جستجوی مقالات مرتبط با کلیدواژه « bentonite » در نشریات گروه « مواد و متالورژی »

Geopolymers can be mentioned as a new class of green cement adhesives. Geopolymers have recently been introduced as a greener alternative to conventional Portland cement (OPC) with the potential to minimize the negative environmental consequences of OPC such as carbon footprint and energy consumption. In this experimental study, the effects of different alkaline activating solutions on compressive, tensile, and indirect flexural strength, water absorption, and acid resistance of bentonite-based geopolymer concrete (GPC) were investigated. Also in this study, a new type of alkaline activator was used. In this study, GPC samples made from bentonite were produced and baked at 90 ° C. The results showed that the addition of NaOH to the mixture after 3 minutes of mixing KOH and Na2SiO3 with dry components (1/3 of the total mixing time) increases the compressive, tensile, and flexural strength and we also see that with this new method, water absorption capacity and the amount of weight loss of geopolymer concrete samples are reduced in acidic conditions.

In recent decades, Iran has been facing severe water deficiency. In all countries, industrial plants are the most water-consuming sectors; thus, industrial wastewater treatment is always a essential subject. Nitro-Toluene derivatives are extensively used in industries, especially the military industry, which itself has an abundant share in industrial wastewater contamination. These compounds are extremely dangerous for living beings and can have irreparable effects, so eradication of them in industrial wastewater is necessary. Photocatalytic processes are one of the particular approaches in industrial wastewater treatment from the advanced oxidation processes subdivision. One of the prominent and most widely used photocatalysts in this process is Titanium Dioxide (TiO2) . This research aims at the investigations for the modification of  TiO2/Bentonite (TB) catalysts for attaining more economical saving and degradation stabilization conditions. To achieve this goal, the Bentonite and TiO2 photocatalyst was synthesized by a co-precipitation procedure, and its catalytic activity on Para Nitro-Toluene (PNT) degradation was examined. The designed TB photocatalyst is made of 5, 10 and 20 % of TB. A suspension reactor and the spectrophotometry was applied for specifying the extent of the degradation. Characterization of modified catalyst was conducted by scanning electron microscopy (SEM), X-ray diffraction (XRD), Fourier transform infrared (FT-IR) spectroscopy and energy dispersive X-ray (EDX). The results highlight that with increasing TiO2 percent, degradation rate augmented, and the highest degradation was attained for TB 20% at 59%. However, Under the same conditions, for pure TiO2, the degradation rate is 64%, but with more TiO2 consumption and time. Finally, in order to further confirm the extent of the degradation, chemical oxygen demand (COD) test was performed on the TA20 sample. The results showed that about 53% of PNT has been converted to minerals.

Photocatalyst nanocomposites of ZnO/bentonite clay are synthesized by Solid-state ion exchange method. Ion exchange intercalation process of clays is used to incorporate the catalyst into the basal space of the layered structure of clays. The purpose of this study is to find a new method, which is focused on simplifying and saving time to prepare ZnO-bentonite composite with photocatalyst property. The synthesis of ZnO-doped bentonite nanocomposite is accomplished by placing bentonite in a melting bath of ZnSO4 for 10, 20, 40, 60 and 90 min. The nanocomposites are characterized by morphological (SEM), optical (UV/vis reflection) and analytical (EDX) techniques. According to SEM results, after ion exchanging, the parent structure of bentonite remains and only the distance between flakes increased significantly. EDX analysis clearly suggest the success of ion exchange of the expense of Ca2+, Na+ and Mg2+ cations with Zn2+. The calculated band gap for the composites were 3.14 eV (10 min), 2.64 eV (20 min) and 2.54 eV at longer times, respectively. All the prepared composites showed acceptable degradation performances. The greatest photocatalytic activity is detected in ZnO/bentonite composite solid-state ion exchanges which lasts 60 and 90 min. Leaching test results showed that the concentrations of Zn are less than 4 mg/l between 0 and 6 h. These results indicated that the photocatalytic property of composites would last longer

Binders are of prime importance in the agglomeration of iron ore concentrates. In this research, strength and density of briquette produced from the magnetite concentrate of Gol-E-Gohar were investigated using different binders at various applied pressures. The results showed that peridor was the most effective binder relative to bentonite and lime. For all types of binders, the increase in binder content increased the strength and decreased the density of briquette. The increase in the applied pressure during the preparation of briquette also increased strength and density, but this occurred at different rates when different types of binders were used.

A natural bentonite obtained from Khorasan, Iran, was submitted to acid activation with sulphuric acid. Sample aliquots (5gr) were leached with 100 ml H2SO4 solutions of various concentrations (2–7N) at 80±2 oC for 2 hours. X–ray diffraction, chemical analysis, infrared spectroscopy and specific surface area measurements were performed in order to evaluate important structural modifications occurring as a result of acid attack. Octahedral sheet was affected by acid activation resulting into the dissolution of cations (Mg2+, Fe2+, Al3+) and consequent decomposition of montmorillonite structure. Bentonite samples were then tested in order to verify their capacity to bleach colza–soybean oil, and their performances were compared to that of a commercial bleaching clay. The bleaching ability of the natural clay was poor when compared with that of the industrial adsorbent. Acid activation of the bentonite sample with 7N sulphuric acid yielded an adsorbent material which was highly efficient in the bleaching of the oil functioned better than the commercial clay product under the same conditions.