Magnetic N-rich carbon nitride framework material for the high selectivity extraction and determination of La(III)

A novel magnetic C 3 N 5 framework material (Fe 3 O 4 /C 3 N 5 ) was developed as a high selectivity extractant for La(III) determination in food samples. The Fe 3 O 4 /C 3 N 5 material was synthesized by thermal deammoniation method and has larger surface area (100.3 m 2  g −1 ) and more effective adsorption sites compared with that of individual C 3 N 5 material (19.4 m 2  g −1 ). It was proved that Fe 3 O 4 /C 3 N 5 material displayed excellent selectivity and adsorption capacity for La(III). In addition, adsorption isotherm and kinetic data indicated that La(III) adsorption based on Fe 3 O 4 /C 3 N 5 material is a monolayer adsorption which is compatible with Langmuir model and follows a pseudo-second-order kinetic equation. By using Fe 3 O 4 /C 3 N 5 material as extractant, an analytical method was established with low limits of detection (3σ, n = 6) of 10.4 μg L −1 , reasonable recoveries ranged from 86% to 106% and good precision with the RSD less than 10.7%. The analytical method was further applied to the determination of trace La(III) in food sample. It evinced that the concentration of La(III) in sea fish is 13.2 μg kg −1 and the content of 138 La is 0.138 μg kg −1 , which is 1.03% of total La(III).