Physicomechanical and Antimicrobial Characteristics of Cement Composites with Selected Nano-Sized Oxides and Binary Oxide Systems

In recent years, increasing attention has been paid to the durability of building materials, including those based on cementitious binders. Important aspects of durability include the increase of the strength of the cement matrix and enhancement of material resistance to external factors. The use of nanoadditives may be a way to meet these expectations. In the present study, zinc, titanium and copper oxides, used in single and binary systems (to better the effect of their performance), were applied as additives in cement mortars. In the first part of this work, an extensive physicochemical analysis of oxides was carried out, and in the second, their application ranges in cement mortars were determined. The subsequent analyses were employed in determining the physicochemical properties of pristine oxides: Fourier transform infrared spectroscopy (FTIR), energy dispersive X-ray fluorescence (EDXRF), scanning electron microscopy (SEM), measurement of the particle size distribution, as well as zeta potential measurement depending on the pH values. Influence on selected physicomechanical parameters of the cement matrix and resistance to the action of selected Gram-positive and Gram-negative bacteria and fungi were also examined. Our work indicated that all nanoadditives worsened the mechanical parameters of mortars during the first 3 days of hardening, while after 28 days, an improvement was achieved for zinc and titanium(IV) oxides. Binary systems and copper(II) oxide deteriorated in strength parameters throughout the test period. In contrast, copper(II) oxide showed the best antibacterial activity among all the tested oxide systems. Based on the inhibitory effect of the studied compounds, the following order of microbial susceptibility to inhibition of growth on cement mortars was established (from the most susceptible, to the most resistant): E. coli < S. aureus < C. albicans < B. cereus = P. aeruginosa < P. putida.

What Makes Cow-Dung Stabilised Earthen Block Water-Resistant

The water-resistance of cow-dung has made it a widely used stabiliser in traditional earthen structures in several Asian and African countries. Multiple studies have shown an improvement in water-resistance with the addition of cow-dung, but none provides insight into this behaviour. The present study investigates the water-resistance behaviour of cow-dung stabilised earthen blocks through an extensive experimental programme to identify and characterise the components of cow-dung responsible for its water-resistance. Fresh cow-dung was collected and separated into fibres (>63 μm), medium-sized microbial aggregates (1-63 μm) and small-sized microbial aggregates (0.5-7 μm). Each component was mixed with soil and samples were prepared at different water contents (optimum water content corresponding to the highest dry density and water content higher than optimum) and compacted with 2.5 MPa force to prepare compressed blocks. The water-resistance of these blocks was evaluated through the immersion and modified drip/rain test. It was found that the small-sized microbial aggregates are almost entirely responsible for water-resistance behaviour of cow-dung stabilised earthen blocks. Small-sized microbial aggregates were further characterised by gas chromatography, mercury intrusion porosimetry, N2- BET surface area, zeta potential measurement and electron microscopy. The results indicate that the small-sized microbial aggregates are composed of clay-sized negatively charged particles that are rich in fatty acids. The hydrophobicity of these particles is hypothesised to be responsible for water-resistance behaviour. These insights are further used to produce stabilised blocks that performed at least 30 times better than the unstabilised blocks in both water-resistance tests. The study concludes with practical recommendations for the use of wet cow-dung over dry cow-dung and a reduction of fibre content to increase the water-resistance of earthen blocks.

The Promising Application of a New Ulnar Nerve Compound Muscle Action Potential Measurement Montage in Amyotrophic Lateral Sclerosis

Objective Detecting peripheral nerve damage by electrophysiology examination accurately and sensitively is important for the follow-up evaluation of amyotrophic lateral sclerosis(ALS). In this study, we applied a new proximal E2 electrode in the ulnar motor nerve conduction study with E1 on abductor digiti minimi(ADM), and investigated its effect on the compound muscle action potential(CMAP) of the ulnar nerve. Methods We included 64 ALS patients and 64 age- and sex- matched controls. Patients characteristics were collected for phenotype, symptom duration and site of onset. The revised ALS Functional Rating Scale(ALSFRS-R) was evaluated at the time of administration to assess the severity of ALS. The ulnar nerve CMAP was recorded using an E1 electrode on the muscle belly and an E2 electrode on distal tendon(traditional montage, CMAP-dE2) and proximal tendon(new montage, CMAP-pE2) respectively. Results The waveform of CMAP-pE2 was steadier presenting a uniform unilobed pattern. In the controls, there were no significant differences between the amplitudes of CMAP-dE2 and CMAP-pE2(p=0.96). In ALS patients, the amplitude of CMAP-pE2 was significantly lower than that of CMAP-dE2(p<0.01), especially for patients with ADM spontaneous activity and muscular atrophy. Using the new method, the damaged axons were more likely to be stratified into more severe decreased levels. Furthermore, the decline of CMAP-pE2 was significantly correlated with ALSFRS-R(p<0.01). Conclusions The new electrode configuration in the ulnar nerve conduction test could reflect the degree of axonal injury much more sensitively after the presence of ulnar nerve degeneration and was more suitable for the evaluation of disease progression.

Manganese in Diagnostics: A Preformulatory Study

This investigation aims to find lipid-based nanosystems to be used as tools to deliver manganese for diagnostic purposes in multimodal imaging techniques. In particular, the study describes the production and characterization of aqueous dispersions of anionic liposomes as delivery systems for two model manganese-based compounds, namely manganese chloride and manganese acetylacetonate. Negatively charged liposomes were obtained using four different anionic surfactants, namely sodium docusate (SD), N-lauroylsarcosine (NLS), Protelan AG8 (PAG) and sodium lauroyl lactylate (SLL). Liposomes were produced by the direct hydration method followed by extrusion and characterized in terms of size, polydispersity, surface charge and stability over time. After extrusion, liposomes are homogeneous and monodispersed with an average diameter not exceeding 200 nm and a negative surface charge as confirmed by ζ potential measurement. Moreover, as indicated by atomic absorption spectroscopy analyses, the loading of manganese-based compounds was almost quantitative. Liposomes containing NLS or SLL were the most stable over time and the presence of manganese-based compounds did not affect their size distribution. Liposomes containing PAG and SD were instable and therefore discarded. The in vitro cytotoxicity of the selected anionic liposomes was evaluated by MTT assay on human keratinocyte. The obtained results highlighted that the toxicity of the formulations is dose dependent.

An Inhibitive Effect of Aeration on the Pitting Corrosion of Steels in Ethanolic Environments

This work is aimed at improving the understanding of the localized corrosion of carbon steel in ethanolic solutions. The role of ethanol dehydration, chloride, and oxygen level in the pitting behaviour of carbon steel in ethanolic environments in the presence of supporting electrolytes was investigated. Open Circuit Potential measurement, Cyclic Potentiodynamic Polarization and Potentiostatic testing were conducted on specimens exposed to ethanolic environments prepared from pure dehydrated ethanol to study the pitting behaviour of carbon steel. Corrosion and passivation potentials significantly reduce due to the change in the cathodic reaction and the decrease in passivation kinetics under de-aerated conditions. SEM and EDX examination indicated that no pitting corrosion is observed without chlorides, and chloride significantly destabilizes the surface film resulting in decreases of both corrosion potential and passivation potential. A decrease in the dissolved oxygen in the solution reduces but does not eliminate the pitting susceptibility. Iron oxide is identified as the significant corrosion product at different water and oxygen content. Therefore, ethanol aeration can be a proper method to increase pitting corrosion resistance in ethanolic solutions.

Enhancing Removal of Cr(VI), Pb2+, and Cu2+ from Aqueous Solutions Using Amino-Functionalized Cellulose Nanocrystal

In this work, the amino-functionalized cellulose nanocrystal (ACNC) was prepared using a green route and applied as a biosorbent for adsorption of Cr(VI), Pb2+, and Cu2+ from aqueous solutions. CNC was firstly oxidized by sodium periodate to yield the dialdehyde nanocellulose (DACNC). Then, DACNC reacted with diethylenetriamine (DETA) to obtain amino-functionalized nanocellulose (ACNC) through a Schiff base reaction. The properties of DACNC and ACNC were characterized by using elemental analysis, Fourier transform infrared spectroscopy (FT-IR), Kaiser test, atomic force microscopy (AFM), X-ray diffraction (XRD), and zeta potential measurement. The presence of free amino groups was evidenced by the FT-IR results and Kaiser test. ACNCs exhibited an amphoteric nature with isoelectric points between pH 8 and 9. After the chemical modification, the cellulose I polymorph of nanocellulose remained, while the crystallinity decreased. The adsorption behavior of ACNC was investigated for the removal of Cr(VI), Pb2+, and Cu2+ in aqueous solutions. The maximum adsorption capacities were obtained at pH 2 for Cr(VI) and pH 6 for Cu2+ and Pb2+, respectively. The adsorption all followed pseudo second-order kinetics and Sips adsorption isotherms. The estimated adsorption capacities for Cr(VI), Pb2+, and Cu2+ were 70.503, 54.115, and 49.600 mg/g, respectively.

Phosphate group functionalized magnetic metal–organic framework nanocomposite for highly efficient removal of U(VI) from aqueous solution

The phosphate group functionalized metal-organic frameworks (MOFs) as the adsorbent for removal of U(VI) from aqueous solution still suffer from low adsorption efficiency, due to the low grafting rate of groups into the skeleton structure. Herein, a novel phosphate group functionalized metal–organic framework nanoparticles (denoted as Fe3O4@SiO2@UiO-66-TPP NPs) designed and prepared by the chelation between Zr and phytic acid, showing fast adsorption rate and outstanding selectivity in aqueous media including 10 coexisting ions. The Fe3O4@SiO2@UiO-66-TPP was properly characterized by TEM, FT-IR, BET, VSM and Zeta potential measurement. The removal performance of Fe3O4@SiO2@UiO-66-TPP for U(VI) was investigated systematically using batch experiments under different conditions, including solution pH, incubation time, temperature and initial U(VI) concentration. The adsorption kinetics, isotherm, selectivity studies revealed that Fe3O4@SiO2@UiO-66-TPP NPs possess fast adsorption rates (approximately 15 min to reach equilibrium), high adsorption capacities (307.8 mg/g) and outstanding selectivity (Su = 94.4%) towards U(VI), which in terms of performance are much better than most of the other magnetic adsorbents. Furthermore, the adsorbent could be reused for U(VI) removal without obvious loss of adsorption capacity after five consecutive cycles. The research work provides a novel strategy to assemble phosphate group-functionalized MOFs.

Screening Friction Reducer Performance Using Zeta Potential

Friction reducers (FRs) are essential additives for water used in hydraulic fracturing treatments for shale reservoirs. These polymers swell and unfurl in the frac water so that polymer chains align along the direction of flow to inhibit turbulence thereby reducing friction at high flow rates. Source water ion content, application pH, and compatibility with the formation are key drivers in deciding which FR chemistries are fit-for-purpose for the operation, balancing desired fluid performance with treatment economics. This investigation explores zeta potential measurement as a novel and meaningful analytical metric to correlate chemical and rheological properties of FRs in a range of source water qualities with their friction reducing performance. The approach of this investigation involves measuring zeta potential of frac fluids formulated using anionic or cationic FRs in waters with varying ionic activity over a range of FR concentrations and pH. The evaluation encompasses a variety of FRs spanning general purpose materials to more sophisticated additives designed to function in fluids with higher concentrations of salt. Dry FR materials as well as corresponding slurry or emulsion forms of the additives are tested. Monovalent and divalent salts and mixtures thereof are used in brine formulations. FR characterization is performed including rheological sweeps, viscoelasticity measurements, and flow loop tests. Results from this study support the conclusion that zeta potential measurement can be used during the FR screening process as a viable supplement to industry standard tests for assessing FR performance in brine.