M. Graça V.S. Carvalho

The assessment of chromophores in bleached cellulosic pulps employing UV-Raman spectroscopy.

UV-Resonance Raman (UV-RR) coupled with UV-visible Diffuse Reflectance (UV-vis DR) spectroscopy was applied to a solid-state study of chromophores in Eucalyptus globulus kraft cellulosic pulps bleached by chlorine dioxide and hydrogen peroxide. The UV-RR spectra were acquired at 325nm laser beam excitation, which was shown to be appropriate for selective analysis of chromophore structures in polysaccharides. The proposed approach allowed the monitoring of chromophores in pulps and to track the extent of polysaccharide oxidation. However, precaution was suggested while performing a quantitative analysis of chromophores at the characteristic band of approximately 1600cm(-1) because of charge transfer complexes (CTCs) that exist in the pulp. These CTCs can affect the intensity of the aforementioned band by diminishing the conjugate state in the chromophore moieties. The amount of carbonyl and carboxyl groups in polysaccharides correlated with the intensity of the band at 1093cm(-1). The analysis of UV-RR spectra revealed xylan as an important source of chromophores in eucalypt kraft pulp.

Contribution of xylan to the brightness development and stability in the final ECF bleaching of eucalypt (Eucalyptus globulus Labill.) kraft pulp

Abstract Xylans isolated from eucalypt kraft pulps have been characterized by modern analytical methods. The pulps were partially bleached (DEOPD) and fully bleached with either a final ClO2 (DEOPDD) or an alkaline H2O2 (DEOPDP) bleaching stage. Alternatively, xylan isolated from the DEOPD pulp was treated with ClO2 or with H2O2 under the same conditions as pulps in a final bleaching stage and were further characterized. 1H nuclear magnetic resonance, size exclusion chromatography, UV-vis spectroscopy in cadoxen solution, and UV-resonance Raman spectroscopy were applied as analytical methods. The final ClO2 stage generated new unsaturated moieties in xylan, whereas H2O2 was very effective in the removal of xylan-related chromophores. The role of xylan to the delay of brightness development in the final ClO2 stage was highlighted by means of a pretreatment with xylanase Pulpzyme HC before the final bleaching stage. By this approach, the final bleachability of the pulp was boosted and the brightness stability of the fully bleached pulp was improved.

Integrated bioconversion of pulp and paper primary sludge to second generation bioethanol using Saccharomyces cerevisiae ATCC 26602.

Primary sludge, from different pulp and paper mills, was used as feedstock in simultaneous saccharification and fermentation (SSF) processes to produce ethanol. SSF was carried out with Saccharomyces cerevisiae ATCC 26602 yeast and NS 22192 enzymatic extract using 150gL(-1) of carbohydrates (CH) from primary sludge. The effect of sterilization, reduction of enzyme dosage and fed-batch vs. batch conditions were studied. The removal of sterilization can be considered since no contamination or atypical by-products were observed, although SSF efficiency slightly decreased. The reduction of the enzyme dosage from 35 to 15FPUgCH(-1) was successful. Despite of initial mixing difficulties, batch SSF enabled higher ethanol concentration (41.7gL(-1)), conversion yield (48.9%) and productivity (0.78gL(-1)h(-1)), compared to the fed-batch process at the same conditions of low enzyme dosage of 5FPUgCH(-1) and high solids content of 21.7%, rarely found in literature.