted chemically followed by anaerobic consortium treatment. Cornhusk fibres were treated with 10% alkali at 120 °C for 60 min followed by anaerobic consortium treatment for 3 days. It was then bleached with hydrogen peroxide and finally washed. Bleached pulp was hydrolysed using 4 N HCl to get the MCC. In the present investigation, we have characterized the MCC prepared from cornhusk fibres thoroughly for its physico-chemical properties and compared with Avicel^®-PH 101, a commercial grade MCC. Scanning Electron Microscopy (SEM), Fourier Transform Infrared Spectroscopy (FTIR), X-Ray Powder Diffraction (XRD) and Differential Scanning Calorimetry (DSC) were used for characterization of samples. Similarly the powder and flow properties of the MCC prepared from cornhusk fibres were also investigated and the results were compared with Avicel^®-PH 101. Our results showed that various properties and the purity of MCC prepared from cornhusk fibres are comparable to the commercial grade MCC. Since, cornhusk is an agricultural waste product, MCC obtained from cornhusk fibres will be from cheaper raw materials than current market MCC.     

Water vapour adsorption on organic and inorganic polymers

Water vapour adsorption on polymers affects their processing behaviour and useful properties. Water vapour adsorption on organic polymers, silk, Nylon 6 fibres in undrawn and permanent set forms, polyester micro fibres, plasticised PVC films with 60 phr dioctylphthalate (DOP) and inorganic polymer sepiolite particles were investigated in this study. The materials were examined using the BET equation. The surface areas of silk, cast Nylon 6 and muss Nylon 6 were determined as 108, 46 and 23 m² g^–1, respectively. Sepiolite did not fit BET equation. Polyester and PVC adsorbed very small amounts of moisture.This revised version was published online in November 2005 with corrections to the Cover Date.     

Characterization and pyrolysis behaviour of different paper mill waste materials

Paper industry generates a considerable amount of wastes. Their composition mainly depends on the type of paper produced and the origin of cellulose fibres. Nowadays, in Spain, 40% of solid wastes generated by the paper and pulp industry are deposited directly in landfill, 25% are used in the agriculture, 13% in the ceramic industry and 7% in the concrete production. In the last years, thermal treatment methods like combustion, pyrolysis and gasification have been widely study as alternative techniques for the valorization of different organic waste materials. The main objective of the present work is to study the pyrolysis behaviour of different paper mill waste materials. For this reason, a wide characterization of eight paper mill waste materials from different origins was performed using SEM, FTIR, DRX and thermogravimetric techniques. Paper mill sludges from recycled paper, mainly wastes obtained from deinking process, showed high CaCO₃ and clays contents. Compared with the elevated total organic matter content (TOM) of paper mill waste materials their low organic carbon content determined by Cr₂O₇²⁻ oxidation reveals the elevated chemical stability of organic matter, due to high content on cellulose fibres. Analysis of samples by SEM indicates that successive recycled processes of paper leads to paper mill waste materials with more degraded fibres. XRD analyses show as crystalline cellulose was present in reject and primary sludge from paper mills that produced paper from virgin wood. However, crystalline cellulose content significantly decreased in waste materials from recycled paper. Finally, thermogravimetric analysis indicates that presence or mineral matter and degradation of cellulose significantly influences their pyrolysis behaviour. In general, weight loss of paper mill waste materials started at lower temperatures than pure cellulose. In waste materials from recycled paper weight loss continues at temperatures highest than 500 °C due to kaolinite dehydration and carbonates decomposition.     

Synthesis and characterization of reactive dyes based on 2-phenyl-3-[4′-(4″-aminophenylsulphonamido)]phenyl-4(3H)-quinazolinone-6-sulphonic acid

A series of new quinazolinone based mono azo reactive dyes (D_1–10) have been prepared by subsequent diazotization of 2-phenyl-3-[4′-(4″-aminophenylsulphonamido)]phenyl-4(3H)-quinazolinone-6-sulphonic acid (C) and coupling with various 4-chloro anilino cyanurated coupling components. These dyes give purple, red, orange and yellow color shades. All the reactive dyes were characterized by their percentage yield, UV–Vis spectroscopy, elemental analysis, IR spectroscopy, ¹H NMR spectroscopy and dyeing performance on silk, wool and cotton fibres. The percentage dye bath exhaustion on different fibres has been found to be reasonably good and acceptable. The dyed fibres show moderate to very good light fastness and good to excellent washing and rubbing fastness.     

Inverse gas chromatography for natural fibre characterisation: dispersive and acid-base distribution profiles of the surface energy

Inverse Gas Chromatography (IGC) is a gas sorption technique to determine the surface energy of natural fibres. The surface energy is directly related to the thermodynamic work of adhesion and it reflects the fibre adsorption capacity and its wettability. However, natural fibres have a complex surface chemistry of numerous organic species and present physical asperities that render the surface energetically heterogeneous. Since IGC is typically performed at infinite dilution where only the higher energetic sites interact with the solvent, a single measure of surface energy is likely to be misleading as the surface energy changes with changing chemical composition. Here we present the dispersive and acid-base surface energy profiles of flax and kenaf fibres as well as continuous filament fibres produced by a dry jet, wet spinning process (cellulose B). We injected a series of n-alkanes at finite dilution to obtain the dispersive energy distribution profile at \(30\,^{\circ }\hbox {C}\) and 0% RH. The acid-base contributions were determined by injection of mono polar probes (dichloromethane, ethylacetate) at the same surface coverages and applying the Van Oss method. The cellulose B fibres were the most energetically homogeneous, while the bast fibres were shown to have a higher polar component and much broader surface energy distributions than the cellulose fibres.     

An oxyluminescence investigation of the auto-oxidation of nylon 66

The kinetics of the thermal oxidation of stabilised and unstabilised nylon 66 fibres and films have been studied by photon counting oxyluminescence methods from 50°C to 150°C. The activation energies for initiation (E₁), propagation (E₃) and termination (E₅) over this temperature range are: E₁ = 16 kcal mol^?1, E₃ = 17·5 kcal mol^?1 and E₅ ≈ 12 kcal mol^?1. The extent of orientation of the polymer does not change the nature of the oxyluminescence curve or E₃ and E₅ above 110°C.Significant losses of critical mechanical properties of the fibres occur in the induction period at 100°C and non-stationary kinetics are described to enable this region to be studied by oxyluminescence. The oxidation rate in the induction period and the limiting rate region in air is one-third the rate in oxygen at atmospheric pressure. Non-stationary methods show that alkyl radical reactions are competitive with alkyl peroxy radical formation in air over the temperature range 100°C to 140°C. This affects the course of the oxidation reaction and the stabiliser efficiency and explains the observation of unsaturated oxidation products by phosphorescence spectroscopy.     

Measurement of the flexibility of wet cellulose fibres using atomic force microscopy

Flexibility and modulus of elasticity data for two types of wet cellulose fibres using a direct force–displacement method by means of AFM are reported for never dried wet fibres immersed in water. The flexibilities for the bleached softwood kraft pulp (BSW) fibres are in the range of 4–38 × 10¹² N^?1 m^?2 while the flexibilities for the thermomechanical pulp (TMP) fibres are about one order of magnitude lower. For BSW the modulus of elasticity ranges from 1 to 12 MPa and for TMP between 15–190 MPa. These data are lower than most other available pulp fibre data and comparable to a soft rubber band. Reasons for the difference can be that our measurements with a direct method were performed using never dried fibres immersed in water while other groups have employed indirect methods using pulp with different treatments.     

Radial structure and property relationship in the thermal stabilization of PAN precursor fibres

Here we report on the role of oxygen in the evolution of radial heterogeneity in the fibre structure and properties of PAN fibres stabilized in air and vacuum at different temperatures. Modulus mapping by Nano-indentation showed heterogeneous modulus distribution in the fibres treated in air, while no variation in modulus was observed in fibres processed in vacuum. Raman spectroscopy and elemental analysis revealed that the temperature dependent oxygen diffusion from skin to core of the fibres assisted in the evolution of higher extent of sp²-hybridized carbons in the skin compared to core of the air treated samples. Conversely, no radial structure variations were observed in the vacuum treated fibres. Higher modulus in the skin of air-treated fibres was due to the formation of compact structures which was associated with the enhanced intermolecular interactions facilitated by the formation of C=C bonds within the polymer backbone, promoted by oxidative-dehydrogenation reaction. Supporting these observations, the fracture morphology examined by SEM showed a brittle fracture in the skin and ductile fracture in the core.     

Derivatization of Humic Compounds: An Analytical Approach for Bound Organic Residues

Abstract

Bound residues of pesticides and their metabolites are defined as being nonextractable with organic solvents, but partly extractable together with the humic matrix by NaOH or other solvents suitable to extract humic compounds. Recently, an improvement in humus extraction from soils was achieved upon derivatization of the organic matter with silylating reagents at room temperature. By this method 70–90% of the organic carbon or nitrogen either from soil or from humin became soluble in organic solvents. The extracts were analyzed by means of ¹³C NMR-spectroscopy. The spectra were well resolved with signal-separation of less than 1 ppm. The extracted humic compounds were of rather low molecular weight, ranging from 300 to 4000 to 6000 d or more.

¹⁴C-labeled residues of pesticides or other xenobiotics found to be nonextractable after exhaustive organic solvent extraction became readily dissolved along with most of the humic matrix using this derivatization procedure. Between 60–80% of ¹⁴C anilazine residues or of ¹⁴C-labeled chlorinated phenols or anilines originating from both previously solvent extracted soil samples or from humin became solubilized in organic solvents.     

Ultrasonic vibration potentials,apparent molal volumes,and apparent molal heat capacities of 1:1 electrolytes in acetonitrile

The ultrasonic vibration potentials and apparent molal volumes for many inorganic and organic electrolytes were measured in acetonitrile at 25°C and combined to obtain ionic contributions to the standard partial molal volumes V°(ion). Monatomic cations and anions of the same size essentially have the same V°(ion). Their size dependence can be interpreted through Hepler's equation. The apparent molal heat capacities were also measured in acetonitrile and used to derive standard values. Various methods of estimating C _p ⁰ (ion) were investigated and an ionic scale is proposed. It is concluded that C _p ⁰ (ion) of large organic ions are very close to the intrinsic heat capacities of the ions, and the solvation contribution to monatomic ions is positive for both cations and anions.     

Effect of the Measurement Temperature on the Dispersive Component of the Surface Free Energy of a Heat Treated SiO2 Xerogel

The surface free energy of a monolithic silica xerogel treated at 1000°C has been measured by inverse gas chromatography in the temperature range 25–150°C using n-alkanes. Values of the dispersive component, _S ^D, vary from 49.07 mJ·m^–2 at 25°C to 17.20 mJ·m^–2 at 150°C. The _S ^D value obtained at 25°C is lower than that found for amorphous and crystalline silicas but higher than that found for glass fibres meaning that the heat treatment at 1000°C changes drastically the structure of the silica xerogel showing a surface similar to a glass. However, the higher value of _S ^D in comparison to glass fibres can be attributed to the mesoporous structure present in the silica xerogel. In the temperature range of 60–90°C there exists an abrupt change of the _S ^D values as well as in the dispersive component of the surface enthalpy, h _S ^D. Such abrupt change can be attributed to an entropic contribution of the surface free energy.     

预聚-酶催化缩聚法合成超支化聚酯及其结构表征

以丙三醇、1,6-己二醇和己二酸为共聚单体,以固定化脂肪酶Novozym435为催化剂,尝试先进行共聚单体的预聚后在有机介质中进行酶催化直接缩聚反应合成脂肪族超支化聚酯的新途径,考察了反应介质和反应温度对酶催化缩聚反应的影响,并采用凝胶渗透色谱和核磁共振确定产物的分子量和结构.结果表明,将单体的预聚与酶催化缩聚反应相结...     

Variation of 14C, 137Cs and stable carbon composition in forest soil and its implications

In Japan, about 70% of land area is covered by forest. Therefore, forest ecosystem plays a vital role in ultimate fate of radionuclides and carbon cycle in terrestrial environment. In this study, three undisturbed forest soil profiles were collected from Ibaraki Prefecture, Japan. The ¹³⁷Cs data illustrate that maximum fallout deposition of ¹³⁷Cs took place around 1964. ¹⁴C determination shows that ¹⁴C also has peak values in the top 10 cm of the soil profiles ascribed to the highest bomb ¹⁴C level in 1960's. The ¹³C data show that the turnover dynamics of soil organic carbon could be described very well by progressive enrichment values of d¹³C.     

An evaluation of trace element analysis in the forensic investigation of fibre samples

The use of trace element analysis in the forensic examination of fibres has been investigated. Samples of both natural and synthetic fibres have been analysed to show that it is possible to both identify and discriminate between samples that would, by present methods, be considered indistinguishable. A number of wool garments of predetermined trace element composition were sent for wear for a period of nine months. The conditions and frequency of wear and cleaning were reported to enable their effect upon the trace element composition of these garments to be determined. The wool samples were analysed by both short (30 min) and long (50 hrs) irradiations in a reactor flux of about 10¹² n·cm⁻²·sec⁻¹. This permitted the concentrations of the elements such as sodium, chlorine, iodine, manganese, cobalt and chromium to be determined. Both sodium iodide and lithium drifted germanium detectors were used to measure the induced activity of the wool samples. The composition of a range of acrylic fibres from a variety of sources has also been examined using a sodium iodide detector. The concentrations of sodium chlorine, bromine, managese, copper, aluminium, titanium, indium and barium were determined in these samples.     

Monitoring chlorophenols in industrial effluents by solid-phase microextraction–gas chromatography–mass spectrometry

A method for the determination of 19 chlorophenols in industrial effluents samples using solid-phase microextraction (SPME) coupled to gas chromatography–mass spectrometry has been developed. Four kinds of different SPME fibres have been studied. Among them, the polyacrylate and carbowax®-divinylbenzene fibres were the most adequate. The extraction process was optimized by means of the experimental design, which allows the study of a large number of factors with a reasonable number of experiments. The optimized method allows the determination of the studied chlorophenols in complex matrices with a high organic content with detection limits down to 0.07?ng?mL^?1 and RSD ranging from 4.4% to 13.8%. The recovery studies with spiked real effluent samples at low levels of chlorophenols ranged from 59.8% to 142.1% for the lowest level (0.5?ng?mL^?1) and from 79.6% to 115.8% for the highest spiked level (2?ng?mL^?1). These results show the suitability of the proposed method to monitor chlorophenols in complex samples. 2,4,5-TCP was detected at concentrations close to its limits of detection in effluents coming from an oil refinery.     

The effect of fibre diameter on filtration and flux distribution — relevance to submerged hollow fibre modules

This paper examines the effect of fibre diameter on filtration and flux distribution with inter-fibre two-phase flow for conditions relevant to submerged bioreactors (SMBR). Hollow fibres of different diameters fixed in a specially designed holder providing shell-side feed were tested for a model biomass feed with pumping and submerged systems. The experimental results showed that the effect of the fibre diameter on filtration increased with the increase in turbulence around the fibres. For filtration with two-phase flow, the performance was sensitive to changes in fibre diameter and significantly lower flux declines were obtained with smaller fibres. On the other hand, a theoretical analysis of flux distribution along the fibre in a submerged system showed the smaller fibres to be disadvantaged. The theoretical model based on the simplified Navier–Stokes equations and filtration equations revealed that the flux distribution along the fibre depends on fibre inner diameter, length and fibre permeability. The effect of these factors can be related to a dimensionless coefficient ζ=4lR_i^−3/2R_m^−1/2. Sensitivity analysis demonstrated that for ζ>2, the maximum flux along the fibre can be approximately estimated by J_max=ζJ_mi. Although, the effect of high initial local flux on performance of filtration is still to be assessed, the flux distribution model is useful in design and operation of the SMBR system.     

Uptake of alkali and alkaline earth metal ions into electrochemically pretreated glassy carbon fibres by flow-through electrolysis

When glassy carbon fibres are used, alkali and alkaline earth metal ions are adsorbed in the micropores which are created or activated by oxidative treatment of the fibres. The average pore radius was estimated to be 2 nm by nitrogen adsorption experiments. Uptake was studied with a flow system consisting of a flow-through carbon-fibre electrode; a dropping mercury electrode at the end of the flow line monitored changes in the metal ion concentrations. The ions were taken up at negative potentials and released at positive potentials. The amount taken up increased in the sequence Na⁺ < Li⁺ < H⁺, suggesting that the ions were desolvated before entering the pore system.