Basic Research On Synthesis Of MgFe₂O₄-based Highly Efficient Heterogeneous Fenton-like Catalysts From Saprolite Laterite Nickel Ore

In recent years,spinel ferrite heterogeneous Fenton-like catalyst MFe2O4(M=Fe,Mg,Cu,Ni,etc.)has become a hot topic in the field of water treatment due to its excellent structural stability and magnetic recovery performance.However,the catalytic activity of these catalysts is not ideal and almost all the reported catalysts are synthesized by pure reagents,which restrict their industrial application,Therefore,the preparation of highly efficient heterogeneous Fenton-like catalysts with low cost and mass production,and construction of a novel highly efficient heterogeneous Fenton-like catalytic system become the key to the treatment of refractory organic wastewater.In this thesis,MgFe2O4-based highly efficient heterogeneous Fenton-like catalysts were synthesized from saprolite laterite nickel ore leaching solution.The effects of synthesis conditions and transition metal doping on the microstructures and catalytic performance of the as-prepared products were systematically studied.Novel highly efficient heterogeneous Fenton-like catalytic system was established and the mechanism for enhancing the catalytic activity was clarified.(Mg,Ni)(Fe,Al)2O4 heterogeneous Fenton-like catalysts were successfully prepared from saprolite laterite nickel ore by an acid leaching-hydrothermal method.The effects of hydrothermal and calcination temperature on microstructures and catalytic activity of the as-prepared products were systematically investigated,and the reaction mechanism of the(Mg,Ni)(Fe,Al)2O4/H2O2 system was also proposed.The results show that higher hydrothermal temperature(over 180?)combined with calcination could promote the migration of Fe3+ions from tetrahedral to octahedral sites almost exclusively located at the surface of the solid spinel ferrites,which was beneficial to improve the activity of formed catalysts through producing more OH radicals.Under the optimal conditions,the degradation efficiency(?)of different types of low-concentration organic dyes and tetracycline reached above 95%.After five consecutive degradation cycles,the ? of Rhodamine B(RhB)still maintained a high value of 97.1%and the reduction of TOC removal efficiency was little(from 44.8%to 42.1%),suggesting an excellent stability and reusability of the as-prepared(Mg,Ni)(Fe,Al)2O4.Cu2+-doped(Mg,Ni)(Fe,Al)2O4 heterogeneous Fenton-like catalysts were synthesized from the leaching solution of saprolite laterite nickel ore by a coprecipitation method.And the effect of CuCl2·2H2O addition on the microstructures and catalytic property of the obtained products were studied in detail.The(Mg,Cu,Ni)(Fe,Al)2O4/H2O2 catalytic system was established and the euhancement mechanism of Cu2+doping on the catalytic activity of(Mg,Ni)(Fe,Al)2O4 was revealed.It is found that the degradation efficiency of different types of low-concentration organic dyes and tetracycline reached above 95%due to the accelerated generation of ·OH radicals by the synergistic effect of Fe3+and Cu2+ions at octahedral sites of formed(Mg,Cu,Ni)(Fe,Al)2O4.After five consecutive degradation cycles,the ? of RhB was still close to 100%and TOC removal efficiency was still maintained a value around 40%,suggesting that the as-prepared(Mg,Cu,Ni)(Fe,Al)2O4 could be effectively reused.By using FeCl3·6H2O as an additive,a pure phase(Mg,Ni)(Fe,Al)2O4 heterogeneous Fenton-like catalyst(named as HF-(Mg,Ni)(Fe,Al)2O4)was synthesized from the leaching solution of saprolite laterite nickel ore by a co-precipitation method.A novel and highly efficient catalytic reaction system HF-(Mg,Ni)(Fe,Al)2O4/H2C2O4/light was developed and constructed.The effects of synthesis conditions and catalytic test parameters on the microstructures of catalysts and the degradation of RhB were discussed in detail.And the catalytic mechanism of HF-(Mg,Ni)(Fe,Al)2O4/H2C2O4/light system was proposed and elucidated.The results show that the ? of organic dyes and tetracycline in low-concentration reached above 90%as the formation of highly photochemical[=Fe(C2O4)3]3-complex ions on the surface of the HF-(Mg,Ni)(Fe,Al)2O4,which promoted the generation of OH radicals for degradation of organic compounds.The ? and TOC removal efficiency for RhB were still over 98.0%and 46.0%after five reuse cycles,respectively,indicating the excellent reusability of the HF-(Mg,Ni)(Fe,Al)2O4.The excellent catalytic performance and recyclability make the MgFe2O4-based heterogeneous Fenton-like catalysts fabricated from natural saprolite laterite ore possess more competitive in dealing with wastewaters contaminated by organic pollutants.