Experimental and theoretical analysis of simultaneous removal of methylene blue and tetracycline using boron nitride nanosheets as adsorbent

Abstract

The adsorption behaviour of boron nitride nanosheets (BNNSs) for the removal of methylene blue (MB) dye and tetracycline (TC) antibiotic from aqueous solution has been reported in this study. BNNSs were synthesized using a bottom-up technique with boric acid and urea as precursors. The synthesized material was characterized using high-resolution transmission electron microscopy, field emission scanning electron microscopy, atomic force microscopy, X-ray powder diffraction, Fourier transform infrared spectroscopy for morphological and structural analysis. Through kinetic studies, it was revealed that the pseudo-second-order model was obeyed by both MB and TC. The isotherm study showed that the adsorption was followed by the Langmuir model for the mixture of MB and TC, indicating that monolayer adsorption was preferred on the adsorbent. The BNNSs adsorbent could remove the mixture of MB and TC, and a maximum adsorption capacity of 322.5 mg/g was found. Further, it was easily separable and exhibited regeneration properties. The simultaneous adsorption characteristics of MB and TC on the surface of BNNSs has been investigated through the density functional theory (DFT) calculations to explore the adsorbing capabilities of BNNSs. This analysis investigates electrostatic potential, atomic charge distribution, electron density contour, and electron localization function projection. The current study demonstrates the sensing potential of BNNSs for adsorption of both MB and TC, simultaneously since the gap between the highest occupied molecular orbital (HOMO) and lowest unoccupied molecular orbital (LUMO), i.e., HLG decreased to 1.54 eV. Further, chemical activity, electrical conductivity is quite high in the adsorption process. Also, negative charge transfer from the contaminant to BNNS takes place. The adsorption energy for MB-BNNS, TC-BNNS and MB+TC-BNNS were calculated to be − 117 kJ mol-1, − 1055 kJ mol-1, and − 844 kJ mol-1, respectively. These theoretical and experimental results show the promise of BNNSs as adsorbents for simultaneous adsorption of dyes and antibiotics from contaminated wastewater.