Application of seaweeds for the removal of cationic dye from aqueous solution

Abstract

The removal of a cationic dye (crystal violet) from aqueous solution by two red seaweeds (Gracilaria edulis and Kappaphycus alvarezii) under different environmental conditions was investigated. Biosorption of crystal violet was studied by varying particle size (0.712–2.36 mm), biomass dosage (2–8 g/L), solution pH (2–9), initial dye concentration (50–1,000 mg/L) and contact time (0–360 min). At optimum seaweed particle size (1.18 mm), seaweed dosage (5 g/L), equilibrium pH (8), initial dye concentration (100 mg/L) and equilibrium time (360 min), G. edulis and K. alvarezii recorded crystal violet uptakes of 181.0 and 171.9 mg/g, respectively. The kinetic data obtained at different initial crystal violet concentrations indicated that biosorption rate was fast for both seaweeds and the data were successfully modelled using the pseudo-first and pseudo-second-order models. The Langmuir, Freundlich and Redlich–Peterson and Sips models were used to describe the crystal violet isotherm data; of which the Sips model described the isotherm data with high correlation coefficients.