Résumé:
Adsorbents prepared from seawater algae, viz. green Ulva
lactuca (PGA) and brown Systoceira stricta (PBA), by chemical activation were
successfully tested for the removal of Supranol Yellow 4GL dye from aqueous
solutions. Impregnation in 20% phosphoric acid for 2 h at 170 °C and
subsequent air activation at 600 °C for 3 h significantly enhanced the adsorption
capacities of both algae relative to their inactivated states. Parameters
influencing the adsorption capacity such as contact time, adsorbent dosage, pH
and temperature were studied. Similar experiments were carried out with
commercially available Merck activated carbon (MAC) for comparative
purposes. Adsorption efficiencies were measured at a pH 2 and dosages of 8 g/
and 12 g/ for PGA and PBA, respectively. Batch adsorption experiments
resulted in maximum adsorption capacities determined from Langmuir models
of up to 263, 93 and 84 mg/g for PGA, PBA and MAC, respectively. BET, FT-IR
analyses, iodine number and Methylene Blue index determination were also
performed to characterize the prepared adsorbents. The adsorption kinetics were
found to comply with the pseudo-second-order model with intra-particle
diffusion being the rate-determining step. Thermodynamic analysis confirmed
that the adsorption reaction was spontaneous and endothermic. These studies
indicate that these seawater algae could be used as low-cost alternatives for the
removal of dyes.
