Effective aqueous arsenic removal using zero valent iron doped MWCNT synthesized by in situ CVD method using natural α-Fe2O3 as a precursor

- Multiwalled carbon nanotubes were synthesized over a natural α-Fe2O3 catalyst.
- The magnetic nanocomposite was characterized by XRD, VSM, FE-SEM and TEM.
- Hematite, nanohybrid and its air oxidized form were employed for arsenic removal.
- Removal efficiencies were 96 and 98.5% for arsenite and arsenate by nanohybrid.
- The arsenic adsorption onto nanohybrid and oxidized sorbent was spontaneous.

This research presents an efficient system for removing aqua's arsenic based on in situ zero valent iron doping onto multiwall carbon nanotube (MWCNT) through MWCNT growth onto the natural α-Fe2O3 surface in chemical vapor deposition (CVD) reactor. The as-synthesized magnetic nanohybrid was characterized by XRD, VSM, FE-SEM and TEM techniques. The result of XRD analysis revealed that MWCNT has been successfully generated on the surface of zero valent iron. Moreover, the material showed good superparamagnetic characteristic to be employed as a magnetic adsorbent. The hematite, nanohybrid and its air oxidized form were used for removing aqueous arsenite and arsenate; however, non oxidized material exhibited greater efficiency for the analytes uptake. Equilibrium times were 60 and 90 min for arsenate and arsenite adsorption using nanohybrid and oxidized sorbent but the equilibrium time was 1320 min using hematite. The adsorption efficiencies of hematite and oxidized sorbent were 18, 74% and 26, 77% for arsenite and arsenate, respectively, at initial concentration of 10 mg L−1. At this situation, the removal efficiencies were 96 and 98.5% for arsenite and arsenate adsorption using raw nanohybrid. Thermodynamic study was also performed and results indicated that arsenic adsorption onto nanohybrid and oxidized sorbent was spontaneous however hematite followed a nonspontaneous path for the arsenic removal.

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