Enhanced Glyphosate Removal by Montmorillonite in the Presence of Fe(III)

N -(Phosphonomethyl)glycine (glyphosate, PMG) is an effective broad-spectrum organic phosphoric herbicide. The mass production and wide use of PMG presents a potential environmental hazard. This study evaluated the feasibility of using montmorillonite (MT) as an adsorbent to remove PMG from wastewater in the presence of Fe(III) ions. The results showed that the PMG adsorption process is dependent on the Fe(III) concentration. Adsorption was fast, and the adsorption kinetics were best described by a pseudo-second-order model. Adsorption of PMG was most effective over the pH range from 1.9 to 4.1. Ionic strength was found to have little effect on PMG removal at pH < 4.1 but to enhance PMG removal at pH > 4.1. Competing ions reduced the PMG removal at low pH (pH < 5.9) but increased the PMG removal at pH > 5.9. The adsorption capacity was found to be greater than 210 mg/g. The mechanism of this removal process is discussed in detail in terms of XRD and species calculations.