Diatomite Support Research Articles

Preparation of porous CuS/modified-diatomite composite via a facile in situ loading process for efficient recovery of silver ion from aqueous solution

The study on the recovery of silver ion (Ag+) from silver-containing wastewater is of great significance to heavy metal pollution control and noble metal retrieval. In this work, a porous CuS/modified-diatomite composite was prepared via a pre-modification followed by a mild in situ coating process. A layer of CuS nanosheets was evenly coated onto pre-modified diatomite, and porosity of the diatomite support reserved. Aperture analysis results suggested that the composite possessed a broader porous distribution, higher specific surface area and pore volume than pure CuS. The neosynthetic composite exhibited outstanding adsorption performance for Ag+, according to the Langmuir adsorption isotherm model, with a maximum adsorption capacity of 822.7 mg/g for Ag+, approximately 84 times greater than that of raw diatomite (9.87 mg/g). The highest removal efficiency of the composite for Ag+ reached 99.9 %, and pH values (3–8) and coexisting ions (Na+, K+, Ca2+ and Mg2+) had little influence on the removal of Ag+. Kinetic studies and adsorption product analysis demonstrated that removal of Ag+ on the composite was occupied by chemisorption, arising from that the abundant porosity of diatomite support prompts Ag+ to diffuse onto the composite, and the uniformly coated CuS nanosheets provide abundant active sites for Ag+ chemisorption.

Fabrication of Cu0-composited CuFe2O4 magnetic nanoparticles on diatomite support for efficient degradation of tetracycline hydrochloride by a Fenton-like system

Paramagnetic Cu/CuFe2O4/DE composites were fabricated by a one-step solvothermal method to design a heterogeneous Fenton-like catalyst to degrade tetracycline hydrochloride (TC). The Cu/CuFe2O4/DE were characterized by SEM, TEM, XRD, BET, and XPS methods. The catalytic activity of CuFe2O4 was improved using diatomite and Cu0. Diatomite (DE) enhanced the dispersity of Cu/CuFe2O4, minimized metal ions leaching, and improved stability. The Cu0 is used for the regeneration of Fe3+. The synergy between Cu+/Cu2+ and Fe2+/Fe3+ redox pairs promotes hydroxyl radical production upon H2O2 decomposition. The synthesized materials were characterized by SEM, TEM, XRD, BET, and XPS, and their catalytic activities were discussed and analyzed. 95.5 % TC was degraded within 90 min (initial conditions, pH = 5.0 and [TC] 50 mg/L), and showing excellent anti-interference ability to the presence of SO42-, Cl-, NO3-, CO32- and humic acid (HA).The presence of active species, viz., •OH and •O2- radicals generated in the Cu/CuFe2O4/DE/H2O2 system were detected by ESR quenching measurements. The •OH and •O2- mediated TC degraded pathways were proposed using the intermediates identified by LC-MS data. The novel heterogeneous Fenton-like process developed using Cu/CuFe2O4/DE/H2O2 is robust for TC degradation as exemplified in its stability and reusability measurements.

FeOOH-MnO2/Sepiolite and Fe2O3-MnO2/Diatomite: Highly efficient adsorbents for the removal of As(V)

As(V) in aquatic environment has posed a great threat to human beings due to its high mobility and toxicity. Developing economical and efficient adsorbents is vital for the removal of arsenic contamination in wastewater. We herein report the synthesis of FeOOH-MnO2/Sepiolite and Fe2O3-MnO2/Diatomite using the hydrothermal treatment method at 180 °C for 12 h with KMnO4, MnCl2, and FeCl3 as metal source and urea as precipitating agent. The FeOOH-MnO2 or Fe2O3-MnO2 composite was in situ grown on the sepiolite or diatomite support, resulting in a significant enhancement in surface area (which was 77.4 and 83.0 m2/g for the supported FeOOH-MnO2 and Fe2O3-MnO2 samples, respectively). FeOOH-MnO2/Sepiolite and Fe2O3-MnO2/Diatomite could effectively remove As(V), with the maximal As(V) adsorption capacities at 25 °C and pH = 7 being 124.3 and 148.2 mg/g, respectively. Furthermore, both samples exhibited good recycle As(V) adsorption performance. In addition. As(V) adsorption mechanisms of the samples were also discussed. The As(V) adsorption on FeOOH-MnO2/Sepiolite and Fe2O3-MnO2/Diatomite obeyed the Freundlich and Langmuir isothermal adsorption models, respectively. Considering their simple synthesis processes and excellent adsorption performance, we are sure that FeOOH-MnO2/Sepiolite and Fe2O3-MnO2/Diatomite are promising adsorbents for arsenic removal from wastewater.

Tetracycline Removal by Activating Persulfate with Diatomite Loading of Fe and Ce.

Persulfate (PS)-based oxidation technology is efficient in removing refractory organics from water. A novel diatomite (DIA) support Fe and Ce composite (Fe-Ce/DIA) was prepared for activating persulfate to degrade tetracycline in water. The Fe and Ce were uniformly loaded on DIA, and the total pore size of Fe-Ce/DIA was 6.99 × 10−2 cm3/g, and the average pore size was 12.06 nm. Fe-Ce/DIA presented a good catalytic activity and 80% tetracycline was removed under the persulfate system. The Fe-Ce/DIA also had photocatalytic activity, and the corresponding tetracycline removal efficiency was 86% under UV irradiation. Fe-Ce/DIA exhibited less iron dissolution rate compared with Fe-DIA. The tetracycline degradation rate was enhanced when the temperature increased. The optimal tetracycline removal efficiency was obtained when the conditions were of persulfate 10 mM, Fe-Ce/DIA dosage 0.02 g/L, and tetracycline concentration 50 mg/L. In addition, Fe-Ce/DIA showed a wide pH application and good reusability and stability.

Ethylene polymerization using diatomite as support for zirconocene dichloride/modified methylaluminoxane

In this paper, we report on a zirconocene dichloride/modified methylaluminoxane catalyst system supported on a natural diatomite in order to provide ethylene polymerization catalysts for gas phase or slurry processes. Such natural diatomite support exhibited similar properties of silica-based molecular sieve because of their similar chemical composition and porous structure. The supported catalysts were shown to be highly active and to form flocculent and fibrous polyethylene as proven by scanning electron microscopy. A natural resource diatomite was successfully applied as a support for zirconocene by us. Such catalyst system performed as a silica-based molecular sieve supported zirconocene in the ethylene polymerization. Polyethylene with flocculent and fibrous structure was obtained.

Perovskite LaFexCo1-xO3-λ deposited SiO2 catalytic membrane for deeply cleaning wastewater

To improve the cleaning efficiency of the membranes for wastewater, perovskite LaFexCo1-xO3-λ deposited SiO2 catalytic membrane (PCM) with functionality of peroxymonosulfate (PMS) induced catalytic oxidation and membrane separation was prepared by employing LaFexCo1-xO3-λ deposited SiO2 as the functional layer on diatomite support. The perovskite LaFexCo1-xO3-λ deposited SiO2 functional layer was modified by doping Fe, which contributed to the generation of oxygen vacancies, resulting in the massive generation of singlet oxygen and sulfate radicals during the pollutant degradation processes. Besides, the heterogeneous catalyst was effectively immobilized by PCM, and the mass transfer was enhanced owing to the adequate curved channels and eddy diffusion, performing a preferable catalytic oxidation efficiency and permeability. The water yield and degrading efficiency for tetracycline hydrochloride aqueous solution (20 mg/L) were 1064.5 L/m2h and 99%, respectively. Simulated wastewater containing organic pollutant and oil was treated by PCM, demonstrating an attractive separation and catalytic performance. Furthermore, cycling and regeneration test indicated that the PCM exhibited favorable stability and regeneration abilities after 10 consecutive cycles. Therefore, PCM with capacities of separation and catalytic oxidation performed potential application in complex wastewater treatment.

Photocatalytic degradation of remazol yellow using polyaniline–doped tin oxide hybrid photocatalysts with diatomite support

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.

Utilization of industrial wastes for preparation of high performance ZnO/diatomite hybrid photocatalyst

The enhanced photocatalytic activity of ZnO was successfully obtained by immobilized ZnO particles on diatomite support using simple impregnation and calcination method. It is interesting that both starting materials (ZnO and diatomite) used for hybrid photocatalyst synthesis in this work were prepared from industrial wastes. A zinc-dust waste derived from hot-dip galvanizing process was used for synthesis of zinc oxide particles and diatomite waste derived from brewery industries was used as a porous substrate. Effects of preparation pH, loading amount of zinc oxide and calcination temperature on the photocatalytic activity for degradation of methylene blue solution of ZnO-immobilized hybrid photocatalyst products were investigated. It was demonstrated that the enhancement in photodegradation performance of ZnO caused by the high absorbability of diatomite support. The hybrid photocatalyst sample prepared by precipitation at pH 10 loading with 20wt% of ZnO on diatomite and calcination at 600°C showed the highest methylene blue degradation efficiency of about 85.90% under UV light irradiation for 2h.

Screening of treated diatomaceous earth to apply as V2O5 catalyst support

In this study, we have modified the properties of diatomaceous earth precursors which are aimed to be used in the synthesis of V2O5 catalysts. Hence, in the first step, three various samples of Iranian diatomaceous earth were provided from Khorasan and East Azerbaijan mines. In the second step, V2O5 catalysts were synthesized with treated diatomite samples. In order to study the efficiency of acid treatment and the effect of diatomite precursors, characterization tests including XRD, ICP, BET-BJH, SEM and TEM were organized for each step. Eventually, results proved that acid treatment modified microstructure of some diatomaceous earth and increased the performance of the catalyst. The object of this research was to find the best treated diatomite support among Iranian mine and various conditions of acid treatment that can be used in commercial V2O5 catalyst. The results show that C15-Mi (catalyst with diatomite Mianeh mine treated with 15% acid concentration) has the best conversion among all samples.

A hierarchically porous diatomite/silicalite-1 composite for benzene adsorption/desorption fabricated via a facile pre-modification in situ synthesis route

A novel, hierarchically porous diatomite/silicalite-1 composite with a high benzene removal efficiency was prepared via a facile coating process. Silicalite-1 nanoparticles (Sil-1nano) were synthesized in situ on the surface of the pre-modified diatomite support by using a mild, low-temperature reflux reaction method. The obtained composite possessed a hierarchically porous structure, involving micropores and stacking mesopores from the silicalite-1 nanoparticles, and it retained the macropores from the diatomite support. The specific surface area and micropore volume of the composite were 348.7m2/g and 0.127cm3/g, respectively, with a zeolite loading amount of up to 60.2%. The diatomite/silicalite-1 composite exhibited considerably higher static and dynamic benzene adsorption capacities (94.9mg/g (Sil-1nano) and 246.0mg/g (Sil-1nano) respectively) per unit mass of zeolite than did the synthesized Sil-1nano and commercial ZSM-5. Moreover, the introduced macroporosity of the diatomite reduced the mass transfer resistance of the nanoparticles because of their improved dispersity, and it provided more possible entryways for benzene molecules, leading to better penetration of benzene than for Sil-1nano or commercial ZSM-5. The composite showed steady reversibility after 4 adsorption cycles, further demonstrating the promise of such a novel synthesized adsorbent for the removal of volatile organic compounds in industrial applications.

Synthesis and structural properties of ZnO and diatomite-supported ZnO nanostructures

Zinc oxide (ZnO) and diatomite-supported ZnO nanostructures were prepared using a direct precipitation and co-precipitation method, respectively. The morphologies of the prepared nanostructures were studied by scanning electron microscopy (SEM), transmission electron microscopy (TEM), X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR) and X-ray photoelectron spectroscopy (XPS). The surface charge of the samples was assessed by zeta potential measurements. The XRD results showed that the size of the prepared nanoparticles were 18nm, which was consistent with TEM consequences. The FT-IR spectrum clearly indicated the formation of an interfacial chemical bond between Zn and O of prepared samples but ZnO characteristic peaks shifted to lower wave numbers at about 467cm−1 for diatomite-supported ZnO. Characterization exhibited that the ZnO particles were successfully distributed in the diatomite support. Prepared nanoparticles have potential for different applications owing to processing facility and more economical reagents.

Preparation of hierarchically porous diatomite/MFI-type zeolite composites and their performance for benzene adsorption: The effects of desilication

Hierarchically porous diatomite/MFI-type zeolite composites were prepared by transforming the natural diatomaceous silica into MFI-type zeolite by a vapor-phase transport method, followed by a desilication treatment. The morphology and macroporosity of the diatomite were well preserved in the parent diatomite/MFI-type zeolite composite (Dt/Z). Treatment of Dt/Z by desilication in aqueous 0.2M NaOH solution at 60°C for 1h resulted in a mesopore size distribution centered at approximately 7nm, without significantly altering the macroporosity and microporosity of the resulting composite. Further desilication treatment (10h) broadened the mesopore size distribution, whereas the macropores sourced from the diatomite support were significantly damaged and a fraction of the micropores was narrowed to approximately 0.49nm. Under the optimal desilication condition (1h), the desilication-treated Dt/Z sample (Dt/Z-A1h) exhibited a higher adsorption capacity, better affinity, and faster adsorption kinetics toward benzene than the parent Dt/Z, as evaluated via a gravimetric method using an Intelligent Gravimetric Analyzer. The excellent benzene adsorption performance of Dt/Z-A1h was attributed both to the increase in porosity and the formation of terminal silanol groups on the surface of newly developed pores after the desilication treatment.

Facile preparation of hierarchically porous diatomite/MFI-type zeolite composites and their performance of benzene adsorption: The effects of NaOH etching pretreatment

Hierarchically porous diatomite/MFI-type zeolite (Dt/Z) composites with excellent benzene adsorption performance were prepared. The hierarchical porosity was generated from the microporous zeolite coated at the surface of diatom frustules and from the macroporous diatomite support. A facile NaOH etching method was employed for the first time to treat the frustule support, followed by hydrothermal growth of MFI-type zeolite at the surface of frustules previously seeded with nanocrystalline silicalite-1 (Sil-1). NaOH etching enlarged the pores on diatom frustules and further increased the coated zeolite contents (Wz). The central macropore size of the diatom frustules increased from approximately 200–500nm to 400–1000nm after NaOH etching. The Wz could reach 61.2%, while the macroporosity of the composites was largely preserved due to more voids for zeolite coating being formed by NaOH etching. The Dt/Z composites exhibited higher benzene adsorption capacity per unit mass of zeolite and less mass transfer resistance than Sil-1, evaluated via a method of breakthrough curves. These results demonstrate that etching of a diatomite support is a facile but crucial process for the preparation of Dt/Z composites, enabling the resulting composites to become promising candidates for uses in volatile organic compounds emission control.

실리카 분말이 코팅된 수처리용 규조토계 세라믹 필터의 특성평가

In this study, diatomite based materials were investigated as a support filter for silica particle coating. The silica sol for coating was synthesized by a st<TEX>$\ddot{o}$</TEX>ber process. The diatomite support was dry-pressed at 10 MPa and sintered at <TEX>$1200^{\circ}C$</TEX> for 1 hour. The coating sol was prepared as a mixture of EtOH and silica sol. The diatomite support was coated by a dip-coating process. Silica coated diatomite filter was sintered at <TEX>$1000{\sim}1200^{\circ}C$</TEX> for 1 hour. The largest pore size was decreased with increasing concentration ratio of coating sol. The gas and water permeability of silica coated diatomite decreased with increasing of concentration ratio of the coating sol.

Effect of the diatomite pretreatment on the catalytic performance of TS-1/diatomite for toluene hydroxylation by H2O2 in fixed-bed reactor

Supporting the TS-1 catalyst on diatomite and adopting fixed-bed reactor technique for the toluene hydroxylation by H2O2 are in favor of the separation of TS-1 catalyst from liquid reactants and continuous production, to reduce the product cost. Diatomite was treated with the H2SO4/HF mixed acids solution and calcined at 1000°C, and the effect of pretreatment on its physicochemical properties was investigated by ICP-AES, XRD, low-temperature N2 absorption and NH3-TPD techniques. After diatomite was treated with H2SO4/HF mixed acid solution and calcined at 1000°C, some mineral impurities (as Al, Fe and Mg) in diatomite were removed and its pores were cleared, resulting in an increase in its surface area and pore sizes; while the acidic strength of relatively strong-acid sites on the diatomite surface was weakened, and its amount of acid sites was increased. Interestingly, the HF concentration in the mixed acid solution would remarkably affect the surface properties of diatomite. As the diatomite support of TS-1 catalyst for toluene hydroxylation by H2O2 in fixed-bed reactor, the suitable ratio of H2SO4/HF in the mixed acid solution is 8/2. After diatomite was treated with the H2SO4/HF (8/2) mixed acid solution and calcined at 1000°C, the catalytic performance of TS-1/diatomite for the toluene hydroxylation was improved remarkably, for instance, the conversion of toluene and utilization of H2O2 at 60°C reached 14.3% and 94.3%, respectively.

The use of a diatomite–kaolin composite coating to design the pore characteristics of a sintered diatomite membrane

Abstract Porous ceramic membranes have lately attracted great interest due to their outstanding thermal and chemical stability. In this paper, we report the results of our efforts to determine whether we could prepare a diatomite–kaolin composite coating to be deposited over a sintered diatomite support layer that could reduce the largest pore size of the sintered diatomite membrane while retaining an acceptable level of permeability. We determined under what conditions such a composite coating over a support layer could be prepared without the generation of micro-cracks during drying and sintering. The pore characteristics of the sintered diatomite membranes were studied by scanning electron microscopy and capillary flow porosimetry.

The fabrication and characterization of sintered diatomite for potential microfiltration applications

Abstract Porous ceramic membranes have lately become a subject of special interest due to their outstanding thermal and chemical stability. We investigated whether a sintered diatomite support layer could also serve as a separation layer to minimize any processing difficulties, and investigated whether the support layer and the separation layer could be made from the same material to avoid a thermal mismatch during a high-temperature sintering process. We prepared sintered diatomite as a porous ceramic membrane for microfiltration, as diatomite particles are inherently porous and irregular. The pore characteristics of the sintered diatomite specimens were studied by scanning electron micrography, mercury porosimetry, and capillary flow porosimetry.

Synthesis of succinic anhydride from maleic anhydride on Ni/diatomite catalysts

The characteristics and catalytic properties of Ni(5 wt%)/diatomite, Ni(5 wt%)/γ-Al2O3, Ni(5% wt)/Bentonite clay and Ni(5 wt%)/attapulgite clay were investigated and compared in terms of catalytic activities for liquid-phase hydrogenation of maleic anhydride (MA). The results showed that the diatomite support exhibited the highest activity and selectivity. Using Ni(7 wt%)/diatomite catalyst, the 100% conversion of MA and 96.20% selectivity to SA were obtained for MA hydrogenation at 190°C. The X-ray diffraction (XRD) studies showed that there is only NiO on the support and no elemental nickel (Ni0) and Ni2O3 was detected in unreduced samples. XRD and H2 temperature-programmed reduction (TPR) studies also showed that NiO species were all converted to metallic nickel (Ni0) after reduction at 350°C.

Diatomite-supported Pd–M (M = Cu, Co, Ni) bimetal nanocatalysts for selective hydrogenation of long-chain aliphatic esters

Diatomite supported Pd–M (M=Cu, Co, Ni) bimetal nanocatalysts with various metal compositions were prepared and characterized by means of X-ray diffraction, transmission electron microscopy, and X-ray photoelectron spectroscopy. It was demonstrated that the metal nanoparticles were uniformly distributed on the support, and their size was centered around 8nm with a relatively narrow size distribution. The catalysts were used to catalyze hydrogenation of long-chain aliphatic esters, including methyl palmitate, methyl stearate, and methyl laurate. It was indicated that the all diatomite-supported Pd-based bimetal catalysts were active to the selective hydrogenation of long-chain esters to corresponding alcohols at 270°C, originated from the synergistic effect between the metal particles and the diatomite support. For the selective hydrogenation of methyl palmitate, Pd–Cu/diatomite with metal loading of 1% and Pd/Cu=3 displayed the highest performance, giving a 1-hexadecanol yield of 82.9% at the substrate conversion of 98.8%.

The Effect of Support on the Electrochemical Performance of Composite Electrode Materials for Supercapacit

Composite electrode materials for supercapacitor were prepared by a combination of incipient wetness impregnation and hydrothermal method in this study. The materials were characterized by XRD, specific surface area and electrochemical testing. The effect of support on the electrochemical performance of the composite electrode materials was investigated. The result shows that the samples prepared by different supports contain nickel nitrate hydroxide hydrate (the electroactive material in the composite) and undecomposed nickel nitrate.The specific surface area decrease after the loading of nickel compounds, which indicates the exisitance of nickel compounds in the pores. The composite prepared by using diatomite support exhibits higher specific capacitance than those prepared by using SBA-15 and Ti-Si molecular sieve, which delivers the specific capacitance of 1162.77 F/g at the scan rate of 5 mV/s.