Synthesis, characterization and activity of an immobilized photocatalyst: Natural porous diatomite supported titania nanoparticles

Abstract

Diatomite, a porous non-metal mineral, was used as support to prepare TiO 2 /diatomite composites by a modified sol-gel method. The as-prepared composites were calcined at temperatures ranging from 450 to 950 o C. The characterization tests included X-ray powder diffraction (XRD), scanning electron microscopy (SEM) with an energy-dispersive X-ray spectrometer (EDS), High-resolution transmission electron microscopy (HRTEM), X-ray photoelectron spectroscopy (XPS), and nitrogen adsorption/desorption measurements. The XRD analysis indicated that the binary mixtures of anatase and rutile exist in the composites. The morphology analysis confirmed the TiO 2 particles were uniformly immobilized on the surface of diatom with a strong interfacial anchoring strength, which leads to few drain of photocatalytic components during practical applications. In further XPS studies of hybrid catalyst, we found the evidence of the presence of Ti-O-Si bond and increased percentage of surface hydroxyl. In addition, the adsorption capacity and photocatalytic activity of synthesized TiO 2 /diatomite composites were evaluated by studying the degradation kinetics of aqueous Rhodamine B under UV-light irradiation.The photocatalytic degradation was found to follow pseudo-first order kinetics according to the Langmuir-Hinshelwood model. The preferable removal efficiency was observed in composites by 750 o C calcination, which is attributed to a relatively 2 appropriate anatase/rutile mixing ratio of 90/10.

Enhanced photocatalytic properties of reusable TiO 2 -loaded natural porous minerals in dye wastewater purification

“…This has been associated to low quantum efficiency in TiO 2 systems.  Agglomeration: the strong tendency of TiO 2 nanoparticles to aggregate may result in a difficult recovering from the solution after treatment and low adsorption capacity for pollutant molecules [8].…”

“…The immobilization of TiO 2 nanoparticles into porous carriers, such as, silica [9] and carbon [10] structures has been proven to prevent their agglomeration which, in turn, increase the surface area and facilitate recovery processes of the composite photocatalyst after organic compounds mineralization. Here, a natural porous non-metallic mineral, diatomite, was used as carrier because of its ability to effectively immobilize TiO 2 nanoparticles (NPs) [8,11]. When compared with other TiO 2 structures, the TiO 2 /diatomite hybrid photocatalyst shows advantageous ordered pore-size distribution with specific properties such as high amorphous silica content.…”

Surface silylation of natural mesoporous/macroporous diatomite for adsorption of benzene

“…8 shows the adsorption isotherms of benzene on Dt and PTES-Dt. The Langmuir adsorption isotherm model demonstrates the best fit for quantitatively describing the adsorption data compared with several commonly used fitting models, such as the 20 Freundlich and Harkins-Jura models [50,51]. The Langmuir model is described by the following equation [52]:…”

“…Consequently, diatomite has been used in a variety of applications, including as adsorbents, filters, fillers, catalysts supports, and mild abrasives [18][19][20]. In particular, diatomite has been predominantly used as a filtration medium (e.g., filter aid) [21] for purifying various beverages and for gasification applications in fluidized bed reactors for two reasons: (i) the bimodal mesoporosity/macroporosity of diatom frustules is usually desirable for filtration because mesopores enhance the specific surface area, while macropores increase the efficiency of the mass-transport and diffusion processes; (ii) diatom frustules are rigid and naturally separated.…”

Low-toxic gelcasting of bulk porous silica with bi-modal pore structure and its application in TiO2 photocatalysts

“…However, there are significant disadvantages inherent to the use of nano TiO 2 powders, as they are difficult to separate from reaction media and have low quantum efficiency, poor thermal stability and low adsorption ability, which limit their use in practice [9]. To remedy this, researchers have investigated the immobilization of fine TiO 2 onto porous materials, including bentonite [10], activated carbon [11], as well as natural silica minerals [12], which not only promote catalytic reaction by offering more active sites but also allow the reuse of catalysts and facilitate a reduction of secondary pollution. However, the use of prepared porous silica as the supporter for TiO 2 catalyst has seldom been tried, especially the utilization of industrial waste as silica raw material.…”