Design,Preparation And Photocatalytic Activity Of 1D And 2D Natural Silicate-based Composite Photocatalysts

As a green and sustainable technology to transfer solar energy into chemical energy,photocatalytic technology possesses a great prospect in environmental remediation and energy crisis alleviation.In the aspect of environment treatment,the major advantage of these systems is that they are able to achieve the degradation of organic pollutants by using visible light from the sun as energy and O₂ in the air as the oxidant under ambient conditions.So it is urgent to develop high-efficient and stable photocatalysts to meet practical demands.Based on above mentioned,we have designed and prepared a few one-dimensional and two dimensional natural silicate based visible-light responsive phtocatalysts in this theis.Systematecial characterizations,such as XRD,TEM,SEM,UV-Vis DRS,PL and so on,are employed to explore the reasons for the improvement of photocatalytic activities and the role palygorskite and phlogopite played in the composites.The main contributions invoved in this dissertation are as follows:1.The natural one-dimensional palygorskite clay was used as a carrier for Ag₃VO₄ nanoparticles,and the resultant Ag₃VO₄/palygorskite hybrid photocatalysts exhibited enhanced photocatalytic activity and stability both in the degradation of azo dyes,Rhodamine B（Rh B）and methyl orange（MO）,and antibiotic,tetracycline hydrochloride（TCH）,of which the 20 wt%Ag₃VO₄/palygorskite nanocomposites manifested optimal photocatalytic performance under visible light irradiation.The synergistic effect,enlarged specific surface area,strong light absorption ability,fast transfer,and valid separation of electron-hole pairs were beneficial for improving photocatalytic activity.2.A novelα-AgVO₃/palygorskite photocatalyst was successfully prepared by a facile in situ deposition precipitation method.The results of FESEM,TEM,XPS,and XRD observations indicated thatα-AgVO₃ nanoparticles with a diameter of approximately 10 nm were uniformly and successfully loaded onto the palygorskite fibers in the 40 wt%AgVO₃/palygorskite nanocomposites.As expected,the AgVO₃/palygorskite nanocomposites exhibited superior visible-light-driven photocatalytic activity both in the photodegradation of RhB and photocatalytic disinfection of E.coli compared to pristine AgVO₃ microbars,especially the 40 wt%AgVO₃/palygorskite nanocomposites.The presence of palygorskite,which acted as stabilizer,dispersant and growth-directing agent,could efficiently decrease the particle size,change exposed active facets,augment active sites,enhance the adsorption ability,accelerate the photogenerated charge carriers separation and transfer,and thus,boost the photocatalytic activity.3.A series of palygorskite/BiOI composites were synthesized via a facile precipitation method,in which self-assembled 3D microspheres with a diameter of about 600 nm were constructed when the mass ratio of palygorskite was 15%.Analyses indicated that the abundant hydroxyl of palygorskite contributed to the fabrication of 3D microspheres and the 15% palygorskite/BiOI composites demonstrated optimal photocatalytic activity in the decomposition of MO under visible light irradiation.Based on the results of a comprehensive study of the photocatalysts,the hierarchial structure was conducive to the segaration of photogenerated carriers,thus enhance the photocatalytic activity.4.One-pot calcination mehod was adopted for the preparation of palygorskite/Bi_xO_yI_zcomposites by using palygorskite/BiOI composites as precusors.We found the mass ratio of palygorskite played a significant role in the calcined products.Without palygorskite,the thermalitreated product was Bi₄O₅I₂.When the mass ratio was 10%and 15%,the products were palygorskite/Bi₄O₅I₂/Bi₅O₇I composites.Continue to increase the content of palygorskite to 20%,the product was palygorskite/Bi₅O₇I composites.The prepared palygorskite/Bi₄O₅I₂/Bi₅O₇I composites microspheres exhibited excellent photocatalytic performance in photocatalytic degradation of Rh B and TCH owing to the construction of type II heterojunction and the 3D assembled morpholpgy.5.The 2D natural silicate—phlogopite was delaminated through solution intercalation method and the prepared exfoliated phlogopite with organo-functional group was employed as carriers for the preparation of Fe OOH/EPhl and Cu₂O/EPhl composites.It is noticeable that the introduction of EPhl efficiently enlarged the specific surface area and reduced the particle size of FeOOH and Cu₂O.The obtained FeOOH/EPhl and Cu₂O/EPhl composites exhibited enhanced photocatalytic activity in photodegradatio of Rh B nder visible light irradiation compared with bare FeOOH and Cu₂O.