Toxic cadmium(II) monitoring and removal from aqueous solution using ligand-based facial composite adsorbent

Developing an eco-friendly composite adsorbent via an eco-friendly process for detection and removing Cd(II) from wastewater is urgently necessary due to the critical hazards of Cd(II) to public health and environmental safety. The chemical ligand of 2,2′-Biquinoline-4,4′-dicarboxylic acid (BIDA) was embedded directly on the mesoporous silica for the fabrication of facial composite adsorbent (FCA) for toxic cadmium (Cd(II)) ion detection and removal from wastewater solutions. The FCA nanostructures were characterized by SEM, TEM, and N2 adsorption/desorption analyzer systematically. The physicochemical properties of FCA, as well as the primary influencing factors and mechanism of Cd(II) detection and adsorption processes, were also investigated. More interestingly, a colorimetric method based on color enhancement upon adding Cd(II) was developed by the FCA to detect low concentrations of Cd(II) ions. The solution pH played a key factor in color formation and neutral pH of 7.0 was selected based on the optimum color formation. The limit of detection was 0.39 µg/L. The preeminent adsorption capacity of FCA toward Cd(II) was (159.21 mg/g) which was mainly ascribed to the complexation of Cd(II) with the functional groups of BIDA coating FCA. The adsorption isotherms and kinetics data preferably conformed to the Langmuir isotherms model with monolayer coverage. The detection and adsorption of Cd(II) were not affected by other cations at the optimum experimental conditions. The FCA exhibited high reusability based on the elution and regeneration performances. The elution was carried out using 0.20 M HCl and then the FCA was ready to use after washing with water without loss in its functionality. The successful removal and detection of Cd(II) water samples demonstrates the great potential of the proposed FCA to remediate Cd(II) polluted water to safeguard water quality.