Abstract

Indigenous red algae commonly found in Malaysian waters, Amphiroa foliacea was used as biosorbent for the removal of a reactive textile dye, Reactive blue 4 (RB4) from synthetic aqueous solution. Investigation on the effects of initial dye concentration on batch sorption of RB4 by A. foliacea was conducted, followed by the isothermic sorption and kinetic modeling of dye removal.  Results revealed that biosorption of RB4 was greatly enhanced by using hydrochloric acid-treated seaweeds (94% of uptake), as compared to the unmodified and base-treated seaweed with 0% uptake of RB4. The sorption mechanism of acid-treated algal-RB4 system complied well with both Langmuir and Freundlich isotherms (R² > 0.97), with maximum adsorption capacity of 55.6 mg/g. This predominant chemisorption of RB4 by acid-treated red seaweed process was best described by the pseudo-second order kinetic model. Further analyses with the Weber-Morris model showed that boundary layer control, surface adsorption and intraparticle diffusion are the possible rate-limiting mechanisms during the sorption of RB4 by using acid-treated A. foliacea.

Key words: Amphiroa foliacea, seaweed, reactive blue 4, biosorption, modeling.