PVDF/SiO₂-g-CDs blended membrane for fluorescence detection and adsorption of metal ions

ABSTRACT

The preparation method of PVDF/SiO₂-g-CDs blended membrane was that the silanized modified carbon dots (CDs) were grafted onto the PVDF/SiO₂ blended membrane surface. The surface composition, morphology, hydrophilicity, fluorescence performance and metal ions adsorption performance of PVDF/SiO₂-g-CDs blended membrane were studied. The fluorescence quenching effect of the membrane with Hg²⁺ and Fe³⁺ was obvious. The quenching mechanism was the complexation of metal ions with the functional groups of CDs including -NH₂, -OH and -COOH. The optical detection limits of PVDF/SiO₂-g-CDs blended membrane for Hg²⁺ was 1.6 nM in the linear range of 0.0025–20 μM, and the optical detection limits for Fe³⁺ was 2.1 μM in the linear range of 0.5–5000 μM. The maximum adsorption capacity of PVDF/SiO₂-g-CDs blended membrane for Fe³⁺ was 47.04 mg·g⁻¹. The adsorption of the membrane conformed to the pseudo-second-order kinetics and Langumir model, and belonged to monolayer chemical adsorption on the membrane surface. Through adsorption thermodynamic analysis, adsorption was a spontaneous endothermic process. The recovery rate of fluorescence and adsorption capacity could still be maintained above 82% after five cycles. The PVDF/SiO₂-g-CDs blended membrane had the ability to regenerate. In summary, the PVDF/SiO₂-g-CDs blended membrane had the dual functions of detecting and adsorbing metal ions, and had broad application prospects in sewage treatment.

GRAPHICAL ABSTRACT

KEYWORDS:

• Carbon dots
• blended membrane
• metal ions
• adsorption
• detection

Acknowledgements

Jingjing Li: Conceptualization, Methodology, Visualization, Writing – original draft. Zhicheng Ji: Investigation, Software. Heyu Sun: Software. Dongdong Zhang: Software. Yiping Zhao: Funding acquisition, Supervision, Writing – review & editing. Li Chen: Resources, Supervision.

Disclosure statement

No potential conflict of interest was reported by the author(s).

Additional information

Funding

This work was financially sponsored by the National Natural Science Foundation of China [grant number 51973158] and the Science and Technology Plans of Tianjin [grant number 18JCYBJC18100], and Program for Innovative Research Team in University of Ministry of Education of China [grant number IRT-17R80] Program for Innovative Research Team in University of Tianjin [grant number TD13-5044].