Evaluation of Aluminum and Magnesium Absorption Following the Oral Administration of an Antacid Suspension Containing Magaldrate in Healthy Women Under Fed Conditions.

INTRODUCTION: Antacids are commonly used during pregnancy, and they are approved for the relief of symptoms of gastroesophageal reflux disease (GERD) during pregnancy. However, there are no reports of the quantification of the absorption of aluminum and magnesium in the antacid magaldrate in women. The aim of this study was to quantify the rate and magnitude of absorption of aluminum and magnesium in magaldrate. METHODS: An open-label, controlled, randomized, one-treatment study with a two-group design was conducted in healthy women in a fed state. The volunteers had a standard breakfast, and 30 min later, they were given a single-medication sachet containing 500 mg of sodium alginate, 267 mg of sodium bicarbonate, 800 mg of magaldrate, and 120 mg of simethicone (group A, n = 8) or no medication (group B, n = 2). Blood samples were obtained 36 h before and up to 12 h after antacid administration. The method used for quantification was inductively coupled plasma-mass spectrometry. RESULTS: There was no absorption of aluminum in any of the blood samples from the healthy volunteers who received the drug or in those from the control group. Magnesium was detected at normal concentrations. CONCLUSION: These findings suggest that the use of this antacid is safe and without risk in healthy women, including pregnant women. CLINICAL TRIAL REGISTRATION: Clinicaltrials.gov registration: NCT06367452.

Efficacy, safety, and acceptability of polyethylene glycol 3350 without electrolytes vs magnesium hydroxide in functional constipation in children from six months to eighteen years of age: A controlled clinical trial.

INTRODUCTION AND AIMS: There are few studies that compare polyethylene glycol (PEG) 3350 and magnesium hydroxide (MH), as long-term treatment of functional constipation (FC) in children, and they do not include infants as young as 6 months of age. Our aim was to determine the efficacy, safety, and acceptability of PEG vs MH in FC, in the long term, in pediatric patients. METHODS: An open-label, parallel, controlled clinical trial was conducted on patients from 6 months to 18 years of age, diagnosed with FC, that were randomly assigned to receive PEG 3350 or MH for 12 months. Success was defined as: ≥ 3 bowel movements/week, with no fecal incontinence, fecal impaction, abdominal pain, or the need for another laxative. We compared adverse events and acceptability, measured as rejected doses of the laxative during the study, in each group and subgroup. RESULTS: Eighty-three patients with FC were included. There were no differences in success between groups (40/41 PEG vs 40/42 MH, p = 0.616). There were no differences in acceptability between groups, but a statistically significant higher number of patients rejected MH in the subgroups > 4 to 12 years and > 12 to 18 years of age (P = .037 and P = .020, respectively). There were no differences regarding adverse events between the two groups and no severe clinical or biochemical adverse events were registered. CONCLUSIONS: The two laxatives were equally effective and safe for treating FC in children from 0.5 to 18 years of age. Acceptance was better for PEG 3350 than for MH in patients above 4 years of age. MH can be considered first-line treatment for FC in children under 4 years of age.

Novel bio-fertilizer based on nitrogen-fixing bacterium immobilized in a hydrotalcite/alginate composite material.

The bacterium Streptomyces sp. is a common genus of the actinomycetes class found in soils and rhizospheres. This bacterium can produce substances with bio-stimulant capacity through the fixation of nitrogen from the air. In this work, the Streptomyces sp. bacterium was immobilized on a ZnMgAl-hydrotalcite clay and embedded in calcium alginate beads to generate a novel bio-composite that functions as a bacterial reservoir and as a controlled release material for bacteria to be used as a bio-fertilizer.The results showed that the novel bacterium-hydrotalcite/alginate bio-composite was very efficient as a bio-fertilizer showing a plant length of 64 mm in only 14 days of growing, which corresponds to an increase of ca. 760% in the lettuce plant growth in comparison with the materials without bacteria. In short, the present results demonstrate that the hydrotalcite and alginate served as an excellent container to keep the bacteria alive, providing nutrients to them and controlling their delivery.

Encapsulation and dispersion of Lactobacillus acidophilus in a chocolate coating as a strategy for maintaining cell viability in cereal bars.

Flour from Pereskia aculeata leaf and green banana were used as ingredients in the formulation of a cereal bar with added Lactobacillus acidophilus LA02-ID-1688. Encapsulation in a calcium-alginate hydrogel reinforced with magnesium hydroxide was used as a strategy to protect the probiotic cells under gastrointestinal conditions and to prolong shelf-life. The results are relevant especially for maintaining cell viability during shelf-life; a challenge for the food industry in relation to dry probiotic products. Encapsulation promoted the protection of probiotic cells in simulated gastric and intestinal conditions, allowing the maintenance of high viable cell counts (> 10 log CFU, colony forming unit). Encapsulation also contributed to cellular protection under extreme temperature conditions, with reductions of cell viability of < 1 logarithmic cycle when the capsules were subjected to 55ºC/10 min. Even at 75ºC/10 min, encapsulation protected the probiotic cells 3-times greater than the free-cells. The food bar proved to be rich in dietary fiber (19 g 100 g-1), lipids (12.63 g 100 g-1) and showed an appreciable protein content (5.44 g 100 g-1). A high viable probiotic cell count on storage over 120 days (12.54 log CFU) was observed, maintaining a probiotic survival rate > 90% and viability levels sufficient to promote health benefits.

Detoxification of sugarcane bagasse hydrolysate with different adsorbents to improve the fermentative process.

Second generation ethanol has the prospect of becoming an important bioenergy alternative. The development of this technology is associated with the lignocellulosic materials' use, with emphasis on agricultural and agroindustrial by-products from which fermentable sugar can be produced. The acid hydrolysis depolymerizes the hemicellulose releasing mainly xylose. Subsequently, the cellulose can be converted into glucose by enzymatic hydrolysis. However, the acid hydrolysis produces toxic compounds, such as furan derivatives, phenolics, and organic acids, which are harmful to fermentative microorganisms. This study investigated different acid concentrations in the sulfuric acid hydrolysis of sugarcane bagasse (1- 5% m/v) and the use of adsorbents with the prerogative to improve the acid hydrolysate (AH) quality for microbial ethanolic fermentation. Cell growth and fermentative yield of Saccharomyces cerevisiae (PE-2) and Scheffersomyces stipitis (NRRL Y-7124) were evaluated. AH was used as a source of pentoses (17.7 g L-1) and molasses (ME) sugarcane as source of hexoses (47 g L-1). The following adsorbents were used: activated charcoal, clay, hydrotalcite and active and inactive cells of PE-2 and NRRL Y-7124, at concentrations ranging (1 - 8% m/v). Results of cell growth and chemical characterization allowed to select the most effective adsorbents with emphasis for active cells that removed 66% furfural and 51% 5-(hydroxymethyl) furfural) (5-HMF) and alcoholic productivity of 23.5 g L-1 in AH and ME substrates, in the presence of mixed culture. These results indicate the application of active yeast cells in the detoxification of acid hydrolysates of the sugarcane bagasse previously to the fermentation.

Comparison of the Efficacy of Oral versus Intravascular Magnesium in the Prevention of Hypomagnesemia and Arrhythmia after CABG.

OBJECTIVE: Cardiac arrhythmias are a common challenge following open-heart surgeries. Hypomagnesemia is believed to be correlated with this condition. Prophylactic intravenous magnesium supplementation has been practiced for a long time in patients undergoing CABG. This study was designed in an attempt to compare the efficacy of oral versus intravenous routes in the prevention of hypomagnesemia and arrhythmia. METHODS: In this interventional clinical study, 82 patients were randomly assigned to 2 groups. All patients were evaluated for baseline serum magnesium level and arrhythmias. One group received 1,600 mg of oral magnesium hydroxide through nasogastric (NG) tube prior to surgery, while the other group received 2 g of magnesium sulfate during the induction of anesthesia. The serum magnesium level was monitored for 48 hours after the operation. The difference in preoperative hypomagnesemia was non-significant (Sig: 0.576). RESULTS: During the operation, the serum magnesium level peaked around 4 mg/dL, and no hypomagnesemia was detected in any patient. Although the curve of oral group declined parallel and below that of intravenous (IV) group, no significant differences were detected during postoperative monitoring. In addition, a prevalence of arrhythmia of 13.9% and 6.5% was noticed in IV and oral groups, respectively (OR: 0.428). CONCLUSION: Providing 1,600 mg of oral magnesium supplement to patients is as effective as 2,000 mg of magnesium sulfate IV in preventing hypomagnesemia and arrhythmia after CABG. Thus, the authors introduce this treatment regimen as a promising and cost-effective method.

Comparison of the efficacy of oral versus intravascular magnesium in the prevention of hypomagnesemia and arrhythmia after cabg

Abstract Objective: Cardiac arrhythmias are a common challenge following open-heart surgeries. Hypomagnesemia is believed to be correlated with this condition. Prophylactic intravenous magnesium supplementation has been practiced for a long time in patients undergoing CABG. This study was designed in an attempt to compare the efficacy of oral versus intravenous routes in the prevention of hypomagnesemia and arrhythmia. Methods: In this interventional clinical study, 82 patients were randomly assigned to 2 groups. All patients were evaluated for baseline serum magnesium level and arrhythmias. One group received 1,600 mg of oral magnesium hydroxide through nasogastric (NG) tube prior to surgery, while the other group received 2 g of magnesium sulfate during the induction of anesthesia. The serum magnesium level was monitored for 48 hours after the operation. The difference in preoperative hypomagnesemia was non-significant (Sig: 0.576). Results: During the operation, the serum magnesium level peaked around 4 mg/dL, and no hypomagnesemia was detected in any patient. Although the curve of oral group declined parallel and below that of intravenous (IV) group, no significant differences were detected during postoperative monitoring. In addition, a prevalence of arrhythmia of 13.9% and 6.5% was noticed in IV and oral groups, respectively (OR: 0.428). Conclusion: Providing 1,600 mg of oral magnesium supplement to patients is as effective as 2,000 mg of magnesium sulfate IV in preventing hypomagnesemia and arrhythmia after CABG. Thus, the authors introduce this treatment regimen as a promising and cost-effective method.

Magnesium hydroxide-based dentifrice as an anti-erosive agent in an in situ intrinsic erosion model.

PURPOSE: To evaluate in situ a magnesium hydroxide-[Mg(OH)2] based dentifrice on enamel erosion. METHODS: Human dental enamel slabs were selected by surface microhardness and randomly assigned to one out of the following three groups (n=18): non-fluoride (control), NaF (1,450 ppm F), and Mg(OH)2 dentifrices. 18 volunteers were enrolled in a randomized, crossover and double-blind study, with three phases in 5 days. They wore acrylic palatal appliances containing two human enamel slabs, which were treated with one of the three dentifrices. During each experimental phase, the specimens were subjected to erosion by immersion in 0.01 M HCl for 60 seconds, 4x/day, followed by a 1-minute treatment with the correspondent slurry (saliva/dentifrice). Enamel changes were determined by the percentage of surface hardness loss (%SHL) and mechanical profilometry analysis. Data were analyzed by ANOVA, followed by Tukey's test (P< 0.05). RESULTS: The means (SD) for %SHL and surface wear (µm) were, respectively, as follows: control [50.67(17.48), 2.70(1.24) ], NaF [45.45(15.44), 1.95(0.70) ] and Mg(OH)2 [53.94(19.48), 1.95(0.67) ]. There was no statistically significant difference among the treated and control groups for %SHL (P= 0.349); however, for wear rates, a statistically significant difference was found between the groups treated with NaF and Mg(OH)2 and the control group (P= 0.04). CLINICAL SIGNIFICANCE: Dentifrices containing magnesium hydroxide or sodium fluoride might be an important strategy to minimize the effects of erosive challenges.

Sorption-desorption of selenite and selenate on Mg-Al layered double hydroxide in competition with nitrate, sulfate and phosphate.

Selenate and selenite are considered emerging contaminants and pose a risk to living organisms. Since selenium anion species are at low concentration in aquatic environments, materials for its retention are required to enable monitoring. Herein, hydrotalcite was calcined and characterised to investigate sorption and desorption of selenite and selenate in competition with nitrate, sulfate and phosphate. Sorption experiments were carried out in batch system and desorption by sequential dilution. Selenite and selenate concentration remaining after N desorption steps was determined by mass balance. The isotherms were adjusted to the dual-mode Langmuir-Freundlich model (R2 > 0.99). Maximum sorption capacity ranged from 494 to 563 meq kg-1 for selenite and from 609 to 659 meq kg-1 for selenate. Sulfate and phosphate ions showed greater competitive effect on the sorption of selenate and selenite, respectively. Low mobilization factors and high sorption efficiency (MF<3%; SE ≈ 100%) indicated that calcined hydrotalcite has the wanted characteristics for retention of relevant selenium anion species in aqueous media.

Enhancement of struvite pellets crystallization in a full-scale plant using an industrial grade magnesium product.

A full-scale struvite crystallization system was operated for the treatment of the centrate obtained from the sludge anaerobic digester in a municipal wastewater treatment plant. Additionally, the feasibility of an industrial grade Mg(OH)2 as a cheap magnesium and alkali source was also investigated. The struvite crystallization plant was operated for two different periods: period I, in which an influent with low phosphate concentration (34.0 mg P·L-1) was fed to the crystallization plant; and period II, in which an influent with higher phosphate concentration (68.0 mg P·L-1) was used. A high efficiency of phosphorus recovery by struvite crystallization was obtained, even when the effluent treated had a high level of alkalinity. Phosphorus recovery percentage was around 77%, with a phosphate concentration in the effluent between 10.0 and 30.0 mg P·L-1. The experiments gained struvite pellets of 0.5-5.0 mm size. Moreover, the consumption of Mg(OH)2 was estimated at 1.5 mol Mg added·mol P recovered-1. Thus, industrial grade Mg(OH)2 can be an economical alternative as magnesium and alkali sources for struvite crystallization at industrial scale.

Evaluación económica de tecnologías para el tratamiento del estreñimiento en Colombia / Economic evaluation of technologies for the treatment of constipation in Colombia

INTRODUCCIÓN: El estreñimiento crónico funcional se define como la presencia de movimientos intestinales infrecuentes asociados a la coexistencia de síntomas como materia fecal dura y en bultos, esfuerzo defecador, sensación de evacuación incompleta y distensión abdomina. El estreñimiento crónico se clasifica en dos categorías: idiopático (primario) y secundario. El estreñimiento primario es un trastorno basado en síntomas que resultan de una disfunción de la regulación del movimiento de las heces junto con falta de coordinación del aparato neuromuscular anorrectal y disfunción del eje-cerebro-intestino. y farmacéuticas, siendo las últimas las más comunes. TRATAMIENTO: El tratamiento depende de si el problema es secundario a medicamentos, condiciones metabólicas, obstrucción luminal colónica o a una disfunción neuromuscular del colon; las aproximaciones generales incluyen retiro de los medicamentos predisponentes o terapias alternativas, educación sobre el estreñimiento, incremento de la ingesta de líquidos y fibra y ritualización del hábito intestinal. Existen agentes de múltiples clases para el tratamiento del estreñimiento: formadores de masa, laxantes estimulantes y osmóticos, laxantes emolientes, secretagogos y agentes serotoninérgicos. La guía de práctica clínica para el diagnóstico y tratamiento del estreñimiento crónico funcional en población. adulta, elaborada en Colombia, recomienda el polietilenglicol, lactulosa, bisacodilo, secretagogos (lubiprostone, linaclotide) y prucalopride. POBLACIÓN: Población : tres posibles poblaciones: Pacientes adultos y niños con estreñimiento crónico funcional. Pacientes adultos con estreñimiento inducido por el uso de opioides. Pacientes con estreñimiento de origen idiopático. INTERVENCIÓN: -Fosfato de sódio,-Lactulosa, -Picosulfato de sódio, -Picosulfato de sodio combinaciones, -Polietilenglicol (PEG) sin electrolitos, -Bisacodilo, -Secretagogos (lubiprostone o linaclotide), -Prucaloprida, -Hidróxido de magnesio sin alumínio. PERSPECTIVA: Se empleará la perspectiva del sistema de salud colombiano, es decir, serán incluidos los costos médicos directos asociados al uso de las tecnologías en salud que son objeto de la evaluación y los beneficios en salud percibidos directamente por los pacientes. DESENLACES Y VALORACIÓN: De acuerdo con las recomendaciones del manual metodológico del IETS, en esta evaluación se propone emplear los AVAC (años de vida ajustados por calidad) como medida de desenlace. La información de las ponderaciones de utilidad se obtendrá de la literatura. En caso que no sea factible emplear AVAC, se emplearán otros desenlaces, que serán justificados en el informe. COSTOS: Se tendrán en cuenta todos los costos asociados a las tecnologías evaluadas y a los desenlaces en salud incluidos en el modelo de decisión planteado. Se utilizarán como fuentes de información bases de datos institucionales de validez nacional, consulta directa y otras fuentes, tal como lo estipula el manual metodológico del IETS. MODELO DE DECISIONES: Se diseñará un modelo de decisión analítico a partir de la revisión de literatura económica existente, los resultados de la evaluación de efectividad y seguridad elaborada por el IETS y la consulta a expertos clínicos y otros actores del sistema de salud relacionados con las tecnologías e indicación de interés. PRESENTACIÓN DE RESULTADOS: En el caso de tecnologías no dominadas, se calcularán las razones incrementales de costo-utilidad o costo-efectividad. Para efectos de interpretación, y de acuerdo con las recomendaciones del manual metodológico del IETS, se realizarán comparaciones entre la razón incremental y 1 PIB per cápita y 3 PIB per cápita en Colombia de acuerdo con las estimaciones actuales del Banco de la República. ANÁLISIS DE SENSIBILIDAD: Se evaluará la incertidumbre en las estimaciones mediante análisis de sensibilidad univariados y probabilísticos. Los resultados de las simulaciones de Montecarlo se presentarán mediante un diagrama de dispersión en el plano de costoefectividad y los resultados del análisis de sensibilidad probabilístico mediante curvas de aceptabilidad.

Hydrotalcite-TiO2 magnetic iron oxide intercalated with the anionic surfactant dodecylsulfate in the photocatalytic degradation of methylene blue dye.

The new magnetic photocatalysts HT/TiO2/Fe and HT-DS/TiO2/Fe, modified with the anionic surfactant sodium dodecylsulfate (DS) were successfully synthesized in this work. Titanium dioxide (anatase) followed by iron oxide were deposited on the hydrotalcite support. Several catalyst samples were prepared with different amounts of titanium and iron. The photocatalysts were characterized by infrared and Raman spectroscopy, X-ray diffraction, scanning electron microscopy. Photocatalytic performance was analyzed by UV-visible radiation (filter cutoff, λ > 300 nm) of an aqueous solution (24 mg/L) of methylene blue (MB). The most efficient catalyst was obtained at an iron oxide:TiO2 molar ratio of 2:3. This catalyst showed high photocatalytic activity, removing 96% of the color and 61% of total organic carbon from the MB solution after 120 min. It was easily removed from solution after use because of its magnetic properties. The reuse of the HT-DS/TiO2/Fe23 catalyst was viable and the catalyst was structurally stable for at least four consecutive photocatalytic cycles.

Removal of boron from oilfield wastewater via adsorption with synthetic layered double hydroxides.

Hydrotalcite is a layered double hydroxide (LDH) consisting of brucite-like sheets of metal ions (Mg-Al). In this work, hydrotalcites were synthesized, and boron removal from oilfield wastewater was evaluated. LDHs were synthesized using the co-precipitation method. The calcined products (CLDHs) were obtained by heating at 500°C and characterized using X-ray diffraction, X-ray fluorescence, thermogravimetric analysis and the specific surface area (BET). The affinity of LDHs for borate ions was evaluated for calcined and uncalcined LDHs as a function of contact time, initial pH of the oilfield wastewater (pH ∼ 9) and the LDH surface area. The tests were conducted at room temperature (approximately 25ºC). The results indicated that 10 min were needed to reach a state of equilibrium during boron removal for calcined LDHs due to the high surface area (202.3 m(2) g(-1)) regardless of the initial pH of the oilfield wastewater, which resulted from the high buffering capacity of the LDHs. The adsorption capacity increased as the adsorbents levels increased for the range studied. After treatment of the oilfield wastewater containing 30 mg L(-1) of boron with Mg-Al-CO3-LDHs, the final concentration of boron was within the discharge limit set by current Brazilian environmental legislation, which is 5 mg L(-1). Pseudo-first-order and pseudo-second-order kinetic models were tested, and the latter was found to fit the experimental data better. Isotherms for boron adsorption by CLDHs were well described using the Langmuir and Freundlich equations.

Preparation of layered double hydroxide/chlorophyll a hybrid nano-antennae: a key step.

In the first step to obtain an efficient nano-antenna in a bottom-up approach, new hybrid materials were synthesized using a set of layered double hydroxides (LDHs) with basic properties and pure chlorophyll a (Chl a). The stability of the adsorbed monolayer of Chl a was shown to be dependent on the nature and the ratio of the different metal ions present in the LDHs tested. The hybrid materials turned out to be adequate for stabilizing Chl a on Mg/Al LDHs for more than a month under ambient conditions while a limited catalytic decomposition was observed for the Ni/Al LDHs leading to the formation of pheophytin. These changes were followed by namely XRD, DR-UV-vis and fluorescence spectroscopies of the hybrid antennae and of the solutions obtained from their lixiviation with acetone or diethylether. On Mg/Al hydrotalcites the stability of the adsorbed Chl a was equivalent for values of the metal atom ratio ranging from 2 to 4. The latter hybrids should constitute a good basis to form efficient nanoscale light harvesting units following intercalation of selected dyes. This work describes an efficient preparation of Chl a that allows scale-up as well as the obtention of a stable Chl a monolayer on the surface of various LDHs.

Chronic functional constipation in children: adherence and factors associated with drug treatment.

OBJECTIVE: The aim of the present study was to evaluate the treatment adherence of children with chronic functional constipation. METHODS: The present study is a prospective and longitudinal study realized at a pediatric gastroenterology clinic of a Brazilian University Hospital, between August 2009 and October 2011. Rome III criteria and the Bristol Stool Scale were used to define constipation and to characterize feces, respectively. Drug treatment was prescribed for patients according to the protocols previously standardized in the clinic. Specific questionnaires, containing questions related to 1 dependent variable and independent variables were completed in the first and sixth months of the treatment. Independent variables related to the patients, their caregivers, the disease itself, and the therapeutic plan were analyzed and compared with the dependent variable (adherence to the treatment). Adherence was considered when the patient returned with >75% of the prescribed medicine containers empty. RESULTS: Fifty children participated in both the first and sixth months of treatment. The mean age of the sample was 77.6 ± 43.8 months and the mean age of the onset of symptoms was 18.8 ± 27.9 months. The adherence rate was 38% in the first month and 30% in the sixth month. Patients who were treated with polyethylene glycol had greater adherence than patients who were prescribed other laxatives, with statistical significance in the second moment of the study (P = 0.19 and P = 0.04, respectively). CONCLUSIONS: The study showed low adherence rates to drug treatment of constipation in children. It is necessary to seek new strategies to increase treatment adherence, while avoiding complications and reducing costs.

A ternary catalytic system for the room temperature Suzuki-Miyaura reaction in water.

The formation of Pd(0) in the absence of any classical reducing agent in a medium containing Mg(2+)/Al(3+) layered double hydroxide (LDH) and N,N-dimethylformamide was evidenced. XRD analysis showed the presence of crystalline phases of palladium in the Pd/LDH composite. Suzuki-Miyaura reactions in aqueous medium were carried out at room temperature, and good yields were obtained with bromoarenes and iodoarenes using the ternary system LDH-Pd-CD (cyclodextrin) as catalyst.

Nutraceutically inspired pectin-Mg(OH)2 nanocomposites for bioactive packaging applications.

This paper reports on the development of bioactive edible films based on pectin as a dietary matrix and magnesium hydroxide (Mg(OH)2) nanoplates as a reinforcing filler. Nanocomposites of high-methoxyl (HM) and low-methoxyl (LM) pectins were prepared using the casting method at concentrations of Mg(OH)2 ranging from 0.5 to 5 wt %. Atomic force microscopy and FTIR spectroscopy were employed to characterize the nanocomposite structure. The tensile properties and thermal stability of the nanocomposites were also examined to ascertain the effect of Mg(OH)2 inclusion and degree of methoxylation. The results provided evidence that the Mg(OH)2 nanoplates were uniformly dispersed and interacted strongly with the film matrix. The mechanical and thermal properties were significantly improved in the nanocomposite films compared to the control. Mg(OH)2 nanoplates were more effective in improving properties of LM pectin. Preliminary migration studies using arugula leaves confirmed that pectin-Mg(OH)2 nanocomposites can release magnesium hydroxide by contact, demonstrating their potential for magnesium supplementation in bioactive packaging.

Brucite nanoplates reinforced starch bionanocomposites.

In this paper the mechanical reinforcement of nano-sized brucite, Mg(OH)(2) in a series of bionanocomposite films based on starch was investigated. Brucite nanoplates with an aspect ratio of 9.25 were synthesized by wet precipitation and incorporated into starch matrices at different concentrations (0-7.5 wt.%). Scanning electron microscopy revealed a high degree of nanoplate dispersion within the starch bionanocomposites and good interfacial adhesion between the filler and matrix. The brucite nanoplates formed agglomerates at high concentrations. The reinforcement factor values of the bionanocomposites were higher than the values predicted from the Halphin-Tsai model, which was attributed mainly to the high surface area of the nanoplates. Brucite (1 wt.%) nearly doubled the elastic modulus of starch films. Thermogravimetric analyses indicated some interaction between starch and the brucite that modified their decomposition profiles. Mechanical tests of glycerol plasticized bionanocomposites showed that the reinforcing efficiency of brucite remained high even at 10 wt.% and 20 wt.% of plasticizer.

Complexation at the edges of hydrotalcite: the cases of arsenate and chromate.

Sorption of CrO(4)(2-) and HAsO(4)(2-) by hydrotalcite, in its chloride form, was studied as a function of anion concentration. In both cases, the shape of the isotherms is langmuirian. The maximum uptake of CrO(4)(2-) equals the ion-exchange capacity of the solid, whereas sorption of HAsO(4)(2-) saturates at a higher value. Chloride ions inhibit the uptake of both anions, the amount of sorbed CrO(4)(2-) declining rapidly to zero. The uptake of HAsO(4)(2-), however, attains a constant value at high chloride concentrations. The excess of arsenate uptake follows, at constant pH, a langmuirian dependence with equilibrium concentration and decreases with increasing pH, depicting a marked change in slope at pH≈pQ(a3). CrO(4)(2-) and HAsO(4)(2-) have notable, albeit different, effects on the electrophoretic behavior of hydrotalcite; the positive particle charge is screened almost completely by CrO(4)(2-), whereas sorption of HAsO(4)(2-) produces charge reversal. These results reflect the formation of inner-sphere arsenate surface complexes at the edges of hydrotalcite particles. The underlying rationale is discussed in terms of the crystal structure of hydrotalcite surfaces.

Synthesis of new pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane-8,11-dione (PCU) cyanosilylated derivatives using sulphated zirconia and hydrotalcite as catalysts in microwave-assisted reactions under solvent free conditions.

A comparison was made of the effectiveness of the functionalization reactions of pentacyclo[5.4.0.0(2,6).0(3,10).0(5,9)]undecane-8,11-dione (PCU) using sulphated zirconia in protection-deprotection reactions and Mg/Al hydrotalcite in a cyanosilylation reaction, under classical thermal conditions and imposing microwave radiation; improved yields and reaction times were considered.