Removal of the Herbicide MCPA by Commercial Activated Carbons:  Equilibrium, Kinetics, and Reversibility

Abstract

The adsorption of the herbicide 4-chloro-2-methylphenoxyacetic acid (CAS 94-74-6) has been studied using four commercial activated carbons (Norit 0.8, Aquacarb 207C, Aquacarb 208A, and Aquacarb 208EA). Adsorption equilibrium isotherms were obtained in the 293-358 K temperature range. The trend of adsorption for MCPA onto the four activated carbon was in the order Norit 0.8 > Aquacarb 207C > Aquacarb 208A > Aquacarb 208EA. Among various adsorption isotherm models, the Freundlich equation best fit the experimental data. Experiments conducted at different temperatures allowed for the calculation of the isosteric heat of adsorption, revealing that the adsorption process was exothermic for three of the four adsorbents studied. The distribution of the herbicide into the pores of activated carbon Norit 0.8 was studied by considering the Dubinin-Radushkevich isotherm. Also, the adsorption kinetics were assessed by means of a simplistic mechanism based on the shrinking-core mass-transfer model. Finally, as a preliminary step in the study of the potential use of wet air oxidation (WAO) for the regeneration of exhausted activated carbon, the reversibility of the adsorption process was tested. Only partial desorption of MCPA was achieved under WAO conditions, which involves a likely double route of activated carbon regeneration, i.e., liquid and surface contaminant oxidation.

Recovery of the main pear aroma compound by adsorption/desorption onto commercial granular activated carbon: Equilibrium and kinetics

“…(2) and (3), representative of favourable isotherms of adsorption, were used to correlate the experimental results. This kind of isotherms has been widely employed by other authors (Gimeno, Plucinski, Kolaczkowski, Rivas, & Alvarez, 2003; González-Serrano, Cordero, Rodriguez-Mirasol, Cotoruelo, & Rodriguez, 2004; Table 1 Experimental conditions Souchon, Rojas, Voilley, & Grevillot, 1996) in order to describe the equilibrium behaviour of similar systems.…”

A review of the pesticide MCPA in the land‐water environment and emerging research needs

“…the chemical formula C 9 H 9 ClO 3 . Usually, MCPA is formulated as a dimethylamine salt (Gimeno, Plucinski, Kolaczkowski, Rivas, & Alvarez, 2003), which takes the chemical form C 11 H 16 ClNO 3 .…”

Carbon supported platinum catalysts for catalytic wet air oxidation of refractory carboxylic acids

“…Among the existing alternatives, catalytic wet air oxidation (CWAO) is interesting for the treatment of industrial wastewaters due to its intrinsic efficiency in the reduction of chemical oxygen demanding species, by means of an oxidizing source under relatively mild conditions (125-220°C, 5-50 bar) in the presence of an adequate catalyst. Recent examples of application include herbicide removal [1], pulp and paper mill effluent [2], printing and dyeing wastewaters from the textile industry [3], alkaloid factory wastewater [4], and wastewaters from nuclear fuel processing plants [5]. Although, some very active homogeneous catalysts can be used, such as copper [6] and iron salts [7], they need to be separated from the treated effluent, which is a drawback for industrial applications.…”