*2.3. Preparation of Microcrystalline Cellulose (C) from the Treated OPEFB Cellulose*

The treated OPEFB cellulose was subjected to concentrated acid hydrolysis with 64% H2SO<sup>4</sup> at 45 ◦C for 1 h under stirring conditions. The suspension was added with 5-fold of cold water to stop the reaction. The cellulose suspension was centrifuged for 15 min at the speed of 7500 rpm and washed with distilled water to remove the acid content. This procedure was repeated at least ten times or until the pH of the solutions reached the value of 7 measured by using a pH meter. The produced microcrystalline cellulose was homogenized at 5000 rpm for 30 s and dried in the oven at 45 ◦C for 24 h.
