Designing of hydroxyl terminated triazine-based dendritic polymer/halloysite nanotube as an efficient nano-adsorbent for the rapid removal of Pb(II) from aqueous media

Abstract

• A novel HNT-G2 adsorbent was synthesized for Pb(II) removal. • Negative ΔG confirms spontaneous removal process of Pb(II) by the prepared adsorbent. • The system obeys Langmuir model, indicating the monolayer adsorption of Pb(II). • The pseudo-second-order rate kinetics indicates a rate limiting step involving chemical reaction. In the present study, the hydroxyl terminated triazine-based dendritic polymer was synthesized and grown on the halloysite nanotubes surface (HNT-G2) to efficiently remove the Pb(II) ions from aqueous solution. The nano-adsorbent morphology and structure were determined through TEM (transmission electron microscope), XRD (X-ray diffraction), FT-IR (Fourier transformation infra-red), TGA (thermogravimetry analysis), BET (Brunauer-Emmet-Teller) isotherm, and EDS (energy dispersive analysis X-ray spectroscopy) methods. The adsorption of Pb(II) resulted a maximum of 75.2 mg/g at 298 K at optimal pH 6 after only 10 min and 2 g/L of HNT-G2. The adsorption kinetic revealed that it followed the pseudo-second-order model while the adsorption isotherms corresponded the Langmuir model. Accordingly, it could be inferred that the Pb(II) was a single-layer adsorption occurring on the adsorbent surface and further, the rate-controlling step was denoted chemical adsorption. Also, the thermodynamic outcome indicated that the adsorption progress could happen spontaneously, and was of the exothermic reaction types (ΔH = −79.99 kJ/mol and ΔG = −7.90 kJ/mol). Surprisingly, the adsorption and desorption efficiency after four cycles was high, while the Pb(II) adsorption mechanism affecting the adsorbent was basically via chelation through the O atoms. Hence, it can be concluded that the HNT-G2 was an effective in efficiently elimination of Pb(II) from the aqueous solution, having high applicability significance.