Methylene blue (cationic dye) adsorption into <i>Salvadora persica</i> stems ash

Abstract

Methylene blue (MB) is the most commonly used substance for dyeing cotton, wood and silk. On inhalation, it can cause difficulty in breathing, while on direct contact, it may cause permanent injury of the eyes of human and animals, burning sensations, nausea, worming, profuse sweating, mental confusion and methemoglobinemia. In the present study, Salvadora persica stem ash was used as an adsorbent for the successful removal of methylene blue (MB) dye from aqueous solutions. The effect of various operating parameters such as initial concentration of dye (20 to 200 mg/L), contact time (5 to 270 min), adsorbent dosage (0.2 to 10 g/L) and pH (2 to 13) was investigated. The results of this study shows that the S. persica stem ash was able to remove up to 97% of MB dye from solutions with various initial dye concentrations at initial pH of 13. Also, the equilibrium data were also fitted to the Langmuir and Freundlich equilibrium isotherm models. It was found that the data fitted better to Freundlich (R2=0.9314) than Langmuir (R²=0.8836) model. Finally, it can be concluded that the S. persica stem ash can be used for textile industry wastewater treatment.

Key words: Methylene blue (MB), adsorption, S. persica, natural adsorbent.