The Influence of Silica Nanoparticles Geometry on the Interfacial Interactions of Organic Molecules: A Simulation Perspective

The role of nanoparticle shape in the interaction and adsorption of organic molecules on the particle surface is an unexplored area. On the other hand, such knowledge is not only...

Influence of Organic Matter/Bacteria on the Formation and Transformation of Sulfate Green Rust

The corrosion processes of carbon steel immersed in natural seawater are influenced by microorganisms due to important biological activity. An analysis of the corrosion product layers formed on carbon steel coupons in natural or artificial seawater revealed that sulfate green rust GR(SO42−) was favored in natural environments. In this paper, the role of organic matter/bacteria on the formation and transformation of this compound are addressed. GR(SO42−) was precipitated from Fe(II) and Fe(III) salts in the presence of various marine bacterial species not involved in the redox cycle of Fe or S. Abiotic experiments were performed for comparison, first without any organic species and then with sodium acetate added as a small organic ion. The obtained aqueous suspensions were aged at room temperature for 1 week. The number of bacteria (CFU/mL) was followed over time and the solid phases were characterized by XRD. Whatever the fate of the bacteria (no activity, or activity and growth), the formation of GR(SO42−) was favored and its transformation to magnetite completely inhibited. This effect is attributed to the adsorption of organic molecules on the lateral sides of the GR(SO42−) crystals. A similar effect, though less important, was observed with acetate.

Aspects of dietary fibre in health and diseases

Dietary fibre is the name collectively given to the indigestible carbohydrates present in foods. These carbohydrates consist of cellulose, gum, pectin and mucilage. Enzymes of gastro-intestinal tracts in humans do not digest these fibres. Plants are the only source of dietary fibre. It is found in grains, vegetables and fruits. Dietary fibre helps to keep the digestive system healthy, and it is vital in reducing the risk of diseases such as coronary heart disease, diabetes, diverticulosis, haemorrhoids and intestinal cancer. Undigested fibres enter the large intestine where bacteria ferments them. Carbon dioxide, nitrogen, hydrogen and short-chain fatty acids are the by-products of the fermentation. Soluble fibre and resistant starch also serve as prebiotic and supports the necessary probiotic for digestive health. In grapes, peas, beans and barley, much of the soluble fibre is extracted. When dissolved in the water, a gel-like substance is formed. Soluble fibre helps to support the growth of friendly bacteria needed to maintain a healthy intestinal system. They also help in slowing down the time taken by the food to pass through the stomach into the small intestine, which helps to slow down the absorption of glucose and controls the blood sugar levels and helps in managing diabetes mellitus and keeps you feeling fuller for a longer time. The diets with high fibre intakes are known to have beneficial health effects as they have water holding capacity, helps in adsorption of organic molecules and facilitates its excretion, hypoglycemic effects and hypercholesterolemic effect. The inclusion of fibre rich food in weight-reducing diets is found to helpful since it provides a feeling of fullness without consumption of excess calories. The present review discusses the definition, nutritional properties of dietary fibre and therapeutic functions of dietary fibres in health and diseases.

Quantitative methods for quantification of montmorillonite content in bentonite clays

This article is devoted to the comparison of various methods for the quantitative determination of montmorillonite content in bentonite clays based on the adsorption of organic molecules and cations. The studies were conducted on samples of natural bentonite clays of the main Russian industrial deposits and the CIS: 10th Khutor (Republic of Khakassia), Zyryanskoe (Kurgan region), Dash-Salakhlinskoe (Republic of Azerbaijan), Dinozavrovoe (Republic of Kazakhstan). All samples selected for the study are characterized by a high content of montmorillonite (more than 70 %). As reference values ​​for the contents of montmorillonite, we used the data of X-ray diffraction analysis according to the Rietveld method. As the tested methods, the most common approaches were used both in the research and industrial sectors of Russia, based on the adsorption of a mixture of rhodamine 6zh and chrysoidine dyes (GOST 28177-89), adsorption of methylene blue dye and adsorption of copper (II) complex with triethylenetetramine (Cu-trien), as well as thermal characteristics after saturation with organic compounds. The best convergence of the montmorillonite content values ​​was shown by modified techniques based on the adsorption of methylene blue dye and the adsorption of the Cu-trien complex. Other methods are characterized by a large measurement error. A common problem with these methods is overs equivalent adsorption on highly charged alkaline bentonites and reduced adsorption on alkaline earth bentonites, as well as the presence of impurity minerals and amorphous phases capable of sorption in the composition of bentonite. The research results can be used to compare the results of the content of montmorillonite, cited by various authors in scientific publications and used in production.

Tuning molecular adsorption in SBA-15-type periodic mesoporous organosilicas by systematic variation of their surface polarity

Adsorption of organic molecules from solution into mesoporous organosilicas is modulated by the relative polarity of the surface.