Adsorptive removal of congo red and sunset yellow dyes from water systems by lady finger stem

Summary: In this research work two anionic dyes, i.e. Congo Red and Sunset Yellow were removed successfully from aqueous media by Lady Finger stem in batch mode. Operational conditions optimization showed that agitation speed and particle size did not affect much in adsorption of these dyes; but contact time, pH, adsorbent dose and temperature of system effects the adsorption rate. Optimized conditions of adsorption for Congo Red dye were: 40 minute contact time, 8.0 pH, 0.5 g adsorbent dose, 40-60 microns mesh sized particles, 150 rpm agitation speed and 50 degree C temperature. Whereas for Sunset Yellow optimized conditions were: 30 minute contact time, 2.0 pH, 2.5 g adsorbent dose, 20-40 microns mesh sized particles, 50 rpm agitation speed and 30 degree C temperature. Suitability of equilibrium data was modulated with Langmuir, Freundlich and Temkin models and found that both physisorption and chemisorption processes play important role in adsorption of these dyes by Lady Finger stem. The results demonstrated that Lady Finger stem can be efficiently employed on larger scale wastewater treatment. (author)