Removal of hexavalent chromium from aqueous media using mediterranean Posidonia oceanica biomass: adsorption studies and salt competition investigation

The biosorption of hexavelent chromium from saline solutions by Posidonia oceanica, a marine biomass, was studied as a function of pH, initial chromium [VI] and salt [NaCl] concentrations in batch system. The sorbent exhibited the maximal chromium [VI] uptake at pH 2 regardless of the presence of increasing salt concentration. Equilibrium uptake increased with chromium [VI] concentration up to 250 mg/ l and decreased slightly in the presence of increasing salt concentrations of salt up to 50 g/l. The biomass adsorbed 14.48 mg of metal per gram of biomass at 100 mg/l initial chromium concentration in the absence of salt. When 50 g/l salt concentration was added to the solution, the value diminished to 11.49 mg/g under the same conditions [i.e. a 20.6% decrease in the biosorption capacity]. The equilibrium sorption data were analyzed using Freundlich, Langmuir and Redlich-Peterson models. The Langmuir equation was the most suitable adsorption model for describing the biosorption equilibrium data of chromium [VI] both in salt free and loaded media. The pseudo-second-order type kinetic model depicted the biosorption kinetics accurately at all chromium concentrations in absence and presence of increasing concentrations of salt

Biosorption of metal dye from aqueous solution onto Agave Americana [L.] fibres

In this research, a new low cost and abundant biosorbent; Agave americna [L.] fibres has been investigated in order to remove metal dye [Alpacide yellow] from aqueous solutions. In order to optimize the biosorption process, the effect of pH, temperature, contact time and initial solution concentration was investigated in batch system. The results indicated that acidic pH=2 was favourable for metal dye removal. The increase of temperature increases the velocity of the biosorption reaction. The biosorption kinetics of alpacide yellow were closer to the pseudo-second order than to the first order model for all concentrations and temperature. The calculated thermodynamic parameters such as rG0, rH0 and rS0 indicated a spontaneous and endothermic biosorption process of metal dye onto Agave americana fibres. The equilibrium data were analysed using the Langmuir and Freundlich isotherms and showed a good fit with Langmuir model at lower temperatures and with Freundlich model at 50 C

Adsorptive removal of textile reactive dye using Posidonia oceanica [L.] fibrous biomass

The Mediterranean seagrass Posidonia oceanica [L.] leaf sheaths were used as low cost, available and renewable biological adsorbent for the removal of reactive textile dye from aqueous solutions. Batch experiments were carried out for sorption kinetics and isotherms. Operating variables studied were temperature, pH and chemical pre-treatment. Biosorption capacity seems to be enhanced by increasing the temperature. Maximum colour removal was observed at pH 5. Pre-treating fibres with H[3]PO[4] and HNO[3] solutions increased the adsorption efficiency up to 80%. Experimental sorption kinetic data were fitted to both Lagergren first-order and pseudo-second-order models and the data were found to follow first-order equation for raw fibres and pseudo-second-order for pre-treated ones. Equilibrium data were well represented by the Freundlich isotherm model for all tested adsorption systems. Besides, the thermodynamic study has showed that the dye adsorption phenomenon onto P. oceanica biomass was favourable, endothermic and spontaneous