| In order to accomplish sustainable and economic development of the paper production, whitewater closed cycling in papermaking is very important. For this closed system, the most important suppression factor is the gather of dissolved and colloidal substances(DCS). DCS is a kind of viscous material, it will have negative effect on the paper quality, and operating problems can arise through deposition machine network. In order to maintain the normal circulation, DCS can be adsorbed on the cycle the minerals in the storage material. And diatomite as a natural, pollution-free mineral, it has large reserves. Diatom particles have a large of surface area, and there are a large number of microporous structure that orderly arranged. It is a good adsorption minerals. So in this paper, the diatomite was adopted to study the adsorption of DCS.In this paper, the first grade diatomite, second grade diatomite and calcined diatomite were stuied by the SEM, FT- IR, XRD, EDS and BET characterization methods. Comparing the analysis results, the raw diatomite was choosed to adsorb the DCS finally.In this paper the resin was selected as DCS, the main factors influencing the adsorption on resin were diatomite dosage, reaction time, pH and temperature. By diatomite dosage, reaction time, pH and temperature to affirm the best adsorption condition, every single factor experiment was done. The results showed that the best condition of adsorption resin of diatomite is: diatomite dosage is 1 g, adsorption time is 4 h, pH of 4, temperature is 45 ℃.The diatomite was modified through acid leaching and alkali leaching. Selecting acid/alkali concentration, time and temperature as investigation object, and each factor was in three levels. Through 3 factors 3 levels orthogonal test, the optimum modification conditions was confirmed by diatomite to methylene blue adsorption rate as index. Optimum process conditions of acid leaching diatomite as: acid concentration 10%, temperature 30 ℃, the processing time of 1 h. Optimum process conditions of alka li leaching diatomite as follows: 10% alkali concentration, temperature of 90 ℃, the processing time of 3 h. Compared to two kinds of modified methods found that alkaline leaching of diatomite modified effect is better than acid leaching. The adsorption rate of Alkali leaching diatomite for DCS was 23.2%, and it was similar with the modified diatomite without modification. This is because the diatomite is electronegative, and adhesive content is electronegative, like charges repel each other. So the cationic modification of diatomite was carried. Polyethyleneimine(PEI) was carried out on the alkali leaching diatomite, and the best concentration of PEI was 0.13 mg/mL.Through the DCS isothermal adsorption with PEI modified diatomite found that the higher temperature is advantageous to the adsorption reaction. The adsorption of DCS is in line with the Freundlich adsorption isotherm and the Langmuir adsorption isotherm. But comparing the R2 found that it is in line with the Freundlich adsorption isotherm better, the correlation coefficient R2 were larger than 0.99. H?=28.99 kJ·mol-1,greater than zero, namely the diatom original soil adsorption gooey solution is endothermic process, the total energy of the reactants is lower than the total energy of the products, heating up easily adsorption. By adsorption isotherm and thermodynamic of DCS, it showed that increasing whitewater temperature is good for removing DCS in the process of paper making. |
PDF Full Text Request