ACCESSIBILITY OF THE MICROPOROSITY OF FILTRASORB 400 ACTIVATED CARBON TO THE HERBICIDE IMAZAMOX AND P-NITROPHENOL MOLECULES

摘要

This paper deals with the adsorption of the herbicide Imazamox and of p-nitrophenol (PNP) from aqueous solutions onto Chemviron Carbon F400. The textural properties of this activated carbon were investigated using various methods: BET, DR, α_s and DFT. A critical comparison of the results provided by these methods, along with a review of the results found in the literature, allowed us to discuss the meaning of the BET specific surface area using criteria proposed by K. Kaneko and F. Stoeckli. Carbon F400 is essentially microporous with a large distribution of slit-shaped pores, which extends from ultramicropores up to narrow mesopores. F400 total surface area is 1010 m~2/g. Adsorption isotherms of Imazamox and PNP were determined and interpreted in terms of accessibility of the microporosity. From an assessment of the dimensions of Imazamox and PNP molecules, followed by a conformational study of Imazamox molecule to find its flattest form, we concluded that the herbicide molecule can hardly enter F400 ultramicroporosity as its minimum thickness is close to 0.6 nm. Conversely, most of F400 surface is accessible to the molecule of PNP. It was found that the maximum amount of Imazamox, adsorbed as a monolayer, corresponds to no more than three quarters of the total surface area of carbon F400.