This study investigates, for the first time, the applicability of seed pods from Capparis flexuosa as an alternative biosorbent to remove methylene blue and bright blue from aqueous medium using continuous and batch systems. The biosorbent was characterized by different techniques, whose particles presented rough surface and large pores and functional groups existing on its surface. In the batch system, an adsorptive capacity of 96.40 mg g-1 and 80% of methylene blue removal was reached with 0.9 g L-1 of adsorbent at pH 10, whereas 109.7 mg g-1 and 83% of bright blue removal was observed using 0.8 g L-1 of adsorbent at pH 2.0. The Elovich model adjusted the experimental data satisfactorily for both dyes. Tóth model for the MB best described the equilibrium data, and the Langmuir model for the bright blue both favored by the increase of temperature and dyes' concentration. The maximum capacities obtained were 280.78 mg g-1 and 342.85 mg g-1 for methylene blue and bright blue, respectively. The thermodynamic parameters indicated spontaneous processes, with endothermic behavior for both dyes. The fixed adsorption experiments using Capparis flexuosa seed pods showed adsorptive capacities of 158.65 and 205.81 mg g-1 for the methylene blue and bright blue, respectively. The overall results indicated that the pods of the Capparis flexuosa could be an ecological, effective, and economical alternative in the removal of dyes for both continuous and batch systems.
Keywords: Biosorbent; Bright blue; Capparis flexuosa; Methylene blue; Thermodynamics.