Adsorption of anionic azo dye from aqueous solution using Strychnos potatorum Linn seeds: isotherm and kinetic studies

Abstract

Dyes from several industry effluents are major concern of environmental pollution. In this study, the efficiency of a cost-effective natural adsorbent Strychnos potatorum Linn (Fam: Loganiaceae) seeds on removing reactive orange-M2R dye from aqueous solution was investigated using batch adsorption isotherms at 30 ± 1 °C and 120 rpm. The efficacy of the adsorbent system was also studied at various parameters viz. contact time, pH, adsorbent dosage and initial dye concentration. Maximum adsorption (q e = 9 mg/g) was observed at pH 2.0, equilibrium time 6 h, initial dye concentration of 100 mg/L and adsorbent dosage of 0.2 g/100 mL. The unit adsorption of dye, q e (mg/g) increased with increase in contact time and initial dye concentration, while it decreased with increase in adsorbent dosage. The adsorption kinetic studies revealed that it follows pseudo-second-order reaction model. Equilibrium adsorption data followed both Langmuir and Freundlich isotherms with good agreement. These investigations suggest that Strychnos potatorum Linn seeds (SPS) could be used as a low-cost adsorbent in treating textile effluents for dye removal applications. The adsorbent (SPS) was also characterized using Fourier transform infrared spectroscopy, powder X-ray diffraction, and scanning electron microscopic technique.