Cellulose impure

The traditional method of carbonising with sulphuric acid is environmentally undesirable and can easily lead to fibre damage. Hence it is not surprising that research has been directed towards alternatives in which enzymes are used to remove the cellulosic impurities from wool. Cellulases and lignases are mainly used but others have been proposed [116] ... 

Carbonising is done to remove the cellulosic impurities from wool by treatment with acid or acid producing salts. Carbonising may be carried out in loose wool or on piece goods after scouring. However, it is common practice to carbonise worsted piece goods as well as woollens. 

An active cellulase will find many uses other than production of sugar (34, 36). These include removal of unwanted cellulose impurities (33) and breakdown of cell walls to improve extraction of a cell component, or to increase digestibility or nutrient availability of feeds (6, 35). Such uses require a preparation free of enzymes that might attack the residue being purified or the substance being extracted. 

Barnes and co-workers have studied mixed-monolayer systems [278,281,283,284] and found some striking nonidealities. Mixed films of octadecanol and cholesterol, for example, show little evaporation resistance if only 10% cholesterol is present [278] apparently due to an uneven granular microstructure in films with cholesterol [284]. Another study of cellulose decanoate films showed no correlation between holes in the monolayer and permeation rate [285]. Polymerized surfactants make relatively poor water evaporation retarders when compared to octadecanol [286]. There are problems in obtaining reproducible values for r [287] due to impurities in the monolayer material or in the spreading solvent. 

Hydroxynaphthol Blue tri-Na salt [63451-35-4] M 620.5, m dec on heating, pKE,t <0. Crude material was treated with hot EtOH to remove soluble impurities, then dissolved in 20% aqueous MeOH and chromatographed on a cellulose powder column with propanol EtOH water (5 5 4) as eluent. The upper of three zones was eluted to give the pure dye which was ppted as the monosodium salt trihydrate by adding cone HCl to the concentrated eluate [Ito and Ueno zfna/ysr 95 583 1970. ... 

A final are we should discuss is color removal. This is perhaps the most difficult impurity to remove from waters. In surface waters color is associated with dissolved or colloidal suspensions of decayed vegetation and other colloidal suspensions. The composition of this material is largely tannins and lignins, the components that hold together the cellulose cells in vegetation. In addition to their undesirable appearance in drinking water, these organics can cause serious problems in downstream water purification processes. For examples ... 

Cellulose acetate is a common membrane material, but others include nylon and aromatic polyamides. The mechanism at the membrane surface involves the influent water and impurities attempting to pass through the pressurized side, but only pure water and certain impurities soluble in the membrane emerge from the opposite side. 

The manuf of NC is similar in that it involves the same nitrating acids as used for TNT, but used to treat cotton linters or wood pulp (raw cellulose) in a series of vats and reactors similar to the ones used for TNT. The crude NC is similarly subjected to a series of w and aq soln washes until it is finally delivered as a purified, fibrous mat — ordinarily wet with w or ale for safety. Again, there are major wastewater streams laden with spent reagents and extracted impurities... 

In summary, although clear, light-colored cellulose solutions are required to start the synthesis, there is no guarantee, a priori, that the targeted DS will be obtained. The reasons are that the state of aggregation of cellulose is dependent on the structural characteristics of the starting material, is sensitive to the pre-treatment employed, and the impurities present. This may result in non-reproducible aggregation states, and may lead to oscillation in cellulose reactivity. Typically, effects of these oscillations may not be readily apparent, because ... 

Fraction A was examinated to purify by affinity chromatography on ConA -cellulose. Some impurities were removed but the separation of... 

Since wool is attacked most rapidly by sulphuric acid of intermediate concentration, it is important that drying is carried out either at a relatively low temperature so that reaction of the acid with wool is slow, or very quickly so that the time of exposure of the wool to the critical acid concentrations is brief [146]. Ideally, all the sulphuric acid in the wool is absorbed chemically as bound acid that causes little hydrolytic damage. It is the free acid that can concentrate locally and cause serious degradation. The acid picked up by the vegetable impurities, on the other hand, is free acid that has the desirable effect of beginning the process of attacking the cellulose [286]. 

Amino benzoic acid 4-Nitro- benzoic acid Cellulose- F254 (Merck) 2-Mthyl propan- l-ol water 5M ammonia (700 30 15) (1) 10% w/v of amino-benzoic acid (2) 0.020% w/v of 4-nitro benzoic acid [in EtOH (96%)] UV-Light (254 nm) Spot obtained with soln. (1) for impurity should not be more than the spot with soln. (2)... 

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