Application of Aqai Stalks as Biosorbents for the Removal of the Dye Procion Blue MX-R from Aqueous Solution

The aqai palm stalk (Euterpe oleracea) is a food residue used in its natural form (AS) and also protonated (AAS) as biosorbents for the removal of the textile dye Procion Blue MX-R from aqueous solutions. This biosorbent was characterized by infrared spectroscopy, scanning electron microscopy, and nitrogen adsorption-desorption curves. The effects of pH, biosorbent dosages, and shaking time on the biosorption capacities were studied. In the acidic pH region (pH 2.0) the biosorption of the dye was favorable. The minimum contact time to obtain the equilibrium was 8 hours for AS and AAS biosorbents. The general order kinetic model provided the best fit to the experimental data compared with the pseudo-first order and pseudo-second order kinetic adsorption models. The equilibrium data were fitted to the Langmuir, Freundlich, and Sips isotherm models. For both dyes the equilibrium data were best fitted to the Sips isotherm model. The enthalpy and entropy of adsorption of PB were obtained from adsorption equilibrium experiments ranging from 298 to 323 K. Simulated dyehouse effluent was used to check the applicability of the proposed adsorbents for effluent treatment. Keywords: adsorptionbiosorptiongeneral order kinetic equationkinetic parametersthermodynamicswastewater treatment ACKNOWLEDGEMENTS The authors are grateful to Conselho Nacional de Desenvolvimento Científico e Tecnológico (CNPq), to Coordenação de Aperfeiçoamento de Pessoal de Nível Superior (CAPES), and to Fundação de Amparo à Pesquisa do Estado do Rio Grande do Sul (FAPERGS) for financial support and fellowships. We are also grateful to Centro de Microscopia Eletrônica (CME-UFRGS) for the use of the SEM microscope. We also thank to Herolab (Wiesloch, Germany) for donating the sealing o-ring of the rotor of the Unicem M centrifuge. Notes *pH of the solution adjusted with 0.10 mol L−1 HCl and NaOH. *Second stage.