In order to optimize the operating hydrolysis conditions, one-variable-at-a-time (OVAT) method was applied in this study to investigate the significance of every hydrolysis parameters in nanocellulose production. The catalytic hydrolysis reaction was initiated by reacting the native cellulosic material (1.0 g, oven dry weight) with Cr(NO3)3 solution (0.1–1.2 M) in a round-bottom flask with constant mechanical agitation using a heating mantle. The reaction was conducted at different temperatures (20–100 °C) and for different hydrolysis times (0.5–2.5 h). The solid–liquid ratio varied from 1:10 to 1:50. After the course of the reaction, the solid residue was separated from the reaction suspension via high-speed centrifugation (higher centrifuge speed can be used to improve separation) and washed thoroughly with cold deionized water until the wash water was maintained at constant pH. Afterward, the collected solid residue was subjected to lyophilization process and finally the fluffy white fiber product was obtained. Three replications were applied in each group of experiments in order to confirm the good reproducibility. The yield of CNCCr(NO3)3 was determined by gravimetric analysis, as described elsewhere .