Removal of antimony from model solutions, mine effluent, and textile industry wastewater with Mg-rich mineral adsorbents
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Abstract Naturally occurring layered double hydroxide mineral, brucite (BRU), was compared with hydromagnesite (HYD) and a commercial Mg-rich mineral adsorbent (trade name AQM PalPower M10) to remove antimony (Sb) from synthetic and real wastewaters. The BRU and HYD samples were calcined prior to the experiments. The adsorbents were characterized using X-ray diffraction, X-ray fluorescence, and Fourier transform infrared spectroscopy. Batch adsorption experiments were performed to evaluate the effect of initial pH, Sb concentration, adsorbent dosage, and contact time on Sb removal from synthetic wastewater, mine effluent, and textile industry wastewater. Several isotherm models were applied to describe the experimental results. The Sips model provided the best correlation for the BRU and M10. As for the HYD, three models (Langmuir, Sips, and Redlich–Peterson) fit well to the experimental results. The results showed that the adsorption process in all cases followed the pseudo-second-order kinetics. Overall, the most efficient adsorbent was the BRU, which demonstrated slightly higher experimental maximum adsorption capacity (27.6 mg g -1 ) than the HYD (27.0 mg g -1 ) or M10 (21.3 mg g -1 ) in the batch experiments. Furthermore, the BRU demonstrated also an efficient performance in the continuous removal of Sb from mine effluent in the column mode. Regeneration of adsorbents was found to be more effective under acidic conditions than under alkaline conditions.Keywords:
Brucite
Langmuir adsorption model
The titanic acid ester was used to modify the brucite by dry method modification,and the optimal modifying condition was found according to the test of activation index.The flame retardance and mechanical property of UPR/brucite composite were examed,the test result indicated that the tensile strength and mechanical property of UPR moulding system could be improved with the brucite added in,when the brucite was modified by titanic acid ester,the flame retarding ability increased and the viscosity of system decreased.The modified brucite could improve the tensile strength.Brucite could affect the impact property of composite material,but it would change better when the modified brucite was taken.
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Anion-exchange membrane fuel cells (AEMFCs) have attracted much attention since they can potentially overcome the stumbling blocks of proton-exchange membrane fuel cells. There are many research approaches to improve the performance of AEMFCs, and one of them is to seek new ion conductors that effectively transport hydroxide ions at the ambient temperature. Ion conductors with not only high ion conductivities but also high robustness are strongly required to realize the high-efficiency and long-life performance of AEMFCs. Among such ion conductors, we have focused on layered double hydroxides (LDHs). The basic layer structure of LDHs is based on that of brucite [Mg(OH) 2 ]. In the brucite lattice, magnesium ions are surrounded octahedrally with hydroxide ions, and these octahedral units form infinite plane of the 2D layers. LDHs are derived by the substitution of a fraction of divalent cations in brucite by trivalent cations, which lead to positive charges in hydroxide layers. These charges are balanced by intercalation of anions and water between the positively charged layers. The possibility of varying the kinds and relative proportions of the di- and trivalent cations as well as the interlayer anions gives rise to the large variety of LDHs with a general formula [M 2+ 1−x M 3+ x (OH) 2 ] x+ [A n− ] x/n ·yH 2 O, where M 2+ and M 3+ are di- and trivalent metal cations respectively, and A n− is an anion. This flexibility in composition of LDHs has induced an increase in interest for many applications, such as catalyst supports, ion-exchange and adsorption, drug-delivery system, etc. In addition, some research groups including our group recently reported that LDHs operated as an OH − conductor, which could be applied for alkaline fuel cells, metal-air secondary batteries, and alkaline secondary batteries. In this study, we focus on the nature of ion conductivities in LDHs. To understand the mechanism of ion conductivities in LDHs in detailed, we synthesized Mg-Al and Mg-Ga LDHs with different relative proportions of di- and trivalent metal cations, and evaluated the influence of the proportion of trivalent cation on their ion conductivities by electrochemical measurements. We chose Mg-Al and Mg-Ga LDHs since they are widely used in LDH studies. We shed light on the structural relationship, which could guide the design of improved or novel hydroxide-conductive materials. Using the co-precipitated method, we successfully synthesized Mg-Al-CO 3 and Mg-Ga-CO 3 LDHs with various proportions of trivalent cations. In the results of X-ray diffraction, as the Mg/Al ratio decreased from 4 to 2, the 003 diffraction peak positively shifted, which indicates that layer height between metal hydroxide layers were diminished. This decrease in the layer height was due to an increase in electrostatic attraction between positive and negative layers. In contrast, resulted LDHs were characterized in similar BET surface areas and mean diameter in spite of changing the proportion of trivalent cations. Both series of LDHs did not displayed a linear increase in ion conductivities as a function of the proportion of trivalent cations, but a sharp raise appeared only for Mg 2+ /Al 3+ = 2 and Mg 2+ /Ga 3+ = 3. Based on the results of electron-diffraction analysis, Mg-Al and Mg-Ga LDHs, showing the highest ion conductivities had the ordered honeycomb cation arrangement within some parts of (0001) hydroxide layers. Other LDHs had complete random cation distribution. The ordered honeycomb structure was a cation distribution that can elude direct contact of M 3+ −M 3+ and diminish the distance of the nearest trivalent cations; “neither near nor far” for individual interlayer anions. These things for the ordered cation arrangements not only demonstrate a helpful strategy for improving ion conductivities of LDHs, but also present new insights into structural relationship between immobile cationic charge centers and mobile interlayer anions.
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Layered double hydroxides (LDHs), also known as hydrotalcite-like compounds, are a large group of natural and synthetic clay materials with high anion exchange capacity (Goh et al., 2008; Zhang et al., 2008). As shown in Figure 6.1, LDHs are layered materials consisting of positively charged metal hydroxide (brucite-like) sheets with octahedra sharing the edges and the interlayer anions. Their chemical composition can be generally expressed as [MImx2+Mx3+(OH)2] [Anm]x/n m yH20, where M2+ and M3+ are divalent and trivalent cations, and Anm an anion in the interlamellar space to balance the positive charge of the brucite-like layer with associated water molecules (Cavani et al., 1991 ). Moreover, due to the relatively weak inter!ayer bonding, anions such as Clm and NO3m,intercalated in the LDHs, are readily exchanged with various organic and inorganic anions. Because of the anion exchange property, LDHs become a promising reservoir for diverse inorganic, organic, and biomolecular anions, as well as anionic polymers and drugs...
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The microstructure of fibrous iron-bearing brucite (nemalite, (Mg,Fe)(OH)2) has been investigated using high-resolution SEM and TEM to reveal the origin of its morphology. The fiber consists of aggregates of flat, lath-like brucite single crystals elongated parallel to <10-10>. Chrysotile tubes, which are also parallel to the fiber, frequently exist, mainly at the grain boundaries of brucite and surrounded by brucite crystals. It is suggested that this unexpected morphology of brucite was formed by crystal growth along the preexisting chrysotile tube surfaces. However, the interface between brucite and chrysotile is not coherent and the arrays of hydroxyl on the surfaces of two minerals are rotated by 30°C to each other. Such orientation relationship is often reported in aggregates of sheet silicates. Brucite crystals frequently contain 180° rotational twins on (0001).
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Zinc Layered hydroxide (ZLH) is a layered material easily synthesized with a structure identical to brucite-like material. Due to the exchangeable anions in the interlayer compensating for the positive charge of a brucite-type layer, ZLH provides a wide application in many fields. This review focuses on the properties and method of synthesis of ZLH by giving an overview of intercalated guest anion in the interlayer of ZLH. The further discussion involved the application of intercalated guest anion in zinc layered hydroxide layer and its properties as a sensitizer, controlled release biomedical, and agriculture to provide the scientific community for research and development by giving current findings. This brief review also presents the success of anion intercalation for controlled release along with the kinetic model involved, which increases the bioavailability and effectiveness of the nanocomposite on its target. It shows the development of research on ZLH nanocomposites toward the sustainability of human life and the environment. This study implies that it is a source of knowledge for researchers about zinc-layered hydroxide materials involving synthesis methods and their application to produce more beneficial nanomaterials.
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The mineralogy of the brucite in Dongqin brucite mine was studied by using electronic microscope and X-ray powder diffraction,and the behavior mineral property of the brucite was determined.It is concluded that the brucite of Xiuyan Dongqin mine belongs to turquoise fiber aggregation,its contents has very few impurity,its grade is high.and it is worthwhile to development further.
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Abstract Iowa highway concretes containing reactive dolomite, (CaMg) 2 CO 3 , aggregate, composed of fine-grained, microporous dolomite, sometimes have service lives of less than 10 years. This premature deterioration may, in part, be caused by expansive forces created by newly formed minerals such as brucite, Mg (OH) 2 , in the cement paste as a result of dedolomitization of reactive dolomite coarse aggregate. Although calcite is the most abundant secondary mineral in cements of poorly-performing concretes, the present study found no evidence that it was expansionary. Brucite is common but less abundant than calcite and occurred chiefly in and near the margins of reactive dolomite in both the aggregate and cement paste of poorly-performing concretes. Most brucite occurs in partially dedolomitized rims around dolomite coarse aggregates. This type of brucite is widely disseminated through the rims, consists of extremely small (<1 m) microcrystalline masses, and was produced by direct precipitation from pore solutions. Smaller amounts of brucite occur in the cement paste. This type is relatively coarse-grained (10 mu m-20 mu m) and most was formed primarily by crystal surface mediated (topochemical) reactions between magnesium-rich pore solutions and portlandite, Ca(OH) 2 . Numerous microcracks are present in cement paste but are not spatially associated with brucite locations. There is no direct evidence for cracking caused by brucite but this is not conclusive evidence against brucite-induced expansion. Brucite is widely disseminated so that expansion at innumerable micro-locations may cause general concrete expansion which should be relieved by cracking at weaker locations in the concretes.
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