Removal of rotenone insecticide by adsorption onto chemically modified activated carbons

The removal of rotenone from synthetic and real wastewaters using modified activated carbons has been investigated. In order to enhance the removal capacity of rotenone, activated carbon was chemically modified through impregnation with NH(3) and (NH(4))(2)S(2)O(8) solutions. The resulting carbons were found to present different surface chemistries, while possessing similar textural properties. The adsorption data obtained at 298 K, on plain and modified carbons were well represented by the Langmuir isotherm model (R(2)>0.997). The highest adsorption capacity (Q(m)=270.3 mg g(-1)) was obtained with the ammonia-treated activated carbon. The relative effect of different surface groups on adsorption capacities were found to be in accordance with the pi-pi dispersive interaction model. The adsorption kinetic models have provided useful insights into rotenone adsorption mechanism. It was concluded that rotenone sorption process followed pseudo-second order model and was controlled by intra-particle diffusion mechanism with a significant contribution of film diffusion. The successful adsorptive removal of rotenone, from real wastewater samples on fixed bed columns, have demonstrated the suitability of this method as an effective alternative solution for the treatment of contaminated wastewaters.