| With the increasing of paper machine speed and secondary fiber using more and more, inorder to maintain the normal operation of paper machine and ensure the quality of paper sheet,various of agents needed in papermaking wet end to assist production. Cationic papermakingadditives has their own advantages and been widely used, basing on the negative chargecharacteristic of fiber in the pulp suspension. White water circulation of mill can save waterand improve the utilization of raw materials and energy, but will also lead to the DCS andinorganic salts accumulation, influencing the efficiency of papermaking agents especiallycationic additives. The colloidal substances can be removed out of the water system withpapersheet by using anionic trash capture agent or fixation agent, while inorganic salt willcontinue to accumulate in water within the water circulation. Therefore, there is a certainpractical significance studying on the influence of inorganic salts on fiber adsorption ofcationic chemical agents.In order to study the adsorption characteristic of CPAM on cellulosic fibers, hardwoodkraft pulp been choosed as adsorption substrate and three different types of CPAM beenchoosed as adsorbate. Firstly adsorption dynamic of CPAM on cellulosic fibers studied insalt-free condition, it’s not appropriate to evaluate adsorption ability of CPAM with differentMw or charge density just from the perspective of the quality adsorption amounts. Theadsorption kinetics of three kinds of CPAM adsorption on fibers agree with quasi secondarydynamic equation and the amount of adsorption controled by CPAM dosage and fiber surfaceproperties. Adsorption amounts increase with the increasing of temperature, isothermaladsorption curve in line with the Langmuir adsorption isothermal adsorption model whichnamely fiber adsorption CPAM as a kind of monolayer adsorption and adsorption has amaximum adsorption capacity. Comparing saturated charge adsorption amount with fibersurface charge under different beating degree for all components and R200, finding that theadsorption quantity and fiber surface charge has a great relevance, showing that the saturatedadsorption amount of fiber adsorption CPAM under the control of the fiber surface charge,which is consistent with adsorption kinetic conforms to the dynamics equation of quasisecondary fiber adsorption. Inorganic salt not only alter adsorption quantity of fiber adsorption CPAM, also changethe adsorption model of fiber adsorption CPAM. Taking Na2SO4for an example, adsorptionquantity of CPAM increases and adsorption model is in line with the Langmuir singlemolecular adsorption model in the conductivity of1000μS/cm. The conductivity of3000μS/cm has an different influence on three kinds of CPAM, high charge density CPAM2adsorption quantity increases and adsorption model is also in line with the Langmuir singlemolecular adsorption model, while CPAM1and CPAM2adsorption amounts decreases andadsorption model is not in conformity with the Langmuir single molecular adsorption model.The mixing time with slurry should be controlled at30s and stirring speed should becontrolled in750r/min to1000r/min when CPAM is used as retention and drainage aids. Theeffect of drainage become better with increasing the amount of CPAM, comparing two CPAMwith different charge density but the same molecular weight, high charge density of CPAMeffects better; two CPAM with the same molecular weight but different charge density, highmolecular weight of CPAM effects better. Pulp Zeta potentials to be near isoelectric point withincreasing the amount of CPAM and use Zeta potential can explain the changing of retentionand drainage better. For CPAM with high charge density, flocculant ability is two strong todecrease sheet formation, tensile strength and tear strength. With the increasing ofconductivity, pulp drainage time increases, the first process retention and filler retentiondecline. Effect of different metal ions is different and bivalent calcium ions has a strongerinfluence than monovalent sodium ions. |
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