Removal Of Refractory Organic Pollutant In Aqueous Solution Based On The New Fenton-like System Of ·SO₄^-

The dissolved and lowly-concentrated persistent organic pollutants not only have a relatively high environmental toxicity,but also are more resistant to be degraded by conventional methods.How to effectively remove these emerging pollutants from water is the main objectives of this study.The Fenton-like system based on·SO₄^-has the advantages of good effect and simple operation as the traditional Fenton system,and has several important characteristics for practical applications,such as wide pH range,strong oxidation capacity,long half-life and good selectivity.As a result,the·SO₄^--based Fenton-like catalytic system has become one of hot topic for the efficient water treatment in recent years.The efficient,stable,safe and cost-effective heterogeneous catalyst is the core of Fenton-like catalytic system for environmental applications.In our study,two novel and efficient catalysts were rationally designed and chemically prepared to construct the heterogeneous Fenton-like catalytic systems for refractory pollutants removal from water environment.The heterogeneous Fenton-like activity,pollutants degradation efficiency under different reaction condition,and the catalyst recycling performance were systematically carried out.Moreover,the degradation pathways of target contaminants,the degradation mechanism of catalytic systems as well as the morphological and structural properties of these two catalysts were studied to reveal the Fenton-like catalytic mechanism based on these two solid catalysts.Transition metal oxides Co₃O₄ was deposited onto the TiO₂ single crystals exposed by the thermodynamically unstable high-energy{001}polar facet to prepare the new heterogeneous Fenton-like catalyst?Co/Ti-001?,with the TiO₂ exposed by thermodynamically stable low-energy{101}polar facet as the reference?Co/Ti-101?.At the bulk pH of 7.0,the degradation percent for RhB of 10 ppm in 1.0 h was more than 90%,with the novel Co/Ti-001 catalyst to generate·SO₄^-from the heterogeneous PMS activation.In comparison,the contribution of catalyst adsorption and the oxidant to the degradation of pollutants were both less than 20%under the similar reaction conditions.At the same time,the degradation percent of Co/Ti-101 catalyst was only60%under the same conditions,and the degradation rate decreased rapidly afther initial one hour,indicating that the catalytic activity of Co/Ti-101 was much lower than that of the Co/Ti-001 catalyst for refractory pollutants degradation in the heterogeneous Fenton-like catalytic system at the mild pH condition.The TOC analysis and the PNP degradation tests further showed that the refractory pollutants degradation in the novel Co/Ti-001-mediated Fenton-like catalytic system was completely mineralized rather than simple conversion.Moreover,the experimental results further indicated that the prepared Co/Ti-001 catalyst also had a much lower Co²⁺leaching during redox cycling for PMS activation and pollutants degradation,indicating that this novel catalyst not only had a high catalytic activity,but also had a low environmental toxicity for practical applications.With the morphological and structural characterization and analysis,it was found that the tailored Co/Ti-001catalyst exhibited a superior heterogeneous activation capacity for PMS oxidation,which is mainly due to the atomic structure,electronic structure and energy structure and good morphology of high energy{001}polar plane with excellent thermodynamic properties.These experiments clearly indicated that the novel Co/Ti-001-mediated Fenton-like catalytic system was feasible and efficient for the removal of refractory pollutants from water and wastewater,and exhibited a good promise for the advanced water treatment.The shape-tailored TiO₂ single crystals exposed by the thermodynamically unstable high-energy{001}polar facet,TiO_2-001,was thermally reduced in the reductive H₂atmosphere at 400^oC to prepare the defective TiO_2-x catalyst with both surface and sub-surface oxygen vacancies(TiO_2-x),and another kind of novel heterogeneous Fenton-like catalytic system was developed.The degradation experiments of potassium sulfate?PDS?activation by TiO_2-x,TiO_2-001 and TiO_2-101-101 clearly show that the catalytic activity of TiO_2-x for PDS heterogeneous activation had been greatly improved after reduction treatment,thus a much higher degradation efficiency was observed in the Fenton-like catalytic system.Under the bulk pH of 7.0,the RhB removal efficiency was more than 90%on the TiO_2-x in 3.0 h reaction period,while the TiO_2-001 and TiO_2-101 catalyst degradation percent was only 33%and 23%under the same conditions.The BPA degradation tests under different reaction conditions and the qualitative and quantitative analysis of degradation intermediates further indicated that the defective TiO_2-x-mediated Fenton-like catalytic system also exhibited a good mineralization capacity for practical applications.