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The sorption of Fe(2+) onto unbleached kraft fibre was investigated at different conditions such as pH, temperature, and concentrations. The sorption, which increased with concentration and temperature, followed the Langmuir isotherm. Thermodynamically, the process was spontaneous and endothermic. It was found that the precipitation of Fe(2+) was highly(More)
The Donnan theory is extended to formulate a model for determination of the distribution coefficient of calcium in slurries of fully bleached and unbleached kraft fibers at different pH, taking into account the presence of both carboxylic and phenolic groups in the fibers. The intrinsic dissociation constants of the carboxylic acid groups and phenolic(More)
Four different titration methods for measurement of fiber charge were used in this study. Each method gave different fiber charge values depending on the acidity of the end point and the interaction between the fiber chemical components and the titrant. Also, the interactions between the ionizable groups on the fiber had significant effects on the(More)
A kinetic model was developed to characterise the heterogeneous nature of kraft delignification kinetics, taking into account the effect of chip thickness. The final form of the model applied to kraft delignification can be represented by a first-order rate equation with a rate constant inversely proportional to a power function of chip thickness. Published(More)
The aim of this work was to study the influence of refining on various pulp properties such as freeness, specific surface area, specific volume, surface charge, total charge and elastic modulus. The results indicated that specific surface area of the pulps increased with increased refining, and at the same freeness level the pine pulp exhibited higher(More)
The sorption of Na+ and Ca2+ from aqueous solutions onto unbleached kraft fiber was investigated. The sorption kinetics was found to be highly dependent on pH, initial concentration, and temperature. The sorption rate increased as the initial concentration and pH were increased. Thermodynamic and kinetic results indicated that the sorption of Na+ and Ca2+(More)
This paper reports on the local reconstruction of a region-of-interest from 3D terahertz imaging data obtained via a quantum cascade laser (QCL). It is an important step in understanding the trade-off between wavelet based techniques and traditional filtered back projection (FBP) for local reconstruction of terahertz images. The advantage of local(More)
In a binary system the sorption of Na(+) and Ca(2+) by kraft pulps follows a second order kinetics, and the isotherms follow the Langmuir model. The sorption capacity is dependent on pH and temperature. The thermodynamic parameters indicate that the sorption is exothermic and spontaneous. In a single-component system, the sorption capacity of the kraft pulp(More)
Pinus radiata kraft pulps with varying carboxyl content were studied using Fourier transform infrared photoacoustic spectroscopy (FT-IR-PAS). The examined pulp samples, with Kappa number ranging from 20.8 to 128, originated from pulping experiments conducted in flow-through reactors utilizing varying effective alkali, temperature, and cooking time. A(More)
A model was developed, based on the power law of growth and Avrami's concepts in nuclei growth to describe the heterogeneous nature of alkaline pulping kinetics, taking into account the effects of effective alkali concentration and temperature. It was then applied against published data to estimate model parameters. The final form of the model applied to(More)