Kraft pulping experimental

Chemical-mediated immune suppression has been identified from the experimental study of several wildlife species. Harbour seals fed either chemically contaminated fish from the Wadden Sea or imcontaminated fish were found to have differing immune responses, with the exposed group showing lowered immune response to microbial infections and certain types of cancer. "" Mink fed fish taken from below a discharge point for bleached Kraft pulp mill effluent have also shown impaired immune function, " showing that the non-accnmillative chemicals in this effluent can actively disrupt endocrine associated functions. 

Further examination of the results indicated that by invocation of Pearson s Hard-Soft Acid-Base (HSAB) theory (57), the results are consistent with experimental observation. According to Pearson s theory, which has been generalized to include nucleophiles (bases) and electrophiles (acids), interactions between hard reactants are proposed to be dependent on coulombic attraction. The combination of soft reactants, however, is thought to be due to overlap of the lowest unoccupied molecular orbital (LUMO) of the electrophile and the highest occupied molecular orbital (HOMO) of the nucleophile, the so-called frontier molecular orbitals. It was found that, compared to all other positions in the quinone methide, the alpha carbon had the greatest LUMO electron density. It appears, therefore, that the frontier molecular orbital interactions are overriding the unfavorable coulombic conditions. This interpretation also supports the preferential reaction of the sulfhydryl ion over the hydroxide ion in kraft pulping. In comparison to the hydroxide ion, the sulfhydryl is relatively soft, and in Pearson s theory, soft reactants will bond preferentially to soft reactants, while hard acids will favorably combine with hard bases. Since the alpha position is the softest in the entire molecule, as evidenced by the LUMO density, the softer sulfhydryl ion would be more likely to attack this position than the hydroxide. 

Because of its simplicity, the concept of Donnan equilibrium is an attractive approach for the modelling of fibre-ion interactions. However, despite its general success in many cases, the Donnan theory alone is not sufficient to describe the experimentally observed distributions. In those cases, it is necessary to use ion-specific complexation equilibria with the acidic groups as a part of the model to describe the observed phenomena satisfactorily. Such behaviour has been shown to exist, for example, with chemically modified highly charged fibres. An apparent systematic deviation in the ionic distribution from the predictions of the Donnan theory has also been noted with common oxygen-delignified kraft pulps, partly, but... 

After the discovery of the softening action of sulfurous acid on wood by Benjamin Tilghman in the U.S.A. in about 1857, the idea was developed experimentally as a chemical method for wood pulping by 1867 [7]. It was adopted on a commercial scale in the next few years, both in the U.S.A. and elsewhere, and rapidly became the dominant chemical pulping method until about 1937, when the volume of kraft pulp produced first exceeded the volume of sulfite pulp. 

These yield results, together with kappa number results, reinforce that employing LMS bio-pretreatments are feasible for kraft pulping. Further experimentation may be required to find the most suitable mediator, mediator dosage, etc., to further enhance the delignification and yield properties of these pulps. 

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