Study On Preparation Of BiOCl/NiAl-Layered Double Hydroxides Composite Photocatalyst And Its Treatment Performance For Dye Wastewater

Photocatalytic oxidation technology is considered as a key technology for the treatment of dye wastewater because of its green,environmental protection and energy saving.Design and preparing efficient and stable photocatalysts is an important research content in the field of photocatalysis.Considering that BiOCl,despite its unique layered structure and excellent photocatalytic properties,limits its application in practice due to its typical broadband gap.Given that layered dihydrogenoxides（LDHs）usually present the ideal morphology of two-dimensional nanosheets or three-position floral microspheres,they not only provide a good structure for binding with other semiconductors,but also facilitate the transfer of photoborne carriers.The purpose of this study is to optimize the preparation of a new BiOCl/NiAl-LDH composite photocatalytic material,using rhodamine B（Rh-B）as the target pollutant,to study the photocatalytic performance of BiOCl/NiAl-LDH,construct an efficient photocatalytic degradation system,and explore the mechanism of photocatalytic carrier degradation and band-structure analysis with the results of radical capture experiment,the photocatalytic degradation of Rh-B.According to UV-vis absorption spectroscopy analysis and reference to existing literature studies,the pathway of photocatalytic degradation of Rh-B is speculated.The main achievements are as follows:（1）The BiOCl/NiAl-LDH prepared at the NiAl-LDH and BiOCl mass ratio was20%,the reaction temperature was 120℃,and the reaction time was 12 h.The BiOCl nanosheets with distinct quartet structure are evenly distributed on the NiAl-LDH surface,forming the composite photocatalyst with 2D/2D structure;the average pore diameter is 28.68 nm and the specific surface area is 23.72 m²/g,which is significantly improved compared with pure BiOCl;The BiOCl/NiAl-LDH composite has higher photocurrent signal and smaller arc radius,which effectively promotes the separation and migration of photoptic carriers.（2）Under the conditions of 0.3 g/L catalyst dosage,initial pH of solution is 5,solution concentration is 50 mg/L,illuminated for 100 min,the degradation rate of Rh-B was 97.11%,Much higher than in the photocatalytic system with pure NiAl-LDH and BiOCl as catalysts,The photocatalytic degradation process of Rh-B fits with the quasi-first-order kinetics,Photocatalytic reaction rate constant of up to0.02898 min^-1,Approximately 4.1 times and 12.5 times that of pure BiOCl(0.00710min^-1)and pure NiAl-LDH(0.00231 min^-1),respectively.After five times of reuse,it still has more than 90%degradation rate and 75%COD_Cr removal rate,with excellent stability.Different concentrations of humic acid and four coexisting inorganic anions of HCO₃^-,SO₄^2-,Cl^-and NO₃^-showed different degrees of inhibition of Rh-B degradation,specifically HCO₃^->SO₄^2->Cl^->NO₃^-.（3）·O₂^-and h⁺are the main active species of the photocatalytic system.The valence and conduction bands of NiAl-LDH and BiOCl are staggered,forming a stable Z-type heterojunction.The unique charge-transfer mode and excellent photocatalytic activity enhance the degradation of Rh-B.The degradation process of Rh B mainly includes deethylation reaction and the destruction of the oxanthene conjugated structure.