A Study of the Dyeing Properties of Natural Dyes Extracted from Simulated Lung Ching Tea Residues

A huge amount of Chinese tea residue forms part of everyday waste. In this paper, one of the daily used Lung Ching tea was selected to perform a series of experiments. A pilot scale of simulating the wasted Lung Ching tea residue was conducted using the fresh tea bought from department stores. Endeavours have been made to find out the optimum extraction conditions including the solvent selection, optimum concentration, temperature and time to extract the dyes from the tea residues. The thermodynamic behaviour of Lung Ching tea dyes such as the standard affinity, enthalpy change, dyeing mechanism, time of half dyeing and activation energy were also taken into account. Furthermore, the shade, depth and colour fastness properties of dyed wool fabric under different dyeing conditions were also investigated. The results showed that water was a good solvent to extract tea dye and the optimum extraction conditions was 100°C at 90 min. Dyeing of wool fabric with tea dye can be carried out at room temperature but the affinity on fabric was relatively low. On the whole, tea dye showed a good result of colour fastness tests except a minute colour change after washing which leaves room for further investigation.