Determination of Hg (II) in tea and mushroom samples based on metal-organic frameworks as solid phase extraction sorbents

Highly effective and accurate monitoring of mercury in drinking water and agriculture products is of great concern for public health. An efficient method for the separation and enrichment of mercury needs to be established. A metal-organic framework (MOF) based on copper and 3,3′,5,5′-azobenzenetetracarboxylic acid, namely JUC-62, caught our attention because of its great hydrogen adsorption performance. In this paper, we studied the new application of JUC-62 as a sorbent for the enrichment of mercury in real samples. The prepared MOF was crystalline and porous and was characterized by scanning electron microscopy, thermogravimetric analysis and N2 sorption-desorption isotherms. The MOF was used as the sorbent for the adsorption of Hg2+ with superior adsorption capacity. The adsorption performances, in both static and kinetic conditions, were investigated strictly and the experimental data fitted the Langmuir model and pseudo-second-order equation very well. The maximum adsorption capacity of JUC-62 for Hg2+ was 836.7 mg/g, which was the largest compared with that of various materials. And the adsorption reached equilibrium in 15 min with the concentration of 0.1 mg/mL Hg2+, offering a fast adsorption process. The sorbent was successfully applied to the pretreatment of tea and mushroom samples for Hg2+ detection with satisfactory results.