Synthesis And Photocatalytic Properties Of BiOI-based Modified Photocatalytic Materials

In recent years,the rapid development of industrialization in our country provids a more convenient life and makes life quality better.However,the environmental pollution problems caused by high-speed industrial development have become increasingly serious,such as the discharge of industrial wastewater and exhaust gas,the continuous consumption of traditional energy sources and non-renewable issues,posing a huge threat to the health of human beings,so as to people's daily life and the ecological balance of the earth.The disruption of industrial wastewater such as ammonia nitrogen wastewater?printing and dyeing wastewater to the natural environment is persistent or even permanent,and human health is facing a huge threat.In the field of environmental remediation,scientists are committed to searching and developing green technologies that can reduce or even eliminate pollutants.Photocatalytic materials use sunlight to degrade pollutants.Moreover,they are clean and will not cause secondary pollution.Among them,bismuth-based photocatalysts have been widely concernd.Bioxyhalide?Bi OX?is a semiconductor compound with a layered structure,in which bismuth iodide oxide?BiOI?is available to be excited by most of the visible light,but its narrow band gap width leads to easy recombination of photogenerated electrons and holes,and insufficient light stability.Based on the existing problems of bismuth iodide oxide,this paper mainly did the following research work:?1?Using p-hydroxybenzoic acid as structural regulator,BiOI photocatalyst was prepared by low temperature liquid phase method,and the optimal synthesis were in the condition of reaction temperature of 15?,organic acid/Bi³⁺molar ratio of 1:1,Bi³⁺/I^-molar ratio of 1:1,the reaction p H of 3,and synthesis time of 3h.The photocatalytic degradation of 20mg/L methyl orange dye solution by BiOI photocatalyst reached 95.5%while illuminating for 2h with LED as the light resource.After 5 recycles,the photocatalytic degradation of methyl orange dye by BiOI photocatalyst reached 80.1%.Photocatalytic degradation of 20mg/L methyl orange dye by BiOI photocatalyst was in accordance with quasi-first-order kinetics,in which the rate constant k was 0.0224 min^-1and the correlation coefficient R²was 0.9873.After 120 minutes of illumination,the photodegradation for 20mg/L methyl orange solution by BiOI photocatalyst reached 95.5%,and under the same conditions,the photodegradation for 50mg/L methyl orange solution by BiOI photocatalyst reached69.2%.The photocatalytic activity of BiOI photocatalyst was significantly higher in weak acid solution than in neutral solution and alkaline solution.XRD indicated that the BiOI photocatalyst had the target structure,and BiOI photocatalyst had high crystal integrity and crystallinity;BiOI photocatalyst had mesoporous structure,large specific surface area?52.2m²/g?,with the energy gap of 1.85e V and the absorption edge of 670nm.FESEM showed that BiOI photocatalyst had a stacked layer structure,and FTIR preliminarily indicated that the BiOI photocatalyst contained target functional groups.XPS showed that the oxidation valence state of Bi element in BiOI was+3 valence and I element was-1 valence.XPS O1s spectrum proved that BiOI photocatalyst had Bi-O bond and hydroxyl group.The main active species of BiOI photocatalyst for photocatalytic degradation of dyes were superoxide radicals?·O₂^-?and holes?h⁺?,and the hydroxyl radicals contributed less during photocatalytic dye degradation.?2?Using para-hydroxybenzoic acid as the structural regulator,the BiOI/GO photocatalyst was prepared by the low-temperature liquid phase method.The optimal synthesis were in the condition of GO content of 1%,reaction temperature of 15?,reaction p H of 3 and reaction time of 3h.After 2h LED illuminating,the photocatalytic degradation of 20mg/L methyl orange dye solution by BiOI/GO photocatalyst reached 96.8%.while the photocatalytic degradation of 50mg/L methyl orange dye solution by BiOI/GO photocatalyst reached 72.1%.After 5 recycles,the photocatalytic degradation of methyl orange dye by BiOI/GO photocatalyst was81.2%,which proved that BiOI/GO photocatalyst could be used for multiple times.The photocatalytic degradation process of 20 mg/L methyl orange dye by BiOI/GO photocatalyst conformed to quasi-first-order kinetics,in which the rate constant k was0.0435 min^-1and the correlation coefficient R²was 0.9902.The photocatalytic activity of BiOI/GO photocatalyst was significantly higher in weak acidic solution than that of the neutral solution and alkaline solution.XRD showed that BiOI/GO photocatalyst had the target structure,and the crystal structure was complete and the crystallinity was high with the band gap width of 1.82e V,and the absorption side of 681nm.BiOI/GO photocatalyst had the specific surface area of 127.435m²/g,and had a mesoporous structure.FESEM showed that BiOI/GO photocatalyst had a layered or lamellar structure and is heavily loaded on the surface of graphene oxide in an in-situ growth.Raman spectroscopy showed that BiOI/GO photocatalyst had graphene oxide composition.XPS showed that BiOI/GO photocatalyst Bi element oxidation valence state was+3 and the element I had a valence of-1.XPS O1s spectrum showed that the BiOI/GO photocatalyst had a Bi-O bond and a hydroxyl group.XPS C1s spectrum confirmed that the BiOI/GO photocatalyst contained graphene oxide.The FTIR spectrum showed that the BiOI/GO photocatalyst had the target functional groups.The main active species of BiOI/GO photocatalyst for photocatalytic degradation of dyes were superoxide radicals?·O₂^-?and holes?h⁺?.The contribution of hydroxyl radicals was small,and the contribution order of active species was h⁺>·O₂^->·OH.