Abstract:

Sodium percarbonate is the adduct of hydrogen peroxide and sodium carbonate, which is safe and stable during its storage, transportation and use. The method of co-precipitation followed by high-temperature calcination was used to prepare Mn₂O₃@α-Fe₃O₄ nanosheet, with which sodium percarbonate (SPC) was activated to generate free radicals to oxidize and degrade azo dye reactive black 5 (RBK5). The Mn₂O₃@α-Fe₃O₄ nanosheet was characterized by transmission electron microscope (TEM), X-ray powder diffractometer (XRD), scanning electron microscope (SEM), Fourier transform infrared spectrometer (FTIR), X-ray photoelectron spectroscopy (XPS) and Brunauer Emmett Teller (BET). The effects of catalyst dosage, SPC concentration, initial pH and RBK5 solution concentration on the degradation efficiency were explored. Under the conditions of SPC dosage 1.0mmol/L, Mn₂O₃@α-Fe₃O₄ dosage 0.3g/L, initial pH=7, the degradation rate of RBK5 in aqueous solution reached 88％ in 90min. The reaction kinetics could be well described by the pseudo first order kinetics model (R²>0.9). ·OH, CO{}_{\mathrm{3}}^{-}·, O{}_{\mathrm{2}}^{-}· and ¹O₂ were the active species in the Mn₂O₃@α-Fe₃O₄/SPC system, and ·OH was the dominant species among them. XPS results reflected the valence states of iron and manganese elements and their synergistic effect. Quenching experiment and XPS were used to analyze the degradation mechanism.

Key words: nanosheet, sodium percarbonate (SPC), reactive black 5, hydroxyl radical, catalyst activation, dynamics

摘要：

过碳酸钠是过氧化氢与碳酸钠的加成化合物，具有在存储、运输和使用过程中安全稳定的优点。本文采用共沉淀-高温煅烧法制备纳米片状Mn₂O₃@α-Fe₃O₄，活化过碳酸钠（SPC）产生自由基氧化降解偶氮染料活性黑5（RBK5）。采用透射电子显微镜（TEM）、X射线粉末衍射仪（XRD）、扫描电子显微镜（SEM）、傅里叶变换红外光谱仪（FTIR）、X射线光电子能谱（XPS）及比表面积测试（BET）表征制备的纳米片状Mn₂O₃@α-Fe₃O₄催化剂，分别探究催化剂投加量、过碳酸钠浓度、初始pH及RBK5溶液浓度对降解效率的影响。当催化剂投加量为0.3g/L、过碳酸钠浓度为1.0mmol/L、初始pH为3、反应时间为90min时，RBK5的降解效率达88%，反应过程符合拟一级动力学（R²＞0.9）。Mn₂O₃@α-Fe₃O₄/过碳酸钠体系中起氧化降解作用的活性物种为·OH、CO{}_{\mathrm{3}}^{-}·、O{}_{\mathrm{2}}^{-}·和¹O₂，其中·OH占据主导地位，XPS反映了铁锰元素存在价态以及双金属间的协同作用，依据猝灭实验及XPS分析降解机理。

关键词: 纳米片状, 过碳酸钠, 活性黑5, 羟基自由基, 催化剂活化, 动力学