Mohamed G. Shahien

Composites of MCM-41 silica with rice husk: hydrothermal synthesis, characterisation and application for perchlorate separation

Abstract Mesoporous MCM-41 silica and rice husk composites were synthesised under hydrothermal conditions using cetyltrimethylammonium bromide (CTAB) as an organic template, aqueous ammonia solution (NH4OH) and rice husk, the latter as a silica source and substrate for the deposition of MCM-41. Both untreated and carbonised rice husks were used for preparing composites at a temperature of 100–120°C for 24–48 h. The as synthesised composites or hybrid materials were characterised by using XRD and SEM and they were found to be useful for the uptake of perchlorate. These composites could be used to separate perchlorate from solutions in column operation without the necessity for their pelletisation because the rice husk substrates are several millimetres in size.

Characterization and Beneficiation of Gold Mining By-products as Source of High-Quality Silica for High Technical Applications; Response Surface Studies and Optimization

This paper aims to evaluate and upgrade the quality of quartz mining by-products through acid leaching process. The quartz samples were collected as gold mine by-products from El Sid- Fawakhir gold mine, Qift-Quseir, Eastern Desert, Egypt and characterized using XRF and polarized transmitted optical microscope. The present magnetic mineral impurities were detected using Frantz Isodynamic Tester. Suitability of acid leaching utilizing oxalic acid as an efficient technique for considerable reduction of the associated impurities was evaluated based on Response Surface methodology and face centered central composite design (CCD). The quartz sample was classified as low-quality quartz with low silica content (99.3%) which can’t match the requirements of wide range of applications. The main detected impurities are muscovite, biotite, sericite, pyrite and iron oxide. The present magnetic impurities represent about 2.72% of the total sample. The leaching process at the optimum conditions of temperature, time and oxalic acid concentration removes ∼

Adsorption behavior of inorganic- and organic-modified kaolinite for Congo red dye from water, kinetic modeling, and equilibrium studies

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Removal of perchlorate by synthetic organosilicas and organoclay: Kinetics and isotherm studies

36% of the iron. This associated with a clear reduction of other magnetic impurities and noticeable enhancing in the silica content to about 99.56%. Magnetic purification followed by oxalic acid leaching for the quartz samples give better results as the iron content was reduced to about 0.001% and the silica content increased to about 99.9% which match the specifications of most of the typical high technical applications.

Perchlorate uptake by organosilicas, organo-clay minerals and composites of rice husk with MCM-48

AbstractRaw kaolinite was used as a precursor for several types of modified kaolinite. The modification processes included modification by sodium hydroxide, sodium phosphate, sodium sulfate, CTAB, and sodium acetate. The structural, morphological, and chemical properties of raw kaolinite and the modified products were evaluated using XRD, SEM, TEM, and FT-IR analyses. The modified products were used as adsorbent materials for acidic Congo red dye from aqueous solutions. The adsorption processes were evaluated as a function of reaction time, initial dye concentration, and adsorbent masses. Phosphate-modified kaolinite achieved the best removal results followed by sulfate-modified kaolinite and kaolinite sample modified by CTAB. Kinetic studies indicated that the adsorption equilibrium was obtained after 360 min for the samples, which were modified by NaOH and CTAB, whereas the modified samples that were treated by phosphate, sulfate and, acetate achieve the equilibrium after 240 min. The adsorption by all the products is of chemical nature occurs through energetically heterogeneous surfaces and fitted well with pseudo-second order kinetic model. The equilibrium studies revealed that the adsorption using kaolinite modified by sodium hydroxide, sodium phosphate, and sodium sulfate occurs in monolayer form and represented well by Langmuir model. The estimated qmax values are 136.98, 149.25, and 135.13 mg/g for the three products in order. The uptake using modified kaolinite by CTAB and sodium acetate shows more fitting with Tamkin and Freundlich isotherm models rather than with Langmuir model. Kaolinite sample was modified by organic and inorganic salts to enhance its adsorption properties. Modified kaolinite samples exhibit changes in the structural and morphological features. The modified samples showed high adsorption capacity than raw kaolinite.HighlightsKaolinite was modified by several inorganic and organic salts.Effect of modification and the structural and morphological features was investigated.The adsorption behavior of the modified products for Congo red dye was addressed.The change in the adsorption behavior was studied through kinetic and isotherm studies.