Peroxydisulfate activation and singlet oxygen generation for effective bisphenol A removal from groundwater and treated wastewater by a novel NiO doped B2O3–porous carbon catalyst

In this study, a novel catalyst was synthesized from hexamethylenetetramine (HMTA), boric acid, and nickel for the efficient removal of bisphenol A (BPA) via peroxydisulfate (PDS) activation. The optimized composite, prepared with a molar ratio of 1:5:0.05 (HMTA: boric acid: nickel), was calcinated under optimized conditions, heated to 550 °C at a ramping rate of 2.18 °C/min over 4 h, and held for 30 min. XRD analysis confirmed the coexistence of crystalline NiO and amorphous B2O3 phases within a porous carbon framework. The removal process was optimized using response surface methodology (RSM) and Box-Behnken design (BBD), with maximum BPA removal efficiencies of 99.9 % in groundwater and 98.9 % in treated wastewater at an initial BPA concentration of 0.5 mg/L achieved under optimal conditions (0.48 g/L of catalyst, 0.85 mM of PDS, pH of 6.97, and 6.5 min of reaction time). Importantly, a high total organic carbon (TOC) removal of over 98 % was obtained, confirming nearly complete mineralization. Quenching experiments demonstrated that singlet oxygen was the dominant reactive species, with GC–MS analysis of intermediates corroborating a non-radical degradation pathway. ICP-OES analysis confirmed negligible metal leaching (<0.01 mg/L), highlighting the catalyst's stability. The catalyst's performance remained unhindered by common coexisting ions and maintained over 95 % efficiency for five consecutive cycles, offering a highly efficient, mineralizing, and reusable solution for BPA removal in aquatic environments.