Implications of confined Mn species on reinforcing adsorption capability of activated coke for a sweetener acesulfame removal

Secondary effluents are regarded as both sources and sinks of emerging contaminants. Adsorption by activated coke (ACO) is successfully being applied in the advanced treatment of secondary effluent from the wastewater treatment plant of China. However, ACO proved ineffective in removing the sweetener acesulfame (ACE). Herein, both mesoporous ACO and microporous activated carbon (AC) were comparatively used for the innovative confinement of Mn oxides within their porous structures by impregnation/calcination to enhance ACE adsorption. The optimal synthesis conditions were determined to be a MnSO 4 ·H 2 O/ACO mass ratio of 1.0% and a calcination temperature of 600°C (Mn-ACO600). Mn-ACO600 exhibited superior ACE adsorption compared to Mn-modified AC. Stable adsorption performance was observed within the neutral pH range, which favors practical applications. The pseudo-second-order model best described the adsorption kinetics, indicating a possible chemisorption mechanism. Both the Langmuir and Freundlich isotherm models could effectively simulate ACE adsorption, with a q max of 299.6 mg/g at 298 K. Thermodynamic analysis indicated a spontaneous and exothermic process (Δ H 0 = −68.51 kJ/mol) with entropy reduction (Δ S 0 = −218.56 J mol −1 ·K −1 ). Both coexisting inorganic anions and natural organic matter had insignificant influences. Furthermore, the recycled Mn-ACO600 retained an acceptable adsorption capability. Three-dimensional fluorescence excitation-emission matrix analysis demonstrated that Mn-ACO600 adsorption effectively removed organic matter from real secondary effluent.