Treatment Of The Pollutant Acetaminophen By The Mn Oxide Based And Mn-Fe Oxide Based Processes

Acetaminophen（APAP）is a ubiquitous pharmaceutical product with potential to damage ecological environment and human health owing to residual in aquatic environment.In this study,two metal oxide materials of Mn oxide and Mn-Fe oxide were fabricated from pure reagents and waste battery resource,respectively.These two metal oxides were employed for treatment of APAP.The APAP removal results and main mechanisms were deeply investigated.The main contents are as follows:（1）Mn₂O₃ with certain oxidative capacity,was fabricated via the gel combustion method with pure reagents,and was applied for oxidative removal of APAP.Under acid aqueous solution,96.1%APAP could be effectively eliminated through direct electron transfer by Mn₂O₃ at pH 3.5.The open circuit potential（OCP）contrast and zeta potential tests illustrated that the oxidative capability of Mn₂O₃ was associated to the surface acid-base behavior of Mn₂O₃ and its surface charge condition.The acid inorganic ions displayed different effects and the removal efficiency of APAP followed SO₄^2->Cl^-≈NO₃^-.The suitable reaction pH and Mn₂O₃ dosage were determined to be pH 3.5 and 0.2 g L^-1,respectively.X-ray photoelectron spectroscopy（XPS）experiments and Mn leaching results imply that Mn（Ⅲ）could capture electron from APAP and realized APAP removal in acid environment;In the meanwhile,Mn（Ⅲ）itself was reduced to Mn²⁺and was released to aqueous phase.The main intermediates of APAP could be ascribed to fragmentation of acetamido radicals and coupling of phenoxy radicals,which were formed through electron transfer from APAP to Mn₂O₃.Mn₂O₃ showed selective oxidation to different contaminants in the acid electron transfer process,and electron-rich pollutants could be oxidized.The efficiency of Mn₂O₃ in degradation of APAP and selective oxidation suggest some promising insights in transformation and removal of APAP or other electron-rich pollutants in the future.（2）Mn₂O₃-Fe₂O₃ catalyst was fabricated from spent alkaline batteries and used for effective elimination of acetaminophen by activating peroxymonosulfate（PMS）.Nearly 100%APAP was eliminated by activated PMS with the waste battery-based Mn₂O₃-Fe₂O₃ in 15 min.APAP removal at various initial pH,its degradation pathway and the stability of catalyst were investigated.The recycling experiments indicated that Mn₂O₃-Fe₂O₃ had relatively acceptable stability and recyclability.The≡Mn（Ⅲ）was inferred to be the primary active site and≡Fe（Ⅲ）could improve the stability and corrosion resistance of Mn₂O₃-Fe₂O₃ through intermetallic interactions.Chemical quenching experiments,electron paramagnetic resonance（EPR）spectroscopy,solvent exchange,open circuit potential and chronoamperometry tests imply that APAP is oxidized by electron transfer through highly reactive surface-adsorbed PMS.Fourier transform infrared（FTIR）,in situ Raman spectroscopy,X-ray photoelectron spectroscopy spectra and ionic strength experiments further revealed the interaction between Mn₂O₃-Fe₂O₃ and PMS.The system of Mn₂O₃-Fe₂O₃/PMS presented selective oxidation towards different contaminants.Linear free energy relationship（LFER）analysis indicates the pollutant with peak potential(E_op)>0.91 V,the steady-state OCP in the Mn₂O₃-Fe₂O₃/PMS system,is hardly oxidized,while that with E_op<0.91 V is easily oxidized and there is a good correlation between apparent first-order rate constant（k₁）and E_op.The system of Mn₂O₃-Fe₂O₃/PMS provides a novel,low cost and environment-friendly system for resource recovery and treatment of organic contaminants.The Mn₂O₃-Fe₂O₃/PMS system could provide some new insights for nonradical electron transfer mechanism,selective oxidation and LFER study.