Magnetic nanomodified activated carbon: characterization and use for organic acids sorption in aqueous medium

A new approach on the sorption of aconitic and citric acids by activated carbon (AC) after nanomodification with Fe3O4(AC-MNP) is proposed in batch procedures and as SPE (Solid Phase Extraction) cartridges for the treatment of complex samples prior to HPLC analysis. AC and AC-MNP were characterized by XRD, SEM, EDS, and FTIR. The mean crystallite size of AC-MNP and MNP were 19.16 and 10.70 nm, respectively, and FTIR bands characteristics of C = C, C-O, OH, and Fe-O were identified. Amaranth red dye sorption by AC and AC-MNP was evaluated and indicated that the surface charge of AC and AC-MNP is predominantly cationic. Experimental AC-MNP sorption capacity (SCexp) for aconitic and citric acids were 52.44 mg/g and 36.88 mg/g, respectively, and these analytes were determined by high performance liquid chromatography (HPLC). Nanomodified activated carbon (AC-MNP) cartridges were prepared to be used as SPE and compared with commercially available C18. The retention capacity of AC-MNP was 75% higher than that of C18, resulting, respectively, in 29.31 mg/g and 30.06 mg/g AC-MNP for aconitic, and 7.81 mg/g and 8.44 mg/g C18 for citric acids. Among the isotherms models used, Freundlich and Langmuir were better adjusted to aconitic and citric acid, respectively. The AC-MNP sorbent seems to be an efficient low-cost alternative to the commercially C18 cartridges most commonly used for sample pretreatment prior to organic acid determination in complex samples analysis by HPLC.

Automated summary

The nanomodified activated carbon (AC-MNP) with Fe3O4 showed improved sorption capacity for aconitic and citric acids compared to commercially available C18 cartridges, making it a cost-effective alternative for sample pretreatment in HPLC analysis of complex samples.