Neutral Water pH Research Articles

DMTMM-mediated amidation of sodium alginate in aqueous solutions: pH-dependent efficiency of conjugation

DMTMM-mediated amidation of sodium alginate is one of the methods used for the chemical modification of alginate with amines. However, there is a limited understanding of how the reaction conditions, particularly the pH value, influence the conjugation efficiency (CE) and the resulting degree of substitution (DS). In this study, we investigated the effect of the pH during the reaction, focusing on both neutral and weakly basic conditions, using water and buffer as solvents. Two model amines with high pKaH values were selected, furfurylamine (FFA, pKaH = 9.12) and 4-(2-aminoethyl)morpholine (AEM, pKaH = 9.93). Sodium alginate with a high mannuronate content (60 mol%) and molar mass of 168 kg·mol−1 was used for amidation. Our results show that both FFA and AEM effectively conjugate to sodium alginate under the selected reaction conditions. We found that pH significantly affects both CE and DS, which varied between 2 % to 40 % and 3 % to 53 %, respectively, depending on the specific reaction conditions. Optimal conditions were observed at neutral pH in water, whereas weak basic pH led to lower CE. Our findings thus offer a recommendation for optimizing the DMTMM-mediated amidation of sodium alginate, emphasizing the importance of pH values during the reaction.

Pollutants abatement in aqueous solutions with geopolymer catalysts: A photo fenton case

Environmental pollution is a serious threat to human health and the natural environment, and it has aroused widespread concern. One of the most effective processes in the removal of pollutants from wastewater is the Fenton reaction. This process is based on the production of highly reactive •OH radicals due to the rapid reaction between Iron ions and hydrogen peroxide under acidic conditions.The hydroxyl radical has a high oxidation potential of E°(•OH/H2O) = 2.8 V/SHE at acidic pH, so they are extremely reactive and non-selective oxidizing agent towards organic contaminants in wastewater.In order to avoid the drawbacks of a standard Fenton reaction, a photo Fenton reaction has been tested working at neutral pH in water in the removal of refractory pollutants. For the first time, a heterogeneous system was experimented, impregnating porous metakaolin-based geopolymers, obtained by using hydrogen peroxide and vegetable oil in different ratios, as foaming agents, with iron working as photocatalyst. The dirty wastewater as scrubber water (SCRW) and liquid fraction of digestate (LFD) were tested obtaining 40–90% abatement of Total Carbon Content.

Relationship between Knowledge and Preventive Behavior of Leptospirosis in Berbah District Sleman Regency Yogyakarta in 2021

Public Health is the resultant from an balance of individual, agent, and environment problems. Individual knowledge and the ability to adapt to the environment vary greatly. The individual awareness and sensibility towards surroundings will contribute to the public health status. Environmental factor in the raining season with high intensity of rainfall cause some risks such as flood. It can be a disaster and destroy the facilities in the area. This can be a transmission media, a new habitat of insects for certain disease, one of them is Leptospirosis. The condition after flood with low level of clean water facilities can make these bacteria live and reproduce, with warm temperatures, neutral pH of water, humidity and also high rainfall. Leptospirosis cases in Indonesia are sufficiently high which in 2019, there are 845 cases with mortality rate for 16.26%. Some factors may affect the number of the case. This research is aimed to know the factors related to the preventive behavior of leptospirosis. It was held in Public Health Center Berbah Yogyakarta. The method of research is quantitative research with design survey method, quasi experiment. The population is the clients visiting to Public Health Center Berbah, with the average number of clients coming are 200 clients/day. The sample is taken by accidental sampling to the clients with the number of daily visits (50 persons). The result shows, that of five analyzed factors, knowledge is the factor related to the preventive behavior of leptospirosis.

Low water pH depressed growth and early development of giant freshwater prawn Macrobrachium rosenbergii larvae

Macrobrachium rosenbergii is one of the shellfish species with high aquaculture value due to its increasing market demand. However, the comparatively low production volume compared to demand coupled with the rapid decline of the natural environment, consequently, drives the potential depletion of the wild population. The decrease in water pH related to anthropogenic pollution is one of the most critical factors affecting the early life performances of M. rosenbergii. Therefore, this study was designed to examine the effect of low water pH on feeding, growth and development of M. rosenbergii early life stages. Experimental water pH was set as neutral (7.7 ± 0.4); mild-acidic (6.4 ± 0.5) and acidic (5.4 ± 0.2) with triplication at a stocking density of 2 larvae/L for 30 days. As expected, M. rosenbergii larvae were highly sensitive to acidic pH with no larvae survived beyond 48 h of exposure. Feeding, survival and growth of larvae were adversely affected by mild-acidic pH exposure as compared to neutral pH. Larvae exposed to mild-acidic water pH experienced a prolonged larval period and only metamorphosed to the post-larval stage at day-30. Whilst under neutral water pH, larval that metamorphosed to post-larval was first observed on day-23. The negative impact of decreased pH, even in mild-acidic pH exposure, on the feeding, survival, growth and development of M. rosenbergii larvae highlights the urgency of periodic pH monitoring during M. rosenbergii larviculture.

Prebiotic triose glycolysis promoted by co-catalytic proline and phosphate in neutral water.

Proline and phosphate promote a near-quantitative aldol reaction between glycolaldehyde phosphate and formaldehyde at neutral pH in water. Our results demonstrate the important role of general acid-base catalysis in water and underscore the essential role that amino acid catalysis may have played in early evolution of life's core metabolic pathways.

2D CoGeSe3 monolayer as a visible-light photocatalyst with high carrier mobility: Theoretical prediction

The production of hydrogen fuel by photocatalytic water splitting is a hot issue in solar-energy harvesting technologies. An ideal photocatalyst should display suitable band gap, adequate band-edge position, and high carrier mobility. In this paper, first-principles calculations were used to reveal the potential of 2D CoGeSe3 monolayer as a promising photocatalyst in water splitting. Indeed, this monolayer demonstrates good dynamic and thermal stability, is insoluble in water, and can easily be synthesized. Its band gap anticipates visible- and ultraviolet-light absorption (at ~105 cm−1). The electron and hole mobility is 601 and 509 cm2V−1s−1, respectively. Good matching to the water redox potential in the neutral pH of water is also manifested.

Research into application of polyaluminum chlorides in coagulation of pollutants in reservoir waters with a wide range of pH

Reservoir waters extracted during exploitation of crude oil and natural gas are a serious threat to the environment. The reason is high content of dissolved salts, mainly chlorides, as well as toxic components, such as: petroleum substances with aromatic hydrocarbons, and various chemicals applied during hydrocarbons production, e.g. corrosion, hydrates and paraffin inhibitors, surfactants, methanol etc. For this reason, the extracted reservoir water should be managed in a way that is least harmful to the environment. One of the methods of management that meets this requirement is injection of reservoir water into the absorptive horizon. In order to provide failure-free injection, with maximum use of the capabilities of an absorptive horizon, it is necessary to prepare the water properly by removing the components (solids, deposits and suspensions) that cause damage of the injection well. One of the most effective methods of water treatment is coagulation. Aluminum(III) sulfate(VI), commonly used in coagulation, requires a neutral pH of water. Exceeding this level results in rapid reduction in coagulation efficiency, and even in increase in the content of suspended solids in purified water. Extracted reservoir waters drastically change their properties from strongly reducing to oxidizing, due to methane removal after pressure reduction and oxygenation in contact with air. Moreover, while changing the electrochemical potential to positive, presence of iron and manganese ions in the water causes precipitation of oxides and hydroxides in the form of suspensions and the pH decreases due to their hydrolysis. Due to the dynamic course of these processes, as well as the additional acidification of water by addition of the coagulant (aluminum(III) sulfate(VI)), adjustment of the pH to the level appropriate for effective coagulation is often a serious problem. The solution could be application of properly selected modern coagulants of much greater efficiency, enabling a decrease of the agent dose as well as reduction of volume and improvement of the structure of post-coagulation sediments. Additionally, they are highly efficient in a wide range of water reactions. The article describes laboratory tests on a selected coagulant (polyaluminium chloride), which allow for determination of the range of deposit water reaction in which this agent can be used. For the tests, Flokor 1ASW was selected due to its high degree of hydrolysis and slight acidity (pH ~3.5) compared with other polyaluminium chlorides, which means low consumption of total alkalinity of purified water. The results obtained show a wide range of water reaction (pH from 8.0 to 4.0), in which the effectiveness of coagulant activity ensures the correct level of purification. In addition, the use of Flokor 1ASW with effective Stabpol K flocculant allows for production of big and quickly settled flocs. Post-coagulation sediments have much smaller volume than when using aluminum(III) sulfate(VI). The results of industrial tests, carried out in order to prepare reservoir water for injection, without pH correction, have been presented in the article. They confirmed the high efficiency of the selected chemicals.

Advanced disinfecting and post-treating the biologically treated hospital wastewater in the UVC/H2O2 and VUV/H2O2 processes: Performance comparison and detoxification efficiency

The present study compares the ultraviolet (UV)-based AOPs for the disinfection and the post-treatment of the biologically-treated hospital wastewater (BHW). It was found that the vacuum UV (VUV) photoreactor was much more efficient than the UVC photoreactor in inactivation of E. coli. A 6.4 and 3.7 log E. coli inactivation (from an initial concentration of 1.09 × 1010 CFU/mL) was achieved in the VUV and UVC photoreactors, respectively, operated under similar conditions at the neutral pH of water. In the case of continuous-flow operation, the complete inactivation of E. coli was achieved in the VUV photoreactor in hydraulic retention time (HRT) of 3 min. However, the UVC photoreactor could not attain the same performance even at the longer HRT of 10 min. Adding H2O2 to the VUV photoreactor improved the removal of total organic carbon (TOC) from the BHW. The TOC removal in the recirculated VUV photoreactor improved from 10.8%–61.7% in the reaction time of 10 min at the presence of the optimum H2O2 amount of 3 mM whereas the TOC removal in the UVC/H2O2 operated at the similar conditions was only 13.1%. When operated under flow-through condition, 93.6% of TOC could be removed from the BHW in the VUV/H2O2 process at the HRT of 10 min where the complete bacterial inactivation and detergent removal was also achieved. The electrical energy consumption was 52.9, 12.2, and 6.5 kW h/m3 in the UVC/H2O2, VUV and VUV/H2O2 processes, respectively, when operated at the HRT of 10 min under identical conditions for TOC removal. The VUV/H2O2 process could also degrade most of the residual substances in the BHW thus efficiently detoxified the BHW to the level sufficient for discharging into the water environment. Accordingly, the VUV/H2O2 process is an efficient, energy-effective, and thus emerging method for the disinfection and the post-treatment of the hospital wastewater.

Development of Chemical Decontamination Process Based on Ozone for System Surfaces with Chromium Containing Oxides

Chromite or chromium containing oxides are formed as a protective oxide film on the stainless steel surface of heat transport systems. The chemical dissolution of these passive oxide films forms an important step in decontamination formulation development for water-cooled nuclear reactor systems. Dissolved ozone as a reagent was tested for effective chemical dissolution of Fe3+ substituted in nickel chromite and individual component oxides. The study showed the importance of the solution pH and temperature on the dissolution kinetics of Cr2O3, NiO, and NiFexCr2-xO4. Neutral water pH or 0.04 mM OH− were better for achieving a high dissolution rate for chromium containing oxides compared to acidic (2.5 mM H+) or alkaline conditions. In an acidic condition, the release of nickel from NiO or nickel chromite was more in the ozone medium compared to a high pH condition. Substitution of Fe3+ in nickel chromite affected the dissolution behavior in the ozone medium. The dissolution of Fe3+ substituted in nickel chromite showed a small increase in the dissolution rate constant with up to composition x = 0.4, and further increase in the Fe3+ composition in the oxide lattice decreased the dissolution rate constant.

Customized tuning of aggregation-induced emission of a napthalimide dye by surfactants and cyclodextrin

The aggregation-induced emission behaviour of an environment sensitive 2,3-substituted napthalimide dye has been investigated at neutral pH in presence of three different surfactants i.e., cationic, anionic, and neutral. The changes observed in the excitation spectrum of the dye compared to its absorption spectra in water in presence of the surfactants above their micellar concentration reveals the transformation of the H-aggregates of the dye to the monomeric form. The alteration of the dye aggregates to its monomeric form and its consequence on emission properties has been utilized to estimate the surfactant concentration parameter for pre-micellar to micellar transformation. The aggregation of the dye molecules has been made reversible by removal of the surfactant molecules from the system upon host-guest complexation with α-cyclodextrin. This switchable aggregation-deaggregation phenomenon of DMN-Bu by employing surfactants and α-cyclodextrin at neutral pH in water is utilized for determining their critical micellar concentration.

SPECIES FORMED ON IRON SURFACE DURING REMOVAL OF COPPER IONS FROM AQUEOUS SOLUTIONS

The subject of the research covered in this paper is the removal of copper (Cu 2+ ) cations from water at low pH (initial values of pH 3 and 6) by means of zero-valent iron. The chemical states and atomic concentrations of solids formed on the surface of zero-valent iron, and the type of deposited polycrystalline substances have been analyzed with the use of XPS and XRD. The type of process causing the copper removal from water at low pH, corresponding to the effect of acid mine drainage, has been identified by analyzing the changes of physicochemical parameters and specified chemicals content in water. Cu 2+ was removed from water for the initial pH of 6 was much more effective than at lower pH. The formation of CuxFe3-xO4 , where x≤1, and to a lesser degree Cu2O, Cu 0 and/or CuO and/or Cu2S, were the basic processes of the removal of copper at almost neutral pH of water (pH about 6), while the formation of copper in metallic form and Cu2O, as well as probably CuO, were the basic processes for lower pH (pH about 3). The adsorption of Cu 2+ on the surface of shell covering square-shaped cold-rolled steel sheet cell was an additional process causing the removal of copper from water at almost neutral pH.

Effect of the Structure and Morphology of Natural, Synthetic and Post-processed Graphites on Their Dispersibility and Electronic Properties

Twenty-two different graphite grades of the families natural, synthetic, intercalated, expanded, amorphous, and turbostratic graphite, as well as platelets and activated carbon, were analyzed on their dispersibility in N-methylpyrrolidone, cyclohexylpyrrolidone and water-sodium cholate solution. They were characterized for their properties (grain size, density, purity, surface area, pH in water) and morphology. Thermogravimetric analysis, Raman spectroscopy studies, and electrical conductivity measurements were also used. XRPD followed by a Rietveld refinement provided information on the amounts of the rhombohedral (3R) and hexagonal (2H) phases for the crystalline part of the material and the interlayer distances. The properties of graphites favoring better dispersibility are: small grain size and bulk density, neutral pH in water. The electrical conductivity in inversely proportional to the Raman D-band intensity and is highest for the graphites with shortest interlayer spacing. The D-, G- and 2D-bands in the Raman spectra of graphites are in an exponential relation.

Catalytic ozonation of 2-isopropyl-3-methoxypyrazine in water by γ-AlOOH and γ-Al2O3: Comparison of removal efficiency and mechanism

Taste and odor (T&O) is a serious problem in drinking water. The T&O compound, 2-isopropyl-3-methoxypyrazine (IPMP), generates an earthy-musty odor in water. In this study, catalytic ozonation by γ-AlOOH (HAO) or γ-Al2O3 (RAO) was used as an effective method for removing IPMP in water. The comparative removal performance and reaction mechanism of IPMP in catalytic ozonation with different aluminum oxides was investigated. The removal of IPMP in neutral water pH by catalytic ozonation in the presence of HAO or RAO was 94.2% and 90.0%, respectively. Both HAO and RAO exhibited the good stability and a low leaching of aluminum ions. The effect of water pH and typical anion experiments indicated that surface hydroxyl group was key reaction sites for HAO but not for RAO. From results of tert-butyl alcohol inhibition, Rct values and ozone consumption efficiency in catalytic ozonation, OH was generated in the solution in HAO catalytic ozonation or around the surface of catalyst in RAO reaction. The roles of oxidants, including ozone molecules and OH, were analyzed quantitatively, confirming that the surface hydroxyl group was key site for ozone decomposition to generate OH in solution in HAO catalytic ozonation. Ozone was adsorbed physically on the surface and concentrated ozone played an important role in IPMP removal in RAO catalytic ozonation. The nitrogen-containing IPMP intermediates generated in catalytic ozonation were determined quantitatively and qualitatively.

Eichhornia crassipes and Nonwoven Fabric Filter for Eutrophic Water Decontamination

ABSTRACT We tested the effects of the floating plant Eichhornia crassipes (water hyacinth) and nonwoven filter for contaminant removal from eutrophic water. Four microcosms were designed for this purpose- (i) water hyacinth plus nonwoven filter; (ii) water hyacinth only; (iii) nonwoven filter only; and, (iv) control with neither water hyacinth nor nonwoven filter. The complex microcosm of water hyacinth and filter had significantly higher percentage removal of total phosphorus (TP) and chemical oxygen demand than found in the treatments without water hyacinth (P < 0.01 or P < 0.05). The complex treatment of water hyacinth and filter maintained a neutral water pH, while pH values in the treatments without E. crassipes reached 10 or even higher within three-five days. The filter treatment eliminated about 60–80% of ammonium nitrogen, nitrate nitrogen, TP, soluble phosphorus, and biochemical oxygen demand in three-six days. The complex treatment of water hyacinth and filter generally had higher removal rates than either the water hyacinth treatment or the filter treatment. These results suggest that interaction between floating plants and filter in the complex wetland can improve contaminant removal capacity.

Aluminum as an endocrine disruptor in female Nile tilapia ( Oreochromis niloticus)

The effects of aluminum on plasma ion, lipid, protein and steroid hormone concentration were evaluated in Oreochromis niloticus broodstock females. Lipid and protein concentrations from the gonads and liver were also measured. Experiments were performed at neutral and acidic water pH. Four groups of fish were tested for 96 h: 1) control conditions at neutral water pH; 2) control conditions at acidic water pH (CTR-Ac); 3) aluminum at neutral water pH (Al-N); and 4) aluminum at acidic water pH (Al-Ac). Aluminum and acidic water pH exposure caused no ionoregulatory disturbances. Total lipid concentration increased in the mature gonads and decreased in the liver, suggesting an acceleration of lipid mobilization to the ovaries in animals exposed to aluminum. However, a decreased protein concentration in ovaries was also observed. Exposure of control fish to acidic water pH caused an increased concentration of plasma 17α-hydroxyprogesterone. However, females exposed to aluminum at acidic water pH showed a decreased of plasma 17α-hydroxyprogesterone and cortisol. No differences in plasma 17β-estradiol were observed. The physiological mechanisms underlying the disturbances observed are discussed focusing on reproduction. We suggest that aluminum can be considered an endocrine disrupting compound in mature O. niloticus females.

NMR Localization of Protons in Critical Enzyme Hydrogen Bonds

Using 15N NMR spectroscopy and hydrogen bond correlations, we have localized a mechanistically critical proton in aspartate aminotransferase in microcrystals and aqueous solution. It is in a H-bond between a carboxylate O of Asp222 and the pyridine nitrogen of pyridoxal-5‘-phosphate. At neutral pH in water, aspartate and pyridine are unprotonated, but they share a proton in the enzyme. It is shown that such a binuclear base is typical for acid−base interactions in aprotic polar solvents. Active site H-bonds to Asp222 assist protonation of the pyridine nitrogen in the enzyme, which is considered a prerequisite for catalytic activity. We also show that acid−base behavior in enzymes should be modeled using aprotic polar solvents rather than aqueous solutions.

Molecular dynamics simulations of the native and partially folded states of ubiquitin: Influence of methanol cosolvent, pH, and temperature on the protein structure and dynamics

A series of explicit-solvent molecular dynamics simulations of the protein ubiquitin are reported, which investigate the effect of environmental factors (presence of methanol cosolvent in the aqueous solution, neutral or low pH value, room or elevated temperature) on the structure, stability, and dynamics of the protein. The simulations are initiated either from the native structure of the protein or from a model of a partially folded state (A-state) that is known to exist at low pH in methanol-water mixtures. The main results of the simulations are: (1) The ubiquitin native structure is remarkably stable at neutral pH in water; (2) the addition of the methanol cosolvent enhances the stability of the secondary structure but weakens tertiary interactions within the protein; (3) this influence of methanol on the protein structure is enhanced at low pH, while the effect of lowering the pH in pure water is limited; and (4) the A-state of ubiquitin can be described as a set of relatively rigid secondary structure elements (a native-like beta-sheet and native-like alpha-helix plus two nonnative alpha-helices) connected by flexible linkers.

Biomimetic phosphoryl transfer catalysed by iron(II)-mineral precipitates

Iron(II) minerals have been found to catalyse the formation of pyrophosphate from activated phosphate compounds and inorganic phosphate at near neutral pH in water. Iron(II) phosphate catalyses the formation of pyrophosphate, from either acetyl phosphate or phosphoenolpyruvate as the activated phosphoryl donor, in yields of up to 25% and 14% respectively. Under similar conditions, these minerals also retard the hydrolysis of pyrophosphate. The catalysis of pyrophosphate formation is tolerant of sulfide ions: pyrophosphate being produced from acetyl phosphate in 12% yield in the presence of equimolar amounts of sulfide. These reactions mimic the extant biosynthesis of ATP from acetyl phosphate or phosphoenolpyruvate; they counter the concern that hydrolysis of polyphosphates would out-compete their accumulation under prebiotic conditions; and hence suggest a possible prebiotic route to polyphosphates under conditions that may have occurred on the early earth.

Potentiometric Titrations of Rutile Suspensions to 250°C

A stirred hydrogen electrode concentration cell was used to conduct potentiometric titrations of rutile suspensions from 25 to 250°C in NaCl and tetramethylammonium chloride media (0.03 to 1.1m). Hydrothermal pretreatment of the rutile improved titration reproducibility, decreased titration hysteresis, and facilitated determination of the point of zero net proton charge (pHznpc). These pHznpc values are 5.4, 5.1, 4.7, 4.4, 4.3 (±0.2 pH units), and 4.2 (±0.3 pH units) at 25, 50, 100, 150, 200, and 250°C, respectively. The difference between these pHznpc values and 12 pKw(the neutral pH of water) is rather constant between 25 and 250°C (−1.45 ± 0.2). This constancy is useful for predictive purposes and, more fundamentally, may reflect similarities between the hydration behavior of surface hydroxyl groups and water. A three-layer, 1pKa surface complexation model with three adjustable parameters (two capacitance values and one counterion binding constant) adequately described all titration data. The most apparent trend in these data for pH values greater than the pHznpc was the increase in proton release (negative surface charge) with increasing temperature. This reflects more efficient screening by Na+relative to Cl−. Replacing Na+with the larger tetramethylammonium cation for some conditions resulted in decreased proton release due to the less efficient screening of negative surface charge by this larger cation.

The relationship between intracellular pH and seasonal temperature in the brown trout Salmo trutta

ABSTRACT Early studies on reptiles demonstrated that plasma pH increases as body temperature falls (Robin, 1962). Rahn (1967) proposed that plasma pH in all poikilothermic vertebrates is regulated as body temperature changes so as to maintain a constant relative alkalinity, i.e. a constant [OH−]/[H+] ratio, and Reeves (1972) suggested a way in which this could be achieved. Known as the ‘imidazole alphastat hypothesis’, it postulates that is regulated (by way of ventilation) so that the fractional dissociation (α) of the imidazole moiety of histidine is kept constant. As the pK′−of imidazole changes with temperature in about the same manner as the neutral pH of water (Heisler, 1986), the alphastat hypothesis is consistent with that of constant relative alkalinity.