Browsing by Issue Date, starting with "2007-03"
Now showing 1 - 2 of 2
Results Per Page
Sort Options
- Enzymatic depolymerisation of cellulosePublication . Pala, Helena; Mota, Manuel; Gama, Francisco MiguelCellulose degree of polymerisation (DP) was determined in paper pulps and commercial powder celluloses before and after the enzymatic treatment with a blend of cellulases and hemicellulases. Three different methods were used: (i) chemical method, based on the measurement of the cellulose reducing power; (ii) viscosimetry; and (iii) gel permeation chromatography. Although based in very different principles, the three methods find similar DP values in the case of pure cellulose with narrow molecular weight distributions. The chemical method is more sensitive to detect enzymatic depolymerisation and appears to provide a good estimation of the number-average DP. GPC data offers more detailed information about the enzymes mode of action on the fibres, showing that cellulose hydrolysis in the presence of the commercial preparation Celluclast 1.5L follows a layer-by-layer solubilisation mechanism. 2006 Elsevier Ltd. All rights reserved.
- Laboratory paper pulp deinking: an evaluation based on image analysis, ISO brightness and ERICPublication . Pala, Helena; Mota, Manuel; Gama, Francisco MiguelImage analysis, ERIC and ISO brightness measurements were used to evaluate the effectiveness of laboratory deinking assays. The accurate measurement of the residual ink amount is difficult and the results depend on the methodology used. The three techniques correlate only when the same paper pulp is analysed and when the ink particle size distribution profile is similar. As the relative amount of each particle size depends on the deinking protocol used, the ink removal effectiveness is measured differently according to each test method. Image analysis was shown to be the most reliable method.