Competitive adsorption of 2,4-dichlorophenoxyacetic acid herbicide and humic acid onto activated carbon for agricultural water management

Abstract

AbstractAdsorptive removal of herbicide 2,4-dichlorophenoxyacetic acid (2,4-D) and humic acid (HA) from their single- and binary solutions was investigated using powdered activated carbon. Both pore- and film diffusion coefficients for 2,4-D calculated based on two resistance diffusion kinetics were higher than those found for HA both single- and binary component systems. Similar trend was also observed for the rate constants calculated by applying pseudo-second-order kinetic model. The L-shaped isotherm curves converted into H shaped with an increase in the temperature from 288 to 318 K indicating the complete removal of both solutes in dilute solutions. A synergetic effect was observed in low-concentration region in binary systems; however, the combined action of 2,4-D and HA was found to be antagonistic in concentrated solutions. The experimental equilibrium results in single-component systems were better predicted by the Freundlich than the Langmuir isotherm equation. The extended Freundlich isotherm ...