1. Introduction
1.1. Basic Dyes
Basic dyes are cationic soluble salts of coloured bases. This is a class of synthetic dyes, that act as bases and when made soluble in water, they form a colored cationic salt, which can react with the anionic sites on the surface of the substrate. They are applied to substrate with anionic character where electrostatic attractions are formed. The dyes produce bright shades with high tinctorial values, on textile materials and they react on the basic side of the isoelectric points.
Basic dyes are called cationic dyes because the chromophore in basic dye molecules contains a positive charge. They are salts, usually chlorides, in which the dyestuff is the basic or positive radical. Basic dyes are powerful colouring agents. It’s applied to wool, silk, cotton and modified acrylic fibres. Usually acetic acid is added to the dyebath to help the take up of the dye onto the fibre. Basic dyes are also used in the coloration of paper, i.e. lignocellulosic materials [1] [2] .
Waste waters from industries like dye manufacturing, textile dyeing, paper and pupl mills, etc., contain appreciable amounts of basic dyes[3] .
1.2. Chrysoidine R
Chrysoidine R (Figure 1) is the azo dye with the molecular formula C13H14N4 [4] . It is used to dye silk, cotton, varnish, printing inks, chromed leather, and cellulose-ester plastics. Also used as a biological stain and as a dye in oils, fats, and waxes for polishes. Colour index is 11320 and molecular weight’s 226 g/mol [4] .
1.3. Methylene Blue
Methylene blue (Figure 2) is a heterocyclic aromatic chemical compound with the molecular formula C16H18ClN3S and molecular weight: 319 g/mol. It has many uses in a range of different fields, such as biology and chemistry [1] . At room temperature it appears as a solid, odorless, dark green powder that yields a blue solution when dissolved in water. The hydrated form has 3 molecules of water per molecule of methylene blue [1] .
Solutions in water or alcohol have a deep blue color. Methylene blue is used as a dye for a number of different staining procedures [4] . Colour index is 52015 [4] .
2. Description of Experiment
2.1. Materials
As native cellulose was used commercial cotton linter. Oxycelluloses OKCEL H-L were prepared by nitroxide-mediated oxidation of linters and bleached MgBi-sulphite wood pulp inSynthesia, Pardubice-Semtin, Czech Republic—see Table 1 [5] .
2.2. Preparation of Oxycellulose Suspension
Oxycellulose as well as cotton linters suspension was prepared by weighing out of 20 g of air dried oxycellulose followed by its dissolution in 1 L of distilled water. The fibres were stirred up in 1 L of distilled water. Before stirring up, the oxycelluloses No. 242, No. 247 and linters were refined in order to reach better homogenization of fibrous suspension [5] .
Refining of oxycelluloses and linters was carried out in 250 mL and 500 mL of distilled water, respectively. The refining of oxycelluloses was carried out in a laboratory blender, using first velocity stage, with duration 4 minutes 30 seconds. The cotton linters refining took place approximately 45 minutes, using second and third velocity stage eventually.
In order to control a sufficient fibres refining, a graduated vessel with the excess of distilled water was used. The small amount of the defibrillated oxycellulose or linters was withdrawn and put into a graduated vessel [5] . The suspension was then shaken up and observed a quality of defibrillation. The refining process was finished in case that no bigger aggregates of fibres were observed in the vessel [5] . As the temperature of the prepared sus-