Properties Of Diatomite Research Articles

Adsorptive removal of Cr (VI) from wastewater using magnetite–diatomite nanocomposite

Abstract Magnetite-diatomite nanocomposite was synthesized through co-precipitation methods as an effective Cr(VI) removal adsorbent. The properties of diatomite, thermochemically modified diatomite (TMD), and magnetic–diatomite nanocomposite (MDN) were investigated using Fourier-transform infrared spectroscopy, X-ray diffraction analysis, Brunauer–Emmett–Teller, and complete silicate chemical analysis. The MDN shows 98.89% adsorption removal at optimized conditions using the response surface methodology of Box–Behnken Design. The kinetic data for Cr(VI) sorption on MDN were well described by pseudo-second order, which indicates the Cr(VI) adsorption was mainly due to chemisorption. The isotherm data show that the Langmuir and Freundlich models better described Cr(VI) ion sorption data. The thermodynamic parameters ΔG°, ΔH°, and ΔS° were estimated, and the results indicate Cr(VI) sorption on MDN was a spontaneous (ΔG° < 0) and exothermic process (ΔH° < 0). The proper Fe3O4 loading into TMD improves the gram susceptibility (Xg) of MDN for magnet separation. The regeneration of nanocomposite material revealed over 80% Cr(VI) removal efficiency after five consecutive adsorption–desorption cycles. The produced MDN was tested for the removal of Cr(VI) from real tannery wastewater. The obtained results suggest the possibility of using this nanocomposite as an effective, efficient adsorbent to remove Cr(VI) laden wastewater.

Physicochemical Characterization of Natural Diatomite from Lampang Province, Thailand as a Solid Catalyst

This paper presents the studies on physical and chemical properties of the natural diatomite originating from Mae Tha District, Lampang the northern of Thailand as solid catalyst. The diatomite was characterized by X-ray diffraction (XRD), X-ray fluorescence (XRF) and nitrogen adsorption-desorption isotherm. The effect of calcination temperature on chemical composition, cyrytalline phase and textural properties of diatomite was also investigated. The XRF results indicated that the diatomite was composed mostly of SiO2, K2O, CaO and MgO. The calcination temperature ranging from 300 to 900 °C had no effect on the crystalline phase of diatiomite. The high surface area and large pore size diameter of diatomite was observed when the calcination temperature was below 900 °C. All the physicochemical results show the existence of SiO2, K2O, CaO and MgO, the high surface area and pore size diameter, indicate that the diatomite could potentially be used to a solid catalyst for biodiesel production.

STRUCTURING OF EFFLUENT PARTICLES BY MEANS OF TREATMENT OF BENTONITE BASE MINERAL CONDITIONERS

The turbidimetric and Z-potentiometric methods were used for the assessment of some properties of diatomite – bentonite based conditioners for dewatering of effluents from the digestate of a biogas plant. These physical conditioners were prepared based on natural porous highly dispersible systems such as bentonite and diatomaceous earth. Three types of modified systems in the forms of CaO were used, which differ from each other in the ratio of the content of bentonite and diatomite. The role of the silica-containing component is to ensure the structuring of these systems. Diatomite was used for this purpose.

Identification of the occurrence of minor elements in the structure of diatomaceous opal using FIB and TEM-EDS

AbstractThe occurrence of minor elements in the structure of biogenic diatomaceous opal-A is an important issue because it is closely related to biogeochemical processes driven by the precipitation, sedimentation, and storage of diatoms, as well as to the properties and applications of diatomite, which is the sedimentary rock composed of diatomaceous opal-A. However, to date, there is no direct microscopic evidence for the existence of minor elements, such as Al, Fe, and Mg, in the structure of diatomaceous opal-A, because such evidence requires observation of the internal structure of frustules to exclude the disturbance of impurity minerals, which is technically challenging using conventional techniques. In this work, transmission electron microscopy (TEM) and scanning electron microscopy (SEM) combined with energy-dispersive X-ray spectroscopy (EDS) mapping analysis were performed on diatomaceous opal-A from three typical diatomite specimens that were pretreated using focused ion beam (FIB) thinning. This technique produces a slice of a diatom frustule for direct TEM observation of the internal structure of the diatomaceous opal-A. The results of this work clearly indicate that minor elements, such as Al, Fe, Ca, and Mg, conclusively exist within the siliceous framework of diatomaceous opal-A. The contents of these minor elements are at atomic ratio levels of 1 (minor element)/10 000 (Si) – 1/100, regardless of the genus of the diatoms. The occurrence of minor elements in the internal structure is likely through biological uptake during biosynthesis by living diatoms. Moreover, surface coatings composed of aluminosilicates on diatom frustules are common, and the contents of elements such as Al and Fe are tens or hundreds of times higher in the coatings than in the internal siliceous structure of diatomaceous opal-A. The discovery of the incorporation of the above-mentioned minor elements in the diatomaceous opal-A structure, both in the internal Si-O framework and on the surface, updates the knowledge about the properties of diatomite.

Preparation of Iron-Aluminum Modified Diatomite and Its Immobilization in Cadmium-Polluted Soil

To improve the in-situ immobilization effect of diatomite on cadmium (Cd)-contaminated soil, diatomite was modified by hydroxyl iron-aluminum (Fe-Al). The soil incubation experiments were carried out to investigate the effect of Fe/Al molar ratio, OH/cation of molar ratio, pillaring agent aging time, (Fe+Al)/diatomite ratio, pillaring temperature, and pillaring product aging time on the immobilization of Cd in soils. The changes in properties of diatomite before and after modification were analyzed by scanning electron microscopy (SEM) and Fourier transform infrared spectroscopy (FTIR). The results showed that:the optimal preparation conditions for modification were:Fe/Al molar ratio=1:8, OH/cation molar ratio 2.0-2.2, pillaring agent aging time=2 d, (Fe+Al)/diatomite ratio=10 mmol·g-1, pillaring temperature=60℃, pillaring product aging time=2 d. The hydroxyl-Fe-Al-modified diatomite significantly reduced the content of exchangeable Cd in soil, and the modification reduced soil exchangeable Cd from 11.83% to 39.52%. The SEM and FTIR analyses of hydroxyl-Fe-Al-modified diatomite revealed increase in the specific surface area of diatomite and the amount of the Si-O-H groups. After modification, the hydroxyl-Fe-Al successfully exchanged into the diatom shell forming available pillars, thus increasing channel spacing and enhancing the microporous surface activity. The modification with hydroxyl-Fe-Al increased the immobilization effect of diatomite on Cd in soil. The modification methods and data from this study will help increase the application of diatomite materials for the immobilization of soil containing heavy metals.

Experiment study on the humidity control performance and indoor environment control of diatom ooze

ABSTRACTAs an important indoor environment parameter, air humidity plays an important role in indoor health, thermal comfort and energy consumption of heating and air-conditioning. In this paper, the experimental study on the humidity control performance and the effect of humidity control in the practical application environment for diatom ooze were carried out. The micro – characterized of research object was carried out by low-temperature nitrogen adsorption-desorption, and the adsorption and desorption properties of diatomite and three kinds were studied, obtaining equilibrium moisture absorption and desorption curves, isothermal desorption and desorption rates, cyclic desorption and desorption properties. Based on the above results, it was concluded that the performance of diatom humidity control of three different construction processes. Then, the room temperature and humidity of three rooms were obtained by testing the indoor environment of diatom ooze room, latex paint room and wallpaper room in different seasons, compering and analyzing the effect of diatom ooze on the indoor thermal and humid environment. Results show that the pore structure characteristics and ambient temperature of diatom ooze have a great influence on its humidity control performance; the diatom ooze is more effective in winter and summer, and the transition season is weaker.

Laboratory Study on Properties of Diatomite and Basalt Fiber Compound Modified Asphalt Mastic

In order to improve the performance of asphalt mastic, some researchers have added diatomite or basalt fiber as a modifier to the asphalt mastic, and the results show that some properties of the asphalt mastic were improved. For the simultaneous addition of diatomite and basalt fiber, two kinds of modifier, compound modified asphalt mastic had not been reported; in this paper, thirteen groups of diatomite and basalt fiber (DBFCMAM) compound modified asphalt mastic with different content were prepared to study the performance. Softening point, cone penetration, viscosity, and DSR tests were conducted, for the high temperature performance evaluation of DBFCMAM, whereas force ductility and BBR tests were used in the low temperature performance study of the DBFCMAM. The results demonstrated that the high temperature performance of DBFCMAM was increased; moreover, the low temperature performance of DBFCMAM improved by diatomite and basalt fiber according to the results of the force ductility test; however, the conclusion of the BBR test data was inconsistent with the force ductility test. In summary, the high temperature and low temperature properties of DBFCMAM had been improved.

Hydrothermal synthesis of tobermorite from diatomite and its adsorption performance for methylene blue

Disposal of dyes wastewater effluents is one of the most important factors in many industries. Methylene blue is the most commonly used dyes in industries and is very difficult to degrade due to its complex structures. Diatomite is one of the excellent adsorbents owing to its unique properties. However, the small powder form of diatomite, which leads to a large amount sludge produced easily, has limited its wide application in environmental engineering. In our study, diatomite was solidified hydrothermally at low temperature (≤ 200°C) on the basis of sustaining the inherent properties of diatomite. The results showed that tobermorite was found to exert a positive effect on its strength and porosity, and also had higher methylene blue adsorption capability compared with diatomite. The thermodynamic parameters indicated that the adsorption of methylene blue with tobermorite formation was an endothermic and spontaneous process.

Utilization of cutting fluids with modified diatomite

The sorption properties of diatomite modified with aluminum sulfate are examined. The adsorption capacity with respect to petroleum products and the possibility of regenerating used material are investigated. Technology for utilization of used cutting fluids using modified diatomite was proposed.

Determination of the properties of various diatomite deposits within Aegean Region of Turkey

Properties of diatomite in general have been outlined, location and reserves of the related deposits in Turkey are given. The results of mineralogical studies, chemical and physical analysis which have been carried out on various samples are tabulated. From the results of these findings possible application areas have been suggested.