Simultaneous biosorption of the two synthetic dyes, Direct Red 89 and Reactive Green 12 using nonliving macrophyte L. gibba L.

Abstract

This study puts into light the capacity of Lemna gibba biomass (LGB) to be used as an effective biosorbent for the simultaneous removal of dyes from contaminated waters. The experiment was carried out at the laboratory scale and focuses on the single and binary biosorption of textile dyes. Direct Red 89 (DR-89) and Reactive Green 12 (RG-12)—two azo dyes—were treated with LGB which was selected as a biosorbent. The results showed that very acidic pH value (pH 1) was the optimal value for dye biosorption. When the aqueous system was charged with the two dyes (≥15 mg/L), the biosorption capacity of each individual dye decreased and the sorption capacity of LGB was reduced by 15%. The kinetic modeling results proved that the single biosorption of DR-89 and RG-12 was better accounted for by the pseudo-second-order (R2 > 0.96). When the two organic pollutants were simultaneously present in the solution, the kinetic process well fitted the pseudo-second-order and pseudo-first-order models for removing, respectively, DR-89 and RG-12 from the mixture.