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An antibacterial composite material based on the incorporation of diatomite (DE), graphene oxide (GO), and silver nanoparticles (AgNPs) was developed. It can significantly increase the antibacterial capability of DE and separation efficiency of GO and AgNPs. GO improves the stability of AgNPs and reduces the loss of Ag(AgNPs/GO/DE) on composites. The Ag content of the AgNP/GO/DE composite was determined by inductively coupled plasma-mass spectrometry (ICP-MS) to be 2340 ppm. The as-prepared AgNPs/GO/DE demonstrated excellent antibacterial properties to E. coli and S. aureus , evaluated by measuring the minimum bactericidal concentration (MBC) using twofold serial dilutions in a lysogeny broth medium. The MBC of AgNPs/GO/DE against E. coli and S. aureus were 5 and 10 mg/mL, respectively. The amount of silver released into the water was 38–46 ppb. Fluorescence staining and SEM results indicated that the bacteria were adsorbed on AgNPs/GO/DE and killed. AgNPs/GO/DE showed a stronger antibacterial effect on E. coli than S. aureus , which was related to the cell wall structure of the bacteria. Unlabelled Image • Silver nanoparticle/graphene oxide/diatomite composite materials was synthesized. • The obtained composite showed good antibacterial activity for E. coli and S. aureus. • The antibacterial performance of silver nanoparticle/graphene oxide/diatomite was determined by fluorescent staining and SEM. [ABSTRACT FROM AUTHOR]

Abstract In this paper, a novel Fe-Mn binary oxide-diatomite (FMBO-Dt) composite was prepared by co-precipitation method. The morphological and structural features of the synthesized composite were characterized by X-ray diffraction, Scanning electron microscopy, Fourier transform infrared spectroscopy, and X-ray photoelectron spectroscopy. The catalytic activity of FMBO-Dt composite was investigated by the degradation of methylene blue (MB) in the presence of H 2 O 2 and the effects of various factors such as Fe/Mn molar ratio, initial pH, and initial H 2 O 2 concentration on MB degradation were evaluated. It was found that FMBO-Dt composite was highly effective for the degradation of MB in the presence of H 2 O 2. In addition, the stability and reusability of the composite was also investigated. Finally, the possible mechanism for the decolorization of MB in the heterogeneous system was proposed. These results suggested that FMBO-Dt composite was a promising candidate for dye wastewater treatment. Graphical abstract Unlabelled Image Highlights • A novel FMBO-Dt composite was prepared by co-precipitation method. • FMBO-Dt composite exhibited high catalytic activity for the oxidation of MB. • The catalyst composite also showed good stability and reusability. • A mechanism for the decolorization of MB was proposed. [ABSTRACT FROM AUTHOR]

Highlights • Self-floating Ti3+/N co-doped TiO 2 /diatomite granule catalyst was prepared. • The floating hybrid granule showed better photoactivity compared to powdery one. • The optimal dosage amount was determined. • The synergy between co-dopants, TiO 2 and diatomite were illustrated. • The hybrid granule showed good stability and recyclability. Abstract Powdery photocatalyst has long been investigated and developed, yet its disadvantages such as low light-harvesting and reuse capability in suspension system have greatly hindered its practical application. The proposal of floating photocatalyst provided an alternative method to overcome the above limitations. In this work, TiO 2 nanoparticles were doped by Ti3+ and N, and dispersed onto natural porous mineral diatomite via sol-gel method. The obtained black powder was granulated to produce floating granule catalyst (black Ti3+/N co-doped TiO 2 /diatomite hybrid granule), denoted as b/N-TDHG. The synergy between Ti3+ and N dopants, as well as diatomite and TiO 2 were studied. The photoactivity of b/N-TDHG was investigated via the degradation of antibiotic tetracycline (TC) solution under visible light irradiation, and then the optimal co-doping amount and granule dosage were determined. The optimal granule catalyst presented its removal rate of TC as 92.0% within 150 min, and its rate constant was 0.0144 min−1, while the corresponding powdery sample showed the removal rate of TC as 90.5% during the same period, with its rate constant as 0.0135 min−1. Moreover, floating b/N-TDHG could simply be filtrated from TC solution, and the removal rate slightly dropped to 89.6% after 5 repetitions, presenting good reusability. [ABSTRACT FROM AUTHOR]

Polyaniline (PANI)-doped tin oxide-diatomite hybrid photocatalysts were synthesized by the adding of tin source and diatomite silica support to prepared PANI solution via chemical oxidative polymerization of aniline monomer. The obtained catalysts were characterized with X-Ray diffraction (XRD), nitrogen adsorption-desorption isotherm, scanning electron microscopy/energy dispersive spectroscopy (SEM/EDS), transmission electron microscopy (TEM), Fourier transform infrared (FTIR) and UV visible diffuse reflectance spectrums (UV–vis DRS) analyses techniques and tested in the photodegradation of Remazol Yellow (RY) dye under UV light. The characterization results showed the evidence of interaction between PANI, diatomite and tin oxide. The TEM images showed that tin settled as nanoneedles and nanograins on the solid surface. The adding of calcined diatomite-tin solid to the PANI solution resulted in high surface area, pore volume and large pore diameter values and also the indirect band gap energy determined by Tauc’s plot was decreased. The degradation of RY was reached 96% within 1 h at 1 g/L catalyst dose. The degradation kinetics of RY in all cases was found to be pseudo-first-order kinetics model. It has been found that the band gap energy has a significant effect on the photocatalytic activity. [ABSTRACT FROM AUTHOR]

[Display omitted] • The dual defects co-regulated V-CoP x-1 with hierarchical diatomite morphology was successfully synthesized. • The P vacancies and V doping heteroatoms affected the crystal structure and decreased the average oxidation states of Co cations. • The V-CoP x-1 electrode exhibited an excellent energy storage capacity and cycling stability. • V-CoP x-1 //AC asymmetric supercapacitor delivered a high energy density of 43.3 Wh kg−1 at a power density of 800 W kg−1. Poor rate performance and low cycling stability are both considered as two major disadvantages when choosing cobalt phosphide as the electrode material of supercapacitor. Herein, we developed an effective strategy to ameliorate above disadvantages by introducing of phosphorus vacancies and doping of vanadium simultaneously (the products labelled as V-CoP x-1). Besides, diatomite was selected as a template to synthesize cobalt phosphide with a diatomite morphology by a mild etching method using KOH aqueous alcohol solution as etching agent. The average oxidation state of Co ions in V-CoP x-1 decreases after the P vacancies are introduced, which can improve the electrical conductivity and provide more active sites for electrochemical reactions. Meanwhile, after the introduction of P vacancies and V heteroatoms, more point defects and unpaired electrons are generated, thus improving the ionic conductivity of the material. The diatomite morphology of V-CoP x-1 and the morphological transformation after the reduction by NaBH 4 make the materials have larger specific surface area and higher porosity. The as-synthesized V-CoP x-1 possesses a superior 829 F g−1 at 1 A g−1 and improved cycling life maintaining 80.84% of its original value after 10,000 cycles. Moreover, a fabricated device with V-CoP x-1 (anode) and commercial active carbon (cathode) exhibits 43.3 Wh kg−1 at 800 W kg−1. This supercapacitor also delivers a superior rate performance maintaining 60% retention of specific capacitance from 1 A g−1 to 20 A g−1. This work provides an efficient strategy of defects regulation to boost the electrochemical performance, which hoped to offer insights for the improvement of cobalt phosphide. [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]

Nanotechnology for water disinfection application gains increasing attention. Diatomite is one kind of safe natural material, which has been widely used as absorbent, filtration agents, mineral fillers, especially in water treatment industry. Nanosilver/diatomite nanocomposites were developed in this publication with a facile, effective in-situ reduction method. The as-prepared nanosilver/diatomite nanocomposites demonstrated amazing antibacterial properties to gram-positive and gram-negative bacteria. The corresponding property has been characterized by UV–vis absorbance, Transmission Electron Microscopy (TEM), Energy Dispersive X-ray (EDX) and X-ray Photoelectron Spectroscopy (XPS). Moreover, the detailed bacteria killing experiments further displayed that 0.5 g of the nanosilver diatomite could kill >99.999% of E. Coli within half an hour time. And the silver leaching test demonstrated that the concentrations of silver in the filtered water under varies pH environment were below the limit for silver level of WHO standard. Considering the low price of natural diatomite, it is believed that the nanosilver/diatomite nanocomposites have potential application in water purification industry due to its excellent antimicrobial property. [ABSTRACT FROM AUTHOR]

[Display omitted] • A novel ternary heterogeneous PANI-TiO 2 /diatomite composite was synthesized. • A high-efficient adsorption-photocatalysis collaborative system was constructed. • The HCHO mineralization pathway were proposed via in situ DRIFTs analysis. • The catalytic process was governed by the large delocalized π-electron conjugation system. A novel ternary polyaniline (PANI)-TiO 2 /diatomite (PANI-TDE) composite with 3D nanostructure was synthesized via a simple self-assembling process and an in-situ polymerization approach. The resulting composite exhibited efficient performance in gaseous formaldehyde removal and antibacterial process (Staphylococcus aureus) under visible light. By tracking the variation of CO 2 concentration during the photocatalytic process, the apparent rate constant of mineralized gaseous formaldehyde of 5%PANI-TDE was up to about 84.26 times, 48.49 times and 3.51 times higher than those of TiO 2 , TiO 2 /diatomite composite and PANI-TiO 2 composite, respectively. Under the simulated indoor actual environment, the HCHO removal rate of the prepared 5%PANI-TDE composite could reach 82.69 % in 12 h. The designed ternary heterogeneous structure with intimate interface contacts among PANI, TiO 2 and diatomite successfully constructed a high-efficient adsorption-photocatalysis collaborative system, and a large delocalized π-electron conjugation system was established due to the construction of organic–inorganic system, which significantly enhanced migration/separation efficiency of the photo-generated carriers. Notably, the reaction pathways with the reaction intermediates were tracked via in-situ DRIFTs. [ABSTRACT FROM AUTHOR]

Diatomite has delicate porous structures and various shapes, making them ideal templates for microscopic core–shell particles fabrication. In this study, a new process of magnetron sputtering assisted with photoresist positioning was proposed to fabricate lightweight silver coated porous diatomite with superior coating quality and performance. The diatomite has been treated with different sputtering time to investigate the silver film growing process on the surface. The morphologies, constituents, phase structures and surface roughness of the silver coated diatomite were analyzed with SEM, EDS, XRD and AFM respectively. The results showed that the optimized magnetron sputtering time was 8–16 min, under which the diatomite templates were successfully coated with uniform silver film, which exhibits face centered cubic (fcc) structure, and the initial porous structures were kept. Moreover, this silver coating has lower surface roughness (RMS 4.513 ± 0.2 nm) than that obtained by electroless plating (RMS 15.692 ± 0.5 nm). And the infrared emissivity of coatings made with magnetron sputtering and electroless plating silver coated diatomite can reach to the lowest value of 0.528 and 0.716 respectively. [ABSTRACT FROM AUTHOR]

Ytterbium-doped titanium dioxide (Yb-TiO 2 )/diatomite composite materials with different Yb concentrations were prepared by sol–gel method. The phase structure, morphology, and chemical composition of the as-prepared composites were well characterized by X-ray diffraction (XRD), Fourier transform infrared spectroscopy, Raman spectroscopy, scanning electron microscopy (SEM), and ultraviolet–visible (UV–vis) diffuse reflection spectroscopy. The XRD and Raman spectroscopy analysis indicated that the TiO 2 existed in the form of pure anatase in the composites. The SEM images exhibited the well deposition and dispersion of TiO 2 nanoparticles with little agglomeration on the surfaces of diatoms. The UV–vis diffuse reflection spectra showed that the band gap of TiO 2 could be narrowed by the introduction of Yb species, which was further affected by doping concentration of Yb. The photocatalytic activity of synthesized samples was investigated by the degradation of methylene blue (MB) under UV light irradiation. It was observed that the photocatalytic degradation followed a pseudo-first-order kinetics according to the Langmuir–Hinshelwood model. Compared to TiO 2 and TiO 2 /diatomite, the Yb-TiO 2 /diatomite composites exhibited higher photocatalytic activity toward degradation of MB using UV light irradiation. [ABSTRACT FROM AUTHOR]

Removal of noxious heavy metal ions (e.g. Pb(II)) by surface adsorption of minerals (e.g. diatomite) is an important means in the environmental aqueous pollution control. Thus, it is very essential to understand the surface adsorptive behavior and mechanism. In this work, the Pb(II) apparent surface complexation reaction equilibrium constants on the calcined diatomite and distributions of Pb(II) surface species were investigated through modeling calculations of Pb(II) based on diffuse double layer model (DLM) with three amphoteric sites. Batch experiments were used to study the adsorption of Pb(II) onto the calcined diatomite as a function of pH (3.0–7.0) and different ionic strengths (0.05 and 0.1 mol L −1 NaCl) under ambient atmosphere. Adsorption of Pb(II) can be well described by Freundlich isotherm models. The apparent surface complexation equilibrium constants (log K ) were obtained by fitting the batch experimental data using the PEST 13.0 together with PHREEQC 3.1.2 codes and there is good agreement between measured and predicted data. Distribution of Pb(II) surface species on the diatomite calculated by PHREEQC 3.1.2 program indicates that the impurity cations (e.g. Al 3+ , Fe 3+ , etc.) in the diatomite play a leading role in the Pb(II) adsorption and dominant formation of complexes and additional electrostatic interaction are the main adsorption mechanism of Pb(II) on the diatomite under weak acidic conditions. [ABSTRACT FROM AUTHOR]

A novel diatomite-immobilized BiOI hybrid photocatalyst has been prepared by a facile one-step deposition process for the first time. The structure, morphology and optical property of the products were characterized by X-ray powder diffraction (XRD), scanning electron microscopy (SEM) and UV–vis diffuse reflectance spectroscopy (DRS). The photocatalytic performance of the as-prepared BiOI/diatomite photocatalysts was studied by photodegradation of Rhodamine B (RhB) and methylene blue (MB) and monitoring photocurrent generation under visible light ( λ > 420 nm). The results revealed that BiOI/diatomite composites exhibit enhanced photocatalytic activity compared to the pristine BiOI sample. This enhancement should be attributed to that diatomite can play as an excellent carrier platform to increase the reactive sites and promote the separation of photogenerated electron–hole pairs. In addition, the corresponding photocatalytic mechanism was proposed based on the active species trapping experiments. This work shed new light on facile fabrication of novel composite photocatalyst based on natural mineral. [ABSTRACT FROM AUTHOR]

A bio-absorbent of Fe-CoNiP coated on the diatomite was fabricated by way of electroless plating of CoNiP and subsequent chemical vapor deposition of Fe. The surface morphology and composition of the above-mentioned diatomite particles at different stage were characterized with the scanning electron microscopy and the energy spectrum analysis respectively, and the results showed that the diatomite was successfully coated with CoNoP and Fe (carbony iron). The complex permittivity and permeability of composites filled with the bio-absorbent and paraffin was measured in frequency range of 2–18 GHz, and then the microwave reflection loss (RL) and the shielding effectiveness (SE) were calculated. The results showed that the permittivity and the permeability were both enlarged as Fe films were coated onto the CoNiP-coated diatomite, which was attributed to the excellent electromagnetic property of carbonyl irons. The composites made with the Fe-CoNiP diatomite had a better absorbing property (minimum RL −11.0 dB) as well as the shielding property (maximum SE 5.6 dB) at thickness 2 mm. It indicated the absorption property was mainly due to the attenuation on the microwave, and the Fe-CoNiP diatomite could be an effective absorbent with low-density. [ABSTRACT FROM AUTHOR]

In this study, a diatomite sample, which is a natural inorganic mineral with inherently high water and oil absorption capacity, was subjected to grinding before surface modification. Afterwards, the diatomite surface was modified via facile methods using a fluorocarbon (FC) chemical and stearic acid (SA) in addition to the sol–gel fluorosilanization (FS) process. The water and oil wettability, and oil absorbency properties of the unmodified and modified diatomites were investigated in addition to diatomite characterizations such as chemical content, surface area, particle size distribution, morphology, and modification efficiency. It was revealed that the wettability was changed completely depending on the surface modification agent and the media used, while the oil absorbency property surprisingly did not change. On the other hand, the oil absorbency was worsened by the grinding process, whereas the wettability was not affected. [ABSTRACT FROM AUTHOR]

The surface properties of the diatomite were investigated using nitrogen adsorption/deadsorption isotherms, TG-DSC, FTIR, and XPS, and surface protonation–deprotonation behavior was determined by continuous acid–base potentiometric titration technique. The diatomite sample with porous honeycomb structure has a BET specific surface area of 10.21 m 2 /g and large numbers of surface hydroxyl functional groups (i.e. Si-OH, Fe-OH, and Al-OH). These surface hydroxyls can be protonated or deprotonated depending on the pH of the suspension. The experimental potentiometric data in two different ionic strength solutions (0.1 and 0.05 mol/L NaCl) were fitted using ProtoFit GUI V2.1 program by applying diffuse double layer model (DLM) with three amphoteric sites and minimizing the sum of squares between a dataset derivative function and a model derivative function. The optimized surface parameters (i.e. surface dissociation constants (log K 1 , log K 2 ) and surface site concentrations (log C )) of the sample were obtained. Based on the optimized surface parameters, the surface species distribution was calculated using Program-free PHREEQC 3.1.2. Thus, this work reveals considerable new information about surface protonation–deprotonation processes and surface adsorptive behaviors of the diatomite, which helps us to effectively use the cheap and cheerful diatomite clay adsorbent. [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]

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: [•] High energy electron beam (HEEB) irradiation and hydrothermal treatment were used. [•] HEEB irradiation could make the impurities in the pores of diatomite loose. [•] Hydrothermal treatment (HT) could remove these impurities from the pores. [•] They could effectively improve pore size distribution and decrease the bulk density. [•] Catalytic performance of the corresponding catalyst was significantly improved. [ABSTRACT FROM AUTHOR]

Abstract: In order to fabricate lightweight flaky electromagnetic particles efficiently, the diatomite was used as the forming template to which the CoNiP coating was deposited by an electroless plating technique. The electroless plating of CoNiP on diatomite was accomplished with the coupling processing before the activation, in which 3-aminopropyltriethoxysilane (APTES) was used as the coupling agent. The effect of coupling processing on the activation and electroless plating of diatomite was characterized by SEM, FT-IR and EDS analysis. The results indicated that with coupling processing before activation, the catalytic effect was improved remarkably than that of direct colloidal palladium activation, which resulted in superior electroless plating on diatomite, even on the surface of submicron holes. The XRD analysis showed that the CoNiP coating was a transitional structure between crystal and amorphousness. The measurement of complex permeability and permittivity in the range of 2–18GHz suggested that the micro flaky electromagnetic particles had promising electromagnetic properties. [Copyright &y& Elsevier]

Abstract: Large-area fibrous network of polyaniline is obtained on the surface of diatomite by in situ polymerization of aniline without stirring. And it is characterized via Fourier-transform infrared spectroscopy, Raman spectroscopy, thermal analysis technology, four-probe technique and cyclic voltammetry, as well as specific surface, total pore volume, average pore size and pore size distribution. This composite contains 85% polyaniline, which conductivity is 5.08Scm−1 at 25°C. It is more significant that its film electrode not only possesses good redox reversibility in the aqueous media ranging from pH 1.0 to 7.0, but also shows good electrochemical cycling stability in the aqueous media of pH 4.0. It will be a promising material for several applications due to increasing the operating pH window in the aqueous media and good conductivity. [Copyright &y& Elsevier]

Abstract: The adsorption isotherm of polyethyleneimine (PEI) on diatomite was studied using UV spectrophotometry, the surface of diatomite was modified with polyethyleneimine by using impregnation method, and the trapping behavior of the modified diatomite for phenol was investigated by using 4-aminoantipyrine (4-AAP) spectrophotometric method. The experiment results show that negatively charged diatomite particles have very strong absorption effect for cationic macromolecule PEI, the adsorption isotherm fits in Freundlich equation. The character that there is a maximum value after intitial sharp increase of adsorption capacity on the adsorption curve indicates that there is strong affinity between diatomite particles and polyethyleneimine macromolecules, and it attributes to the strong electrostatic interaction. After modification with PEI, the electric property of diatomite particle surface changes essentially, and the isoelectric point of diatomite particles moves from pH 2.0 to 10.5. In acidic solution, phenol exists as molecular state, and the modified diatomite particles adsorb phenol through hydrogen bond interaction. However, the hydrogen bond interaction between nitrogen atoms on PEI chains and phenol is weaker because of high degree of protonation of polyethyleneimine macromolecules, so the adsorption quantity is lower. In basic solution, phenol exists as negative benzene–oxygen ion, and the modified diatomite particles adsorb phenol through electrostatic interaction. However, the electrostatic interaction between PEI and negative benzene–oxygen ion is very weak because of low degree of protonation of polyethyleneimine macromolecules, so the adsorption quantity is much lower. The modified diatomite particles produce very strong trapping effect for phenol in neutral aqueous solution via the cooperating of strong electrostatic interaction and hydrogen bond interaction, and the saturated adsorption capacity can attain to 92mgg−1. [Copyright &y& Elsevier]

Abstract: A fibrillar polyaniline/diatomite composite was prepared by one-step in situ polymerization of aniline in the dispersed system of diatomite, and was characterized via Fourier-transform infrared spectra (FT-IR), UV–vis–NIR spectra, wide-angle X-ray diffraction (WXRD), thermogravimetric analysis (TGA) and transmission electron microscopy (TEM), as well as conductivity. Morphology of the composite is uniform nanofibers, which the diameters of nanofibers are about 50–80nm. The conductivity of polyaniline/diatomite composite contained 28% polyaniline is 0.29Scm−1 at 25°C, and temperature of thermal degradation has reached 493°C in air. The composite has potential commercial applications as fillers for electromagnetic shielding materials and conductive coatings. [Copyright &y& Elsevier]

Abstract: A sample of an Algerian diatomite is characterized and treated in order to use it as gas chromatographic solid column support. This sample has been characterized by various analytical methods such as X-ray diffraction, scanning electron microscopy (SEM), atomic absorption and emission spectrometries and mercury porosimetry. Tests of separation of various hydrocarbon and alcohol mixtures have been performed. Results show that the prepared supports have similar performances than those of commercial products. On the other hand, enrichment process does not show any significant increase in the support quality. [Copyright &y& Elsevier]

Diffuse reflectance infrared Fourier transform spectroscopy (DRIFT), Raman spectroscopy of adsorbed pyridine molecules (Py-Raman) and in situ Py-IR have been used to investigate the hydroxyl species and acid sites on diatomite surfaces. The Lewis (L) and Brønsted (B) acid sites, and various hydroxyl species, including isolated hydroxyl groups, H-bonded hydroxyl groups and physically adsorbed water, are identified. The L acid sites in diatomite samples are resulted from the clay impurities, and the B acid sites are resulted from some moderate strength H-bonded hydroxyl groups. At room temperature, both of the isolated and H-bonded silanols associate with the physically adsorbed water by hydrogen bond. After calcination treatment, physically adsorbed water will be desorbed from the silanols, and the silanols will condense with the increase of temperature. Generally, the H-bonded silanols condense more easily than the isolated ones. The properties of surface hydroxyl species of diatomaceous silica are more similar to precipitated silica rather than fumed silica. [Copyright &y& Elsevier]

A conducting diatomite was obtained by polyaniline on surface modification of diatomite, and was characterized via Fourier-transform Raman spectra, UV-Vis absorption spectra, thermogravimetric analysis and scanning electron microscope, as well as conductivity. The results of spectroanalysis illustrate that polyaniline is not simply blended with diatomite. An interaction exists at the interface of diatomite and polyaniline, which may associate with hydrogen bond formed between the surface of diatomite with electronegativity and N&z.sbnd;H bond in polyaniline macromolecule. The results of thermogravimetric analysis suggest that the conducting diatomite only contains 8% polyaniline by mass, but its conductivity has reached 2.8×10−2 S cm−1 at 20 °C. [Copyright &y& Elsevier]

In this paper, adsorption isotherm of urokinase on two typical local diatomites were determined at 25 °C and their surface electrical potentials (ζ), isoelectrical point values (IEP) were determined. The properties of diatomites, the relationship among diatomite structure, pore-size distribution, surface ζ and adsorption isotherm were discussed. The adsorption equation of urokinase was calculated from the adsorption isotherm. The adsorption mode of urokinase on diatomite surface was judged by the configuration function α. The relationship between the amount of adsorbed urokinase and IEP value was also discussed. [Copyright &y& Elsevier]

• Diatomite-supported birnessite–type MnO 2 were synthesized by two methods. • Mnx/DM-AO showed excellent performance for HCHO removal than Mnx/DM-MT. • The crystal defective, surface –OH and lattice oxygen were responsible for the reactivity. • The synergistic effect between diatomite and MnO 2 improved catalytic performance. Diatomite-supported birnessite–type MnO 2 (δ-MnO 2) with different loadings were synthesized through in-situ reduction method by methanol (Mnx/DM-MT) and hydrothermal reduction method by ammonium oxalate (Mnx/DM-AO), respectively. The as-synthesized catalysts were characterized by N 2 adsorption-desorption, X-Ray diffraction, transmission electron microscope, scanning electron microscope, Raman, H 2 -temperature programmed reduction, thermogravimetric, X-ray photoelectron spectroscopy, and in-situ diffuse reflectance infrared Fourier transform spectrometry, and then utilized to catalytic oxidation of formaldehyde at ambient temperature and low temperature (50–250 °C). Compared with the Mnx/DM-MT catalyst, the Mnx/DM-AO catalyst exhibited superior catalytic activity in degrading HCHO at ambient temperature and low temperature. The highly defective structure, abundant hydroxyl groups, rich lattice oxygen and Mn3+ species were responsible for the excellent performance of Mnx/DM-AO. Meanwhile, the Mnx/DM-AO still exhibited good stability obtained from the cyclic testing. In-situ DRIFTS analysis indicated that δ-MnO 2 provided the reactive site, while the diatomite carrier dispersed MnO 2 and also provides a small number of active sites. The synergistic effect between diatomite and δ-MnO 2 benefits the catalytic performance in removal HCHO. The advantages of high activity, low-cost and environment-friendly, suggested that Mn/DM-AO catalyst exhibits promising application foreground in catalytic oxidation of formaldehyde at the temperature from ambient to 250 °C. [ABSTRACT FROM AUTHOR]