Mechanistic insights into the capture of bisphenol homologs by macroporous chitosan-bentonite composite foams.

Bisphenols (BPA, BPF and BPS) are emerging contaminants with well-documented endocrine-disrupting effects, and their environmental occurrence often coincides with heavy metals and microplastics. In this study, a three-dimensional chitosan/bentonite composite foam (CBF) was fabricated via directional ice-templating and systematically evaluated as a recoverable adsorbent for bisphenols. The CBF exhibited stable adsorption performance, with kinetics following the pseudo-second-order model and isotherms well described by the Langmuir model, achieving moderate maximum capacities of 13.69 to 16.27 mg/g under a monolithic, manually recoverable design. High removal efficiencies were maintained over a wide pH range (2.0-10.0) and under varying ionic strength conditions. Spectroscopic and thermodynamic analyses indicate that bisphenol adsorption is governed by hydrogen bonding, polar interactions, and pore confinement effects, with selectivity among analogues modulated by their analogue-specific interaction pathways with the functional groups of CBF. The positive enthalpy change and increasingly negative Gibbs free energy further support a spontaneous and endothermic adsorption process. Preliminary tests further indicated that the macroporous framework was capable of capturing heavy metal ions (Pb(II), Cd(II)) and physically entrapping representative microplastics (PLA, PS, PE), suggesting potential applicability beyond bisphenols. Within its intended design scope of prioritizing operational simplicity over maximum capacity, CBF offers a monolithic platform with facile manual separation and minimal secondary turbidity. This combination of low-cost raw materials, monolithic recoverability, and multi-class pollutant applicability distinguishes CBF from conventional powdered adsorbents and is relevant to the practical treatment of bisphenol contaminated water under complex matrix conditions.