Reaction characteristics on the green surface of moso bamboo (Phyllostachys pubescens Mazel) treated with chromated phosphate

Standing moso bamboo (Phyllostachys pubescens Mazel) calm is attractive to many people for its green color, but it fades readily if it is not chemically treated. Chromated phosphate (CP) has been successfully used to protect the green color of bamboo. In order to understand the mechanisms of such protection with CP, this study was performed using various surface analytical methods (FTIR, ESCA, and ESR) to examine the characteristic structures on the CP treated bamboo surface. The results revealed that pigments remaining in the bamboo epidermis did not affect the color of bamboo during subsequent green-color-protection treatment. After CP treatment, chromium and phosphorous from CP were located in the epidermis and cortical parenchyma of bamboo epidermal tissue. CP oxidized the chemical components on the bamboo surface and consequently generated a large number of carbonyl groups and radicals. Meanwhile, the valence states of Cr were reduced from Cr(VI) to Cr(V) and then to Cr(III).