Cu(II) and Zn(II) metal ions’ sorption utilising halloysite nanotubes derivative

Abstract

Designing and developing clay-based adsorbents with a strong preference for removing copper and zinc metal ions, reduced cost, eco-friendliness, and good recyclability is a good strategy for water remediation. Herein, halloysite nanotubes (HNT) were activated by (3- chloropropyl) trimethoxy silane (CPTM) as a linker for polyethyleneimine to give HN-PEI. The hybrid organic/inorganic sorbent HN-PEI was analysed by Fourier-transform infrared spectroscopy, CHN/O (elemental analysis), scanning electron microscopy, textural properties (via the Brunauer–Emmett–Teller technique), X-ray diffraction, and thermogravimetry coupled with differential scanning calorimetry. The HN-PEI’s textural properties show a reduced specific surface of 10.92 m2/g and pore size of 18.2 nm compared to its Pristine HNT (65.33 m2/g) and pore size (⁓10.1 nm), respectively with a dominant mesoporous structure. The selectivity and sorption characteristics of the Cu(II) and Zn(II) metal ions were exploited, while HN-PEI exhibited a remarkable improvement in terms of removing these ions from the aqueous media. At pH 4.5, the sorption capacities for Cu(II) were 2.8 mmol g−1 and for Zn(II) were 1.8 mmol g−1, with equilibrium reached within 120 and 150 min, respectively. There was an acceptable fitting of the pseudo-second-order and Langmuir equations, and the experimental data enabled mono-layer chemisorption reactions. The sorption was exothermic and spontaneous. The sorbent HN-PEI shows high durability over multiple cycles, and after 3 cycles, the sorption/desorption efficacy decreased by less than 6% using HCl (1 M) for Cu(II) and H2SO4 (1.5 M) for Zn(II). According to the bi-system solution sorption test, KSC(Cu(II)/Zn(II)) was ⁓2.0. Finally, HN-PEI had excellent selectivity and efficiency for Cu(II), Pb(II), and Zn(II) ions, especially for Cu(II).