Biosorption of the Anionic Dye Direct Red 89 by the Aquatic Plant Callitriche obtusangula

Abstract

The use of aquatic plant biomass as sorbent is an economic way to mitigate water pollution because of abundance and low cost of this kind of biomass. In this study, we proposed the species Callitriche obtusangula (C. obtusangula) for the elimination of the azo dye Direct Red 89 (DR-89) which is a dangerous pollutant for humans, animals and their environments. Batch experiments were carried out to assess optimal parameters such as contact time, biomass dosage, agitation speed, pH and temperature. The results show that the maximum percentage of pollutant elimination was 46% after 90 min of treatment for an initial dye concentration of 50 mg/L, an agitation speed of 200 rpm, a biomass dose of 2 g/L, and a pH equal to 1. Thermodynamically, the study proved that the phenomenon was endothermic (∆H = 34.84 kJ/mol) and spontaneous (∆G < 0). The Infra-Red analysis (FT-IR) was used to determine the mechanism of DR-89 sorption by identifying the functional groups involved in the present phenomenon. The spectra showed that the Callitriche biomass contains Carboxylic Acid, Aromatic ring, Amines, Alcohol, Alkane which were responsible for the dye retention on the biomass surface.