Treatment of glyphosate wastewater by Zr-amino bi-functionalized worm-like mesoporous silica absorbents

Abstract

As the most common weed killer used worldwide in farms and home gardens or lawns, glyphosate's excessive discharge has caused serious harm to the water environment and human health. Therefore, effective treatment of glyphosate wastewater becomes a matter of emergency. In this paper, novel modified mesoporous silica absorbents were prepared and used to treat glyphosate wastewater. First, worm-like mesoporous silica (HECMS) was prepared using the sol–gel method with cheap and resourceful hydroxyethyl cellulose (HEC) as the template and sodium metasilicate as the silica source, respectively. After that, 3-aminopropyltrimethoxysilane (APTMS) was grafted on the surface of HECMS and then zirconium was introduced onto AP-HECMS through the coordination of Zr⁴⁺ with the amino groups in APTMS, denoted as Zr-AP-HECMS. For the adsorption of glyphosate on Zr-AP-HECMS, the optimal pH range was found to be 3–6, and the maximum adsorption amount was 107.38 mg g⁻¹. The adsorption process followed the pseudo-second-order dynamics model and the adsorption equilibrium followed the Langmuir model. The adsorption mechanism was also investigated as the electrostatic attraction of the protonated amino group on Zr-AP-HECMS to the glyphosate ion in water, as well as the ligation between Zr⁴⁺ and P–O in glyphosate, and the ligation is stronger than the electrostatic attraction. The preparation of the adsorption material is simple and the cost is low. What is more, it can effectively remove glyphosate in water. This work would provide some guidance for the modification and application of mesoporous silica in pesticide wastewater treatment.