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

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.

Suppression of Hydrogen Sulfide Generation via the Coexistence of Anaerobic Sludge and Goethite-Rich Limonite/Polyethersulfone Composite Fibers.

Limonite-polyethersulfone (PES) composite fibers were prepared by the wet spinning method to suppress hydrogen sulfide (H2S) generation from anaerobic microbial sludge. The H2S adsorption of the prepared limonite composite fibers followed the Langmuir type, with a maximum adsorption capacity of 3.7-4.4 g H2S/g, indicating mesopore adsorption. The in vitro H2S fermentation environment with anaerobic microbial sludge with the coexistence of limonite composite fibers exhibited suppression of H2S generation. The coexistence of limonite composite fibers also suppressed the amount of CO generation produced by microbial fermentation, so the fibers also affected the metabolism of anaerobic microorganisms. During the anaerobic digestion process, particularly at 672-840 h (28-35 days), the mesopores of limonite in the composite fibers disappeared and changed to macropore adsorption, and the reaction of limonite with hydrogen sulfide produced pyrite (FeS2) and iron sulfate (Fe2(SO4)3) as products, which remained in the fiber with conversion efficiencies of 6.8 and 32.4%, respectively. The in vitro hydrogen disulfide action of limonite composite fibers was found to be able to suppress the generated environment of about 300 ppm to about 0.4 ppm.