Appraisal of adsorptive potential of novel one-walled meso-phenylboronic acid functionalized calix[4]pyrrole for liquid phase sequestration of paracetamol

Abstract

It is critical to design an ecological and economically benign adsorbent for the decontamination of micropollutants from the aquatic realm. Supramolecular functional materials have garnered remarkable attention in recent times owing to their various potential applications. A supramolecular meso-phenylboronic acid functionalized calix[4]pyrrole (mPBA-C4P) was fabricated via a green synthetic approach utilizing a deep eutectic mixture of N,Ń-dimethylurea and L-(+)-tartaric acid, which was subsequently applied as an advanced adsorbent for paracetamol (PC) removal from aqueous phase. The characterization of mPBA-C4P was accomplished with NMR (1H and 13C), FTIR, high-resolution mass spectrometry (HRMS), SEM-EDX, Brunauer-Emmet-Teller (BET) analysis, and elemental mapping. The mPBA-C4P unveiled a commendable adsorption characteristics adsorbing > 92% PC within 20 min from simulated water having 30 mg L−1 PC concentration. The isotherm modeling inferred the Freundlich model to appropriate the equilibrium data, with high Langmuir adsorption capacity (479.30 mg g−1 at 298 K). The ΔH° (–53.98 kJ mol−1) along with a drop in adsorption capacity with temperature implied the process to be exothermic. The kinetics was in accord with the pseudo-second order model specifying chemisorption mechanism. However, the bt (2.56 kJ mol−1) and E (1.08 kJ mol−1) implied physical adsorption, suggesting, thereby, that the adsorption of PC occurred via concurrent physisorption and chemisorption. The mPBA-C4P maintained a decent removal rate after five consecutive adsorption–desorption cycles speculating its good reusability and practicality. Salting out effect was responsible for the enhancement in PC confiscation in presence of different ions. Based on FTIR spectral data, pH, isotherm, kinetic, thermodynamic and ionic studies, the proposed mechanism governing the uptake of PC by mPBA-C4P involved hydrogen bonding, π-π, n-π, anion-π and cation-π interactions, respectively. These findings indicated that mPBA-C4P could be weighed as a potentially superior adsorbent for alleviating paracetamol-laden waters.