Extraction of flavonoid dyes from vine tea (Ampelopsis grossedentata) waste and application in bleached pulp dyeing

Abstract Natural dyes are receiving more attention due to wide and renewable resources and their functionalities. This study delved into the optimal conditions for extracting Ampelopsis grossedentata flavonoid dyes (AGFDs) from vine tea waste, resulting in a dye sample with a total flavonoid extraction percentage of 27.4 %. Ultraviolet (UV), Fourier‐transform infrared (FTIR) and liquid chromatography–mass spectrometry (LC–MS) analysis revealed the presence of 18 flavonoids in AGFD. Additionally, various factors, including pH, light exposure, temperature, metal ions, and redox agents were found to impact the stability of AGFD. Moreover, the dyeing performance of AGFD for the bleached chemical pulp was investigated. Under optimal conditions, the AGFD‐dyed pulp displayed a vibrant yellow hue and excellent colour fastness when using aluminum potassium sulphate dodecahydrate (KAl(SO 4 ) 2 ·12H 2 O) as a mordant with a dyeing uptake level up to 88 %. FTIR and scanning electron microscopy (SEM) analysis demonstrated that AGFD chemically bound to the pulp fibre. Remarkably, the hand sheet made from the AGFD‐dyed pulp exhibited thermal stability, physical strength properties and antibacterial activity against Escherichia coli and Staphylococcus aureus . Furthermore, the peroxide value of cheese packaged with the AGFD‐dyed pulp hand sheet was only 43 % of that of the undyed one, indicating its good antioxidant properties. This study highlights the promising potential of AGFD in the production of functional coloured paper.