The potential use of spent chai tea to remove cationic dyes such as crystal violet (CV) and malachite green (MG) from aqueous solutions was investigated at room temperature in batch systems. Chai tea samples were characterized by scanning electron microscopy before and after the adsorption of the dyes, showing a heterogeneous surface and no substantial changes in the morphology and texture upon adsorption. The adsorption of CV and MG was strongly affected by the pH and adsorbent dose, reaching a maximum adsorption of 98% and 84% for CV and MG, respectively at pH 6. Dye removal was also tested in the presence of salts and heavy metal ions, indicating a strong negative effect of ionic strength and competition for the adsorption sites with Pb(II) and Cu(II) ions. Lastly, in order to evaluate the recyclability and recovery of the dyes, desorption experiments were conducted, reporting up to 25% dye removal with diluted ethanol solutions. These results indicate that CV and MG are strongly and efficiently adsorbent onto spent chai tea, presumably through a combination of polar and hydrophobic forces between the adsorbent and the dyes.
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