I have tried to prepare cellulose whiskers (CW) from Brazil nut shells, but I obtained spheric nanoparticles instead of whiskers. 

During the preparation, I remove the extractives (waxes) with water and ethanol, then I treat the chopped shells in an alkaline medium in order to remove lignin. Next, I employ sodium chlorite  and acetic acid for bleaching, and finally I do and acid hydrolisis with sulfuric acid (64% w). 

In the last step, the fiber suspension turns black immediately. After 2 h, I obtain a suspension with a black supernatant and a black precipitated. In other papers I read that the suspension turns grey or turbid.