A novel approach for the preparation of nanocrystalline cellulose by using phosphotungstic acid

•NCC was prepared by the use of phosphotungstic acid (HPW).•The size of the NCC is 15–40 nm in width and hundreds of nanometers in length.•The prepared NCC has much higher thermal stability than the sulfated NCC.•HPW can be easily recovered and reused for the preparation of NCC.

In this work, a sustainable and green process to prepare nanocrystalline cellulose (NCC) from bleached hardwood pulp was demonstrated. Rod-like nanocrystalline cellulose with the size of 15–40 nm in width and hundreds of nanometers in length was obtained through H3PW12O40 (HPW)-catalyzed hydrolysis of bleached pulp fibers under the mild reaction conditions. Thermogravimetric analysis revealed that the resulting NCC exhibited much higher thermal stability than the partially sulfated NCC (prepared by sulfuric acid). In addition, the concentrated HPW could be easily recovered and recycled through the extraction with diethyl ether, and the recovered HPW could be reused for several rounds of cellulose hydrolysis without activity lost. These fundamental studies are of crucial importance for the development and application of NCC products/NCC-based biomaterials with good thermal stability.