Arsenic removal adsorbent using limonite-polyethersulfone composite fiber via continuous flow column process.

ABSTRACT

This research introduces an enhanced limonite-based composite fiber adsorbent for arsenic (As) removal. The modification involves creating polyethersulfone (PES)-limonite composite fibers loaded with 60 wt% limonite powders, designed to be applicable in water flow environments. The fibers were prepared using a wet-spinning process based on phase inversion, with varying concentrations (10, 20, and 30 wt%) of PES in NMP solution. The composite fiber with 10 wt% NMP exhibited a porous structure and demonstrated efficient absorption of both As(III) and As(V). Adsorption followed the Langmuir model, with qm values of 1.5 mg/g for As(III) and 3.2 mg/g for As(V) at pH 6. In column experiments, As removal rates increased with contact time, attributed to decreased flow rates (1 mL/min). Moreover, increasing fiber column height led to enhanced removal rates, as indicated by the Adams-Bohart model. The mechanism for As(V) removal involved the formation of an inner-sphere complex through ion exchange between α-FeOOH and HAsO4 - and H2 AsO4 2- in an aqueous solution at pH 6.8. PRACTITIONER POINTS Changing the polyethersulfone ratio in the composite leads to variations in the appearance of limonite within each composite fiber. Limonite composite fibers effectively remove As(III) and As(V) at neutral pH. The adsorption behavior follows Langmuir kinetic model, the qm of 1.5 mg/g for As(III) and 3.2 mg/g for As(V). Longer columns and contact times enhance arsenic (As) removal in practical water treatment systems. Adam-Bohart model aids in predicting breakthrough and saturation time in As adsorption column design.