generate 10 treatment combinations, with time and alkali concentration
as independent variables. The design variables time (A) and
alkali concentration (B) were shown in Table 2. The design is represented
by a second-order polynomial regression model, Eq. (1),
to generate response surface plots:
Y
=
ˇ0 +
ˇ1A
+
ˇ2B
+
ˇ11A2 +
ˇ22B2 +
ˇ12AB
central composite design (CCD), with k = 2, was used in order to
50 ◦C for subsequent analysis.
2.2.3. Hydrogen peroxide pretreatment
The substrate at a solid loading of 10% (w/v) was pretreated in
autoclave with hydroxide peroxide at concentrations of 2% (w/v) as
soaking agent for residence time 40 min at 121 ◦C temperature and
15 psi pressure. After cooling, the contents were filtered with two
layers of muslin cloth and residues were washed several times in
tap water to neutralize the pH followed by a final rinse in distilled
water, after that residue was air dried by spreading on paper at
50 ◦C for subsequent analysis.