Adsorption of diuron, fluridone and norflurazon on single-walled and multi-walled carbon nanotubes

The sorption behaviors of diuron (DIU), fluridone (FLU) and norflurazon (NOR) by a single-walled carbon nanotube (SWCNT) and three multi-walled carbon nanotubes (MWCNT) samples including MWCNT10 (< 10 nm, outer diameter), MWCNT20 (10–20 nm), and MWCNT40 (20–40 nm) were investigated. All adsorption isotherms were nonlinear and were well fitted with the Freundlich model and Dubinin Ashtakhov (DA) model. The linear relationships between the organic carbon (OC)-normalized saturated adsorption capacity (Q0OC) and surface area (SA) suggest that SA is presumably responsible for the adsorption of DIU and NOR on CNTs. While FLU, DIU, and NOR OC-normalized distribution coefficients (logKOC) of CNTs increased with increasing their hydrophobicity (logKOW) and the positive relationships between the logKOW-normalized logKOC (i.e., logKOC/logKOW) of FLU, DIU, and NOR and their hydrogen bonding ability indicate that the adsorption of FLU, DIU and NOR was mainly controlled by the hydrophobic interaction and hydrogen bonding. The higher logKOC or Q0OC values of MWCNT10 and SWCNT relative to other large MWCNTs and carbonaceous adsorbents suggest that MWCNT10 has the potential to serve as an adsorbent used to reduce the mobility of herbicides in agricultural and environmental applications.

► Freundlich and Dubinin–Ashtakhov models described sorption isotherms well.
► Surface area is responsible for adsorption of diuron and norflurazon on CNTs.
► Hydrogen bonding and hydrophobic interaction dominated herbicide sorption on CNTs.
► MWCNT10 (< 10 nm) had a potential advantage to serve as an adsorbent of herbicides.