In the bleaching process (Table 2), we used two bleaching
chemicals: chlorine dioxide in the first stage and hydrogen peroxide
in the second stage. In the first stage, we used 5% active
chlorine dioxide by dry weight of the material to be bleached at
pH 3.5. Temperature, time duration, and initial pH were 80 C,
60 min, and 3.5, respectively. The pH was controlled by the addition
of sulfuric acid. In the second stage, we used 5% active hydrogen
peroxide by dry weight of the material. Temperature, time
duration, and initial pH were 80 C, 60 min, and 12, respectively.
The pH was controlled by the addition of sodium hydroxide. The
second stage was repeated until the brightness of the handsheet
was over 80%. We used two red algae species (G. amansii, which
was collected from Jeju Island in the Republic of Korea; G. corneum,
which was imported from Morocco in a dried state). Tables 1 and 2
show the extraction and bleaching conditions used in the preparation
of the paper samples from these two red algae species.