A flexible magnesium silicate coated electrospun fiber adsorbent for high-efficiency removal of a toxic cationic herbicide

Organic cationic herbicides have been widely used in modern agriculture and their discharge into the environment has become a serious problem. In this study, magnesium silicate functionalized PAN (MgSi/PAN) fibers were synthesized using an electrospinning technique and a hydrothermal approach, which were explored as attractive adsorbents for cationic herbicide polluted wastewater treatments. The batch adsorption behavior toward the cationic herbicide diquat by MgSi/PAN fibers was investigated, including effects of pH, adsorption kinetics, adsorption isotherms and ionic strength. It was found that the adsorption isotherm of MgSi/PAN composite fibers was fitted better with the Langmuir isotherm model. The adsorption behaviors showed a maximum adsorption capacity of 197.53 mg g−1 for diquat, which was higher than those of many other adsorbents. Kinetics of the diquat adsorption were found to follow a pseudo-second-order rate equation. Meanwhile, the adsorbent had a good recyclability and the removal efficiency remained at 83% after five adsorption–desorption cycles. Most importantly, the MgSi/PAN fibers could remove 99.1% of diquat by dynamic filtration experiment. These findings demonstrate that the MgSi/PAN fiber membranes could be potentially applied to the efficient removal of diquat in wastewater treatment.