Mesoporous silica nanoparticles modified with stimuli-responsive polymer brush as an efficient adsorbent for chlorophenoxy herbicides removal from contaminated water

The contamination of water with herbicides poses a serious threat to the environment as a result of their widespread use in the agricultural field. Herein, mesoporous silica nanoparticles (MSNs) were synthesised and grafted with poly(2-(tert-butylamino)ethyl methacrylate) brushes (MSN-PTBAEMA) using the SI-ATRP technique on the inner and outer surface of the solid particles. The porous structure of the MSNs along with thepH-responsive feature of the polymer brush allowed it to efficiently remove the targeted herbicide, 2,4,5-trichlorophenoxyacetic acid (TCA), with steady extraction efficiency over a wide pH range of 3-7. A maximum adsorption capacity of 290 mg/g was achieved, which was much higher than other adsorbents for the removal of organic pollutants. The adsorption process followed the Freundlich isotherm model, which indicates that a multilayer adsorption mechanism occurred on the surface of the adsorbent. The kinetic study results show that the adsorption of TCA occurred in two-stage adsorption kinetics with the intraparticle diffusion process being the rate-determining step in the adsorption process. Furthermore, the adsorption kinetics were found to fit better to the pseudosecond-order model than the pseudofirst-order model. The present study proved that MSN-PTBAEMA could be potentially applied for the effective removal of herbicides from aqueous environments.