Wood cellulose fibers were oxidized by periodate to obtain dialdehyde cellulose (DAC) fibers. The aldehyde group content, degrees of crystallinity and polymerization, and fiber length of treated fibers were characterized. The tensile strength of the test sheets made of treated fibers was also measured. The results show that periodate oxidation significantly increased the aldehyde group content and the dry and rewet tensile strengths of the test sheets. Sulfonation of the oxidized fibers by bisulfite improved the undried fiber water absorbency and the dry and rewet tensile strengths of the test sheets made of sulfonated fibers.

Magnesium-based alkali is another attractive alkali source in the peroxide bleaching process of high-yield pulps. This work investigated the effluent characteristics in the high-consistency retention stage and pulp properties of triploid poplar P-RC APMP (that is, so-called preconditioning followed by refining chemical treatment, alkaline peroxide mechanical pulp) by partially substituting MgO for NaOH. The results showed that the pH, dissolved and colloidal substances (DCS), chemical oxygen demand (CODCr), cationic demand, and conductivity of the effluent in the high-consistency retention stage decreased with the increase of the substitution percentage of MgO for NaOH. Meanwhile, both the light-scattering coefficient and the bulk of the pulps increased, but the tensile index and internal bond decreased. The tensile index and internal bond had a good linear relationship with bulk.