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Phase change behaviors of organic phase change materials (PCMs) confined in porous silica matrices, which are determined by the pore characteristics as well as interfacial interactions between PCM molecules and supporting solid, are crucial to PCMs for thermal energy storage performance. In this paper, a series of shape-stabilized phase change materials (ss-PCMs) were engineered with three silica matrices as support and paraffin as PCMs through solution impregnation. These porous silica matrices serve as an ideal skeleton for shape stabilization of melted paraffin PCMs and yield desirable thermal properties of paraffin confined in silica pores. The textural and chemical properties, crystallization, interfacial interactions, and thermal properties and stability are investigated using various techniques including nitrogen adsorption-desorption isotherms, Fourier transformation infrared (FT-IR) spectroscopy, small- and wide-angle X-ray diffraction (XRD), and scanning electron microscopy, as well as differential scanning calorimetry (DSC) analysis. The effect of the pore structure on crystallization of PCMs was studied and a novel phase change was unveiled. The phenomena of melting point depression and confinement effects are in line with theoretical thermodynamics, and the physical state of paraffin at the interfacial region in mesopore channel is analyzed considering pore geometric factors, revealing a non-melting interface layer in MCM-41. This evaluation of various silica matrices may provide important and general implications for the fundamental understanding of porous silica ss-PCMs performance with cost-effective and readily available raw materials. [ABSTRACT FROM AUTHOR]

Three kinds of novel diatomite/ground calcium carbonate composite humidity control materials were prepared with different calcination temperatures using diatomite and ground calcium carbonate (GCC) as raw materials. The microstructure and morphology properties of samples were studied by nitrogen gas adsorption, mercury intrusion porosimetry (MIP) and fractal dimensions on the basis of gas adsorption isotherms with FHH methods. Fourier transform infrared spectroscope (FTIR), scanning electron microscopy (SEM) and transmission electron microscopy (TEM) were used to characterize the mineral composition and surface properties. Furthermore, X-ray diffraction (XRD), thermo-gravimetry and differential scanning calorimetry (TG-DSC) were used to analyze the formation mechanism of composite material. It was indicated that DG750 showed the better moisture adsorption performance. The 72 h moisture adsorbed amount of DG750 reached 11.66%, 8.81% and 8.00% at 98%RH, 85%RH and 75%RH, respectively, which improved about 0.46, 0.54 and 0.53-fold as those of diatomite. The hydrophilic calcium silicate, calcium oxide and calcium hydroxide were formed in the DG750 during the calcinations process. As compared with the raw materials, the content of mesoporous component increases in the DG750, which is in favor of capillary condensation and improving moisture adsorption ability. [ABSTRACT FROM AUTHOR]

[Display omitted] • Diatomite decorated with BiOCl/TiO 2 was prepared for formaldehyde degradation. • Effects of key parameters on the photocatalytic performance was studied. • Optimal pH values, calcination temperature, and mass ration was confirmed. • BiOCl/TiO 2 @diatomite showed excellent performance of formaldehyde degradation. The diatomite decorated with BiOCl/TiO 2 (BiOCl/TiO 2 @diatomite) composites were prepared by supporting BiOCl/TiO 2 heterogeneous junction on the surface of diatomite with precipitation-calcination method. This work systematically studied the effects of terminal pH, calcination temperature, and TiO 2 /BiOCl ratio. Furthermore, the relationship between structure and photocatalytic performance of the composite was investigated. The results demonstrated that composite with optimized performance (84.1% formaldehyde degradation rate of 1.0 g photocatalyst) can be obtained at terminal pH of 6, calcination temperature of 500 °C, and TiO 2 /BiOCl ratio of 55/45. It is indicated that the phase structure, grain size, and porous structure can be significantly affected by the above preparation parameters. In conclusion, the formaldehyde adsorption and degradation properties can be enhanced by the construction of porous structure and heterogeneous junction of composites. Overall, BiOCl/TiO 2 @diatomite composites exhibited excellent formaldehyde degradation performance under visible light due to the multi-layer structure and the combination of TiO 2 and BiOCl on the surface of diatomite. [ABSTRACT FROM AUTHOR]

Graphical abstract Highlights • Natural porous minerals were used as VOCs adsorbents. • Adsorption capacity of mineral is linearly related to its specific surface area. • Models fit breakthrough curves, isotherm and kinetic processes well. • The acid stellerite could be a promising adsorbent for VOC adsorption. Abstract The abundance of natural porous minerals and their low cost make them the potential adsorbents for VOCs (volatile organic compounds). In this paper, three natural minerals (diatomite, stellerite and vitric tuff) and their corresponding acid-treated minerals were used as adsorbents. The adsorption performances of minerals were investigated by the adsorption breakthrough curves of VOCs. The results indicated that the properties of organic compounds such as boiling point and polarity and the surface area and pore volume of minerals had obvious effects on the adsorption of VOCs over minerals. Increasing adsorption temperature and relative humidity would have negative effects on the VOC adsorption of minerals. The adsorption capacity of 2-heptanone over acid stellerite decreased by 7.2% as the temperature rose from 25°C to 45°C. The adsorption capacity of acid stellerite for 2-heptanone reduced by 60.9% when relative humidity increased from 0% to 75%. Minerals were tested for five adsorption-regeneration cycles to study the reusability. Better fittings of Thomas model, pseudo-first order kinetics model, and Freundlich model were showed in fitting the adsorption. Overall, porous minerals with high specific surface area and pore volume have promising prospect in VOCs adsorption. [ABSTRACT FROM AUTHOR]

Diatomite-based recyclable photocatalysts containing single lanthanide doped TiO 2 nanoparticles (NPs) were synthesized by using simple sol–gel method. Photocatalytic activities of the prepared Ce- or La- single doped TiO 2 /diatomite catalysts were estimated by the degradation of Rhodamine B (RhB) under simulated sunlight irradiation. The XRD and Raman spectra shown only anatase phase of TiO 2 for the un-doped and Ce-doped samples. The TEM images revealed uniform distribution of TiO 2 NPs on the matrix, indicating that diatomite played an important role to prevent the agglomeration of TiO 2 NPs. Ce-TiO 2 /diatomite showed a red shift in UV–visible light absorption edge with enhanced absorption intensity than un-doped sample, whereas La-TiO 2 /diatomite showed a blue shift. The bandgap energy of 1.5%-Ce doped sample is as low as 2.75 eV. The XPS spectra showed the presence of both Ce 3 + and Ce 4 + oxidation states for Ce dopant. The photoluminescence spectra of the Ce-doped samples showed first decrease in the recombination centers with the maximum decrease for 1.5%-Ce doped sample and then started increase with the increasing Ce in the samples. As compared to the La-doped samples, a desired behavior was observed for the Ce-doped hybrid due to the redox Ce 4 + /Ce 3 + pairs acting as electron scavengers and localized unoccupied Ce 4 f level narrowing the band gap. The incorporation with diatomite as support of TiO 2 nanoparticles is contributed for the improved reusability and also gives a promising strategy to enable the application of nano-photocatalysts in a real wastewater remediation treatment. [ABSTRACT FROM AUTHOR]

[Display omitted] • A ternary 3D "PIZZA"-like Bi 2 MoO 6 -TiO 2 /diatomite composite was synthesized. • An adsorption-photocatalysis system was constructed by the instruction of diatomite. • Excellent photocatalytic mineralization property of HCHO was obtained under visible light. • The effect of water on the mineralization of HCHO was studied via in-situ DRIFTs analysis. • The O 2 and H 2 O molecules were involved in the photocatalytic mineralization process of HCHO. The application of TiO 2 -based photocatalysts in air pollution control has attracted much attention thanks to their advantageous green and sustainable performance. However, how to improve the degradation efficiency under visible light is still challenging. Herein, we report a ternary three-dimensional "PIZZA"-like Bi 2 MoO 6 -TiO 2 /diatomite (BTD) composite with high-efficient mineralization and recycling performance towards gaseous formaldehyde (HCHO) under visible light. The high-efficient adsorption-photocatalysis collaborative system with intimate interface combination is successfully established among Bi 2 MoO 6 (BMO), TiO 2 and diatomite. The HCHO mineralization rate constant of BTD-1:2 composite is up to around 4.03 times and 2.18 times higher than those of bare BMO and binary Bi 2 MoO 6 -TiO 2 composite, respectively. It is indicated that the introduction of diatomite increases active sites and plays the vital role in the improvement of photocatalysis. In addition, the photogenerated holes (h+) and hydroxyl radical (OH) are proved to be the main active species for HCHO mineralization. Furthermore, there is a competitive adsorption relationship between water (H 2 O) molecules and HCHO molecules, and both H 2 O molecules and oxygen (O 2) molecules participated in the reaction of HCHO mineralization based on in-situ DRIFTs spectra analysis. Our work would give a new perspective on gaseous HCHO purification. [ABSTRACT FROM AUTHOR]

Highlights: [•] TiO2 nanoparticles/diatomite composite was synthesized and characterized. [•] The composite exhibited a good photocatalytic performance in Cr (VI) reduction. [•] The photocatalyst showed good photocatalytic stability. [•] The composite is a promising material for Cr (VI) photocatalytic reduction. [ABSTRACT FROM AUTHOR]

Highlights: [•] We have prepared three amorphous silica minerals as supports for TiO2 catalysis. [•] We characterized by XRD, SEM, FT-IR, TEM and XPS. [•] We investigated the UV-assisted degradation of Rhodamine B (RhB). [•] TiO2/DE photocatalyst exhibits better catalytic performance at different calcined temperatures. [ABSTRACT FROM AUTHOR]

Distinctive Cr-MOF@Da composites have been constructed using chromium-based metal-organic frameworks (MOFs) and diatomite (Da). The new materials have hierarchical pore structures containing micropores, mesopores and macropores. We have synthesized various morphologies of the MOF compound Cr-MIL-101 to combine with Da in a one-pot reaction step. These distinctive hierarchical pore networks within Cr-MIL-101@Da enable exceptional adsorptive performance for a range of molecules, including hydrogen (H2), carbon dioxide (CO2) and water (H2O) vapor. Selectivity for H2 or CO2 can be moderated by the morphology and composition of the Cr-MIL-101 included in the Cr-MOF@Da composite. The encapsulation and growth of Cr-MIL-101 within and on Da have resulted in excellent water retention as well as high thermal and hydrolytic stability. In some cases, Cr-MIL-101@Da composite materials have demonstrated increased thermal stability compared with that of Cr-MIL-101; for example, decomposition temperatures >340 ℃ can be achieved. Furthermore, these Cr-MIL-101@Da composites retain structural and morphological integrity after 60 cycles of repeated hydration/dehydration, and after storage for more than one year. These characteristics are difficult to achieve with many MOF materials, and thus suggest that MOF–mineral composites show high potential for practical gas storage and water vapor capture. [ABSTRACT FROM AUTHOR]

Graphical abstract The zeolite X was synthesized from diatomite via hydrothermal method. The proposed crystallization mechanism is displayed in the following illustration. The intermediate species of zeolite X appears on the surface of solid particles. And the β cages build up the intermediate species, which was consist of four-membered rings (4R) and six-membered rings (6R). Then the β cages interconnect via double six-membered rings to form the framework of zeolite X. Highlights • The intermediate species of zeolite X appears on the surface of solid particles. • The β cages build up the intermediate species, which was consist of four-membered rings (4R) and six-membered rings (6R). • The double six-membered ring (D6R) played a critical role for the crystallization process. • The β cages interconnect via double six-membered rings to form the framework of zeolite X. Abstract Here we systemically investigated the crystallization process of zeolite X using diatomite, a natural cost-effective silica precursor by the hydrothermal method. To decipher the mechanism, solids were separated from the mixtures at various stages of crystallization and were characterized by XRD, SEM, solid state NMR, FT-IR, UV-Raman and XRF. The XRD patterns revealed that the crystallization started between 3 and 3.5 h and ended by 5 h. The SEM images showed that the intermediate species of zeolite X appear on the surface of particles. The FT-IR and UV-Raman spectra suggested the presence of double six-membered rings (D6R) in the framework of zeolite X and they played a critical role in the crystallization process. Furthermore, the UV-Raman spectra indicated that the secondary building units of β cages formed the intermediate species and they were interconnected via double six-membered rings to form the framework of zeolite X. [ABSTRACT FROM AUTHOR]

The TiO 2 /diatomite composite was synthesized through a mild hydrolysis of titanyl sulfate. The prepared composite was characterized by X-ray diffraction, N 2 adsorption–desorption, scanning electron microscopy, transmission electron microscopy, X-ray photoelectron spectroscopy and UV–vis diffused reflectance spectroscopy. The results demonstrate that the anatase TiO 2 nanopartilces anchored on the surface of diatomite with Ti–O–Si bonds between diatomite and TiO 2 . The photodegradation of gaseous formaldehyde under UV irradiation by the TiO 2 /diatomite composite was studied under various operating conditions, including relative humidity, illumination intensity and catalyst amount, which have significant influence on the degradation process. The TiO 2 /diatomite composite exhibited better photocatalytic activity than pure TiO 2 , which could be attributed to the favorable nanoparticles dispersibility and strong formaldehyde adsorption capacity. In addition, the composite exhibited outstanding reusability over five cycles. The TiO 2 /diatomite composite shows great promising application foreground in formaldehyde degradation. [ABSTRACT FROM AUTHOR]

Carbon @ diatomite (C@DE) nanocomposite was synthesized using glucose as precursor and purified diatomite as carrier through a facile hydrothermal carbonization process. The microstructure and interface properties of the obtained nanocomposites were characterized by SEM, TEM, FTIR, XPS and zeta potential analyzer. A batch adsorption study showed that the adsorption process was very fast and the kinetic data well fitted with pseudo-second-order kinetic model. Compared to pure carbon materials, the C@DE nanocomposite exhibits higher adsorption ability for Cr (VI). This kind of nanocomposite is a promising candidate as an adsorbent for the removal of Cr (VI) ions from wastewater. [ABSTRACT FROM PUBLISHER]

Novel fluorine doped TiO 2 /diatomite (F-T/DE) composites with visible-light responding activity were fabricated through a facile sol-gel method in this study. The as-synthesized F-T/DE-1.0% (1.0% fluorine content) composite exhibited enhanced photocatalytic activity in degrading rhodamine B (RhB) under visible-light illumination, the reaction rate constant of which was nearly up to 4.4 times and 26.1 times higher than that of F-T-1.0% (fluorine doped TiO 2 with 1.0% content) and pure TiO 2 , respectively. It is indicated that the anatase TiO 2 nanoparticles were firmly and homogeneously loaded on the surface of diatomite and fluorine ions were successfully incorporated into the lattice of TiO 2 . In addition, the construction of composite can effectively promote the generation of oxidative radicals and reduce the recombination probability of photogenerated electron-hole pairs and thus contribute to the enhancement of photoactivity under visible light. The enhanced photocatalytic activity of F-T/DE can be attributed to the fluorine doping induced oxygen vacancies and much more exposed highly active (001) facets, as well as the carrier effect (smaller grain size, well distribution and enhanced adsorption ability). [ABSTRACT FROM AUTHOR]

This study investigated the performance and optimal operating conditions of a pilot-scale centrifugal separator for low-grade diatomite purification using response surface methodology (RSM). The individual and interactive effects of the feeding concentration (mass concentration of solids in the feeding slurry), centrifugal speed, feeding rate, and feeding time on the mass concentrations of centrifugal overflow and the SiO2contents of centrifugal concentrate was investigated by RSM. Two second-order polynomial equations between the response and independent variables were proposed to describe the influence of different variables on the mass concentrations of the centrifugal overflow and SiO2contents of centrifugal concentrate. It is indicated that the feeding concentration has the greatest influence on the tailing concentration. The operating conditions of the centrifugal separator were further optimized and the SiO2content of purified diatomite was increased from 80.17% to 86.89% under the optimal conditions. Compared with raw minerals, the purity and porosity of diatomite were significantly improved after purification from chemical, x-ray diffraction (XRD), and scanning electron microscopy (SEM) analyses. It is concluded that this type of pilot-scale centrifugal separator is a potentially reliable instrument for low-grade diatomite purification at low cost in the industry. [ABSTRACT FROM AUTHOR]

The highly efficient g-C 3 N 4 /TiO 2 heterojunction was deposited over diatomite supports through an in situ deposition process. The microstructure, morphology and optical properties of the novel g-C 3 N 4 /TiO 2 @diatomite composite were studied by X-ray diffraction (XRD), scanning electron microscopy (SEM), high resolution transmission electron microscopy (HRTEM), Fourier transform infrared spectroscopy (FTIR) and UV–visible diffused reflectance spectroscopy (UV–vis DRS). The photocatalytic efficiency of g-C 3 N 4 /TiO 2 @diatomite composite was evaluated by the degradation of rhodamine B and methylene blue under visible light and simulated solar light. It is indicated that the as-synthesized g-C 3 N 4 /TiO 2 @diatomite composite displayed higher photocatalytic performance than pure g-C 3 N 4 and TiO 2 . This enhancement should be ascribed to that diatomite can play as an excellent catalyst carrier to improve the dispersity of g-C 3 N 4 /TiO 2 and increase the reactive sites for dye pollutants degradation. The CN/T@DE-10% exhibited the highest efficiency towards RhB, which was around 2.5 times under visible light and 3.5 times under solar light as much as that of the pure g-C 3 N 4 . In addition, the final removal rates of RhB reach to 96% within 3 h under solar light and 83% within 6 h under visible light, respectively. On the other hand, the g-C 3 N 4 /TiO 2 @diatomite composite can be easily separated from suspension and presents a good durability during five cycles. The outstanding properties of g-C 3 N 4 /TiO 2 @diatomite composite and high photocatalytic efficiency make it promising for the potential application in the dye wastewater treatment. [ABSTRACT FROM AUTHOR]

V-doped TiO 2 /diatomite composite photocatalysts with different vanadium concentrations were synthesized by a modified sol–gel method. The diatomite was responsible for the well dispersion of TiO 2 nanoparticles on the matrix and consequently inhibited the agglomeration. V-TiO 2 /diatomite hybrids showed red shift in TiO 2 absorption edge with enhanced absorption intensity. Most importantly, the dopant energy levels were formed in the TiO 2 bandgap due to V 4+ ions substituted to Ti 4+ sites. The 0.5% V-TiO 2 /diatomite photocatalyst displayed narrower bandgap (2.95 eV) compared to undoped sample (3.13 eV) and other doped samples (3.05 eV) with higher doping concentration. The photocatalytic activities of V doped TiO 2 /diatomite samples for the degradation of Rhodamine B under stimulated solar light illumination were significantly improved compared with the undoped sample. In our case, V 4+ ions incorporated in TiO 2 lattice were responsible for increased visible-light absorption and electron transfer to oxygen molecules adsorbed on the surface of TiO 2 to produce superoxide radicals O 2 – , while V 5+ species presented on the surface of TiO 2 particles in the form of V 2 O 5 contributed to e – –h + separation. In addition, due to the combination of diatomite as support, this hybrid photocatalyst could be separated from solution quickly by natural settlement and exhibited good reusability. [ABSTRACT FROM AUTHOR]

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 °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 °C calcination, which is attributed to a relatively appropriate anatase/rutile mixing ratio of 90/10. [ABSTRACT FROM AUTHOR]

TiO 2 /purified diatomite composite materials were prepared through a modified hydrolysis-deposition method under low temperature using titanium tetrachloride as precursor combined with a calcination crystallization process. The microstructure and crystalline phases of the obtained composites prepared under different preparation conditions were characterized by high resolution scanning electron microscope (SEM) and X-ray diffraction (XRD), respectively. The photocatalytic performance of TiO 2 /purified diatomite composites was evaluated by Rhodamine B as the target pollutant under UV irradiation, and the optimum preparation conditions of composites were obtained. The TiO 2 crystal form in composites prepared under optimum conditions was anatase, the grain size of which was 34.12 nm. The relationships between structure and property of composite materials were analyzed and discussed. It is indicated that the TiO 2 nanoparticles uniformly dispersed on the surface of diatoms, and the photocatalytic performance of the composite materials was mainly determined by the dispersity and grain size of loaded TiO 2 nanoparticles. [ABSTRACT FROM AUTHOR]

Abstract: Natural porous mineral supported (TiO2/diatomite) photocatalyst was prepared via a modified sol–gel method using titanium (IV) butoxide (TBOT) and diatomite. The effect of TBOT dosage on adsorption capacity and photocatalytic activity for Rhodamine B (RhB) solution was investigated. The morphology and elemental distribution were determined by scanning electron microscopy with attached energy-dispersive X-ray detector. The porous and crystalline structures were characterized using nitrogen adsorption–desorption and X-ray diffraction techniques, respectively. The prepared TiO2/diatomite hybrid catalyst has shown relatively even porous structure and dispersion of TiO2 over the surface. This suggests that the diatomite matrix prevented the agglomeration of TiO2 particles. Initially, the surface area and pore volume of the hybrid catalyst were increased by adding TBOT then decreased for dosages higher than 1.0ml. The crystalline size of TiO2 immobilized on diatomite matrix by sol–gel method was around 20nm. When the experiments were carried out in the absence of diatomite, this value was increased to 33.73nm. The use of diatomite also promoted an increase of the transformation temperature of the crystalline phase anatase to rutile for the TiO2. The as-prepared TiO2/diatomite composite exhibited high photocatalytic activity (96.0% for 0.5h UV-light irradiation) for the degradation of RhB from wastewater as a result of its unique porous structure and optimum TiO2 loading. In addition, it can be easily separated from suspension and possess a good durability. This hybrid material holds great promise in the engineering field for the environmental remediation. [Copyright &y& Elsevier]

Abstract: This study presented a novel method for purification of three different grades of diatomite from China by scrubbing technique using sodium hexametaphosphate (SHMP) as dispersant combined with centrifugation. Effects of pH value and dispersant amount on the grade of purified diatomite were studied and the optimum experimental conditions were obtained. The characterizations of original diatomite and derived products after purification were determined by scanning electron microscopy (SEM), X-ray diffraction (XRD), infrared spectroscopy (IR) and specific surface area analyzer (BET). The results indicated that the pore size distribution, impurity content and bulk density of purified diatomite were improved significantly. The dispersive effect of pH and SHMP on the separation of diatomite from clay minerals was discussed systematically through zeta potential test. Additionally, a possible purification mechanism was proposed in the light of the obtained experimental results. [Copyright &y& Elsevier]

A novel CoNi 3 O 4 /diatomite hybrid is constructed through vertically oriented growth of 2D CoNi 3 O 4 nanoribbons with atomic layer-thickness on cost-effective diatomite template. Distinct from stacked CoNi 3 O 4 with a large portion of "dead surface", diatomite derived CoNi 3 O 4 nanoribbons possess abundant exposed edges, sharp corners, and open diffusion channels. These unique characteristics offer CoNi 3 O 4 /diatomite hybrid excellent peroxymonosulfate activation efficiency in real water bodies. • 2D CoNi 3 O 4 nanoribbons were fabricated via vertically oriented growth on diatomite. • CoNi 3 O 4 /diatomite showed rich exposed edges, sharp corners and diffusion channels. • CoNi 3 O 4 /diatomite presented excellent PMS catalytic activity in real water bodies. • S O 4 - • , OH and 1O 2 were generated and functioned in CoNi 3 O 4 /diatomite/PMS system. • O 2 − contributed to reversible redox cycle of Co2+/Co3+ and Ni2+/Ni3+. The reactive oxygen radicals generated by peroxymonosulfate (PMS) activation exhibit great potential to deal with refractory contaminants of emerging concern. However, mass production of efficient and cost-effective catalysts for PMS activation is still a long-term goal for its widespread practical application. Herein, a novel CoNi 3 O 4 /diatomite hybrid is constructed through vertically oriented growth of 2D CoNi 3 O 4 nanoribbons with atomic layer-thickness on cost-effective diatomite template. Distinct from stacked CoNi 3 O 4 , CoNi 3 O 4 /diatomite composite possesses abundant exposed edges, sharp corners, and open diffusion channels. Abundant exposed edges and sharp corners create more open space and active sites for PMS activation. Open diffusion channels accelerate the migration of PMS and contaminants. Such characteristics offer CoNi 3 O 4 /diatomite hybrid excellent PMS activation efficiency. Furthermore, sulfate radical plays the dominant role in atrazine degradation. Superoxide radical contributes to reversible redox cycle of Co2+/Co3+ and Ni2+/Ni3+. This study provides a novel strategy for cost-effective mass production of various Fenton-like 2D catalysts. [ABSTRACT FROM AUTHOR]

• Novel ternary heterogeneous SnO 2 /g-C 3 N 4 /diatomite composite was synthesized. • The photocatalytic property of the prepared composite was evaluated by reduction of Cr(VI). • The prepared composite showed superior photoreduction performance with aid of citric acid. • The possible enhancement mechanism and reduction pathway were proposed. • The intermediates in the Cr(VI) reduction process were identified. A novel ternary SnO 2 /g-C 3 N 4 /diatomite (SCN/DE) nanocomposite was rationally designed and successfully synthesized via a two-step method with in-situ polymerization and self-assembling. Under visible light illumination, the resulting SCN/DE composite exhibited superior photocatalytic performance and good reusability for the photoreduction of Cr(VI) to Cr(III) in the presence of citric acid, the apparent rate constant of SCN/DE composite was up to around 22.68 times, 13.53 times and 8.65 times as much as those of g-C 3 N 4 (CN), g-C 3 N 4 /diatomite (CN/DE) and SnO 2 /g-C 3 N 4 (SCN) composites, respectively. The citric acid is a co-catalyst (chelating agent) rather than a reactant during the reactive process. Besides, the intimate interface contact and ternary heterogeneous structure were established among the SnO 2 , g-C 3 N 4 and diatomite. The induced positive charged surface of diatomite should be the key factor in enhancing photoactivity of the resultant SCN/DE composite, which significantly accelerated the charge separation of photogenerated electron-hole pairs as well as improved the adsorption performance towards Cr (VI). In particular, a possible reduction pathway of Cr(VI) to Cr(III) by SCN/DE composite with the assistance of citric acid was first investigated and proposed. This work provides a novel strategy for synthesizing highly efficient mineral-based photocatalysts with great promising application foreground for Cr(VI)-containing wastewater treatment. [ABSTRACT FROM AUTHOR]

• Diatomite and CoFe 2 O 4 was effectively assembled to activate peroxymonosulfate. • CoFe 2 O 4 /diatomite catalyst has lower metal dissolution rate. • Surface structure and crystallization dispersion improve activation performance. • The 1O 2 was the primary active substance for BPA degradation. • Weak basic condition enhanced PMS activation and increased BPA degradation. Porous magnetic CoFe 2 O 4 /diatomite catalyst (CFD) was rationally synthesized via a facile citrate combustion process. The relationship between catalytic performance and material properties of the prepared catalysts was comprehensively investigated by various characterizations, especially for the interface interaction between CoFe 2 O 4 and diatomite as well as crystallization regulation of CoFe 2 O 4. Overall, higher specific surface area, overspreading surface hydroxyl groups, better crystal dispersion and abundant surface-active sites make CFD have better degradation performance of bisphenol A (BPA) than pure CoFe 2 O 4 in the presence of peroxymonosulfate (PMS), and the pseudo-first-order reaction rate constant of 40-CFD (40% CoFe 2 O 4 /diatomite) is almost 5.32 times higher than that of pure CoFe 2 O 4. Besides, CFD has excellent magnetic properties, lower metal dissolution rate and good reusability. In addition, electron paramagnetic resonance (EPR) and radical quenching experiments show that sulfate radicals (SO 4 −) and singlet oxygen radicals (1O 2) generated from the electron transfer of BPA molecule and valence state change of transition metals should be the predominant oxidation species. Moreover, possible degradation pathways of BPA are determined by the detection of intermediates derived from the results of liquid chromatograph–mass spectrometer (LC–MS). In brief, it is indicated that the CoFe 2 O 4 /diatomite composite material is an efficient and environmentally friendly catalyst, which has a great potential application in wastewater treatment by activating PMS. [ABSTRACT FROM AUTHOR]

Zeolite X powder was synthesized using natural low-grade diatomite as the main source of Si but only as a partial source of Al via a simple and green hydrothermal method. The microstructure and surface properties of the obtained samples were characterized by powder X-ray diffraction (XRD), scanning electron microscopy (SEM), wavelength dispersive X-ray fluorescence (XRF), calcium ion exchange capacity (CEC), thermogravimetric-differential thermal (TG-DTA) analysis, and N2 adsorption-desorption technique. The influence of various synthesis factors, including aging time and temperature, crystallization time and temperature, Na2O/SiO2 and H2O/Na2O ratio on the CEC of zeolite, were systematically investigated. The as-synthesized zeolite X with binary meso-microporous structure possessed remarkable thermal stability, high calcium ion exchange capacity of 248 mg/g and large surface area of 453 m2/g. In addition, the calcium ion exchange capacity of zeolite X was found to be mainly determined by the crystallization degree. In conclusion, the synthesized zeolite X using diatomite as a cost-effective raw material in this study has great potential for industrial application such as catalyst support and adsorbent. [ABSTRACT FROM AUTHOR]