Effects Of Various pH Values Research Articles

A negatively charged polyethersulfone nanofiltration membrane enriched with Ag-functionalized titanium silicon carbide for the removal of organic pollutants from water

Developing high-performance nanofiltration membranes for treating wastewater contaminated with organic pollutants requires special attention. The toxic nature and side effects of organic pollutants, such as dyes and antibiotics, make them hazardous. Therefore, wastewater containing organic pollutants must be treated properly before entering water environments. Herein, we synthesized the Ti3SiC2 MAX phase via the reactive sintering technique. To make the Ti3SiC2 more hydrophilic and compatible with the polyethersulfone (PES) membrane, its surface was modified in one step with Ag NPs/polyvinyl alcohol (Ag-MAX). Different quantities (0–1 wt%) of Ag-MAX filler were embedded into the PES membrane via the phase inversion process. The presence of 0.75 wt% Ag-MAX filler enhanced hydrophilicity, porosity, surface roughness, pore size, and negative charge of PES membrane, which are beneficial for permeance and antifouling features of Ag-MAX mixed matrix membranes (MMMs). The optimized membrane containing 0.75 wt% of Ag-MAX demonstrated the uppermost pure water flux of 72.5 L/m2 h with a flux recovery ratio of 82.8 %. The optimized membrane showed rejection efficiency of 99.4, 99.6, and 99.7 % for Direct Black 38, Acid Blue 113, and Disperse Red 153 dye solutions, along with a satisfactory rejection of 70.7, 65.9, and 58.5 % for Basic Violet 1, Alizarin Red S, and Ceftriaxone solutions, respectively. Furthermore, the effects of various pH values, various salt types, and cyclic filtration experiments on the separation performance of 0.75 wt% Ag-MAX MMM were investigated. The rejection efficiency of 0.75 wt% Ag-MAX MMM toward Acid Blue 113 is almost constant and higher than 98.5 % in different conditions, demonstrating that the Ag-MAX MMM could be a suitable candidate for the treatment of wastewater contaminated with organic pollutants.

Non-covalent complexes of lutein/zeaxanthin and whey protein isolate formed at different pH levels: Binding interactions, storage stabilities, and bioaccessibilities

Lutein (Lut) and zeaxanthin (Zx) are promising healthy food ingredients; however, the low solubilities, stabilities, and bioavailabilities limit their applications in the food and beverage industries. A protein-based complex represents an efficient protective carrier for hydrophobic ligands, and its ligand-binding properties are influenced by the formulation conditions, particularly the pH level. This study explored the effects of various pH values (2.5–9.5) on the characteristics of whey protein isolate (WPI)–Lut/Zx complexes using multiple spectroscopic techniques, including ultraviolet–visible (UV–Vis), fluorescence, and Fourier transform infrared (FTIR) spectroscopies and dynamic light scattering (DLS). UV–Vis and DLS spectra revealed that Lut/Zx were present as H-aggregates in aqueous solutions, whereas WPI occurred as nanoparticles. The produced WPI–Lut/Zx complexes exhibited binding constants of 104–105 M−1, which gradually increased with increasing pH from 2.5 to 9.5. FTIR spectra demonstrated that pH variations and Lut/Zx addition caused detectable changes in the secondary WPI structure. Moreover, the WPI–Lut/Zx complexes effectively improved the physicochemical stabilities and antioxidant activities of Lut/Zx aggregates during long-term storage and achieved bioaccessibilities above 70% in a simulated gastrointestinal digestion process. The comprehensive data obtained in this study offer a basis for formulating strategies that can be potentially used in developing commercially available WPI complex-based xanthophyll-rich foods.

Case study of hydrogen sulfide release in the sulfate-rich sewage drop structure

Abstract H2S is one of the principal odor gases released from sewer networks and understanding the rate of H2S release into sewer air space and ventilation to the atmosphere is crucial for preventing or minimizing odor and corrosion issues in sewer systems. TOXCHEM model was used to simulate the fate of H2S gas in roads for this study. The model was calibrated for the spring and summer seasons and validated for the remainder of the seasons. The predicted behavior showed good correlation to measurements on real samples following statistical analysis, with R2, R, and RMSE results between (0.93–0.97), (0.8–0.82), and (0.000438–0.000838), respectively. A sensitivity study was performed to assess the effect of various pH values, drop heights, tailwater depths, stream widths, and sewer ventilation rate levels. The results showed that the emissions concentrations for winter, spring, summer, and autumn reached 3500, 5044, 6425, and 4045 ppm respectively. All the emissions levels from this DS can be considered hazardous, and this was particularly evident during the summer months. This study has helped to clarify the fate and emission of hydrogen sulfide gas at the DS by simulation using a TOXCHEM model.

Effect of substrate ratios on the simultaneous carbon, nitrogen, sulfur and phosphorous conversions in microbial fuel cells

The columbic efficiency, removal efficiency and voltage production of seven different combinations of carbon (acetic acid, albumin and sucrose) with nutrients (C:N, C:P, C:S, C:N:S, C:P:S, C:N:P and C: N:S:P) were investigated at three different ratios (20:1, 15:1 and 10:1). The effects of various pH values were also explored for these combinations of carbon, and sulfur compounds (pH 6–8). The highest columbic efficiency (75.8%), COD removal efficiency (86%) and voltage (667 mV) were recorded when the acetic acid was used in the MFC and the lowest columbic efficiency (12.8%), removal efficiency (37.6%) and voltage (145 mV) were observed in case of albumin. A marked increase in columbic efficiency, removal efficiency and voltage production were seen with the rise in the pH value from 6 to 8. The lowest columbic efficiency, removal efficiency and voltage production were seen at pH 6 and highest at pH 8. At each investigated pH, the highest removal efficiency, columbic efficiency, and voltage were found at substrate ratio of 20:1 while lower at 10:1. At all pH values, the carbon to nutrient ratios seemed to have followed a similar trend i.e., the COD removal efficiency, columbic efficiency and voltage generation was found in the order C:N > C:N:S > C:N:S:P > C:N:P > C:S > C:P:S > C:P. In all cases, nitrogen showed a higher removal as compared to phosphorous and sulfur.

Effects of temperature and pH on the structure of a metalloprotease from Lactobacillus fermentum R6 isolated from Harbin dry sausages and molecular docking between protease and meat protein.

Microbial protease can interact with meat protein in fermented meat products at a certain pH and temperature. To investigate the effects of various pH values and temperatures on the structural characteristics of Lactobacillus fermentum R6 protease, which was isolated from Harbin dry sausages, spectroscopy techniques and molecular dynamics were utilized to evaluate structural changes. The protease exhibited a stable spatial structure at pH 7 and 40 °C, and the extension of the protease structure was also promoted. Although the structure of the protease could be changed or destroyed by pH 8 and 70 °C, it was mainly determined by the changes of secondary and tertiary structures such as α-helix, β-sheet, β-turn and random coil. In addition, carbonyl vibration, -NH vibration, C-H stretching vibration and disulphide bonds were present in L. fermentum R6 protease under various pH and temperature conditions. Molecular docking showed that the protease can interact with myosin light chain, myosin heavy chain, actin and myoglobin. The protease can maintain stable structure and interact with meat protein, which reflected certain application prospects in the fermentation of Harbin dry sausages. © 2021 Society of Chemical Industry.

Modulating Kinetics of the Amyloid-Like Aggregation of S. aureus Phenol-Soluble Modulins by Changes in pH.

The pathogen Staphylococcus aureus is recognized as one of the most frequent causes of biofilm-associated infections. The recently identified phenol-soluble modulin (PSM) peptides act as the key molecular effectors of staphylococcal biofilm maturation and promote the formation of an aggregated fibril structure. The aim of this study was to evaluate the effect of various pH values on the formation of functional amyloids of individual PSM peptides. Here, we combined a range of biophysical, chemical kinetics and microscopic techniques to address the structure and aggregation mechanism of individual PSMs under different conditions. We established that there is a pH-induced switch in PSM aggregation kinetics. Different lag times and growth of fibrils were observed, which indicates that there was no clear correlation between the rates of fibril elongation among different PSMs. This finding confirms that pH can modulate the aggregation properties of these peptides and suggest a deeper understanding of the formation of aggregates, which represents an important basis for strategies to interfere and might help in reducing the risk of biofilm-related infections.

The effect of various pH values on foaming properties of whey protein preparations

The influence of pH on foaming of whey protein isolates (WPI) and concentrates (WPC 80 and WPC 65) dispersions was investigated due to the lack of studies on the whipping process on the protein aggregation in prefoam solutions, resulting foams and drainage serum. The WPI foams were superior compared to WPC ones. pH values of 5.0 and 9.0 were optimal for the foaming of all preparations, while pH 3.0 caused a deterioration of their foamability. For the WPI foams, a correlation was found between the yield stress and phase angle. pH 9.0 promoted the protein aggregation, especially in the prefoam WPI solutions.

UV-stabilized self-assembled amphiphilic triblock terpolymers supramolecular structures with low cytotoxicity as doxorubicin carriers.

Amphiphilic polystyrene-b-poly[(7-(Allyloxy)-2H-chromen-2-one)-co-(2-hydroxyethyl methacrylate)]-b-poly(2-(dimethylamino)ethyl methacrylate) (PS-b-P(AC-co-HEMA)-b-P(DMAEMA)) triblock terpolymers were synthesized by atom transfer radical polymerization (ATRP). PS-b-P(AC-co-HEMA)-b-PDMAEMA triblock terpolymers were characterized using proton nuclear magnetic resonance (1H NMR) and gel permeation chromatography (GPC). The effect of various pH values on solution self-assembly behavior of PS-b-P(AC-co-HEMA)-b-P(DMAEMA) triblock terpolymers was investigated. Field emission scanning electron microscopy (FE-SEM), transmission electron microscopy (TEM), fluorescence microscopy, and dynamic light scattering (DLS) were used to observe the size and morphology of the assembled triblock terpolymers. With altering pH value, different morphologies were obtained including spherical micelles, Janus snowman, and spherical Janus as well as cubic-hexagonal structures. UV light was used to stabilize the self-assembled morphologies and FE-SEM results showed that morphology remained unchanged after photo-dimerization. The self-assembled triblock terpolymers before and after photo-crosslinking were loaded with doxorubicin (DOX) and drug release behavior was examined at different conditions. Due to photo-crosslinking of self-assembled terpolymers, cumulative release was decreased. Thus, they might be more controllable drug carriers in drug delivery systems.

English

English

Fast mineralization of acetaminophen by highly dispersed Ag-g-C3N4 hybrid assisted photocatalytic ozonation

Highly dispersed Ag-g-C3N4 hybrid was synthesized successfully by a simple calcination method in present study. The samples were characterized by TEM, XRD, XPS, BET and UV–vis DRS. The results indicate that Ag element are existent as metallic silver and highly dispersed in the matrix of g-C3N4 nanosheet. It was used as active catalyst for photocatalytic ozonation of acetaminophen (ACE) (solar light/Ag-g-C3N4/O3). The results showed that the apparent rate constant of mineralize ACE by solar light/4% Ag-g-C3N4/O3 during 120 min is almost 2 times as large as that with solar light/g-C3N4/O3. The mechanism of photocatalytic ozonation with 4% Ag-g-C3N4 was further confirmed. In this system, Ag acts as not only a good photo-generated electron acceptor for photocatalysis but also a beneficial decomposition center for ozone. Subsequently, holes and hydroxyl radicals both make contribution to the mineralization of ACE in solar light/4% Ag-g-C3N4/O3 process. A superior synergistic effect was observed in mineralization of ACE according to the synergy index of 5.3. Furthermore, Effects of various pH values and silver contents on the ACE mineralization were evaluated. The pathway of ACE degradation in photocatalytic ozonation system with 4% Ag-g-C3N4 was also proposed.

Antioxidant assays by reducing potential and 2,2-diphenyl-1-picrylhydrazyl radical scavenging techniques as affected by pH and ion concentrations

The aim of the study is to investigate the effect of varying pH and different metal ion concentrations on the analyses of antioxidants by reducing potential (RP) and 2,2-diphenyl-1-picrylhydrazyl (DPPH) radical scavenging techniques. The investigation was conducted by examining the effects of various pH values (4, 5, 6, 7, 8 and 9) and potassium chloride concentrations (50, 100, 150, 200, 250 and 300 ug/mL) on the optical densities of reducing potential and DPPH radical scavenging potential of aqueous infusions of Cassia alata (L.) Roxb. The determinations were also conducted on the extraction media with the intention of identifying the probable source of variation in the investigation. The antioxidant potentials for both the aqueous infusion and media were most efficient at the least pH 4.0. Moreover, the antioxidant potentials decrease as the ion concentrations increase. The study revealed that the colorimetric methods for the determinations of DPPH radical scavenging and RP could be liable to errors arising from slight changes in acidity and concentrations of the metal ions thus affecting the performance characteristics in terms of repeatability and reproducibility of reports and meaningful comparisons of antioxidant capacity of dietary products among different authors.

Role of phenol red in the stabilization of the Sabin type 2 inactivated polio vaccine at various pH values.

To analyze the effects of phenol red at various pH values on the Sabin type 2 inactivated polio vaccine (sIPV2), several biophysical techniques were used to evaluate the particle size and capsid protein for conformation. sIPV2's size was assessed via transmission electron microscopy and dynamic light scattering. The effects of various pH values (from 4.0 to 7.0) on the biophysical characters of sIPV2 particles in solution were determined by dynamic light scattering and zeta potential. The results clearly indicated that aggregation and instability occurred in the solution of sIPV2 particles at a pH of 6.0. Under similar conditions, by dynamic light scattering and zeta potential, the virus particles in solution showed more dispersion and were stable with the addition of 0.05 mM phenol red. According to circular dichroism and intrinsic tryptophan fluorescence data, it was observed that the secondary and tertiary structures of the sIPV2 particles were more stable with the protection of phenol red. At a pH below 6.0, the sIPV2 solution with phenol red had more D-antigen content, which was confirmed by enzyme-linked immunosorbent assay and rat experiments. These results strongly suggested that phenol red improved the pH stability of the sIPV2. The study indicated the potential of phenol red in preserving vaccine potency of the sIPV2 at various pH values.

The effect of experimental hyperoxia on erythrocytes’ oxygen-transport function

ABSTRACTThe aim of this study was to investigate the effect of hyperoxia, calcium ions and pH value on the composition of major phospholipids in human erythrocyte membranes and erythrocytes’ oxygen-transport function. To create a model of hyperoxia, we saturated the incubated mixture with oxygen by constant passing of oxygen–air mixture through the incubation medium. To assess the effect of elevated calcium ion concentrations, CaCl2 was added to the incubation medium. An incubation medium with different pH was used to study the effect of various pH values. Lipids were extracted from erythrocytes and chromatographic separation was carried out in a thin layer of silica gel deposited on a glass plate. The thiobarbituric acid (TBA)-active products and the content of diene conjugates (DC) in erythrocytes were determined. The oxygen-binding capacity of haemoglobin was evaluated using Raman spectroscopy. The obtained results indicated that hyperoxia causes deep changes both in the composition and character of bilayer lipids of erythrocyte membranes, which affects the functional characteristics of erythrocytes, primarily the oxygen-transport properties of erythrocyte haemoglobin. It should be noted that a combination of Ca2+ ions and change in the pH value intensify the processes associated with disruption of phospholipids’ composition. The findings indicate that the lipid phase is one of the key elements in the functioning of erythrocytes in norm as well as during development of various pathological processes.

A chromotropic acid modified SBA-15 as a highly sensitive fluorescent probe for determination of Fe3+ and I− ions in water

A novel organic–inorganic hybrid nanomaterial (SBA-15-CA) was prepared by covalent immobilization of chromotropic acid onto the surface of mesoporous silica material SBA-15. Different techniques such as XRD, TEM, FT-IR, N2 adsorption–desorption and TGA analyses were employed to characterize the grafting process. The data showed that the organic moiety (0.41 mmol g−1) was successfully grafted to the SBA-15 and the primary hexagonally ordered mesoporous structure of SBA-15 was preserved after the grafting procedure. SBA-15-CA has been realized as a highly sensitive and selective fluorescent probe towards Fe3+ and I− ions in aqueous media. SBA-15-CA exhibited a remarkable fluorescent quenching in the presence of Fe3+ ion over other competitive cations including Na+, Mg2+, Al3+, K+, Ca2+, Cr3+, Mn2+, Fe2+, Co2+, Ni2+, Cu2+, Zn2+, Cd2+, Hg2+, and Pb2+ as well as I− ion among a series of anions including F−, Cl−, Br−, CO32−, HCO3−, CN−, NO3−, NO2−, SCN−, SO42−, H2PO4−, HPO42−, and CH3COO−. A good linear response was observed between the concentration of the quenchers (Fe3+ and I− ions) and fluorescence intensity of SBA-15-CA with detection limits of 1.5 × 10−7 M for Fe3+ and 0.2 × 10−7 M for I−. Moreover, the effects of various pH values on the sensing ability of SBA-15-CA were investigated. Finally, the proposed method was successfully utilized for the determination of Fe3+ and I− ions in river water, well water and tap water samples.

Effects of lithium-active manganese trioxide coating on the structural and electrochemical characteristics of LiNi0.5Co0.2Mn0.3O2 as cathode materials for lithium ion battery

Li2MnO3-coated LiNi0.5Co0.2Mn0.3O2 materials are successfully synthesized by sol–gel method. The effects of various pH values and Li2MnO3 contents on the structural and electrochemical properties of LiNi0.5Co0.2Mn0.3O2 cathode materials are systematically investigated, respectively. Scanning electron microscope, transmission electron microscope and energy dispersive spectrometer confirm that the particles of LiNi0.5Co0.2Mn0.3O2 are completely coated by crystalline Li2MnO3 phase. Electrochemical tests show that suitable Li2MnO3-coated samples exhibit higher rate capacity and better cycling performance than those of the pristine one. This improvement can be attributed to the synergetic contribution from the neutral pH value and appropriate Li2MnO3 amount. The neutral pH environment can protect the core material from damaging during the coating process and is conducive to relieving the rapid moisture uptaking problem of LiNi0.5Co0.2Mn0.3O2. While, suitable Li2MnO3 coating can protect the bulk from directly contacting the electrolyte and offer a fast Li+ diffusion path at the interface of bulk and electrolyte.

Cadmium Removal from Aqueous Systems Using Opuntia albicarpa L. Scheinvar as Biosorbent.

The aim of this research was to investigate the use of a natural adsorbent like nopal (Opuntia albicarpa L. Scheinvar) for removing cadmium from aqueous solutions with low concentrations of this metal. Two treatments were applied to the cladodes: a dehydration to get dehydrated nopal (DHN) and heating up to 90°C to obtain a thermally treated nopal (TN). After examining the effect of various pH values (2–7), the capacity of each biosorbent was examined in batch sorption tests at different dosages (0, 500, 1000, 1500, 2000, and 3000 mg L−1). The results indicated that adsorption of cadmium to biomass of DHN and TN was highly dependent on pH and biosorbent dosage. The best removal of cadmium (53.3%, corresponding to q e of 0.155 mg g−1) was obtained at pH 4.0 by using the TN sorbent. Infrared and Raman spectra confirmed that cadmium removal occurred via adsorption to –OH functional groups.

Effects of root exudates and pH on Plasmodiophora brassicae resting spore germination and infection of canola (Brassica napus L.) root hairs

Clubroot, caused by Plasmodiophora brassicae, is emerging as a serious threat to canola production on the Canadian Prairies. Germination of soil-borne resting spores (RSs) and their subsequent infection of canola root hairs are important requirements for the establishment of the clubroot pathogen in canola. Stimulation of RS germination by certain non-host plant species and elevation of soil pH by application of calcium-rich compost may provide some level of clubroot control in the field. Experiments were conducted under controlled conditions to determine the effects of (i) host and non-host root exudates (REs) and different pH values on the germination of RSs, and (ii) different pH values either alone or in conjunction with a Ca-containing nutrient solution (NS) on root hair infection of a susceptible canola cultivar. The percentage of RS germination was significantly enhanced when incubated with REs prepared in NS from three plant species compared to a NS alone or sterile dH2O. Non-host REs from perennial ryegrass (Lolium perenne L.) produced higher spore germination than exudate preparations from canola (Brassica napus L.) and Chinese cabbage (Brassica rapa var. pekinensis, cv. Granaat) roots. The percentages of RS germination were higher at pH values ranging from 5.0 to <7.0, and lower at pH values >7.0 in both the presence and absence of REs. The effects of various pH values on the percent of root hair infection varied. Root hair infection was higher at relatively lower pH values (6.0–7.0) compared to either lower or higher pH values when a NS was added. It was however lower at pH values below 6.5 compared to those above 6.5 when the experiment was conducted in the absence of a NS. The possible impacts of REs, different pH values, and calcium levels in the soil on the severity of clubroot on canola are discussed.

The Effect of pH Value on Phase Transformation of Calcium Phosphate Cement

The effects of various pH values of sodium phosphate buffer solution (PBS), 4.0, 6.0, 8.0, and 9.0 on calcium phosphate cement (CPC) prepared by mixing monocalcium phosphate monohydrate (MCPM), calcium carbonate, and PBS were studied. The phase evolution takes place in three steps: Firstly, the MCPM and calcium carbonate crystals dissolve in the PBS and precipitate in the form of DCPD crystals. Then, after 12 h, DCPD begins to convert to amorphous calcium phosphate (ACP). Finally, the metastable ACP phase converts into stable CDHA. With an increase in the pH of the PBS, the CDHA content in the CPC increased.

Effect of various pH values, ionic strength, and temperature on papain hydrolysis of salivary film

Stimulated human whole saliva (WS) was used to study the dynamics of papain hydrolysis at defined pH, ionic strength, and temperature with the view of reducing an acquired pellicle. A quartz crystal microbalance with dissipation (QCM-D) was used to monitor the changes in frequency caused by enzyme hydrolysis of WS films, and the hydrolytic parameters were calculated using an empirical model. The morphological and conformational changes of the salivary films before and after enzymatic hydrolysis were characterized by atomic force microscopy (AFM) imaging and grazing-angle Fourier transform infrared (GA-FTIR ) spectra, respectively. The characteristics of papain hydrolysis of WS films were pH-, ionic strength-, and temperature-dependent. The WS films were partially removed by the action of papain, resulting in thinner and smoother surfaces. The infrared data suggested that hydrolysis-induced deformation did not occur on the remnants of salivary films. The processes of papain hydrolysis of WS films can be controlled by properly regulating pH, ionic strength, and temperature.

Comparing nonsynergistic gamma models with interaction models to predict growth of emetic Bacillus cereus when using combinations of pH and individual undissociated acids as growth-limiting factors.

A combination of multiple hurdles to limit microbial growth is frequently applied in foods to achieve an overall level of protection. Quantification of hurdle technology aims at identifying synergistic or multiplicative effects and is still being developed. The gamma hypothesis states that inhibitory environmental factors aiming at limiting microbial growth rates combine in a multiplicative manner rather than synergistically. Its validity was tested here with respect to the use of pH and various concentrations of undissociated acids, i.e., acetic, lactic, propionic, and formic acids, to control growth of Bacillus cereus in brain heart infusion broth. The key growth parameter considered was the maximum specific growth rate, mu(max), as observed by determination of optical density. A variety of models from the literature describing the effects of various pH values and undissociated acid concentrations on mu(max) were fitted to experimental data sets and compared based on a predefined set of selection criteria, and the best models were selected. The cardinal model developed by Rosso (for pH dependency) and the model developed by Luong (for undissociated acid) were found to provide the best fit and were combined in a gamma model with good predictive performance. The introduction of synergy factors into the models was not able to improve the quality of the prediction. On the contrary, inclusion of synergy factors led to an overestimation of the growth boundary, with the inherent possibility of leading to underestimation of the risk under the conditions tested in this research.