Surface bleaching of CTMP paper using hydrogen peroxide and sodium perborate assisted by cold plasma.

The effect of cold plasma assistance for hydrogen peroxide and sodium perborate surface bleaching of paper obtained from Douglasiana pine CTMP was evaluated. CTMP was obtained from pinus douglasiana chips using 3% sodium sulfite and 2% sodium hydroxide at 130degreesC and 15 minutes cooking time in a pressurized vessel equipped with a defibrillation device. The pulp was refined in an atmospheric Sprout-Waldron 30cm diameter disc refiner, at 60degreesSR degree. Hydrogen peroxide or sodium perborate solutions were applied on the surface of lab paper sheets and were introduced in a cylindrical 13.56 MHz frequency rotating cold plasma reactor, and treated under argon and oxygen plasma. The plasma treatment accelerates the bleaching reactions compared with a bleaching at the same conditions but without plasma. Using 1.5% hydrogen peroxide on the paper and 10 minutes plasma treatment time, a final brightness of 55.8% is obtained from one unbleached pulp brightness of 44.7%. For sodium perborate at the same conditions of plasma treatment, a final brightness of 53.6% is obtained. The vector L* in the CIE color scale reached the maximum value with the highest charge of hydrogen peroxide and highest plasma treatment time. The vectors a* and b* are decreased with the hydrogen peroxide charge, and vector a* also is reduced with the plasma treatment time. By DR-FTIR by spectra, it is shown an increase of intensity at 1659 cm(-1), 1606 cm(-1), and 1510 cm(-1) bands; and a reduction in the regions of 1735. 1375-1232 cm(-1), and 1094 cm(-1) bands.