2.2.2. Acid treatment
A similar procedure was followed for the pre-treatment of the
biomass samples with acid. A sample of 4 g (90e500 mm) was dissolved in an acid solution (80 ml) and was stirred on a magnetic
stirrer at constant temperature for a specific amount of time. After
this treatment, the pH of the solution was measured as a reference
value, ranging between 1 and 3. The solution was filtered under
vacuum and washed with distilled water until the pH reached a
value of 5. The solid was then dried in an oven at 80 C for 22 h. The
weight of the cooled sample was finally measured.