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Physicochemical characteristics of calcined MnFe2O4 solid nanospheres and their catalytic activity to oxidize para-nitrophenol with peroxymonosulfate and n-C7 asphaltenes with air
Journal of Environmental Management ( IF 8.7 ) Pub Date : 2020-12-29 , DOI: 10.1016/j.jenvman.2020.111871
Lucía Mateus , Carlos Moreno-Castilla , María V. López-Ramón , Farid B. Cortés , Miguel Á. Álvarez , Oscar E. Medina , Camilo A. Franco , África Yebra-Rodríguez

Manganese ferrite solid nanospheres (MSNs) were prepared by a solvothermal method and calcined at various temperatures up to 500 °C. Their surface area, morphology, particle size, weight change during calcination, surface coordination number of metal ions, oxidation state, crystal structure, crystallite size, and magnetic properties were studied. The MSNs were used as catalysts to activate potassium peroxymonosulfate (PMS) for the oxidative degradation of para-nitrophenol (PNP) from water and for the oxidation of n-C7 asphaltenes in flowing air at atmospheric (0.084 MPa) and high pressure (6 MPa). Mn was in oxidation states (II) and (III) at calcination temperature of 200 °C, and the crystalline structure corresponded to jacobsite. Mn was in oxidation states (III) and (IV) at 350 °C and in oxidation states (II), (III), and (IV) at 500 °C, and the crystalline structure was maghemite at both temperatures. MSN catalysts generated hydroxyl (HO·) and sulfate (SO4·-) radicals in the PMS activation and generated HO· radicals in the n-C7 asphaltene oxidation. In both reactions, the best catalyst was MSN calcined at 350 °C (MSN350), because it has the highest concentration of Mn(III) in octahedral B sites, which are directly exposed to the catalyst surface, and the largest total and lattice oxygen contents, favoring oxygen mobility for Mn redox cycles. The MSN350 sample reduces the decomposition temperature of n-C7 asphaltenes from 430 to 210 °C at 0.084 MPa and from 370 to 200 °C at 6.0 MPa. In addition, it reduces the effective activation energy by approximately 77.6% in the second combustion (SC) region, where high-temperature oxidation reactions take place.



中文翻译:

煅烧后的MnFe 2 O 4固体纳米球的理化特性及其对过氧一硫酸盐和n -C 7沥青质与空气氧化硝基苯酚的催化活性

锰铁氧体固体纳米球(MSNs)通过溶剂热法制备,并在高达500°C的各种温度下煅烧。研究了它们的表面积,形态,粒度,煅烧过程中的重量变化,金属离子的表面配位数,氧化态,晶体结构,微晶尺寸和磁性。所述的MSN被用作催化剂来激活过一硫酸钾(PMS)为的氧化劣化从水和氧化硝基苯酚(PNP)ñ -C 7大气(0.084 MPa)和高压(6 MPa)下流动的空气中的沥青质。Mn在200℃的煅烧温度下处于(II)和(III)的氧化态,其晶体结构对应于菱锰矿。Mn在350℃下处于氧化态(III)和(IV),在500℃下处于氧化态(II),(III)和(IV),并且晶体结构在两个温度下均为磁赤铁矿。MSN催化剂在PMS活化中生成羟基(HO ·)和硫酸盐(SO 4 ·-)自由基,并在n -C 7中生成HO ·自由基沥青质氧化。在这两个反应中,最好的催化剂是在350°C下煅烧的MSN(MSN350),因为它在直接暴露于催化剂表面的八面体B位中具有最高的Mn(III)浓度,并且具有最大的总氧和晶格氧含量,有利于锰氧化还原循环的氧迁移率。MSN350样品将n -C 7沥青烯的分解温度在0.084 MPa下从430降低到210°C,在6.0 MPa下从370降低到200°C。此外,它在发生高温氧化反应的第二燃烧(SC)区域中将有效活化能降低了约77.6%。

更新日期:2020-12-30
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