Novel magnetic covalent organic framework loaded ligand for rapid removal and selective detection of mercury(II) from water

The present work aimed to prepare a novel magnetic covalent organic framework loaded ligand (MCM), which is going to be utilized to obtain efficient adsorption, rapid removal, and detection with high selectivity and sensitivity for mercury(II) ions. The structure, morphology, adsorption behavior, and detection properties of MCM were characterized with FTIR, TG, XRD, BET, SEM, TEM, UV-VIS, and XPS. To optimize the effects of process parameters, the influence of pH, contact time, and initial concentration on the adsorption behavior, color optimization, and detection limit of the mercury(II) ions was investigated. Under the optimal condition, MCM showed the efficient adsorption ability, rapid removal rate, high selectivity, and detection with excellent sensitivity for the mercury(II) ions. The color of MCM changed from light grey to yellow by observing with naked-eye in the presence of the mercury (II) ions, and the corresponding detection limit was 0.01 mu g/L. MCM also has a high removal rate of mercury (II) ions in industrial wastewater, which can meet the industrial discharge standard (residual concentration of mercury(II) ions in the solution is 0.05 mg/L). What's more, MCM could be used in a portable column unit to separate mercury(II) ions from actual water samples, rapidly reducing the mercury(II) concentration from 10.0 mg/L to 10.0 mu g/L within 15 s. Kinetic studies showed that the MCM adsorption behavior for mercury(II) ions was in good agreement with the pseudo-second-order model, and the MCM adsorption equilibrium data for mercury(II) ions belonged to the Langmuir model. Furthermore, the adsorption amount of MCM for mercury(II) ions after five adsorptions was 96.89% of the adsorption amount of MCM for the first adsorption of mercury(II) ions, which showed that MCM has good regeneration ability. Consequently, MCM provided an excellent alternative to mercury(II) ions adsorption or enrichment materials, and this method showed great potential in the routine monitoring of trace mercury(II) ions in liquid substrates.