Enhanced adsorption of arsenite from aqueous solution by an iron-doped electrospun chitosan nanofiber mat: Preparation, characterization and performance.

A novel iron-doped chitosan electrospun nanofiber mat (Fe@CTS ENM) was synthesized, which was proven to be effective for the removal of arsenite (As(III)) from water at neutral pH condition. The physiochemical properties and adsorption mechanism were explored by SEM-EDS and X-ray photoelectron spectroscopy (XPS). Batch adsorption experiments were carried out to evaluate the As(III) adsorption performance of the Fe@CTS ENM with various process parameters, such as adsorbent dose, solution pH, initial As(III) concentration, contact time, ionic strength, coexisting anions, and natural organic matter. The experimental results indicated that the maximum adsorption capacity was up to 36.1 mg g-1. Especially, when the adsorbent dosage was higher than 0.3 g L-1, the As(III) concentration was reduced from 100 µg L-1 to less than 10 µg L-1, which indicated the Fe@CTS ENM could effectively remove trace As(III) from water over a wide pH range (from 3.3 to 7.5). Kinetics study demonstrated that the adsorption equilibrium was achieved within 2.0 h, corresponding to a fast uptake of As(III). The presence of common co-ions and humic acid had little effect on the As(III) adsorption. XPS analysis suggested that the FeO, COH, COC and CN groups on the adsorbent surface play dominant roles in the adsorption of As(III). Adsorption-desorption regeneration test further demonstrated that no appreciable loss in the adsorption capacities was observed, which confirmed that the Fe@CTS ENM maintained a desirable life cycle that was free of complex synthesis processes, expensive and toxic materials, qualifying it as an efficient and low-cost As(III) adsorbent.

Electrospun Chitosan Nanofiber Membrane for Adsorption of Cu(II) from Aqueous Solution: Fabrication, Characterization and Performance.

The preparation, characterization and application of chitosan (CS) based electrospun nanofiber membrane for the adsorptive removal of Cu(II) from water were systematically investigated. Homogeneous, porous polyvinyl alcohol (PVA)/CS nanofiber membrane with amorphous structure, and average fiber diameter of 49 nm was successfully fabricated. The adsorption of Cu(II) onto the positively charged PVA/CS nanofiber membrane (pH < 6) was due to chemisorption rather than electrostatic adherence, and was highly pH-dependent. The adsorption equilibrium of Cu(II) by the PVA/CS nanofiber was established within 120 min, which was much faster than that by CS beads, and the adsorption kinetics followed pseudo-second-order model well (r 2 > 0.995). The adsorption isotherm data were well fitted with Langmuir model, and the maximum Cu(II) adsorption capacity of PVA/CS nanofiber membrane was 90.3 mg·g-1, which was much higher than that of CS beads. The adsorbed Cu(II) formed strong inner-sphere complex with the adsorbent. Coexisting cations of iron, lead, cadmium, nickel, calcium, and magnesium have insignificant effect on the Cu(II) adsorption, indicating the adsorbent has good selectivity for Cu(II) adsorption. FTIR and XPS analysis reveal amine, hydroxyl and ether groups are responsible for the Cu(II) adsorption. This work demonstrates the electrospun PVA/CS nanofiber membrane is a promising adsorbent for heavy metal removals.