Experimental and density function theory-guided mechanistic insights into triclosan removal using a tripartite AgNPs/nanobiochar/Co-MOF composite

Abstract

A tripartite composite comprising nanobiochar, nanoparticles (AgNPs), and cobalt-based metal organic frameworks (Co-MOF) - AgNPs/nanobiochar/Co-MOF was synthesized and characterized. The incorporation of AgNPs and nanobiochar onto Co-MOF was confirmed via Fourier transform infrared spectroscopy (FTIR), energy-dispersive X-ray (EDX) results, and molecular docking optimization. The adsorption mechanism was investigated experimentally and computationally using Density functional theory (DFT). The pH of maximum adsorption and point of zero charge of the AgNPs/nanobiochar/Co-MOF composite was observed at 4 and 8.8, respectively. The composite removal efficiency of triclosan (TRC) decreased with initial concentration and temperature but increased with contact time and adsorbent dose. The adsorption processes followed were best fitted to the Freundlich isotherm with a maximum monolayer adsorption (q max ) of 117.88 mg g −1 and appropriately described by pseudo-second order kinetics. Thermodynamic parameters revealed spontaneous and exothermic adsorption with negative enthalpy (-ΔH°) and decreasing free energy (-ΔG°) values with an increase in temperature (303–333 K). The DFT-guided molecular docking (DFT) revealed that the adsorption process was exergonic, involving an electron transfer mechanism from triclosan (TRC) to the composite. The interaction in complex [HO---Co and Ph 2 O---Co] was more energetically favourable than complex [Cl---Co] as reflected by higher binding energy and shorter interatomic distance.