Enhanced removal of trace arsenate by magnetic nanoparticles modified with arginine and lysine

• Arginine/lysine modified magnetic nanoparticles were synthesized.
• The modification greatly enhanced As(V) adsorption of MNPs.
• As(V) can be effectively removed by the modified adsorbents in a wide pH range.
• Phosphate did not significantly inhibit As(V) adsorption.
• Both modified adsorbents exhibited good potential for repeated use.

Two types of adsorbents, arginine (Arg) and lysine (Lys) modified Fe3O4 magnetic nanoparticles (Arg-MNPs and Lys-MNPs), were synthesized by employing conventional co-precipitation process and used to remove trace arsenate [As(V)] from water. Various techniques including transmission electron microscopy (TEM), powder X-ray diffraction, Föurier transform infra-red spectroscopy, energy dispersive X-ray spectrometry, and thermogravimetric analysis were utilized to characterize the synthesized adsorbents. TEM images showed that both fabricated materials were spherical with diameter of approximately 10 nm. With saturation magnetization of around 73.0 emu/g, both adsorbents could be easily separated from water with a simple magnetic process in 5 min. The As(V) adsorption capacities of Arg-MNPs and Lys-MNPs were 29.14 and 23.86 mg/g, respectively, which were twice larger than that of bare MNPs (12.12 mg/g). Both adsorbents (0.1 g/L) could remove over 90% of As(V) (100 μg/L) from water over a wide pH range from 3 to 9. Moreover, natural organic matters (humic acid and alginate) and competitive anions including sulfate, bicarbonate, silicate, and phosphate did not obviously affect the adsorption of As(V) by the modified adsorbents. The removal of As(V) maintained above 83% even with extremely high concentration of phosphate (50 mg/L). As(V) could also be effectively removed from challenge water and real river water by the modified adsorbents. Both magnetic particles could be easily regenerated in alkali solutions and their adsorption capacities were still greater than 10 mg/g even in the fifth cycle.

Figure optionsDownload as PowerPoint slide