Preparation and Application of Cationic Modified Cellulose Fibrils as a Papermaking Additive

This paper deals with cationic modified cellulose fibrils obtained by reacting the cellulose fibrils with 2,3-epoxypropyltrimethylammonium chloride (EPTMAC). The physical and chemical properties of unmodified cellulose fibrils (UMCF) and cationic modified cellulose fibrils (CMCF) were characterized by SEM, FTIR, degree of substitution, colloid titration, zeta potential, and thermogravimetric analysis. The experimental results showed that, after cationization, surface charge density and zeta potential reversed, thermal stability decreased, and new functional groups appeared, while the surface morphology did not show much difference from the UMCF. With the addition of three kinds of additives (UMCF, CMCF, and cationic starch (CS)) to BCTMP, the addition of UMCF and CMCF had little effect on zeta potential, while the addition of CS changed zeta potential obviously. With the increasing of additive amount, the bulk of paper sheets added CMCF did not change obviously, while the bulk of paper sheets added UMCF and CS decreased rapidly. With regard to physical strength, all the three kinds of additives could improve the tensile index and tear index; the tensile index of paper sheets added CS was higher than that of added UMCF and CMCF, while the tear index of paper sheets added CMCF was the highest among the three additives.

Determination of partially hydrolyzed polyacrylamide in wastewater produced from polymer flooding by colloid titration

Colloid titration has been widely used to determine the charge carried by macromolecules and the concentration of anionic and cationic polyelectrolytes in paper making and food service industries. This method is simple and the materials used are non-volatile and harmless, but it has not previously been used to determine the partially hydrolyzed polyacrylamide (HPAM) in wastewater produced from polymer flooding. In this paper, colloid titration was used to determine the HPAM in wastewater produced from polymer flooding in an oilfield. When the HPAM concentration (Cp) was <200 mg/l, the relationship between the Cp and the titration value (Vp) was linear. This linear relationship was influenced by the pH of wastewater and the hydrolysis degree of HPAM; Vp increased with the pH and the hydrolysis degree. However, it was independent of the concentration of solubilized crude oil and salt concentration in the wastewater and the molecular weight of the HPAM. Recovery tests showed that the determination of HPAM in the wastewater by colloid titration was reliable. It was also found that the colloid titration and starch iodide method had similar accuracies for determination of the HPAM and that colloid titration was a better method for the analyst.

Cell surface and exopolymer characterization of laboratory stabilized activated sludge from a beverage bottling plant

Fermentor-stabilized activated sludge from an industrial beverage bottling plant was grown on three different food sources: normal plant wastewater, plant wastewater containing high sucrose concentrations, and a synthetic glucose-based feed stock. Surface charge, hydrophobicity, and exopolysaccharide composition were measured on the stabilized bacterial flocs. Cell surface charge was measured by electrophoretic mobility, dye exchange titration, and a standard colloid titration, while cell hydrophobicity was determined using the bacterial adhesion to hydrocarbons (BATH) test. Exopolysaccharide profiles were determined by measuring concentrations of glucose, galactose, mannose, glucuronic, and galacturonic acids in digested exopolymer extractions using HPLC. Changes in the physical surface properties of the bacteria and the chemical composition of the extracted exopolymers were correlated with differences in the three food sources. Cell surface hydrophobicity was similar for cultures grown on different plant wastewaters, while the culture grown on synthetic food produced less floc hydrophobicity. Electrophoretic mobility measurements, charge titrations, and dye exchange titrations showed different total surface charge as well as varying charge availability. Additionally, total surface charge and total exopolysaccharide concentrations appeared less dependent on food source than the food-to-mass ratio. High concentrations of biodegradable food produced dispersed growth and high concentrations of exopolysaccharides that contributed to poor settling.