Basic dyestuffs removal from textile effluents using feathers: equilibrium, kinetic and column studies

This research work has been focused in the study of gallinaceous feathers, a waste that may be
valorised as sorbent, to remove the Dark Blue Astrazon 2RN (DBA) from Dystar.
This study was focused on the following aspects: optimization of experimental conditions through
factorial design methodology, kinetic studies into a continuous stirred tank adsorber (at pH 7 and
20ºC), equilibrium isotherms (at pH 5, 7 and 9 at 20 and 45ºC) and column studies (at 20ºC, at pH 5,
7 and 9). In order to evaluate the influence of the presence of other components in the sorption of
the dyestuff, all experiments were performed both for the dyestuff in aqueous solution and in real
textile effluent.
The pseudo-first and pseudo-second order kinetic models were fitted to the experimental data, being
the latter the best fit for the aqueous solution of dyestuff. For the real effluent both models fit the
experimental results and there is no statistical difference between them. The Central Composite
Design (CCD) was used to evaluate the effects of temperature (15 - 45ºC) and pH (5 - 9) over the
sorption in aqueous solution. The influence of pH was more significant than temperature. The
optimal conditions selected were 45ºC and pH 9. Both Langmuir and Freundlich models could fit the
equilibrium data. In the concentration range studied, the highest sorbent capacity was obtained for
the optimal conditions in aqueous solution, which corresponds to a maximum capacity of 47± 4 mg g-1.
The Yoon-Nelson, Thomas and Yan’s models fitted well the column experimental data. The highest
breakthrough time for 50% removal, 170 min, was obtained at pH 9 in aqueous solution. The
presence of the dyeing agents in the real wastewater decreased the sorption of the dyestuff mostly
for pH 9, which is the optimal pH. The effect of pH is less pronounced in the real effluent than in
aqueous solution. This work shows that feathers can be used as sorbent in the treatment of textile
wastewaters containing DBA.