Effect of dye auxiliaries on chemical oxygen demand and colour competitive removal from textile effluents using <i>Posidonia oceanica</i>

<div><p>The use of an abundant and widely distributed seagrass species, <i>Posidonia oceanica</i>, as a biosorbent for the direct dye Yellow 44 was successfully shown. The studies were performed on the single dyestuff dissolved in water and in a dyebath containing agents commonly used in the textile industry, i.e. a surfactant (Lavotan TBU), a sequestring agent (Meropan DPE), a softening agent (Eurosoft CI10) and a salt (NaCl). The colour reduction results showed that <i>P. oceanica</i> was found to be more efficient for removal of Yellow 44 from an aqueous solution (162 mg g<sup>−1</sup>) than from a dyebath solution (135 mg g<sup>−1</sup>), according to the Langmuir isotherm model. For the single dyestuff sorption, Fourier transform infrared and X-ray photoelectron spectroscopy studies highlighted chemical sorption between the dye alcohol function and the sorbent acid function. The chemical oxygen demand removal percentages were found to be 54.9 and 76.6% for Yellow 44 dissolved in aqueous solution and in dyebath solution, respectively. This confirmed the both sorption of the chemical auxiliaries and the dye on <i>P. oceanica</i>.</p></div>