Processing natural bamboo into white bamboo through photocatalyzed lignin oxidation.

Scalable and highly efficient bamboo whitening remains a great challenge. Herein, an effective bamboo whitening strategy is proposed based on photocatalyzed oxidation, which involves HO infiltration and UV illumination. The as-prepared white bamboo well maintains the nature structure of natural bamboo and demonstrates high whiteness and superior mechanical properties. The absorbance value is significantly decreased to 3.5 and the transmittance is increased to 0.04 % in UV-visible wavelength range due to the removal of light-absorbing chromospheres of lignin, resulting in a high whiteness when the UV illumination time is 8 h. In addition, the white bamboo displays a high tensile strength of 30 MPa and a high flexural strength of 36 MPa due to the well-preserved lignin units (lignin preservation is about 89 %). XRD patterns and analysis show that photocatalyzed oxidation has no effect on the crystal parameters of cellulose. Compared with the traditional bamboo whitening technology, our photocatalyzed oxidation strategy demonstrates significant advantage including chemical and time conservation, high efficiency, environment friendliness, and mechanical robustness. This highly efficient and environmentally friendly photocatalyzed oxidation strategy for the fabrication of white bamboo may pave the way of bamboo-based energy-efficient structural materials for engineering application.