Cationic Dye Biosorption by Salvinia minima: Equilibrium and Kinetics

Abstract

The aim of this work was to investigate the biosorption of a cationic dye (methylene blue (MB)) by Salvinia minima. Biomass was characterized using the point of zero charge and scanning electron microscopy. The effects of pH (2–10), biosorbent dose (1–6 g/L), initial MB concentration (49.14 ± 1.03, 99.60 ± 0.67, 148.91 ± 2.00, 198.24 ± 1.91, 243.74 ± 2.32 mg/L), and time (20, 40, 60, 120, 180, 240, 300, 360 min) on MB biosorption and removal were evaluated. The MB biosorption kinetics were analyzed using pseudo-first- and pseudo-second-order kinetic models, as well as Elovich and intraparticle diffusion models, and Langmuir, Freundlich, Temkin, and Dubinin-Radushkevich isotherms were used to analyze the equilibrium biosorption. A positive effect of pH on MB biosorption and removal was observed when pH was increased from 2 to 4 (28.18 ± 0.30 and 110 ± 0.05 mg/g, 23.20 ± 0.27 and 90.50 ± 0.01 %, respectively), while an increase in the biomass dose from 1 to 6 g/L reduced biosorbent efficiency from 157.30 ± 2.59 to 38.23 ± 0.02 mg/g. The adsorption kinetic data fit the pseudo-second-order equation, suggesting that chemisorption was the rate-determining step during MB biosorption by S. minima biomass. Equilibrium biosorption was described by the Freundlich model, implying that MB multilayers form on the heterogeneous surface of the biomass. S. minima biomass can be used as a biosorbent for the removal and adsorption of cationic dyes from water or wastewater.