A silanized magnetic amino-functionalized carbon nanotube-based multi-ion imprinted polymer for the selective aqueous decontamination of heavy metal ions

Abstract

In this work, a novel highly selective adsorbent comprising a silanized magnetic amino-functionalized carbon nanotube-based multi-ion imprinted polymer (SMACNT-MIIP) is introduced as an ideal candidate for the simultaneous and selective adsorptive remediation of Hg(II), Cd(II), Cu(II), and Ni(II) heavy metal ions from contaminated water. Diverse investigation methods such as FTIR, XRD, VSM, BET, FESEM, and EDX analyses were employed to study the structural characteristics of the as-prepared adsorbent. The environmental conditions of adsorption like solution pH, adsorbent mass, contact time, and initial metal ion concentrations were optimized via central composite design and the desired adsorbent mass (20 mg), solution pH (6.5), contact time (30 min), Hg(II) concentration (30 mg L⁻¹), Cd(II)/Cu(II) concentrations (20 mg L⁻¹), and the Ni(II) concentration (12 mg L⁻¹) were obtained. The optimized adsorption data were well interpreted by the isotherm, kinetic, and thermodynamic studies. The Langmuir maximum adsorption capacity values of SMACNT-MIIP for Hg(II), Cd(II), Cu(II), and Ni(II) were 105.34, 91.79, 75.03, and 63.54 mg g⁻¹, respectively, which were greater than 28.41, 25.36, 21.24, and 19.57 mg g⁻¹ of the silanized magnetic amino-functionalized carbon nanotube-based non-imprinted polymer (SMACNT-NIP) for Hg(II), Cd(II), Cu(II), and Ni(II), respectively. The adsorption process showed a good fit with the pseudo-second-order kinetic model, and the thermodynamic study disclosed the feasibility, naturalness, and endothermic nature of the adsorption process. Interestingly, the interference studies revealed that the prepared adsorbent was highly selective for target ions in the presence of other interfering ions and the maximum adsorption capacity of the adsorbent did not decrease dramatically. The mechanism of heavy metal ion remediation using SMACNT-MIIP is mainly based on shape complementarity and surface complexation, leading to the development of an advanced adsorbent endowed with prominent features such as magnetic separation, reusability, fast kinetics, and especially, excellent selectivity for the adsorption of target ionic heavy metals.