Investigation On The High-consistency Electrochemical Deligniifcation Mediated With Violuric Acid And Its Kinetics

Electrochemical bleaching technology is a promising approach for thedevelopment of environmentally friendly processes in pulp bleaching. Electrochemicalbleaching process with violuric acid as a mediator is attractive not only due to itsdelignification efficiency but also based on its delignification selectivity. Thistechnology is relative clean, compared with traditional pulp bleaching process. In thepresent work, the device of high-consistency electrochemical delignification wasdesigned with violuric acid as a mediator. We shall attempt to investigate theelectrochemical delignification of poplar kraft pulp, in addition, investigate thegeneration of violuric radicals and the kinetics of delignification. This providestheoretical and technical basis for the application of this method in pulp industry.The device of high-consistency electrochemical delignification was designedaccording to the technology of electrochemically mediated delignification. A betterdelignification effect was obtained with poplar kraft pulp as the material and violuricacid as the mediator. It turned out that a better delignification was obtained with pulpconsistency between3%⁵%, electrolyte recycling0.5l/min and processing time8h.30%of delignification ratio was achieved. The delignified pulp has good subsequentbleachability. A better bleaching effect was obtained with bleaching sequence of EMEQPand EMQP. Pulp whiteness can reach about81%ISO and84%ISO respectively withH₂O₂dosage of2.0%and3.0%, in addition, the pulp viscosity is always more than850cm³·g^-1Trace Iodine Estimation is the method for the determination of VIO radicalelectrochemically generated during the electrochemical delignification process. Thevoltage, temperature and pH value have important effects on the generation of VIOradicals. The amount of VIO radicals reaches the maximal concentration more quickly,but later it decreases more., moreover, the maximal concentration and total amount ofVIO radicals decrease with the increasing of cell voltage, temperature and pH valuetemperature. The diaphragm can help VIO convert to VIO radical. The VIO·generation rate was the rate-limited step of the electrochemical mediated delignificationsystem.The kinetics of electrochemical delignification under different technical parameterswas investigated. The electrochemical delignification process is considerable complex. The reaction rate is not determined by a particular factor alone, but by the result ofinteraction of many factors.The kinetic equation of electrochemically mediated delignification:-dK/dt=A e^-E/RT[VIO]^1.031[V]^2.197K^6.25The kappa number estimation function of poplar kraft pulp with theelectrochemical treatment of is:K（t）={2.89×10^-7+5.25k[VIO]^1.031[V]^2.197t}^-0.19...