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Montmorillonite (Mt) is a ubiquitous swelling clay mineral and major component of soft rocks, sediments, and soils with an inherent capability to sorb metal cations. This unique feature renders Mt important for the enrichment and mobilization of environmentally important metal cations, retardation of heavy metals and radionuclide ions, the evolution of clay mineral itself, soils and sediments, and other geological processes. Understanding the interfacial interactions of Mt with metal cations at the molecular level is of fundamental importance in all these processes, but still remains elusive, due to the chemical and structural complexity of Mt surfaces and the diverse chemistries of metal cations. In this Review, we aim to provide the reader with a comprehensive overview of the adsorption modes of metal cations on basal and edge surfaces of Mt, local chemical environments of the cation binding sites, the driving forces for metal sorption, and factors influencing the dynamics of cation uptake onto Mt surfaces. Various surface complexation models [i.e., nonelectrostatic model (NEM), constant capacitance model (CCM), diffuse layer model (DLM), and triple-layer model (TLM)], advanced spectroscopic techniques (i.e., NEM, CCM, DLM, and TLM), and atomistic simulation methods (i.e., MD, DFT, and FPMD) have been used in conjunction with macroscopic adsorption experiments to gain detailed insights into the interfacial interactions of metal cations on Mt. Mt adsorbs metal cations via three independent pathways: (1) cation exchange; (2) surface complexation; and (3) nucleation and surface precipitation. The principal driving force for cation exchange is electrostatic interaction, while chemical bonding governs the two other mechanisms that depend on the basal and edge surface properties of Mt. The siloxane cavities on the tetrahedral basal plane exhibit the strongest adsorption sites for cation exchange and are greatly affected by the the degree of Al3+/Si4+ tetrahedral substitutions. At the amphoteric edge surfaces bearing hydroxyl groups, metal cations could form mono/multidentate surface complexes on Mt [010] and [110] edges. Ionic strength, pH, the presence of competing cations, temperature, and layer charge have been shown to affect the adsorption mechanisms and quantity of adsorbed cations. The updated information on the interfacial interactions of metal cations with Mt basal and edge surfaces presented in this review provides an improved understanding of the enrichment of metals, formation of metal ores, and natural biogeochemical cycles, as well as may promote technological and engineering applications of this important clay mineral in environmental remediation, geological repository, petroleum exploration and extraction, and extraterrestrial research. [ABSTRACT FROM AUTHOR]

Hectorite is trioctahedral clay mineral that possess unique characteristics of surface reactivity and adsorption, cation exchange capacity and easy delamination in water into individual nano layers. Thus, hectorite can be a promising nanocarrier with biocompatibility, high payload and controlled release of drug. Therefore, in the present study, hectorite has been used for the delivery of two hydrophobic molecules; chemotherapeutic drug DDP [Cis-diamminedichloroplatinum (II)] and natural photosensitizer hypocrellin A (HA) for combinatorial therapy. The experimental results has been fitted to l-type (Langmuir) adsorption isotherm. The adsorption isotherm showed higher affinity of DDP toward the hectorite with almost comparable CEC value of initial silicate layer of hectorite. The loading of drug into nanoclay was further characterize by using SEM, FTIR, XRD, DLS and TGA, which suggest the presence of DDP molecules in between the interparticle and photosensitizer on the surface of nanoclay. After, adsorption the characteristic properties such as photostability and photobleaching of HA has been significantly improved. The photobleaching efficiencies of free HA and Ht-DDP-HA was 72.8 and 55.2%, respectively, and the 1O2 generation quantum yield was 0.86. The in vitro release rate is twofold higher in the presence of laser light and ultrasonic waves. The drug release profile was found to be best fitted by Higuchi square root model, which implicate that release of drug from matrix as square root of time-dependent process and diffusion controlled. The in vitro efficacy of Ht-DDP-HA showed the potent anti-cancerous ability due to combinatorial effect by 2.01 and 1.69 fold times higher efficacy than free DDP and HA, respectively. Flow cytometry data shows the synergistic effect of combined therapy by showing maximum apoptotic and necrotic percentage. [ABSTRACT FROM AUTHOR]

Hydroxyapatite-based bone adhesives have strong bond strength and good adsorbability, however, they also have some disadvantages such as poor mechanical strength, fast curing reaction rate and high exothermic strength, which limit their wide application in bone tissue engineering. In this study, hydroxyapatite-based bone adhesive was prepared by solid-liquid blended crosslinking followed by heating. The prepared bone adhesive has two components: (i) is a mineral composed of calcined dolomite and montmorillonite and (ii) is organic composite composed of citric acid and gelatine. The optimum solid-liquid ratio (0.50 g/mL) of the bone adhesive was determined based on the bond strength of nano-hydroxyapatite/calcined dolomite/citric acid/gelatin system. The best physicochemical properties of the bond adhesive were obtained when the composition of the bone adhesive was as follows: 20 wt% citric acid, 17 wt% gelatin and 12 wt% calcined dolomite. The acquired curing time of bone adhesive was 10.5 min, comparable to the necessity for surgery (5–30 min); moreover, the adhesive strength and compressive strength of the bone adhesive were 12.18 MPa and 9.36 MPa respectively, obtained after being placed in the air for 168 h; besides, the porosity (16.8 %) was found quite suitable. Upon this, a certain amount of montmorillonite was added with calcined dolomite to prepare bone adhesive, resulting reduction in the adhesive strength (10.19 MPa) and compressive strength (7.109 MPa), but improved the biocompatibility of the system. The absorbency of the hydroxyapatite-based bone adhesives in deionized water and Tris-HCl buffer solution was found to be 27.19 % and 18.68 %, respectively, ascertaining that such bone adhesives are efficient in absorbing certain blood and tissue fluid in the biological body and promoting the absorption of required nutrients in the process of bone repair. In addition, the formation of osteoid apatite in the In-vitro study, proved by FTIR and EDAX analysis, rationalized for improving the osteogenic activity. Furthermore, after 56 days of immersion in the Tris-HCl buffer solution, the weight loss rate of the bone adhesive reached up to 42.73 %, indicating that the bone adhesive had satisfactory degradation performance. Finally, in the cytotoxicity test, the survival rate of mouse precranial bone cells was found to be greater than 80 % after adding the prepared bone adhesive, demonstrating its sufficient biocompatibility. • Hydroxyapatite-based bone adhesive made of calcined dolomite - citric acid/gelatin crosslinked composite (sol/liq-0.5 g/mL) • The incorporation of small montmorillonite improves the biodegradability of bone adhesive in DI water and Tris-HCl buffer solution. • In in-vitro study, formation of bone-like apatite layer and Ca/P ratio (1.65) confirmed good osteogenic activity of the prepared bone adhesives • In vitro biodegradable study showed the weight loss rate of bone adhesives after soaking in Tris-HCl buffer solution was quite appreciable. • In biocompatibility study by CCK-8 kit showed that the survival rate of MC3T3-E1 cells was more than 80 %. [ABSTRACT FROM AUTHOR]

Catalyst deactivation by carbon deposition (coking) remains a major obstacle in many important industrial processes, such as catalytic gas-phase oxydehydration of glycerol. Understanding the chemical nature and development of coke species during the time-on-stream (TOS) of the catalytic solids is therefore crucial for mitigating the extent of coking and in the design of regeneration process of the coked catalysts. In this study, multiple analytical techniques, including SEM, XRD, FTIR, Raman, GC-MS, XPS, and 13C solid-state MAS NMR were employed to gain insights into the coking behavior of acid-activated montmorillonite (HMMT) supported Mo-V-O catalysts with modulated metal ratios, along with soluble and insoluble coke compositions and their evolution over time. Insoluble coke was comprised of polycyclic aromatic compounds with 5 or more fused-benzene rings containing different types of oxygen-bonded groups, such as −OCH 3 , −COOH, −CHO, and −OH. The major chemical constituents of soluble coke were mononuclear aromatic derivatives (i.e., xylenes, 2,4-di-tert-butylphenol, and 1-hydroxycyclohexyl phenyl ketone) and paraffinic hydrocarbons with 12–18 carbon atoms. The latter coke species is thought to be formed via the deoxygenation of linear oligoglycerols. The insights presented in this study may aid in understanding the carbon deposition process during gas-phase oxydehydration of glycerol for improved design of supported Mo-V-O catalyst materials with high coking resistance. • Quantitative metal composition–coking relationships of Mo-V/HMMT catalysts for gas-phase glycerol oxydehydration. • Structural and compositional studies of soluble and insoluble cokes with time-on-stream. • Linear oligoglycerols are precursors to long-chain paraffins in soluble coke. • Aromatic cluster size in the insoluble coke is comprised of 5-7 fused ring structures. • Polycyclic aromatic compounds in the insoluble coke contain various carbon-oxygen groups. [ABSTRACT FROM AUTHOR]

Dolomite can form as a major mineral component of marlstones and limestones and is an important sink for magnesium in the marine environment. Dolomite is widely distributed in time and space and is considered an intrinsic ingredient in the evolution of the Earth's crust. The crystal structure and genesis of dolomite record fundamental geochemical and environmental processes of significance in the Earth's element cycle process, carbon storage, and paleoenvironments, with relevance to the exploration for minerals and fossil fuels, management and maintenance of the environment, and the use of carbonate minerals by industry. The review brings together new advances and insights from recent studies on dolomite structure, geological genesis, laboratory synthesis, and applications. In the mantle, dolomite may adapt to increasing pressure by structural rearrangement and undergoes crystal phase transitions. At present, four high-pressure polymorphs have been identified. The phase transitions allow dolomite to survive subduction into the mantle, possibly into the transition zone, but stability is not fully predictable and is influenced by factors that include initial degree of cation ordering in dolomite and Fe and Mn substitution for Mg in the dolomite crystal lattice. The presence of Fe and Mn is influenced by the environment of dolomite formation. The key factors controlling formation of dolomite, including transition or recrystallization from precursor high-Mg calcite or proto-dolomite, at low temperatures remain ambiguous. Sulfate-reducing bacteria, methanogens, and aerobic bacteria, the exudates or relevant extracellular polymeric substances, fluctuating environmental conditions, and the negatively charged surfaces of clay minerals all can mediate high-Mg calcite/proto-dolomite formation at low temperature. As for secondary dolomite, formed by Mg2+ replacement of Ca2+ in carbonate minerals, several models have been proposed and widely adopted, including: near-surface dolomitization, burial dolomitization, and hydrothermal dolomitization. The formation of massive deposits of dolomite in marine sediments probably involves multiple dolomitization processes. Yet the "dolomite problem" remains enigmatic. Mg isotope analysis, an emerging technology, offers a new approach to further investigate the genesis of dolomite. In the laboratory, synthesis of dolomite at low temperature has yet to be achieved. Fundamental scientific research on dolomite is expected to inform the sustainable use of dolomite resources. Traditional uses of dolomite typically in construction materials, refractory, and flux continue. Now, the use of dolomite and its calcined products is being expanded into environmental protection, soil improvement, thermochemical energy storage and biomedical materials. [Display omitted] • New insights into structure of dolomite at high T and under ultrahigh P • Examining new findings and interpretations on the genesis of dolomite • Implications of dolomite synthesis for understanding dolomite genesis • Potential for efficient and cleaner uses of dolomite in various industries • Opportunity to link basic research on dolomite with improved industrial applications [ABSTRACT FROM AUTHOR]

Glycerol can be converted to allyl alcohol via deoxydehydration using molybdenum-vanadium, rhenium and iron based catalysts. However, the dehydration causes severe coking at strong acid sites on the surface of catalyst. Molybdenum-vanadium oxide supported on calcium oxide-intercalated montmorillonite (MoV-CaMMT) was prepared by oxalate anion intercalation followed by impregnation. MoV-CaMMT displayed the best catalytic performance of 86.5% glycerol conversion and good stability in 5 h. Correlating the results of XRD, XPS and TG analysis, it can be demonstrated that the addition of CaO in the catalyst preparation is conducive to the crystallization and dispersion of vanadium oxides, and reduces the acid strength, while the presence of a few vanadium dioxide and the stable conversion of V4+ and V5+ are the reasons for enhancing coking-resistance of MoV-CaMMT. Additionally, NH 3 -TPD analysis proved the coexistence of weak and strong acid sites in MoVO x , which are conducive to the formation of acetol. [Display omitted] • Coking resistance catalyst was prepared by CaO intercalated method and impregnation. • Basic sites promotes the dehydration or deoxydehydration of glycerol to alcohols. • CaO in the catalyst preparation is conducive to the crystallization and dispersion of vanadium oxide. • CaO improves the coking resistance of Mo/V catalyst. • MoOx created new active sites in the weak and strong acid sites of the catalyst. [ABSTRACT FROM AUTHOR]

• The contribution of Mo, V and W oxides supported on Mt to coking was unveiled. • Quantitative analyses revealed that coke was predominantly formed in Mo-Mt and W-Mt catalysts. • Composition of Mo5+ and Mo6+ prior to the reaction hindered full oxidation to Mo6+. • Incorporation of V oxide in mixed Mo-V-Mt and W-V-Mt helped reduce coke. Mo, V and W oxides supported on montmorillonite (Mt) have shown good activity in catalytic glycerol oxidehydration. However, these catalysts deactivate rapidly due to coking. Understanding the role of Mo, V and W oxides in coke formation is essential to overcome the coking problem. Herein, individual and combination of Mo, V and W oxides supported on Mt were investigated to reveal the contribution of Mo, V and W oxides to coke formation. Among single metal oxide catalysts, Mo-Mt and W-Mt suffered more from coke formation than V-Mt. A mixture of Mo5+ and Mo6+ in the Mo-Mt catalyst hindered full oxidation during the oxidehydration, thus promoting coking. The oxidation of V4+ to V5+ helped diminish coke in mixed Mo-V-Mt and W-V-Mt. This work is expected to provide new information for designing high-performance Mo, V and W oxide catalysts with superior coke resistance. [Display omitted] [ABSTRACT FROM AUTHOR]

Layered double hydroxides (LDH) is an attractive solid base catalyst for transesterification of glycerol with dimethyl carbonate. A major challenge in enhancing the catalytic performance of LDH for this process is to overcome the internal diffusion limitations and increase the availability of basic sites. Herein we present ultrasonic and hydrothermal post-synthesis strategies in uniformly coating of LDH on mesochannels of mesoporous silica. The effects of precursors, preparation methods and morphologies on preparing LDH/SBA-15 nano-composites were investigated. Rice-shaped LDH/SBA-15 nano-composite catalysts exhibited better performance with a 78% glycerol conversion and 90% selectivity of glycerol carbonate than the catalysts with morphologies of short-rods, and long-rods. The results revealed that hierarchical nanostairs at the edge and well-ordered mesochannels stacked along the long axis direction reduced internal diffusion path lengths and increased availability of basic sites. This approach in morphology controlling synthesis of LDH based nano-composite catalysts shed light on the uniformly coating of other diatomic and triatomic metal LDH within mesochannels of mesoporous silica to fabricate novel nano-composite catalysts. [Display omitted] • Mesoporous silica with tunable morphologies were synthesized via a facile method. • Layered double hydroxide were uniformly coated on as-synthesized mesoporous silica. • The novel structured nanocomposites with tunable morphologies were prepared. • Rice-shaped nanocomposites showed promising activity for transesterification of glycerol. • Hierarchical nanostructure of rice-shaped catalyst enabled the basic sites accessible. [ABSTRACT FROM AUTHOR]

• Layered double hydroxides crystallite were in situ fabricated on inner wall of capillary. • Thickness and morphology of LDH film on inner-wall of capillary was finely controlled. • Au NPs were immobilized on layered double hydroxides film. • Au/LDH film showed good catalytic activity in carbonylation of glycerol with urea. • The productivity of glycerol carbonate reached 3.78 g•h−1•g−1 on Au/LDH catalytic film. Microreactor is capable of intensifying catalytic reaction processes. The fabricating of catalytic film inside microchannels for catalytic reaction remains a challenge. Here we report a facile method for in situ fabrication of layered double hydroxide (LDH) film immobilizing gold nanoparticles in capillary microreactor. Through adjusting the reaction condition of in situ hydrothermal crystallization process and flow deposition process inside microchannel, film thickness, film morphology and Au loading of Au/LDH coating can be finely controlled. Such Au/LDH film inside microchannel exhibited good performance in catalytic carbonylation of glycerol with urea. The yield of glycerol carbonate reached 31.9% at flow rate of 10 µl/min, residence time of 6.62 min and reaction temperature of 413 K under atmospheric pressure. The maximum productivity of 3.78 g∙h−1⋅g−1 was obtained at flow rate of 40 µl/min and residence time of 1.65 min under same reaction temperature and pressure. Continuously running the microreactor for 30 h proved the high stability of this catalytic film inside microchannels. This approach could be extended to fabricate other diatomic and triatomic metal LDH films immobilizing metal nanoparticles inside microchannels for heterogeneous catalysis. [Display omitted] [ABSTRACT FROM AUTHOR]

Excessive phosphorus (P) in water bodies causes eutrophication, which threatens the health of the environment. In the present study, a novel rice husk biochar–calcite composite (BRH-C) was prepared. The pyrolysis conditions and phosphate removal processes were optimized using central composite design. The optimized pyrolysis conditions for the preparation of BRH-C were as follows: a pyrolysis temperature of 700 °C, pyrolysis time of 2.3 h, and rice husk–calcite (RH-C) ratio of 4.2:1 (w/w). The maximum removal and adsorption capacities of optimized BRH-C were 87.3% and 1.76 mg/g, respectively, at low phosphate concentrations. The pyrolysis temperature had positive linear and quadratic effects on the phosphate removal, whereas the pyrolysis time had a negative quadratic effect. The RH-C ratio had a positive quadratic effect. The maximum phosphate removal (54.2%) and adsorption capacity (10.72 mg/g) were achieved at phosphate concentration of 95 mg/L, 0.24 g of BRH-C, pH 5.4, and contact time of 11.75 h. Phosphate removal by BRH-C was maximum at lower concentrations (10–25 mg/L), whereas phosphate removal by calcite was maximum at higher concentrations (75–125 mg/L). Calcite altered the yield and textural properties of BRH-C and imparted characteristics calcite functional groups and minerals to BRH-C. Freundlich adsorption isotherm and second-order kinetic model suggested heterogeneous and multilayer chemisorption of phosphate onto both BRH-C and calcite. Presence of NaCl, NaNO 3 , KCl, and NaHCO 3 in solution reduced the amount of phosphate removal by BRH-C. Promising results for phosphate removal were achieved only for up to two cycles of BRH-C regeneration. BRH-C is a cost-effective and ecofriendly adsorbent prepared from rice husk and calcite, with no need for sophisticated instruments or chemicals. It was developed as an optimized adsorbent for the efficient removal of phosphate at low concentrations. [Display omitted] • An optimized rice husk biochar–calcite composite (BRH-C) for phosphate removal was prepared. • Optimized pyrolysis conditions were 700 °C, 2.3 h, and rice husk–calcite ratio of 4.2:1. • The calcite affected the textural and functional properties of BRH-C. • BRH and calcite synergistically removed phosphate better than calcite at low concentrations. • Phosphate removal occurred via pore filling, electrostatic interaction, and precipitation. [ABSTRACT FROM AUTHOR]

Mycotoxins, bacteria, heavy metals and other toxic contaminants in feed have adverse effects on the health of animal. The decontamination of feed to reduce the content of harmful substances before feeding is inevitably needed. Clay minerals are a promising effective feed additive due to their cost-effectiveness and nearly without side effects. Montmorillonite (Mt) has high adsorption for mycotoxins, bacteria, heavy metals in animal feed and body. This review made a comprehensive and critical review of how Mt as an ingredient in animal feed functions. It covers the recent understanding of removing mycotoxins, bacteria and heavy metals onto Mt and the relevant influences of Mt on animal intestinal health, growth performance and product quality. Mt as feed additive can remove mycotoxins and bacteria in feed and gastrointestinal tract of the animal by surface adsorption, electrostatic adsorption and intermolecular force. In addition, Mt can adsorb heavy metals effectively in feed by the exchangeability of interlayer cations and by the swellability due to cation hydration. Modification of Mt by metal ions, metal oxides, and organic cations can improve the adsorption efficiency of mycotoxins, bacteria, heavy metals in vitro and in vivo. Mt and its modified products as feed additive can remarkably enhance the intestinal health and growth performance of livestock, aquatic and poultry. Utilization of Mt as feed additive can effectively improve the quality of milk, egg and meat. Unlabelled Image • Montmorillonite for removing mycotoxins, bacteria and heavy metals from animal feed. • Insights into mechanisms of removing mycotoxins, bacteria and heavy metals. • Effect of montmorillonite in vivo on intestinal health and growth performance. • Montmorillonite-added feed improves the quality of milk, egg and meat. • Existing problems and future work on montmorillonite as feed additive. [ABSTRACT FROM AUTHOR]

A high acidity extent, as a result of the activation process of bleaching earth, is a major drawback in the production of bleached-palm oil. The high acidity of bleaching earth generates problems for the process equipment as well as the product, which are economically disadvantageous. Addressing this pivotal issue in the manufacture, a more environmentally friendly and efficient activation process of bleaching earth using thermal activation is evaluated. Two types of bentonite-bleaching earth collected from two different locations were used throughout this study; that is from Pacitan and Ponorogo, coded as GS and SS, respectively. The effect of the proportion ratio of GS to SS (1:4, 2:3, 3:2, and 4:1), and variations in thermal activation temperature (150, 250, and 350 °C), to the bleaching performance were investigated. Thermal-activation at 150 °C can efficiently activate the bleaching earth without significant cation exchange capacity decrement. The pilot-scale bleaching process demonstrated that the prepared bleaching earth with GS to SS ratio of 3:2 (coded as M-03) could remove 96% of β-carotene from crude palm oil; which is the best among the investigated samples and also higher than the commercial bleaching earth (only 85–90% β-carotene removal). The feasibility of the production of M-03 at the industrial scale was analyzed by scaling up on the pilot scale. M-03 was able to be produced on an industrial scale by using a fluidized-bed dryer; this result has been adapted by a bleaching earth producing factory located in Madiun, Indonesia. Economic analysis on the factory demonstrated a payout time of 2 years and 10 months and the breakeven point of 21.5%. This paper shows the success of bringing the experimental results in laboratory-scale into the industrial-scale production of bleaching earth. Image 1 [ABSTRACT FROM AUTHOR]