Paraquat and Diquat Sorption on Iron Oxide Coated Quartz Particles and the Effect of Phosphates

The covering of quartz particles (Q) with Fe oxides provides high capacity sorption and immobilization of both paraquat (PQ) and diquat (DQ) as well as phosphates (P), that can be used to remediate contaminated environments due to their persistence. Both PQ and DQ have higher sorption strength on crystalline iron oxide coated quartz particles (QFec) than on amorphous iron oxides (QFea), but the highest is for PQ, which might be due to its strongest interaction. The increasing addition of P contributes to the increase of quat maximum sorption on iron oxide coated quartz particles, because the cosorption of P causes the surface charge to become more negative, facilitating the sorption of positively charged quats, but this happens in a different way for both quats. It was also seen that the formation of phosphate−quat complexes has a lower affinity than P by the coated quartz particles. The characteristics of the coated quartz particles would allow increased sorption of these quaternary ammonium herbicide contaminants.