Nanosized lanthanum peroxide-loaded biochar composites for simple and effective glyphosate removal from wastewater: Behavior and mechanisms

The extensive use of glyphosate-based herbicides and its high solubility in water have led to its accumulation in aquatic environments, posing a risk to the ecological environment and human health. Therefore, an effective method for removing glyphosate from wastewater is urgently needed. Herein, a novel nanosized lanthanum peroxide-loaded biochar composite (n-LBC) was prepared using a simple precipitation method, in which biochar served as a dispersant and catalyst to improve the oxidation ability of nanosized lanthanum peroxide. Compared with other common metal peroxide systems, n-LBC exhibited better oxidation ability and achieved a glyphosate removal efficiency of 99.6%. Moreover, n-LBC retained the self-buffering effect of lanthanum peroxide and thus remained effective over a wide pH range, overcoming the problem of pH elevation observed in other metal peroxide systems. The mechanism for glyphosate removal was found to be a combined process of electrostatic attraction, oxidation, and inner-sphere complex formation. Most glyphosate could be oxidized to H2PO 4- by breaking the C-N bonds, and H2PO4- could be attracted to the material surface simultaneously by electrostatic attraction, forming La-O-P inner-sphere complexes. Thus, n-LBC is a simple and highly effective material for glyphosate removal.