Alkaline pH Values Research Articles

The Biosorption Capacity of the Marine Microalga Phaeodactylum tricornutum for the Removal of Toluidine Blue from Seawater

A wide variety of dyes, such as toluidine blue (TB), are used daily for a multitude of purposes. After use, many of these compounds end up in aqueous effluents, reaching natural environments, including marine environments. The removal of these pollutants from marine environments must be considered a priority problem. The search for natural techniques, such as biosorption, is a preferred option to eliminate pollution from natural environments. However, biosorption studies in seawater are scarce. For this reason, the living biomass of the marine microalga Phaeodactylum tricornutum was studied to determine its ability to remove TB from seawater. The kinetics of the biosorption process, the isotherms, and the effect of light and pH were determined. This biomass showed a maximum TB removal capacity of 45 ± 2 mg g−1 in the presence of light. Light had a positive effect on the TB removal capacity of this living biomass. The best fitting kinetics was the pseudo-second order kinetics. The efficiency of the removal process increased with increasing pH. This removal was more effective at alkaline pH values. The results demonstrated the efficacy of P. tricornutum living biomass for the efficient removal of toluidine blue dye from seawater both in the presence and absence of light.

Asparagine-Glucose Amadori Compounds: Formation, Characterization, and Analysis in Dry Jujube Fruit.

Amadori rearrangement products of asparagine with glucose (Asn-Glc-ARP) were first prepared through Maillard model reactions and identified via liquid chromatography-mass spectroscopy. With the study on the effect of the reaction temperature, pH values, and reaction time, the ideal reaction condition for accumulation of Asn-Glc-ARP was determined at 100 °C for 40 min under pH 7. Asparagine (Asn) was prone to degrade from Asn-Glc-ARP in alkaline pH values within a lower temperature range, while in an acidic environment with high temperatures, deamidation of Asn-Glc-ARP to Asp-Glc-ARP (Amadori rearrangement products of aspartic acid with glucose) was displayed as the dominant pathway. The deamidation reaction on the side chain of the amide group took place at Asn-Glc-ARP and transferred it into the hydroxyl group, forming Asp-Glc-ARP at the end. Considering that lyophilization as pretreatment led to limited water activity, a single aspartic acid was not deamidated from Asn directly nor did it degrade from Asp-Glc-ARP even at 120 °C. The degradation of Asn-Glc-ARP through tandem mass spectrometry (MS/MS) analysis showed the obvious fragment ion at m/z 211, indicating that the stable oxonium ion formed during fragmentation. The structure of Asn-Glc-ARP was proposed as 1-deoxy-1-l-asparagino-d-fructose after separation and purification. Also, the content of Asn-Glc-ARP within dry jujube fruit (HeTianYuZao) was quantitated as high as 8.1 ± 0.5 mg/g.

Nitzschiatranstagensis Morales, Novais, Wetzel, Morais & Ector (Bacillariophyceae) - the second record in the Mediterranean Region.

The Mediterranean Region holds significant ecological importance, characterised by its unique climate, biodiversity and the crucial role it plays in global ecosystems. Mediterranean streams are naturally highly-stressed environments mainly due to fluctuations in water quantity. River flow generally varies from perennial to ephemeral and temporary rivers constitute significant water resources. Streams that flow through Balearic Islands are subjected to these conditions. The majority of these streams sustain water flow for 4-5 months annually, with exceptions noted for streams associated with springs, which typically maintain water throughout most of the year.Benthic diatoms are widely recognised as reliable bioindicators of water quality, used in many aquatic ecosystems. Analysing diatom communities and their biodiversity serves as a valuable tool to ensure the ecological and sustainable utilisation of water resources as well as the accurate development of guidelines for their conservation.The field of diatom taxonomy and distribution plays a crucial role in advancing our understanding of aquatic ecosystems and their biodiversity. Species of the genus Nitzschia are extensively found throughout the Mediterranean Region, including the Balearic Islands. However, they have rarely been investigated in temporary streams. This study presents the first record of Nitzschiatranstagensis Morales, Novais, Wetzel, Morais & Ector, outside the type locality and being the second record in Europe. In this study, the authors found this taxon in one temporary stream of Majorca Island, Torrent des Castellot in November 2005 (Balearic Islands). Nitzschiatranstagensis occurred at 2.6% abundance in this stream with oligotrophic waters (0.052 mg∙l-1 of nitrate), slightly alkaline pH values (7.8) and water conductivity levels of 626.5 µS cm-1. This species was recorded in the biofilm of the stones together with other taxa such as Achnanthidiumminutissimum (Kützing) Czarnecki (39.2%), Gomphonemarosenstockianum Lange-Bertalot & Reichardt (28.9%) and Halamphoraoligotraphenta (Lange-Bertalot) Levkov (20.4%). The Nitzschiatranstagensis frustules found in the examined material have similar dimensions and a higher fibulae count (8-11 in 10 μm vs. 6-10 in 10 μm) compared to the type material of Nitzschiatranstagensis. The habitat characteristics in which this species was found are described, together with LM micrographs of this taxon.

Fabrication and characterization of mesoporous calcium silicate and silver-incorporated mesoporous calcium silicate nanoparticles with low cytotoxicity and antibacterial properties as a dental biomaterial

AimThis study aimed to fabricate and characterize Mesoporous calcium silicate nanoparticles (MCSNs) and silver-incorporated Mesoporous calcium silicate nanoparticles (Ag-MCSNs) as bioactive nanoparticles either for hybridization with contemporary endodontic materials to improve their bioactivity by using (MCSNs) as a drug delivery system, and to achieve both low cytotoxicity and enhanced antibacterial activity by incorporating Ag which is avery potent antibacterial agent to form (Ag-MCSNs) as new multifunctional materials. MethodsThe MCSNs and Ag-MCSNs nanoparticles were made using the template method. Both nanoparticles' mesoporous structure, specific surface area, pore volume, pore size, and shape were examined and characterized by FTIR, XRD, EDS, DLS, and FE-SEM. The ion release, pH change, cytotoxicity by MTT assay, and antibacterial properties against planktonic Enterococcus faecalis were further investigated by colony forming units (CFUs) counting technique. ResultMCSNs nanoparticles were prepared and successfully incorporated with silver as Ag-MCSNs. MCSNs and Ag-MCSN nanoparticles had the characteristic mesoporous material shape and over time showed sustained ion release (Ca2+,Si4+ and Ag+) ,with an alkaline pH value (8.2–9.0). Both materials showed no obvious cytotoxicity but more cell viability with MCSNs (vitality value is >70%). Both nanoparticles showed antibacterial activity against Enterococcus faecalis (p < 0.05). With MCSNs containing Ag (Ag-MCSNs) showing higher antibacterial effect. ConclusionBoth mesoporous calcium silicate nanoparticles (MCSNs) and mesoporous calcium silicate nanoparticles loaded with silver (Ag-MCSNs) displayed a characteristic mesoporous structure, ion release, alkaline pH, minimal cytotoxicity, and outstanding antibacterial performance with MCSNs containing Ag (Ag-MCSNs) showing higher antibacterial effect. This substance may be improved to provide a better root canal filler material, sealer, or novel intracanal medicament in dentistry.

Structural characteristics and stability analysis of coconut oil body and its application for loading β-carotene

In this work, we investigated structural characteristics and stability analysis of the coconut oil body (COB) and its application for loading β-carotene (β-CA). The COB contained neutral lipids (81.1 ± 2.1 %), membrane proteins (0.6 ± 0.0 %), and moistures (18.3 ± 3.2 %), in which the molecular weights of membrane proteins ranged from 12 kDa to 40 kDa, as analyzed by the SDS-PAGE. The COB exhibited a small droplet diameter (5.1 ± 0.3 µm) with a monomodal diameter distribution, as reflected by the dynamic light scattering. The COB showed stable states at alkaline pH values (pH 8–10) and instability against ionic strengths (50–200 mmol/L) and thermal treatment (30-90℃) after analyzing the instability indexes. COB-based emulsions were favorable for the loading and retention of β-CA, as reflected by free fatty acids release rates and bioaccessibility in the simulated gastrointestinal digestion. This study will contribute to using the coconut oil bodies for loading bioactive nutraceuticals to enhance their bioaccessibility.

Preparation and Properties of Porous Concrete Based on Geopolymer of Red Mud and Yellow River Sediment.

Red mud (RM) and Yellow River sediment (YRS) are challenging to handle as waste materials. In this study, RM with geopolymer and heavy metal adsorption characteristics was combined with YRS and ground granulated blast furnace slag (GGBS) to develop a porous geopolymer with high strength and high adsorption performance. A geopolymer cementitious material with high strength was prepared using high temperature water bath curing of 90 °C and different dosages of YRS, and a porous geopolymer concrete was further prepared. The compressive strength, fluidity and setting time of geopolymer cementitious materials were tested, and the compressive strength, porosity and permeability of porous geopolymer concrete were also tested. The environmental impact assessment of geopolymer cementitious materials was further conducted. The hydration products and microstructure of geopolymer gel materials were analyzed by XRD, SEM and FT-IR tests. The results show that the addition of YRS can effectively prolong the setting time of the geopolymer cementitious material, and the enhancement rate is as high as 150% compared with the geopolymer cementitious materials without the addition of YRS. An appropriate amount of YRS can improve the compressive strength of the geopolymer cementitious materials, and its early compressive strength can be further improved under the high temperature water bath curing of 90 °C, and the compressive strength at an age of 3 d can be up to 86.7 MPa. Meanwhile, the compressive strength of porous geopolymer concrete at an age of 28 d is up to 28.1 MPa. YRS can participate in geopolymer reactions, and high temperature water bath curing can promote the reaction degree. Curing method and YRS dosages have little effect on the porosity and permeability of the porous geopolymer concrete. The porous geopolymer has a good heavy metal adsorption effect, and the alkaline pH values can be gradually diluted to neutral.

Development and Characterization of Sustainable Coatings on Cellulose Fabric and Nonwoven for Medical Applications

The modification of cellulose woven fabrics and viscose nonwovens was carried out with the aim of preparing sustainable coatings from biodegradable natural polymers. The modification of fabrics with biodegradable natural polymers represents an ecological alternative to other textile modifications, such as the sol-gel process. Coatings were prepared from erythritol, gelatin, and collagen in various formulations with the addition of propolis and alginate fibers and a natural plasticizer (glycerin). The morphology of the materials was determined before and after modification with Dino-Lite. Moreover, the pH value, the drop test method, the angle recovery angle, the thickness, and the mass per unit area were monitored before and after modification. The results have shown that modifications had no significant effect on the thickness or mass per unit area. In contrast, in a larger proportion, they show hydrophilic properties, which favor their application for medical purposes—for example; for the absorption of exudates in wound dressings; etc. In addition, due to the neutral and slightly alkaline pH values of the modified samples, they can be suitable for external application on the skin. The results of the recovery angle of the modified samples proved that the samples did not tend to crease and that they retained their elasticity after modification with a very pleasant textile feel (fabric hand), making them even more suitable for everyday applications.

Water quality and microecosystem of water tanks in karst mountainous area, Southwest China.

Karst mountainous areas in Southwest China, the world's largest bare karst area, are faced with growing water shortages. Rainwater harvesting plays an important role in alleviating water shortage. However, there remains a substantial gap in the research regarding the water quality of tanks. Water samples were seasonally collected from ten tanks to investigate the physicochemical properties, microbial communities, and their key influencing factors. The result showed that pH, turbidity, chroma, DOC, and CODMn exceeded drinking water guidelines. The alkaline pH value and the deterioration of sensory properties was the main feature of tank water, from which the over-standard rate of the uncleaned water tanks was higher. Moreover, principal component analyses suggested that tank water quality was influenced by human activities, catchment areas, and material cycling processes within the tanks, of which in-tank microbial activities were the most important driving factors in water quality variation. Proteobacteria, Actinobacteria, Bacteroidetes, Cyanobacteria, Firmicutes, and Verrucomicrobia were the predominant bacterial phyla in water tanks. Acinetobacter, Cyanobium-PCC-6307, CL500-29-marine-group, Candidatus-Aquiluna, and Exiguobacterium were the most abundant genera. The bacterial communities were significantly affected by the management practices. Higher relative abundance of Cyanobacteria and lower relative abundance of Proteobacteria was detected in the uncleaned tanks, which was a sign of tank water quality deterioration. The microbial community structure was closely related to the environmental factors. There was evidence that the water quality was affected by the existence of a microecosystem dominated by photosynthetic microorganisms in the water tanks. In addition, Acinetobacter, Enterobacter, Pseudomonas, and Legionella identified as the potential opportunistic pathogenic genera were frequently detected but the relative abundances except Acinetobacter were low in the tanks. Overall, our findings indicated that management style influences water quality and bacterial communities of tank water.

REE and Y distribution and speciation in fossil water: The northwestern African Continental Intercalaire aquifer, Algerian Sahara

The Continental Intercalaire aquifer is a part of the Northwestern Sahara Aquifer System which, extending through Algeria, Tunisia and Libya with over one million km2, is one of the largest fossil aquifers in the world, with an age of about 775,000 years, water resource estimated at ∼31,000 × 109 m3 and negligible recharge rate at 1 × 109 m3/year. The fossil water of the Algerian Sahara, part of the Continental Intercalaire aquifer, was examined, for the first time, for its REE + Y composition, speciation, and geochemical significance in order to constrain the processes affecting the REE + Y distribution and fractionation pattern in a peculiar aquatic system.The fossil water of the Algerian Sahara has total mineralization in the 1170 and 2309 mg/l range and the prevailing hydrochemical facies is Na-Cl-SO4. The recorded REE + Y concentrations increase downstream, along with the dissolved silica content and temperature, as a function of water flow. The water samples are in equilibrium with 2:1 and 1:1 clay minerals with the exception of few upstream samples, characterized by alkaline pH values, that are in equilibrium with Na- and K-feldspars.The REE + Y speciation is mainly controlled by carbonate species. The Ln(CO3)+ species increase and the Ln(CO3)2− species decrease downstream as the carbonate rocks of the aquifer dissolve and the PCO2 equilibrating pressure increases. The LnSO4+ species are mostly LaSO4+ downstream the aquifer and, more in general, LaSO4+ largely prevails up to pH between 6.9 and 7.2.The low negative cerium anomalies affecting most of the samples might be explained by the CeO2 precipitation following Ce3+ transformation to Ce4+. Ce oxidation is probably promoted by Mn-minerals by oxidative scavenging, whereas positive Ce anomaly could be due to the preferential desorption of Ce3+ over Ce4+. Finally, the pronounced negative samarium anomaly observed in some samples may reflect depletion of organic matter and Sm adsorption onto clay minerals.

Effect of alkaline pH values on physical and functional properties of edible films made from calcium caseinates

Films are an important tool in food packaging, delivery, and preservation of food products. Milk based films have shown the potential to be renewable, edible, and provide a lower cost option to replace plastic films, but there is still a need to find formulations that have superior physical properties and can be made with cheaper materials. Research has suggested that pH modification of the film solution into alkaline conditions could improve film properties. Calcium caseinate based films were made with increased pH to study their physical qualities. Film strength for CaCN films reached a relative maximum at pH 8. CaCN films also showed increasing strength and decreasing elongation with aging. Increasing pH above 10 yielded the lowest oxygen permeabilities for both recipes. Calcium caseinate films with modified pH have many beneficial properties, performing better than previously reported milk-based films in a number of categories and are promising candidates for food applications.

Spatial characteristics of hydrochemistry and stable isotopes in river and groundwater, and runoff components in the Shule River Basin, Northeastern of Tibet Plateau

Water resources play a crucial role in constraining the high-quality development of the arid, necessitating an in-depth investigation and understanding of hydrological processes, hydrochemical characteristics, and their influencing factors amidst climate change. This study meticulously examined and analyzed the hydrochemistry and stable isotope composition (δ18O and δD) of river and groundwater within the Shule River Basin (SRB). Results showed that both river (mean: 8.01) and groundwater (mean: 7.92) had alkaline pH values, while average total dissolved solids were measured at 709.25 mg/L in river and 861.88 mg/L in groundwater, indicating predominance of fresh water sources. HCO3−, SO42−, Na+ and Ca2+ were the most abundant ions, influenced by evaporation-crystallization processes and rock weathering. The dominated hydrochemical facies in both river and groundwater were Ca–HCO3 type in the upper (UR) and the middle reaches (MR), while Ca–Mg–Cl type in the lower reaches (LR). The local meteoric water line (LMWL) was defined as δD = 8.01δ18O + 18.48 (R2 = 0.98, n = 163; P < 0 0.001). The more negative δ18O and δD values in river and groundwater were plotted nearby and lower right of the LMWL, implying that the important recharge source of those waters is from precipitation. The relationship between river δ18O and elevation showed an increase of 0.14‰/100 m in the UR, but a negative correlation with a rate of −0.47‰/100 m in the MR and LR. Precipitation, groundwater, baseflow and meltwater accounted for 62.5%, 19.8%, 11.9% and 5.8% of the UR river, respectively, during the observed period, according to the end-member mixing analysis. These runoff components displayed distinct seasonal variations, primarily driven by precipitation during the early and groundwater/baseflow during the rapid and end-stage ablation periods. The observed alterations in hydrological elements present both opportunities and challenges for water resource management across the SRB, and adaptive measures have been proposed based on our study. These findings provide valuable insights into efficient utilization of water resources from water chemistry and environmental isotopes.

Autotrophic nitrogen polishing of secondary effluents: Alkaline pH and residual nitrate control S0-driven denitratation for downstream anammox treatment

Energy-lean nitrogen removal technologies, such as partial nitritation/anammox, often encounter effluent issues due to elevated nitrate and ammonium levels. This study proposed a novel autotrophic polishing strategy coupling sulfur-driven denitratation with anammox. To explore the denitratation potential in obtaining stable and sufficient nitrite accumulation, the effects of pH, residual nitrate level, and biomass-specific nitrate loading rate (BSNLR) were investigated in an S0-packed bed reactor at low hydraulic retention time (i.e., 0.2 h). Implementing pH and residual nitrate control strategies would be easier in practice than BSNLR control to polish secondary effluent. Alkaline pH values could realize successful nitrite accumulation without residual nitrate, and further intensify the accumulation under increased residual nitrate levels. The nitrate level was positively correlated with the nitrite accumulation efficiency. At pH 8.5 and nitrate concentration of 1.0 ± 0.8 mg N L−1, sulfur-driven denitratation could successfully maintain nitrite accumulation of 6.4 ± 1.0 mg NO2−-N L−1, ideally for the downstream anammox in case of residual ammonium levels of around 5 mg N L−1. Since Thiobacillus members play a key role in managing nitrite accumulation, their abundance should be guaranteed in the practical application.

Assessment of the in situ biomethanation potential of a deep aquifer used for natural gas storage

In response to the challenges of sustainable development and the H2 sector, it is foreseeable that H2 will be stored into geological storage, such as deep aquifers. However, CO2 evolves in deep aquifers because it may be naturally present there; it may also be a constituent of the stored gas mix, or could even be voluntarily stored in the context of the fight against global warming. Autochthonous microorganisms can consume them as sources of energy and carbon (methanogens, (homo)-acetogens and sulfate-reducers). This was already demonstrated in a previous experiment (Haddad 2022) and under operating conditions (Lobodice, Czech Republic ; Smigan 1990). Understanding these mechanisms and quantifying them appear necessary to assess the modifications generated by this type of microorganisms on the properties of the gas. The methanogenesis reaction (CO2 gas + 4H2 gas → CH4 gas + 2H2O liquid) induces a lowering of pressure, since 5 gas molecules are transformed into a single gas molecule: CH4 (water being condensed at subsurface conditions). In situ biomethanation technique could represent a potential on several scales larger than conventional catalytic or biological methanation reactors, due to the very large reservoir volumes involved. Biomethanation in geological reservoirs would enable us to reduce our consumption of fossil fuels, so as not to emit more CO2, while meeting the growing energy needs of a region and ensuring its independence from hydrocarbon-producing countries. A deep aquifer already used as UGS was selected for this study. Formation waters from 17 control wells in this aquifer (Fig. 1) were sampled to assess the potential activity of indigenous methanogenic populations, as well as sulfate-reducers. Despite relatively low sulfate concentrations for a deep aquifer (0.025-1.35 mM), sulfate reducers were found at all sites targeting and quantifying the dsrB gene, which is characteristic of this metabolic group (between 1.8∙101 ±2.0x100 and 1.3∙104 ±2.0∙103 dsrB gene copy numbers.mL-1). In contrast, methanogenic archaea based on the mcrA gene quantification were detected at only 10 of the 17 sites (up to 4.3∙102 ±8.3∙101 mcrA gene copy numbers.mL-1). The choice was made to focus the rest of the study on 7 of these 10 sites. The potential for methanogenesis was assessed on cultural tests with formation water alone or supplemented with calcite (CaCO3), a mineral present in the formation. Results indicate that initial times and controls are controlled by the sulfate variable, since the latter was not consumed by sulfate-reducers. Biotic trials in the presence of calcite and H2/CO2 (abiotic controls and final times) are logically characterized by higher concentrations of calcite, bicarbonate and calcium, but this is not the case for trials in the presence of H2 alone. We therefore deduce that methanogenesis took place mainly via gaseous CO2, but that without the latter, calcite was a source of carbon for lithoautotrophs. Cultures incubated with H2 as the sole gas phase have the highest methane concentrations, logically associated with the lowest sulfate concentrations (consumed by sulfate-reducers), the lowest Eh (probably due to the presence of sulfides) and more alkaline pH values up to 10 (which may have led to precipitation of carbonate and calcium ions). All the sites studied showed sulfate consumption and methane production. Analysis of taxonomic diversity (MiSeq; 16S rRNA gene V4-V5) showed the dominance of three genera of sulfate-reducers with Thermodesulfovibrio-Desulfovibrio-Desulfotomaculum and methanogenic populations belonging to the Methanobacterium genus. These initial results show a strong potential of in situ biomethanation for the deep aquifer studied. All these experiments were carried out at near-atmospheric pressure, and the results still need to be confirmed and refined in the laboratory under conditions that simulate real-life conditions as closely as possible (rock, pressure, nature of gases).

Nanotubes/nanorods-like structures of La-doped ZnO for degradation of Methylene Blue and Ciprofloxacin

In this study, nanotubes/nanorods-like structures of Zn0.97La0.03O compound were synthesized at different pH values (pH = 8, 9, 10, 11, and 12), and the photocatalytic response for Methylene Blue (MB) dye and Ciprofloxacin (CIP) drug were investigated. It was verified that the pH variation directly impacts the ZnO crystal structure, morphology, optical and photocatalytic properties. The basic and alkaline pH values cause a decrease in the crystallite size and these differences may have contributed to the band gap energy values variations. Oxygen vacancy defects (VO, VO+, and VO++) were abundant in the La-doped ZnO samples, which also demonstrated to be formed from mesopores, as seen in N2 adsorption/desorption results. The photocatalytic response of the materials was verified in MB and CIP solutions under UV irradiation conditions. The sample synthesized at pH 9 (ZL9) demonstrated greater capacity to remove MB (91.45 %) and CIP (87.6 %) in typical pseudo-first-order kinetics. Using different inhibitors, it was observed that the •OH radicals were the species involved in the photocatalysis of pollutants for the ZL9 sample. In addition, this material demonstrated a satisfactory ability to remove pollutants even after three consecutive uses. This study demonstrates that pH is an important parameter to consider in the synthesis process of ZnO nanostructures, directly influencing the structural, optical, and morphological properties and the degradation of highly dangerous dyes and drugs.

ZnO-based heterojunction catalysts for the photocatalytic degradation of methyl orange dye

In this study, a variety of ZnO-based heterojunctions with disparate wt.% doping of WO3 and BiOI have been prepared for the photodestruction of methyl orange (MO) dye in aqueous solution. The composites were analysed by scanning electron microscopy, energy-dispersive X-ray spectroscopy, X-ray diffraction, optical studies, and nitrogen adsorption-desorption isotherms. The SEM images revealed non-uniform surfaces of the ZnO–BiOI based composites while mostly nodular morphology was observed for all three samples of ZnO-WO3. As the WO3 loading increased, more clustering was detected. The analysed samples exhibited characteristic peaks representative of the triclinic phase of WO3 and the hexagonal wurtzite structure of ZnO, while the diffractogram observed from the materials displayed distinct peaks corresponding to the crystalline phases of both BiOI and ZnO in their pure forms. Further evidence of the samples' characteristics includes the presence of distinct crystalline patterns without any impurity peaks, a red shift in the absorption spectra of the heterostructure, the detection of only the reference elements, and mostly Type IV isotherm adsorption. This study identified the ZnO-[10%]BiOI and ZnO-[10%]WO3 heterojunctions as the best performing photocatalysts, as MO was completely destroyed in 120 and 90 min, respectively. Thus, confirming 10% wt. as the optimal doping concentration for the best photo-activity in this study. The impact of varying process parameters demonstrates that at an elevated photocatalyst mass of 40 mg, both heterojunctions effectively degraded MO. The photodegradation efficiency of MO was more pronounced in strong acidic conditions (pH 2) when compared to high alkaline conditions (pH 11) for the ZnO-[10%]BiOI heterostructure. However, a decrease in performance was observed for both strong acidic and high alkaline pH values when the ZnO-[10%]WO3 heterostructure was applied. The kinetic analysis of the photodegradation study reveals that all the photodegradation experiments can be represented by the pseudo-first-order kinetic model. The findings from this investigation propose that the ZnO-[10%]BiOI heterojunction photocatalyst holds significant potential for the effective treatment of dye-contaminated wastewater.

Impact of redox fluctuations on microbe-mediated elemental sulfur disproportionation and coupled redox cycling of iron

Elemental sulfur (S0) plays a vital role in the coupled cycling of sulfur and iron, which in turn affects the transformation of carbon and various pollutants. These processes have been well characterized under static anoxic or oxic conditions, however, how the natural redox fluctuations affect the bio-mediated sulfur cycling and coupled iron cycling remain enigmatic. The present work examined S0 disproportionation as driven by natural microbial communities under fluctuating redox conditions and the contribution of S0 disproportionation to ferrihydrite transformation. Samples were incubated at either neutral or alkaline pH values, applying sequential anaerobic, aerobic and anaerobic conditions over 60 days. Under anaerobic conditions, S0 was found to undergo disproportionation to sulfate and sulfide, which subsequently reduced ferrihydrite at both pH 7.4 and 9.5. Ferrihydrite promoted S0 disproportionation by scavenging biogenic sulfide and maintaining a suitable degree of sulfate formation. After an oxic period, during the subsequent anoxic incubation, bioreduction of sulfate occurred and the biogenic sulfide reduced iron (hydr)oxides at a rate approximately 25 % lower than that observed during the former anoxic period. A 16S rDNA-based microbial community analysis revealed changes in the microbial community in response to the redox fluctuations, implying an intimate association with the coupled cycling of sulfur and iron. Microscopic and spectroscopic analyses confirmed the S0-mediated transformation of ferrihydrite to crystalline iron (hydr)oxide minerals such as lepidocrocite and magnetite and the formation of iron sulfides precipitated under fluctuating redox conditions. Finally, a reaction mechanism based on mass balance was proposed, demonstrating that bio-mediated sulfur transformation maintained a sustainable redox reaction with iron (hydr)oxides under fluctuating anaerobic-aerobic-anaerobic conditions tested in this study. Altogether, the finding of our study is critical for obtaining a more complete understanding of the dynamics of iron redox reactions and pollutant transformation in sulfur-rich aquatic environments.

Design of Noble-Metal-Free Membrane Electrode Assemblies Based on Metal Chalcogenides for Electrochemical Hydrogen Production Via Alkaline Seawater Electrolysis

The production of large amounts of green hydrogen (H2) by electrochemical water splitting represents one of the key pillars to reach net-zero by 2050. As one of the major drawbacks, both low-temperature proton-exchange membrane (PEM) as well as anion-exchange membrane (AEM) electrolysis still rely on the utilization of noble metals in the catalyst layers driving the evolution of H2 and oxygen (O2) on the cathode (HER) and on the anode (OER), respectively. Beyond that, the requirement for highly pure water feeds to prevent degradation of the cell performance over time was previously addressed as one of the main concerns. In particular, this holds true for arid regions located close to the ocean. Advantageously, these coastal arid zones provide essentially unlimited access to seawater, coupled with ample solar irradiation and wind throughout the entire year.[1]One of the major challenges for direct seawater electrolysis lies in the development of selective catalysts, especially for the anode due to the inherently faster reaction kinetics of the competing two-electron chlorine evolution reaction (ClER). Nickel-iron layered double hydroxides (NiFe-LDH) were identified as active and selective OER electrocatalysts in a previous study[2] by our group. Dionigi et al.[3] recently reported a general design principle for selective seawater electrolysis, in which alkaline pH values > 7.5 are claimed to favor OER over ClER for overpotentials < 480 mV.At the cathode, state-of-the-art electrolyzers utilize Pt-based catalysts for an efficient HER.[2] For direct seawater electrolysis, however, not only the high cost but also the weak stability due to chloride-induced corrosion restrict the applicability of Pt-based electrodes. In our contribution, we thus present noble-metal free catalyst materials based on metal chalcogenides with high HER activity and improved stability in alkaline seawater electrolyte in a single-cell electrolyzer setup. Membrane-electrode assemblies (MEAs) with superior corrosion-resistance by a modification of the porous transport layers (PTLs) for both cathode and anode will be presented, which outperform reference MEAs containing Pt-based cathodes in alkaline seawater electrolysis. The optimized noble-metal-free electrode design (fig. 1) combined with well-controlled electrolyte feeding enables alkaline seawater electrolysis operating at industrially relevant current densities.

Back Gate Bias Influence on BESOI ISFET Sensitivity

The application of Field Effect Transistors (FETs) to sensors and biosensors allows a mass production, low cost, small size, fast response and, also, the possibility of integrating the device and conditioning signal circuit in the same integrated circuit (IC). The Ion Sensitive Field Effect Transistor (ISFET), invented in 1970 by Piet Bergveld (1), is a device similar to the conventional Metal-Oxide-Semiconductor Field Effect Transistor (MOSFET), except that the metal gate is replaced by an inert electrode/pseudo electrode and a sample solution, in order to expose the gate oxide layer to ions present in the solution. The solution charges change the electrical potential in the gate oxide surface and, consequently, the device threshold voltage changes as a function of the ion concentration in the sample solution, being used as a pH sensor. Thus, the ISFET is a very promising device to Point-of-Care (POC) monitoring, such as COVID-19 control (2) and for continuous in vivo monitoring ion activity in biological processes (3)-(6).The BESOI (Back Enhanced Silicon-On-Insulator) MOSFET is a device patented in 2015 by João Antonio Martino and Ricardo Cardoso Rangel (7). This device is easy to fabricate and low cost. In the last years, the research using this device as a sensor/biosensor has been done (8)-(14). This paper presents, for the first time, the BESOI MOSFET working as an Ion Sensitive Field Effect Transistor (ISFET): the BESOI ISFET. Therefore, the focus of this work is to study the device electrical behavior influenced for pH standard solutions.The BESOI ISFET was fabricated at Integrated System Laboratory (LSI) from University of Sao Paulo (USP), Brazil. It is a planar device made on a SOI (Silicon-On-Insulator) wafer with three conventional photolithography steps, in an analogous way to previous work (15) and one more photolithography step to create microchannel and microreservoirs with SU-8 (16) layer to contain the sample solution. The wafer has no doping process (there is only the natural wafer doping of 1015 cm-3). The silicon channel layer and the gate oxide (SiO2) thicknesses are 10 nm and 25 nm, respectively. The buried oxide layer thickness is 200 nm. The drain and source contacts are fabricated with nickel and the contact pads using aluminum. The Figure 1 presents the final device layout and the Figure 2 shows the device schematic drawn.Differently from a conventional ISFET, where the drain current flows at the front interface, in the BESOI ISFET the drain current flows at the back interface. As the BESOI ISFET is a non-intentionally doped device, the free conduction charge layer is formed by biasing the Back Gate electrode (VGB). When a positive enough VGB is applied, electrons are attracted and accumulated at the back interface, and therefore, current flows from source to drain when VDS (Drain bias) is applied. A Platinum (Pt) pseudo-electrode is used to apply front-gate voltage (VGF) to the sample solution.The experimental drain current (IDS) as a function of the front-gate voltage (VGF), for 25 V applied at the back-gate (VGB), is presented in Figure 3.A, which is possible to observe that the neutral pH (pH7) curve stayed between the acid pH (pH4) curve, in the left, and alkaline pH (pH10) curve, in the right. This result shows that the threshold voltage (VTH) is lower for acid pH and higher for alkaline pH, what is compatible with the conventional ISFET results present in the literature (17). To corroborate the experimental measurement result, the device simulation was made with TCAD-Sentaurus (18), based in the paper (19). Figure 3.B shows the same trend for the simulated device with pH solution for any VGB value.In Figure 4, the threshold voltage was analyzed as a function of the pH for different VGB values. The VTH increases (becomes more positive) for alkaline pH values, regardless of the VGB applied. However, the VTH variation in the pH range, between pH4 and pH10, is different for different VGB values. With higher VGB applied, higher is the VTH variation. In Figure 5 Is possible to see clearly that the sensitivity (ΔVTH /ΔpH) increases with the VGB increase probably due to the small influence of the series resistance. In another hand, the acquired sensitivity values for VGB higher than 15 V in this work (about 25-33 mV/pH, approximately), is compatible with results present in the literature for conventional ISFETs with silicon dioxide (SiO2) for gate insulator (20). Figure 1

Acid Attack Resistance of Concrete Produced by Partial Replacement of Cement with Limestone Dust and Locust Bean Pod Ash

Concrete, a widely used construction material, has an alkaline pH value of 12 – 13.5, which makes it susceptible to acid attacks. In this study, effect of acid (H2SO4) attack on concrete produced by partially replacing cement with limestone dust (LSD) and locust bean pod ash (LBPA) was investigated. LBPA was constant at 5% while LSD was varied at 5% intervals from 0 to 25% by weight of cement. Sulphuric acid solution of 5% concentration was used to examine the resistance of concrete specimens for a total exposure period of 28 days. The performance of the degraded specimens was evaluated by measuring the strength loss. The results show that the control mix’s compressive strength dropped from 31 N/mm2 before immersion to 23.15 N/mm2 after 28 days of immersion in a 5% H2SO4 solution. At 10% LSD-LBPA mix, the compressive strength before immersion dropped from 24.33 N/mm2 to 23.81 N/mm2 after immersion in a 5% H2SO4 solution. The least amount of strength loss of 2.14 percent was obtained at 10% mix. The control mix suffered the greatest loss of strength of 25.32 percent. Water absorption in the mixes decreased up to 10% mix, and then increased when LSD and LBPA were further added. At a 10% mix, the lowest rate of water absorption of 16.28 percent was obtained. Based on the findings, a 10% LSD-LBPA (5% LSD + 5% LBPA) mix produces concrete with better H2SO4 acid resistance than the control mix and is hereby recommended for concrete production in acidic environments.

Fly Ash-Based Na-X Zeolite Application in Separation Process of Bovine Serum Albumin from Aqueous Solution in the Presence of Organic Substances with Anionic Character.

The main purpose of the investigations was to explore the protein adsorption on porous materials, as well as to identify the mechanisms of protein attachment without and with other common environmental contaminants, such as drugs, polymers or surfactants. This study applied the Na-X zeolite for the adsorption of bovine serum albumin (BSA) from solutions with various pH values. Electrophoretic mobility measurements and potentiometric titrations were conducted in systems containing both protein and/or PAA (poly(acrylic acid) polymer/DCF (diclofenac) drug/SDS (sodium dodecyl sulfate) surfactant to investigate the protein binding mechanisms in the complex adsorbate systems. In addition, aggregate size and stability measurements were performed in the investigated systems. Based on the research results, it was possible to conclude that the protein adsorbed most preferably on the zeolite surface at a pH value close to its isoelectric point (pI) (102.15 mg/g), and protein adsorption was the lowest in the solutions with strongly alkaline (29.61 mg/g) or acidic (77.45 mg/g) pH values. Thus, the examined zeolitic material can be considered an effective adsorbent for protein removal from an aqueous solution.