Sorption potential of different biomass fly ashes for the removal of diuron and 3,4-dichloroaniline from water

Abstract Hazardous contaminants in water and biomass fly ash spillage are causes for environmental and health concern. We selected five fly ashes generated from olive-mill (O,P, G and H) and greenhouse vegetable (I) waste used as biomass fuel in order to quantify their capacity to remove diuron and 3,4-dichloroaniline (DCA) from water. To understand the sorption processes involved, four kinetic models and two adsorption isotherms were assayed. The pseudo second-order kinetic showed the best fit (R 2  > 0.99). The initial adsorption rate constant was found to be faster for DCA than for diuron. The Freundlich adsorption constants of ashes O, P, G and H for diuron were more than 2-fold higher than for DCA (Kf = 109–16 μg 1−1/n  g −1  mL −1 ). The alkaline pH of these fly ashes plays an important role in the adsorption process. Sorption/desorption processes were significantly affected by iron oxide content. DCA sorption was also influenced by particle size and carbon content. Low hysteresis coefficient values (H = 0.01–0.26) revealed an irreversible sorption process. The study presents novel information on the immobilization of hazardous chemicals in water by biomass fly ashes generated from olive-oil industry and greenhouse crop waste.