Studies On Hydrothermal Syntheses Of Zinc And Manganese Zinc Ferrites And Their Application In Microwave Removal Of Organic Pollutants

Currently, there were more and more researches about microwave (MW)induced catalytic degradation of organic pollutants in waste water. In Microwaveinduced catalytic reactions the microwave is combined with the catalyst, then theactivated catalyst will participate in corresponding activities. In most researches thepopular "sensitizer" was activated carbon. The ferrite catalysts were seldom used inmicrowave (MW) induced degradations. Absorbing properties and the grain size offerrites can be adjusted by using different preparation method and composition.There were haven’t yet had reports about the impact of preparation conditions on thecatalytic properties of ferrites.In this paper, different ferrites prepared by traditional hydrothermal method andmicrowave hydrothermal method, and their application in MW induced catalyticactivities on the degradation of organic pollutants were investigated.Well crystallized nano-sized zinc ferrites were synthesized with hydrothermalmethod and developed for the microwave (MW)-induced degradation of BPA as amodel contaminant in aqueous solution. The effects of selected process parameterssuch as Fe: Zn ratio, precusor acidity Hydrothermal-treatment temperature and time,FeCl3concentration, MW irradiation time, initial BPA concentration, catalyst dose,and MW power on the degradation were studied in details. Under given conditionsof10mg/L and25mL BPA solution,4.0g/L catalyst dose and MW irradiation of750W power and2450MHz frequency, high extents of degradation (64.3%) wereobtained using Fe:Zn=1.5:1within5.0min MW irradiation. And58.7%and52.4%for Fe:Zn=2:1and2.5:1under the same condition. When the addition amount addedto10mg/L the degradation reached to57.7%，66.3%and73.4%under otherconditions keeping the same. The precusor acidity, hydrothermal-treatmenttemperature and time, FeCl3concentration, MW irradiation time, initial BPAconcentration, catalyst dose, and MW power also have impact on the on the degradation ratio.Mn-Zn ferrites prepared by an environmental friendly method, MicrowaveHydrothermal method AR-B in aqueous solution can be degraded rapidly andeffectively under MW irradiation in the presence of ferrites as catalyst. The resultsindicate that at the conditions in question, degradation ratio of AR-B could reach5.87%,30.21%and76.67%, or25mL total volume with25mg/L AR-B solution and2.0g/L nanometer MnFe2O4,Mn0.2Zn0.8Fe2O4and ZnFe2O4under3.0min MWirradiation,MW power750W respectively. The results showed that M-H preparedZnFe2O4have the drawbacks of high absorption and low magnetic properties andreuse ability. Although MnFe2O4had high magnetic properties but its degradationratio is very low. The Mn0.2Zn0.8Fe2O4overcame the disadvantages of ZnFe2O4andMnFe2O4。The influences of the precursor acidity and zinc content, M-H pressure,M-H treated time, calcine temperature, MW irradiation time, reused times on thedegradation were discussed in details. The results showed that by microwavehydrothermal method we can syntheses Mn-Zn ferrites. Overall, the Mn-Znferrites/MW process exhibited many advantages including short irradiation time, noresidual intermediates and no secondary pollution. Therefore, it may be fit for dealingwith kinds of AR-B wastewater on a large scale.Ferrites with catalytic activities can be prepared by hydrothermal method.theprepared ferrit used in microwave catalytic degradation of organic pollutants whichhave the advantages of high efficiency, short reaction time, low cost, nointermediates and no secondary pollution, etc., suitable for organic pollutants inwater treatment.