Rice straw was cut and milled to 2 mm length. Then, 20 g of milled rice straw was subjected to three consecutive steps: (1)soaking in concentrated NaOH solution based on straw dry weight
and then washed with 1 L deionized water, (2) hydrolysis by dilute HCl and then washed with 1 L deionized water, and (3) treatment in dilute alkaline solution (2% (w/w) NaOH). During the first alkaline soaking step, the optimum condition from our previous work was performed. Rice straw was treated in 20% (w/w) NaOH and 38% (v/v) ethanol for 15 h at room temperature (Narkchamnan &
Krongtaew, 2012). After the final step of dilute alkaline treatment,isolated fibers was washed several times with 1 L deionized water and finally homogenized to micro-/nano-fibers using high shear homogenizer for 15 min.