Degradation Of Biodiesel Pollution By Activation Of Persulfate With Fe-mn Bimetallic Catalyst

In this paper,Fe-Mn bimetallic catalyst?FMO?was prepared and used to degrade biodiesel pollution activated by persulfate activation.Analyses upon degradation conditions optimization,the best operation conditions of FMO/PS system for biodiesel wastewater and biodiesel contaminated soil treatment,the intermediates path of oxidation and proposed mechanism were determined.FMO were prepared by two-step hydrothermal method?reaction temperature of110?,reaction time of 10 h?.According to characterization,the flower-folding appearance were observed by SEM and TEM,and the crystal structure of Fe₃O₄ and MnO₂ were confirmed by XRD analysis.The redox properties was analyzed via hydrogen temperature-programmed reduction?H₂-TPR?and cyclic voltammetry?CV?and the finding indicated the superior redox activity of FMO than pure MnO₂.The magnetic hysteresis loop of FMO indicated the magnetic properties for magnetic recycle.The efficiency of biodiesel waste water degradation by FMO/PS system was investigated to identify best operation conditions.Under the condition of initial pH=9,the FMO dosage of 1.2 g/L,the PS concentration of 3 mM,biodiesel waste water concentration of 50 mg/L,the removal rate could reach 95.2%in 60 minutes.Comparing with XPS result of FMO catalysts before and after reaction,the synergistic effect of Fe and Mn were confirmed.The cycles of Mn⁴⁺-Mn³⁺and Fe³⁺-Fe²⁺,improved the efficiency of PS activation.Gas chromatography mass spectrometry?GC-MS?analysis was performed to determine intermediates of biodiesel,in order to suggest possible degradation pathway.The pathway was that SO₄^·-and·OH were generated to react with C=C,change C=C to C-C,and then attack the ester group?-COOR?in edge of biodiesel,continuously remove the ester group,change the biodiesel to small molecule alkanes,finally biodiesel was mineralized to CO₂.The FMO/PS system were also used for soil remediation to estimate the utilization possibility.The influence of experimental parameter?e.g.,catalyst dosage,persulfate dosage,and soil-water ratio?were explored biodiesel degradation efficiency in soil.The optimal degradation conditions were achieved under the dosage of catalyst was0.01 g/g,the dosage of persulfate was 0.4 mmol/g and soil-water ratio was 1:5.Quenching experiments verified the existence of SO₄^·-and·OH in the FMO/PS system.Among that,SO₄^·-was major free radicals.The degradation of biodiesel in different types of soil,including kaolin,red soil,red soil,black soil and paddy soil,proved the applicability of FMO/PS system for various kind of soil,due to the high removal rate larger than 68%.