A sensitive ligand embedded nano-conjugate adsorbent for effective cobalt(II) ions capturing from contaminated water

• Nano-conjugate adsorbent (NCA) was based on organic-inorganic immobilization.
• The Co(II) capturing showed high functionality in terms of sensitivity/selectivity.
• The Co(II) ions can be detected without using of high-tech instruments.
• The NCA is efficient and eco-friendly for Co(II) treatment from water samples.

In this study, specific ligand embedded nano-conjugate adsorbent (NCA) was prepared and used for cobalt (Co(II)) monitoring and removal from wastewater. The organic ligand of N,N(octane-1,8-diylidene)di(2-hydroxyl-3,5-dimethylaniline) was synthesized and anchored onto inorganic mesoporous materials by direct immobilization method for Co(II) ions. The interaction of this material with various metal ions was evaluated, and it exhibited distinct color change (π–π transition) from whitish to green in the presence of Co(II) ions, detectable even to the naked-eye. The low detection limit for Co(II) was 0.19 μg/L and competitive monitoring studies revealed no significant interference from diverse metal ions. The effects of solution pH, contact time, competing ions and initial concentration on Co(II) sorption on NCA were investigated under optimum conditions. The NCA exhibited rapid sorption property for Co(II) ions, and the maximum sorption capability approached to 165.83 mg/g. The presence of other coexisting metal ions did not decrease the Co(II) sorption capacity and the NCA adsorbent had almost no sorption capacity to these coexisting metal ions, which suggested the high sorption selectivity of NCA to Co(II) ions at optimum conditions. The adsorbed Co(II) was eluted with 0.10 M HCl eluent and simultaneously regenerated into the original form for next operation without significant loss in its initial performances. The data also clarified that the NCA adsorbent is an efficient and eco-friendly adsorbent for Co(II) treatment. Therefore, the proposed adsorbent can be considered as a potential candidate for Co(II) ions monitoring and removal from wastewater in large-scale operations.

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