Diatom and Diatomite: Different Focus on Natural Media to Material Science Path

Bio-silica issued from diatom, a microalgae, is attracted increasing attention in material science thanks to its peculiar nanoarchitecture and related properties with versatile applications. The present work is a deep analysis on morphological and chemical properties of bio-silica issued from fossil origin (diatomaceous earth) and living one (algal paste). An optimization in purification protocol was performed to obtain multiparous bio-silica from its raw media with keeping its original shape entirely. Multiple characterization methods as scanning electronic microscopy (SEM), infrared spectroscopy, x-ray diffraction (DRX), X-ray photoelectron spectroscopy (XPS), energy dispersive X-ray spectroscopy (EDX), nitrogen adsorption and inverse gas chromatography (IGC), were used to check the purification protocol efficiency as well as to gather accurate information on morphology and chemical composition of diatom material obtained in large amount.

Surface reconstruction,modification and functionalization of natural diatomites for miniaturization of shaped heterogeneous catalysts

Since the discovery of mesoporous silica in 1990s,there have been numerous mesoporous silica-based nanomaterials developed for catalytic applications,aiming at enhanced catalytic activity and stability.Recently,there have also been considerable interests in endowing them with hierarchical porosities to overcome the diffusional limitation for those with long unimodal channels.Present processes of making mesoporous silica largely rely on chemical sources which are relatively expensive and impose environmental concerns on their processes.In this regard,it is desirable to develop hierarchical silica supports from natural minerals.Herein,we present a series of work on surface reconstruction,modification,and functionalization to produce diatomite-based catalysts with original morphology and macro-meso-micro porosities and to test their suitability as catalyst supports for both liquid-and gas-phase reactions.Two wet-chemical routes were developed to introduce mesoporosity to both amorphous and crystalline diatomites.Importantly,we have used computational modeling to affirm that the diatomite morphology can improve catalytic performance based on fluid dynamics simulations.Thus,one could obtain this type of catalysts from numerous natural diatoms that have inherently intricate morphologies and shapes in micrometer scale.In principle,such catalytic nanocomposites acting as miniaturized industrial catalysts could be employed in microfluidic reactors for process intensification.

Adsorption of Anionic Dyes onto Chitosan-modified Diatomite

The purpose of this work is to study the possibility of anionic dyes Reactive Red M-8B（RR） and Direct Green B（DG） adsorbed on chitosan-modified diatomite. The characteristics of adsorbent, adsorption isotherms and the influence of adsorption time, temperature and pH were researched in this work. The results show that the mo- dified diatomite had a much better adsorption capability than the natural diatomite. The adsorption capacities of chitosan-modified diatomite for RR and DG were 94.46 and 137.0 mg/g, respectively. Both adsorption time and adsorption temperature provided a positive effect on the dye adsorption. Within the experimental pH range, the adsorbance was enhanced at lower pH but reduced sharply at high pH. On the basis of the experimental results and discussion, electrostatic attraction is considered as the main mechanism of this chemisorption.

Ag/Diatomite复合材料及其对禽流感病毒的杀灭研究

依据Ag具有强烈杀毒抗菌的特性,开展对禽流感病毒的杀灭实验。通过TEM、XRD对载银硅藻土测定,反映了Ag以纳米状态负载于硅藻土的表面,没有产生化学反应。1g载银硅藻土能强烈吸附杀灭6mL溶液中的病毒液,血凝效价为零。洗脱上清液接种鸡胚的半致死数统计说明,0.35靏/mL的剂量对病毒有明显的杀灭作用,可进一步作饲料添加剂用于禽流感防治。对人体流感病毒交叉感染的防护隔离也是一个新的途径。

Preparation of nano-TiO_2/diatomite-based porous ceramics and their photocatalytic kinetics for formaldehyde degradation

Diatomite-based porous ceramics were adopted as carriers to immobilize nano-TiO2 via a hydrolysis-deposition technique. The thermal degradation of as-prepared composites was investigated using thermogravimetric-differential thermal analysis, and the phase and microstructure were characterized by X-ray diffraction, Fourier transform infrared spectroscopy, and transmission electron microscopy. The results indicated that the carriers were encapsulated by nano-TiO2 with a thickness of 300-450 nm. The main crystalline phase of TiO2 calcined at 650~C was anatase, and the average grain size was 8.3 nm. The FT-IR absorption bands at 955.38 cm1 suggested that new chemical bonds among Ti, O, and Si had formed in the composites. The photocatalytic （PC） activity of the composites was investigated un- der UV irradiation. Furthermore, the photodegradation kinetics of formaldehyde was investigated using the composites as the cores of an air cleaner. A kinetics study showed that the reaction rate constants of the gas-phase PC reaction of formaldehyde were k = 0.576 mg＇m3·min^-1 and K = 0.048 m3/mg.

Improvement of wood properties by composite of diatomite and “phenol-melamine-formaldehyde” co-condensed resin

We improved the overall performance of fast-growing poplar by utilizing a low-cost, effective and simple method. The fast-growing poplar was modified by a vacuum-pressure impregnation method with three types of modification solutions composed of phe- nol-melamine-formaldehyde （PMF） co-condensed resin, diatomite, and 3-aminopropyl （diethoxy） methylsilane. We measured the weight percent gain （WPG）, bulking, leaching, anti-swelling efficiency （ASE）, wa- ter-repellent effectiveness （WRE）, and oxygen index of the modified specimens. All of the wood physical properties, which are beneficial for human uses, were significantly improved by the treatment. We improved various characteristics of wood and the oxygen index of poplar above 48.6% after the modification using diatomite and PMF co-condensed resin.

Controlled synthesis of nanosized Si by magnesiothermic reduction from diatomite as anode material for Li-ion batteries

Li-ion batteries(LIBs)have demonstrated great promise in electric vehicles and hybrid electric vehicles.However,commercial graphite materials,the current predominant anodes in LIBs,have a low theoretical capacity of only 372 mAh·g?1,which cannot meet the everincreasing demand of LIBs for high energy density.Nanoscale Si is considered an ideal form of Si for the fabrication of LIB anodes as Si–C composites.Synthesis of nanoscale Si in a facile,cost-effective way,however,still poses a great challenge.In this work,nanoscale Si was prepared by a controlled magnesiothermic reaction using diatomite as the Si source.It was found that the nanoscale Si prepared under optimized conditions(800°C,10 h)can deliver a high initial specific capacity(3053 mAh·g?1 on discharge,2519 mAh·g?1 on charge)with a high first coulombic efficiency(82.5%).When using sand-milled diatomite as a precursor,the obtained nanoscale Si exhibited a well-dispersed morphology and had a higher first coulombic efficiency(85.6%).The Si–C(Si:graphite=1:7 in weight)composite using Si from the sand-milled diatomite demonstrated a high specific capacity(over 700 mAh·g?1 at 100 mA·g?1),good rate capability(587 mAh·g?1 at 500 mA·g?1),and a long cycle life(480 mAh·g?1 after 200 cycles at 500 mA·g?1).This work gives a facile method to synthesize nanoscale Si with both high capacity and high first coulombic efficiency.

Hydration Characteristics and Humidity Control Performance of Calcium Silicate Board Prepared from Mine Tailing and Diatomite

The feasibility of utilizing molybdenum tailing and diatomite as siliceous materials to prepare calcium silicate board was explored.The influences of molybdenum tailing/diatomite proportion on hydration characteristics,thermal conductivity,water absorption,flexural strength and moisture adsorption-desorption property of calcium silicate board were investigated in detail.The experimental results reveal that molybdenum tailing is environmentally friendly to prepare building materials.The main hydration products in calcium silicate board under autoclaved condition are C-S-H with low crystallinity and tobermorite.Molybdenum tailing is favorable to the formation of tobermorite.The flexural strength and bulk density of the calcium silicate board gradually increase when the content of molybdenum tailing increases.Netlike C-S-H is formed with the increase of diatomite content during autoclaved curing process,resulting in the enhancement of moisture adsorptiondesorption performance and the reduction of thermal conductivity.The optimal content of molybdenum tailing is 20%,furthermore,the flexual strength and thermal conductivity of calcium silicate board at this content meet the Chinese standard JC/T564.1-2008.

Fabrication and Characterization of Diatomite-supported Activated Carbon Functional Ceramic

Using porous diatomite ceramic as carrier and phenolic resin as carbon precursor, the activated carbon functional ceramic with the activated carbon fixed into porous ceramic was prepared by the impregnation load phenolic resin, carbonization and activation isolated air. The influences of impregnation, curing, carbonization, activation etc. on the material property were discussed. The iodine value, SEM, elemental analyzer, BET and spectrum analysis chart were used to characterize the microstructures and performance of material at different conditions. The results showed that the excellent comprehensive property of activated carbon functional ceramic was gained when it adsorbed phenolic resin in 4 h under vacuum condition at curing temperature of 150 ℃ for 0.5 h and carbonization temperature of 600 ℃ for 1.0 h, and then put into 25wt% KOH for 4.0 h at activation temperature of 700 ℃ for 1.5 h. The iodine value is 176.9 mg/g, the specific surface area can reach 86.3 m2/g and the yield of carbonization is 50.48%.

Hydrothermal Solidification of Diatomite and Its Heat Insulating Property

To meet the commercial requirements of inorganic heat insulators,the mixture of diatomite and Ca(OH)2 are evenly dispersed,mold-compacted,and then hydrothermally solidified due to the formation of tobermorite under an autoclaved process.Systematic investigations of the preparation conditions(including mix ratio,autoclaved factors,mold pressure,etc)were carried out to optimize the serving properties of such tobermorite-based products.As a result,a compressive strength of more than 30 MPa was realized for the specimen in high density(about 1.30(g·cm-3)).On the contrary,the specimen in light weight for example 0.63(g·cm-3)typically showed a thermal conductivity of around 0.12(W·m-1·K-1).The present work developed a feasible way to produce and to control the serving properties of diatomite-based heat insulators by a process of hydrothermal solidification,in which the optimized value of Ca/Si ratio was proposed to be 0.6~0.7,while the water content is 25% in weight,and hydrothermal reaction is performed at 180 ℃ for no more than 24 hours.

Preparation and Properties of PMMA Modified Silica Aerogels from Diatomite

Diatomite was used as raw material to prepare sodium silicate with a modulus of 3.1 by alkali dissolution method and the resulted sodium silicate solution was employed as a precursor. Methyl methaerylate monomers were introduced in wet gels through solution-immersion, and upon heating at 70 ℃, the mesoporous surfaces throughout the skeletal framework were coated with the polymer layer. PMMA modified silica aerogels were successfully synthesized via ambient pressure drying. The properties were investigated by FT- IR, NMR, TGA, nitrogen adsorption-desorption, FESEM and nano-indentation, etc. Results indicate that with the increasing of PMMA incorporated into silica aerogels, the bulk density and the BET surface area increase, the porosity decreases. Through the observation of FESEM, it is found that the interconnecting pores and the big pores add, the pore size distribution expands from 5-17 to 28-150 urn. By comparison, the PMMA modified silica aerogels achieve a 52-fold increase in hardness and a 10-fold increase in modulus.

Enhanced visible-light-assisted peroxymonosulfate activation over MnFe_(2)O_(4) modified g-C_(3)N_(4)/diatomite composite for bisphenol A degradation

The MnFe_(2) O_(4)/g-C_(3) N_(4)/diatomite composites(Mn/G/D) were prepared via a facile precipitation-calcination method in this study.The Mn/G/D possessed higher specific surface area,lower electron-hole pairs' recombination rate,as well as wider and stronger visible light absorption capacity.Since the synergistic effect between g-C_(3 )N_(4) and MnFe_(2) O_(4),the photogene rated electron could transfer from g-C3 N4 to MnFe_(2) O_(4),which could promote the migration of electrons as well as enhance the photocatalytic activity and peroxymonosulfate(PMS) activation efficiency.Mn/G/D-5% composite displayed the excellent degradation performance of bisphenol A(BPA) with the removal efficiency of 99.9% under PMS/Vis system,which was approximately 2.47 and 63.8 times as high as that of the Mn/G/D-5%/PMS and Mn/G/D-5%/Vis system,respectively.Moreover,negative electricity derived from diatomite surface also promoted the photogenerated carriers' migration,and the degradation rate constant was around 2.4 times higher than that of MnFe_(2) O_(4)/g-C_(3) N_(4)(Mn/G).In addition,quenching experiments showed that both radical pathway(h^(+),·OH,·O_(2)^(-)and SO_(4)·^(-)) and non-radical pathway(^(1) O_(2)) were responsible for the degradation of BPA.

Application of diatomite as an effective polysulfides adsorbent for lithium-sulfur batteries

The lithium–sulfur batteries show the great potential to be the most promising candidate for high energy applications. However, the shuttling of soluble polysulfides deteriorates the battery performance tremendously. To suppress the diffusion of soluble polysulfides, diatomite that has abundant natural three-dimensional ordered pores is incorporated into the cathode to trap polysulfides. The composite cathode material(S-DM-AB for short), including sulfur(S), diatomite(DM), and acetylene black(AB) is prepared by an impregnation method. For comparison, another composite cathode material(S-AB for short) including sulfur and acetylene black is also prepared by the same method. The battery with S-DMAB composite cathode material delivers a discharge capacity of 531.4 m Ah/g after 300 cycles at 2 C with a capacity retention of 51.6% at room temperature. By contrast, the battery with S-AB composite cathode material delivered a capacity of only 196.9 m Ah/g with a much lower capacity retention of 18.6% under the same condition. The addition of diatomite in the cathode is proved to be a cheap and effective way to improve the life time of the lithium sulfur batteries.

Enhanced chemical trapping and catalytic conversion of polysulfides by diatomite/MXene hybrid interlayer for stable Li-S batteries

Lithium-Sulfur (Li-S) batteries with high theoretical energy density are promising energy storage systems in the next decades, while the lithium polysulfides (LiPSs) shuttling caused by the sluggish sulfur redox reaction severely lowers the practical performance. The use of interlayer between the cathode and separator has been widely investigated to physically or chemically block the LiPSs, while the introduction of catalytic materials is a more effective strategy to accelerate the conversion of LiPSs. MXene with rich surface chemistry has shown its potential for facilitating the catalytic conversion, however, the aggregation of MXene sheets usually leads to the loss of the catalytic active sites. Herein, we report a diatomite/MXene (DE/MX) hybrid material as the bifunctional interlayer for improving the adsorption/conversion of LiPSs in Li-S batteries. The diatomite with porous structure and rich silica-hydroxyl functional groups could trap LiPSs effectively, while prevent the aggregation of MXene. The DE/MX based interlayer showed bifunctions of enhancing the chemical adsorption and promoting the conversion of LiPSs. The Li-S batteries with the DE/MX interlayer delivered an improved cycling stability with a low capacity decay of 0.059% per cycle over 1000 cycles at 1.0 C. Moreover, stable 200 cycles can be realized with a high sulfur loading electrode up to 6.0 mg cm^(−2). This work provides an effective strategy to construct bifunctional interlayers for hindering the shuttling of LiPSs and boosting the practical application of Li-S batteries.

Characteristics of Cationic Red X-GRL Adsorption by Diatomite Tailings

As secondary mineral resources, diatomite tailings（DT） got from the Linjiang region of China were prepared and characterized by SEM, XRF and XRD. Mono-factor experiments were carried out to investigate the effects of the operation factor, including contact time, adsorbent concentration, initial p H value of the dye solutions, adsorption temperature and initial concentration of cationic Red X-GRL（X-GRL） on the adsorption of X-GRL. The adsorption kinetics, isotherms, thermodynamics and mechanisms for X-GRL were also studied. It was efficient for DT to adsorb X-GRL from aqueous solutions, and it was even discovered to have higher adsorptivity for X-GRL than diatomite concentrate（DC） in our previous test. The adsorption processes fit very well with the pseudo-second-order model and the Langmuir isotherm equation. In addition, various thermodynamic parameters, such as standard Gibbs free energy（ΔG°）, standard enthalpy（ΔH°） and standard entropy（ΔS°） have been calculated. From thermodynamic studies, it was seen that the adsorption was spontaneous and endothermic. The main driving forces of the physical adsorption on DT are electrostatic attraction. The reason why DT showed higher adsorptivity for X-GRL than DC was that there were more clay mineral particles within, which has a remarkable ability of dye adsorption due to its high surface area. DT as a cheap absorbent for X-GRL removal would replace or partially replace the activated carbon.

Preparation and Properties of Foam Glass-ceramic from Diatomite

The results of the study of raw mix preparation and foam glass-ceramics production using diatomite as a raw material were presented in the following article. A mixture of diatomite and 40% NaOH solution was subjected to heating at a constant temperature of 775 ℃. Samples of foam glass-ceramic from diatomite with an average density of 290-580 kg/m^3, compressive strength of 1.7-7.8 MPa and thermal conductivity of 0.08-0.14 W/（m·K） were obtained. The investigations have shown that the hydrothermal pretreatment of mixture at the temperature of 90 ℃ may lead to the acceleration of the leaching of amorphous SiO_2 from diatomite. It was discovered that the resulting soluble alkali silicates promote the process of foaming during heating and reduce the average density of the obtained samples. The optimal duration of the leaching process was estimated to be 30 minutes, which corresponds to the yield of SiO_2 equal to 42.5% by the weight of dry diatomite.

Effect of Diatomite Additive on the Mechanical and Dielectric Properties of Porous SiO2-Si3N4 Composite Ceramics

Porous SiO2-Si3N4 composite ceramics with high porosity and excellent mechanical properties were fabricated by pressureless-sintering at relatively low temperature of 1 500 ~C using diatomite as pore forming agent. The effects of diatomite on flexural strength, fracture toughness, shrinkage, porosity and phase transformation of the porous ceramics were investigated in detail. Compared with that of the ceramic without adding diatomite, the porosity of the ceramic with 10% diatomite is increased by about 27.4%, the flexural strength and fracture toughness reaches 78.04 MPa and 1.25 MPa.m1/2, respectively. As the porosity increases, the dielectric constant of porous SiO2-Si3N4 ceramic decreases obviously from 3.65 to 2.95.

STUDIES OF PURIFYING OF CLAYEY DIATOMITE

This article discusses the purifying method of the clayey diatomite or clay ——bearing diatotnite minerals found in China. And the processes of acidizing, beneficiation and gravitational fluidized dry sepa-ration are reviewed.

SCIENTIFIC BASES FOR PREPARATICN OF DIATOMITE AND PERLITE FLTER-AID

According to the filtration mechanism and filtration formula, it is considered that the surface area, bulk density and grain size distri- bution of filter-aid are the main factors affecting the filtration rate. On the basis of analysing phy- sical and chemical properties of diatomite and per- lite, the scientific bases for preparation of filter aid are discussed. It is possible that the complex filter aid, which is made up of low grade diatomite and perlite, is favourable to build-up a fine 'steely-bridged structure' for the filter cake, and its filtration performance of beer could be improved as good as that of commercial filter-aid made from high grade diatomite. The above points have been demonstrated by the results of laboratorial and industrial experiments of beer filtration.

Functionalization of diatomite with glycine and amino silane for formaldehyde removal

Two amino-functionalized diatomite(DE)composites modified by 3-aminopropyltriethoxysilane(APTS)or glycine(GLY)(i.e.,APTS/DE and GLY/DE)were successfully synthesized via the wet chemical method for the time-and cost-efficient removal of indoor formaldehyde(HCHO).First,the optimal preparation conditions of the two composites were determined,and then their microstructures and morphologies were characterized and analyzed.Batch HCHO adsorption experiments with the two types of amino-modified DE composites were also conducted to compare their adsorption properties.Experimental results indicated that the pseudo-second-order kinetic and Langmuir isotherm models could well describe the adsorption process,and the maximum adsorption capacities of APTS/DE and GLY/DE prepared under optimal conditions at 20°C were 5.83 and 1.14 mg·g^(-1),respectively.The thermodynamic parameters of the composites indicated that the adsorption process was spontaneous and exothermic.The abundant amine groups grafted on the surface of DE were derived from the Schiff base reaction and were essential for the high-efficient adsorption performance toward HCHO.