Key Engineering Materials Vol. 800

Abstract: In this study, the dependence of corrosion inhibition and microbial effects of four N-hydroxymethylated amino acids, on their molecular and electronic structure is analyzed using density functional theory calculations. Quantum chemical parameters such as highest occupied molecular orbital energy (E_HOMO), lowest unoccupied molecular orbital energy (E_LUMO), energy gap (ΔE) were calculated at the B3LYP/6-311G++(d,p) basis set. Although no simple relationship between the inhibition performance and the calculated data could be discerned, the comparison of inactivation rate constants with energetic parameters suggested that microbial effects of the compounds can be explained in terms of their side chain disparities.

Abstract: An alternative daily cover (ADC) is a recommended part of the modern waste landfill. Developed by ADC, involving clay minerals available in Latvia as well as wood fibers; 2 appropriate composites are selected. The coating's effectiveness has been estimated for odour in the environment, and the coating has been tested in field conditions. The obtained coating shows the ability to maintain a physical condition more than a month without changing its consistency. Compared with commercially available daily cover, which is many times higher in price, the developed coating exhibits the same odour characteristics. It is recommended to continue testing and assess the ability to absorb harmful elements by using this coating.

Abstract: Ecological harm and human health risks caused by environmental pollution with active pharmaceutical ingredients (API) nowadays is recognised as issue of growing concern. Widespread presence of human and veterinary API in aquatic environment clearly indicates persistence and low removal efficiency of these compounds at conventional pharmaceutical and municipal wastewater treatment plants (WWTP). Bioaugmentation of activated sludge systems with specialized microorganisms could be a powerful and environmentally friendly tool to enhance the removal efficiency of recalcitrant API. Selection of inoculum strains, that have appropriate enzymatic pathways to metabolise complex molecules of API, belonging to different therapeutic classes, is of great importance. This study evaluated the potential of pure cultures of 10 bacteria, 10 yeasts and 3 filamentous fungi previously isolated from activated sludge of pharmaceutical WWTP to degrade less investigated API – Oxytocin, Zopiclone and Meldonium dihydrate as sole carbon source and in cometabolic manner with presence of skim milk powder as additional nutrient source. Bacteria Sphingobacterium thalpophilum and filamentous fungi Fusarium solani and Fusarium udum showed very high treatment efficiency of all tested API in laboratory-scale bioaugmentation tests and were recognized as culture with high metabolic potential to be used in bioaugmentation for removal of pharmaceutical micropollutants.

Abstract: Microwave-assisted hydrothermal synthesis of TiO₂ nanofibers under various temperature and pressure conditions were done in this research. High quality TiO₂ nanofiber coatings where obtained when temperature was in range 240 – 245 °C and pressure was 27.3 – 29.1 bar. Obtained TiO₂ nanofiber coatings are with a specific surface area of ​​151.5 to 158.9 m²· g^-1 before calcination. Comparing with nanopowder photocatalysts nanofiber coatings photocatalysts can be much easier removed from solution after the photocatalysis process. Such coatings with relative large specific surface area are with higher potential application in industry.

Abstract: Recycling of paper materials or other type of cellulose fibres is important regarding saving nature resources and environmental protection. Cellulose dissolution and regenerating from various materials is one of recycling possibilities. Cellulose dissolution by NaOH/urea system has a great potential due to the use of harmless reagents, and at the same time is challenging due to the forming of gel-like substances, when cellulose has degree of polymerization more than 1000. It was found that microcrystalline cellulose and cotton cellulose were dissolved in NaOH/urea, but tissue paper, filter paper and waste paper were not dissolved completely. Additives of Kraft pulp and pulp waste dissolved and regenerated from NaOH/urea and cupriethylendiamine (CuETD) in amount 0-30% from paper composition increased mechanical properties of paper sheet. CuETD additive was more effective than NaOH/urea additive, however latter has potential for further research as environmentally friendlier.

Abstract: This study examines the elimination potential of bacterial biomass (Streptomyces rimosus) against lead (II). The biomass was used in a raw state and treated with NaOH. The adsorption was influenced by pH, temperature and contact time. Treated biomass eliminates the largest amount of lead (II) compared to raw biomass. The Langmuir isotherm is the most appropriate to describe our results with maximum capacity of 47.63 mg/g for lead at 45°C. These results suggest that microbial species as bacterial biomass can be used successfully in the treatment of wastewater contaminated by pollutants such as heavy metals.

Abstract: The objective of this study was the synthesis of various activated carbons from grape marc issued from oenological by-product as a biosorbent. The biosolid was then applied to remove an industrial dye (red bemacid ETL) in aqueous solution. Activation of the synthesized charcoal was carried out using a solution of zinc chloride induced by two physical methods (microwaves and heating at 300°C). The obtained materials are characterized by FTIR and SEM methods. Results from batch adsorption tests have shown that pH solution, initial dye concentration and contact time affect the adsorption mechanism. Removal of the industrial dye revealed second order kinetics, exothermic adsorption and isothermal adsorption of BET type.

Abstract: The efficiency of bacterial biomass as an adsorbent for the removal of Chromium in a fixed column was the subject of this study. The effect of different parameters such as initial Cr (VI) concentrations (25, 50, and 100mg/L), flow rate (0.5, 0.75, and 1 mL/min), and bed depth (8, 16, and 24 cm) on Cr (VI) biosorption were investigated. The breakthrough data obtained for Cr (VI) removal was more adequately described by the Clark and Yan model with high correlation coefficients (R² = 0,996). According to the results obtained, fixed bacterial biomass was estimated as possible biosorbent for removal of chromium (VI) from aqueous solutions in a dynamic process.

Abstract: Nowadays, many studies focus only on the removal of dyes from water in single solution. In real applications the colored effluents contain more than one component to eliminate. In this study, the adsorption of two textile dyes – Red Bemacid-ETL (RB-ETL) and Bezaktiv Turquoise Blue-VG (BTB-VG) – was investigated in a binary mixture. The derivative spectrophotometry was used to determine the specific wavelength for each dye. The effect of pH, contact time and initial dye concentrations was considered. The results show that diatomite has a good potential to eliminate both of dyes simultaneously. The competitive statistical rate theory model fits the adsorption kinetic data of the binary system well. The adsorption isotherm data for both dyes is well described by multicomponent Langmuir isotherm model. A high competition effect was observed, but BTB-VG dye was more selectively adsorbed by heat treated diatomite than RB-ETL dye.

Abstract: ZnO/TiO₂ nanocomposites with several ratio of the components were prepared by sol-gel method using titanium isopropoxide and titanium butoxide as titania precursors. Phase formation and photocatalytic activity of ZnO/TiO₂ nanocomposites depend on ratio of the components and calcination temperature. The photocatalytic activity in dependence on calcination temperasture, phase composition was determined by degradation of methylene blue solution under Hg lamp and solar light imitating illumination. The highest photocatalytic activity showed ZnO/TiO₂ nanocomposites containing 99 mol.% ZnO and 50 mol% ZnO when hexagonal ZnTiO₃ phase was formed. ZnO/TiO₂ nanocomposites exhibited enhanced photoactivity under solar light with respect to Hg lamp irradiation.