Use of agricultural waste sugar beet pulp for the removal of Gemazol turquoise blue-G reactive dye from aqueous solution

The potential use of dried sugar beet pulp, an agricultural solid waste by-product, as an biosorbent for Gemazol turquoise blue-G, a copper–pthalocyanine reactive dye commonly used in dyeing of cotton, was investigated in the present study. Batch adsorption studies were carried out to examine the influence of various parameters such as initial pH, temperature and initial dye concentration. The results indicated that adsorption was strongly pH-dependent and slightly temperature-dependent. At 800mgl−1 initial Gemazol turquoise blue-G concentration, dried sugar beet pulp exhibited the highest Gemazol turquoise blue-G uptake capacity of 234.8mgg−1 at 25°C and at an initial pH value of 2.0. The Freundlich, Langmuir, Redlich–Peterson and Langmuir–Freundlich, the two and three parameters adsorption models were used for the mathematical description of the biosorption equilibrium and isotherm constants were evaluated depending on temperature. Both the Langmuir and Redlich–Peterson models were applicable for describing the dye biosorption by dried sugar beet pulp in the concentration (100–800mgl−1) and temperature (25–45°C) ranges studied. Simple mass transfer and kinetic models were applied to the experimental data to examine the mechanisms of biosorption and potential rate controlling steps such as external mass transfer, intraparticle diffusion and biosorption process. The sorption process was found to be controlled by both surface and pore diffusion with surface diffusion at the earlier stages followed by pore diffusion at the later stages. Pseudo first-order, pseudo second-order and saturation type kinetic models described the biosorption kinetics accurately at all concentrations and temperatures studied. The thermodynamic analysis indicated that the sorption process was exothermic and the biosorption of dye on dried sugar beet pulp might be physical in nature.