Sustainable chloramine-functionalized iron hydroxide nanofiber membrane for arsenic(Ⅲ) removal via oxidation-adsorption mechanism.

Arsenic-contaminated groundwater is an intractable environmental problem worldwide, particularly As(III), which is not only highly toxic but also resistant to removal. In this study, sustainable chloramine-functionalized iron hydroxide cellulose nanofibrous membrane (Fe-CNFM-Cl) was prepared by electrostatic spinning followed by chemical grafting for As(III) decontamination. In situ engineered iron hydroxides were uniformly dispersed in cellulose nanofibers for As adsorption. The oxidative chlorine (+1) in the grafted chloramine could oxidize As(III) to readily removable As(V). Benefiting from oxidation-enhanced adsorption, Fe-CNFM-Cl was able to remove As(III) reliably. Using Fe-CNFM-Cl, As(III) levels were purified from 1418.73 μg L-1 to meet drinking water standards within 300 min. Additionally, Fe-CNFM-Cl exhibited high iron utilization with a normalized As adsorption capacity of 214.55 ± 15.52 mg g-iron-1. Fe-CNFM-Cl performed effectively over a broad pH range of 3-9. Common anions and humic acid hardly inhibit As(III) removal except at high concentrations of phosphate. During the removal of As(III), a portion of As(III) was oxidized to As(V) by activated chlorine. The adsorption and oxidation capacity of the used Fe-CNFM-Cl could be well recovered by desorption with NaOH solution followed by chlorination with NaClO solution. In addition, it could reliably purify the As(III) levels in natural groundwater to below 10 μg L-1. The study contributes a novel strategy for the development of multifunctional iron-based cellulose biocomposite sorbents for the effective removal of As(III) from water.