A multifunctional composite Fe₃O₄/MOF/<scp>l</scp>-cysteine for removal, magnetic solid phase extraction and fluorescence sensing of Cd(<scp>ii</scp>)

Abstract

Fe₃O₄/MOF (metal organic framework)/l-cysteine was synthesized and applied for the removal of Cd(ii) from wastewater. The adsorption kinetics and isotherms were investigated, and the results indicated that the adsorption obeyed the pseudo-second-order kinetic model and Langmuir isotherm. The maximum adsorption capacity was calculated to be 248.24 mg g^-1. Fe₃O₄/MOF/l-cysteine was further applied to determine trace amounts of Cd(ii) in real water samples using ICP-AES (inductively coupled plasma-atomic emission spectroscopy) based on magnetic solid-phase extraction (MSPE). The determination limit was 10.6 ng mL^-1. Additionally, Fe₃O₄/MOF/l-cysteine can also be used as a fluorescent sensor for "turn-off" detection of Cd(ii), and the detection limit was 0.94 ng mL^-1.