含锌尘泥可控构筑多元掺杂α-Fe2O3@ZnFe2O4异质结光催化材料的基础研究

Zn-bearing dust is a complex system containing multiple metal values, and the conversion of such kind of dust into some valuable materials remains a challenge yet. A lot of researches focus on the recycling of some single component in the dust but, the synergetic behaviors among the multiple elements remain unknown. A novel strategy is proposed in this project to controllably build the multi-doped α-Fe2O3@ZnFe2O4 heterojunctions as photocatalysts from the Zn-bearing dust by combination of sulfolysis and step coprecipition. For understand the effects of technologic parameters on the doping groups and evolvement of heterojunctions, it is firstly revealed that the thermodynamic and kinetic mechanisms behind the synergetic behaviors of precipitation of the target ions, their grouping precipitation, nucleation of the precipitates and their growth in the complex solution. Secondly, the conjugated effects of multi-doping and heterojunctions on the structures and photocatalytic behaviors will be systemically studied to build the theoretical model of structure-activity relationship for the dust-derived α-Fe2O3@ZnFe2O4 heterojunctions. To verify the reliability of the theoretical model obtained from the simulative dust systems, the practical Zn-bearing dust from iron-steel enterprise was used as raw material to prepare multi-doped α-Fe2O3@ZnFe2O4 heterojunction powders according to the obtained theoretical model, and bring it improvements by revaluating the relations of compositions, structures, and photocatalytic activities. Finally, the photodegradation of organic pollutants over the dust-derived α-Fe2O3@ZnFe2O4 heterojunctions will be investigated to explore the mechanism behind the photodegradation behaviors of such dust-derived photocatalyst. The results will help promote the research of resource cycling and photocatalytic materials, and provide effective recycling of metallurgical solid wastes with theoretical and technical support.

含锌尘泥是多种有价元素共存的复杂固废体系，其材料化利用研究是一个富有挑战性的课题。现有研究多关注单组元的材料化，其材料化过程的多元协同行为尚不清楚。为此，拟以模拟尘泥为研究体系，采取酸解和分级沉淀控制策略，系统研究、寻求含锌尘泥可控构筑低成本高性能多元掺杂α-Fe2O3@ZnFe2O4异质结光催化材料的新方法。着重研究复杂溶液体系中多离子淀析的协同行为，及组合淀析、成核和生长的热力学成因、动力学机制，查明构筑条件与产物的掺杂组合、异质结之内在联系和调控方法，诠释多元掺杂和异质结对α-Fe2O3@ZnFe2O4的结构和光催化性能的共轭作用机制。由此建立含锌尘泥制备多元掺杂异质结的构效关系的理论模型，用实际尘泥为原料对模型进行检验、修正，并系统研究产物光催化降解有机污染物的活性、机理和循环催化性能。项目的实施将有助于丰富资源循环和光催化材料学科的科学内涵，为冶金废弃物高附加值利用提供科学依据。

以探索含锌尘泥构筑多元掺杂α-Fe2O3@ZnFe2O4异质结光催化材料为目标，本项目系统研究了Al、Mn、Mg各组合掺杂对α-Fe2O3@ZnFe2O4组织、结构和光催化活性的影响，探明含锌尘泥制备具有分级孔结构的掺杂型α-Fe2O3-ZnFe2O4异质结复合微球的调控方法，初步查明产物结构形貌的调控方法、产物的组织结构和光催化活性的对应关系及相关机制。研究结果表明：（1）含锌尘泥中的ZnFe2O4是限制Zn、Fe浸出率的主要因素，650℃煅烧2 h可使ZnFe2O4分解为酸溶性Fe、Zn氧化物，提高Fe、Zn酸解浸出率；硫酸浓度5 mol/L、液固比10:1、酸解温度90℃、酸解时间4 h时，含锌尘泥Fe、Zn浸出率均达95%以上。（2）1%~5%掺杂量范围内，对Al、Mn、Mg、Al-Mn、Al-Mg、Mn-Mg、Al-Mn-Mg七种掺杂组合进行了研究。Mg、Al-Mg掺杂使α-Fe2O3@ZnFe2O4的光吸收边红移，明显提升产物光催化活性，掺杂量~3%为宜；其它掺杂组合均使α-Fe2O3@ZnFe2O4的光吸收边蓝移，抑制其光催化活性；Mn掺杂显著降低产物光催化活性。（3）α-Fe2O3@ZnFe2O4异质结复合材料的光催化活性比单相α-Fe2O3和ZnFe2O4分别提高17.7%和44.8%，Mg、Al-Mg掺杂分别使α-Fe2O3@ZnFe2O4的光催化活性进一步提高106.5%和49.9%，掺杂和异质结的共轭加成效应显著。Al、Mn单掺杂和其它二元掺杂及三元掺杂均降低α-Fe2O3@ZnFe2O4的光催化活性。（4）以含锌尘泥酸解液为起始反应物、乙二醇为形貌调控剂，在不添加任何其它起始反应物的情况下，采用恒温回流均相沉淀法成功制备出花菜状α-Fe2O3@ZnFe2O4异质结复合微球。研究表明，含锌尘泥酸解液反应体系的弱硅酸环境及其中多种金属离子离子与乙二醇的协同作用，是α-Fe2O3@ZnFe2O4异质结复合微球的花菜状形貌和分级孔隙结构形成的可能原因，恒温回流均相沉淀阶段的回流时间是调控产物Fe/Zn比的主要因素。含锌尘泥构筑的花菜状α-Fe2O3@ZnFe2O4异质结复合微球具有更高的光电响应、载流子输运能力和光生电子/空穴分离效率，相较于相同工艺条件下由化学试剂制备的产物，光催化活性提升44.4%。