Combined Effect Of pH Research Articles

The combined effect of pH and NaCl on the susceptibility of Listeria monocytogenes to rhamnolipids

The use of natural and sustainable additives, that are less aggressive to the environment, is a trend in the food industry. Rhamnolipids (RL) biosurfactants have shown potential for controlling food pathogens however, due to the presence of free carboxyl groups, the pH and ionic strength may influence the properties of such surfactants. In this study, we describe the antimicrobial activity of RL under different pH values and NaCl concentrations, towards both planktonic and biofilms of Listeria monocytogenes. RL were effective at pH 5.0 and the addition of 5 % NaCl improved the bactericidal efficacy for planktonic and sessile cells. The effect of NaCl was more pronounced at pH above 6 showing a significant increase in RL antimicrobial activity. At pH 7.0 planktonic population was eradicated by RL only when salt was present whereas biofilm viability was decreased by 5 log with MBIC varying from > 2500.0 mg/L (RL) to 39.0 mg/L (RL + 5 % NaCl). Larger vesicular and lamellar RL self-assembly structures were predominant when NaCl was present, suggesting their association with the antimicrobial activity observed. The pH and ionic strength of the medium are important parameters to be considered for the development of RL-based strategies to control L. monocytogenes.

Combined effects of pH and dissolved organic matter on the availability of pharmaceuticals and personal care products in aqueous environment

The interaction between pharmaceuticals and personal care products (PPCPs) with dissolved organic matter (DOM) can alter their bioavailability and toxicity. Nevertheless, little is known about how pH and DOM work together to affect the availability of PPCPs. This study investigated the impact of pH and DOM on the availability of seven PPCPs, namely Carbamazepine, Estrone, Bisphenol A, Testosterone Propionate, Triclocarban, 4-tert-Octylphenol and 4-n-Nonylphenol, using negligible depletion solid-phase microextraction (nd-SPME). The uptake kinetics of PPCPs by the nd-SPME fibers increased proportionally with DOM concentrations, likely due to enhanced diffusive conductivity in the unstirred water layer. At neutral pH, the partitioning coefficients of PPCPs for Humic Acid (log KDOC 3.87–5.25) were marginally higher than those for Fulvic Acid (log KDOC 3.64–5.11). Also, the log KDOC values correlated linearly with the log DOW (pH 7.0) values of PPCPs, indicating a predominant role for hydrophobic interactions in the binding of DOM and PPCPs. Additionally, specific interactions like hydrogen bonding, π-π, and electrostatic interactions occur for certain compounds, influenced by the polarity and spatial conformation of the compounds. For these ionizable PPCPs, the log DDOC values exhibit a strong dependence on pH due to the dual influence of pH on both DOM and PPCPs. The log DDOC values rose from pH 1.0 to 3.0, peaked at pH 5.0 to 9.0, and then (sharply) declined from 11.0 to 13.0. The reasons are that in strong acidic circumstances, the coiled and compressed shape of DOM inhibits the hydrophobic interaction, whereas in strong alkaline conditions, significant electrostatic repulsion reduces the sorption. This study reveals that the effects of DOM on the bioavailability of PPCPs are dependent on both pH and the specific compound involved.

Response of antioxidation and immunity to combined influences of pH and ammonia nitrogen in the spotted babylon (Babylonia areolata)

Spotted babylon were exposed to three different pH levels (7.0, 8.0 and 9.0) and four different concentrations of ammonia nitrogen (0.02, 1.02, 5.10 and 10.20 mg/L) in seawater to determine their acute toxicity and physiological responses to environmental fluctuation. The study evaluated four antioxidant enzymes: catalase (CAT), alkaline, superoxide dismutase (SOD), peroxidase (POD) and glutathione peroxidase (GSH-PX), and two immunoenzymes: acid phosphatase (ACP) and phosphatase (AKP). Over time, the immunoenzyme activity was significantly affected by pH and ammonia nitrogen concentration. After being exposed to pH and ammonia nitrogen, the spotted babylon showed signs of unresponsiveness to external stimuli, reduced vitality, slow movement, and an inability to maintain an upright position. Over time, the spotted babylon exhibited a trend of increasing and then decreasing GSH-PX, CAT, and SOD activities to adapt to the changing environment and enhance its immunity. On the contrary, the POD and ACP activities exhibited a decreasing trend initially, followed by an increasing trend over time and the AKP activity showed a gradual increase with time. The combined effect of pH and ammonia was found to be stronger than the effect of either factor alone. The interaction between pH and ammonia increased the activity of the spotted babylon antioxidant enzymes, induced oxidative stress, and reduced the ability of the spotted babylon's non-specific immune system to reverse it. Thus, the reverse-back of the spotted babylon was higher when pH and ammonia stress were dual than when pH or ammonia were single-factor stresses. The study results will establish a theoretical basis for analyzing the risk of multiple factors to the spotted babylon, and also enrich the basic information about the shellfish immune system.

Rainbow trout (Oncorhynchus mykiss) sperm collected post-mortem could be revitalised by short-term storage

Post-mortem semen collection in fisheries is a frequently used breeding method for wild fish species with high mortality rates after capture. Moreover, breeders are interested in the possibility of using milt from fish that have died during the spawning season. This study aimed to investigate the possibility of revitalising rainbow trout (Oncorhynchus mykiss) sperm with the use of short-term storage of undiluted and diluted semen samples collected from the fish post-mortem. We found that the pH decreased rapidly in the semen within 8 h of the fish's death, while lactic acid concentration increased simultaneously. We found that nearly immotile rainbow trout sperm collected from the fish body 2, 4, 6, and 8 h after its death regained their motility as a result of short-term storage. In the samples taken 10 h after the fish's death, sperm revitalisation was significantly lower compared to the samples taken 2, 4, 6, and 8 h after the death of the fish. After this time, only samples diluted with artificial seminal plasma (ASP) were able to regain about 20% motility. Completely recovered motility was observed when the semen was collected within 2 h after the fish's death and the samples were diluted in an ASP solution. Our in vitro study showed that sperm exposed only to low pH (7.5) did not decrease their motility within hours, as it was observed in vivo. We found that the addition of different lactic acid concentrations to semen samples in ASP with low pH (7.5) caused a significant and rapid decrease in sperm motility, which is reversible, however, only when not more than a 10 mM concentration of lactic acid was used. In conclusion, we believe that the combined effect of pH and lactic acid accumulated in the gonads after the fish's death may be responsible for the permanent immobilisation of rainbow trout sperm.

The combined effect of pH and dissolved inorganic carbon concentrations on the physiology of plastidic ciliate Mesodinium rubrum and its cryptophyte prey

Ocean acidification is caused by rising atmospheric partial pressure of CO2 (pCO2) and involves a lowering of pH combined with increased concentrations of CO2 and dissolved in organic carbon in ocean waters. Many studies investigated the consequences of these combined changes on marine phytoplankton, yet only few attempted to separate the effects of decreased pH and increased pCO2. Moreover, studies typically target photoautotrophic phytoplankton, while little is known of plastidic protists that depend on the ingestion of plastids from their prey. Therefore, we studied the separate and interactive effects of pH and DIC levels on the plastidic ciliate Mesodinium rubrum, which is known to form red tides in coastal waters worldwide. Also, we tested the effects on their prey, which typically are cryptophytes belonging to the Teleaulax/Plagioslemis/Geminigera species complex. These cryptophytes not only serve as food for the ciliate, but also as a supplier of chloroplasts and prey nuclei. We exposed M. rubrum and the two cryptophyte species, T. acuta, T. amphioxeia to different pH (6.8 - 8) and DIC levels (∼ 6.5 - 26 mg C L-1) and assessed their growth and photosynthetic rates, and cellular chlorophyll a and elemental contents. Our findings did not show consistent significant effects across the ranges in pH and/or DIC, except for M. rubrum, for which growth was negatively affected only by the lowest pH of 6.8 combined with lower DIC concentrations. It thus seems that M. rubrum is largely resilient to changes in pH and DIC, and its blooms may not be strongly impacted by the changes in ocean carbonate chemistry projected for the end of the 21st century.

Source, Distribution, and Risk Estimation of Hazardous Elements in Farmland Soils in a Typical Alluvial-Lacustrine Transition Basin, Hunan Province.

Increased concentrations of heavy metals in soil due to anthropogenic activities pose a considerable threat to human health and require constant attention. This study investigates the spatial distribution of heavy metals (Cd, Pb, Zn, Sb) and metalloids (As) in a typical alluvial–lacustrine transition basin and calculates the bioavailable forms of elements posing a direct threat. Qualitative and quantitative methods were used to identify the sources of contaminants, after which an ecological risk assessment was conducted. Total (T) As, Pb, and Zn decreased with the depth, whereas Cd and Sb increased in surface (0–20 cm) soil. Bioavailable (Bio) Cd and Pb in the topsoil were regulated by pH and organic matter, whereas Bio-Zn was regulated by soil pH. Within deeper soil layers, the combined effects of pH, organic matter, and clay contents regulated the bio-elements. The results of multiple methods and local investigation showed that TSb (65.3%) was mainly derived from mining activities, TCd (53.2%) and TZn (53.7%) were derived from direct pollution by industrial production and agricultural fertilizers, respectively, and TA (55.6%) was mainly derived from the soil parent material. TPb was related to vehicle exhaust emissions and atmospheric deposition from industrial activities. Although the potential ecological risk in the study area remains relatively low, there is a need for continuous monitoring of the potential ecological risks of Cd and Sb. This study can act as a reference for the prevention and mitigation of heavy metal contamination of alluvial–lacustrine transition basins.

A statistical modeling-optimization approach for photocatalytic degradation of diflouro triazole acetophenone using Ag-Fe co-doped TiO2: response surface methodology.

In this research, the performance of Ag-Fe co-doped TiO2 (Ag-Fe CT) nanophotocatalyst for degradation of diflouro triazole acetophenone (DTA) from aqueous solutions under solar and UV radiations was compared. The novel photocatalyst was synthesized using a sol-gel method with varying Ti to Ag mole ratio (10, 25, 30, 40, 55). Synthetic wastewater was prepared from diflouro triazole acetophenone (DTA concentration 8g/L and COD = 75,000mg/L). Ag-Fe CT 30 photocatalyst has shown maximum COD removal efficiency for solar and UV irradiation. Ag-Fe CT 30 photocatalyst was able to absorb visible and UV radiations. Recyclability test proved that Ag-Fe CT 30 can be reused 3 times effectively for a not significant decrease in COD removal efficiency. A response surface methodology (RSM) was used to study the single and combined effects of pH, photocatalyst dose, and Ti to Ag mole ratio parameters. Model showing relation of parameters with COD reduction efficiency has been developed and optimization has been carried out for solar and UV radiations. Results revealed that the optimal conditions for DTA removal were initial pH 5, photocatalyst dose of 3g/L, and Ti to Ag mole ratio of 30. Maximum COD removal efficiency of 76% and 86% was observed under solar and UV radiations, respectively. This study would be useful for the removal of non-biodegradable organics from high-strength COD effluent in an economical and eco-friendly way.

Effect of Black Bean Koji Enzyme on Fermentation, Chemical Properties and Biogenic Amine Formation of Fermented Fish Sauce

ABSTRACT This study aimed to study the combined effect of pH and sodium chloride on black bean koji enzyme activities and the effects of these enzyme on fermentation, chemical properties, and biogenic amine formation of fermented fish sauce. A pH of 5 was optimal for the amylase and protease activity of the black bean koji enzyme. Higher sodium chloride concentrations exerted more detrimental effects on the protease than the amylase enzyme. Protease activity clearly decreased with sodium chloride concentrations higher than 5%. In contrast, during fish sauce fermentation, the protease activity in samples containing 40% koji increased over 12 weeks of fermentation, which correlated with an increase in total soluble nitrogen. The histamine content in 40% koji fish sauce samples was 13.83–16.86 mg/L, which was lower than the commercial product, and no other biogenic amines were detected. Therefore, active proteolytic enzymes from black bean koji could be used as accelerant enzymes for fish sauce fermentation and reduce the risk of scombroid fish poisoning.

The Effects of Testing Conditions on Corrosion Behaviours of SS316L for Bipolar Plate of Proton Exchange Membrane Fuel Cell

Proton exchange membrane fuel cell (PEMFC) has been regarded as the most promising technology for solving problems, such as energy shortage, environmental pollution and global warming caused by fossil fuels due to its high efficiency, low operating temperatures, near zero emission and unlimited sources of hydrogen. However, large-scale commercial application of PEMFC is still hindered by high cost, limited performance and durability. As one of the key components, bipolar plate (BPP) has a great impact on performance, durability and cost of PEMFC. Stainless steel 316L (SS316L) has been considered to be one of the most appropriate candidates for automotive application because of its high thermal and electrical conductivity, superior mechanical properties, ease of manufacture and relatively low cost. However, release of metal ions and improvement of interfacial contact resistance (ICR) caused by corrosion of stainless steel BPP in PEMFC working environment still remains a big challenge. The corrosion of BPP may lead to deteriorate of performance and durability, or even the damage of PEMFC. Therefore, it is important to improve the performance, durability and lower the cost by seeking the appropriate base or coating materials for BPP. Because of the complexity of working conditions for BPP in a PEMFC, it is also critical to determine a reliable assessment method for evaluating corrosion resistance of materials for BPP. The typical working environment of PEMFC is normally considered to be weak acidic with pH in the range of 3 ~ 6 and contain different cations, such as F-1 and Cl-1 while the temperature is in the range of 60 ~ 80 ℃. However, most of the studies for measuring the corrosion resistance of BPP materials are conducted in a much harsher condition of 0.5 ~ 1 M H2SO4 (pH about 0.3 ~ 0) and 2 ppm HF with temperature in the range of 70 ~ 80 ℃. Although a few researches have been carried out to study individually the effects of pH or temperature on corrosion resistance of stainless steel for BPP, the combined effects of pH, temperature and bubbled gas on corrosion resistance of SS316L have not been investigated. In addition, the effects of high potential on corrosion behaviours of SS316L are neglected in former studies. In this work, the effects of temperature, pH, bubbled gas and potential on corrosion behaviours of SS316L are studied comprehensively. Moreover, SEM, EBSD and EDX are performed to reveal the mechanism of microstructure and chemical composition evolution of SS316L under different testing conditions mentioned above. The results reveal that temperature, pH and bubbled gas all have significant influences on corrosion potential (Ecorr.), corrosion current density (Icorr.) and passive current density (Ip) of SS316L. Besides, the influence of any one of the aforementioned factors on corrosion behaviour of SS316L is determined by the other two factors. Icorr. of SS316L in logarithm is generally proportional to pH at all temperatures in both argon or oxygen bubbled solutions. There are distinct passive regions for the Tafel curves of SS316L when potentiodynamic tests are performed in accelerated solutions with pH in the range of 0 ~ 1. On the contrary, pseudopassive behaviour would occur when SS316L are tested in the simulated conditions with pH in the range of 3 ~ 5. The results also indicate that severer corrosion would appear as higher potential is applied on SS316L. Pitting are shown to be the main corrosion for SS316L subjected to simulated solutions while the main corrosion mechanism is shifted to intergranular or uniform corrosion for SS316L under harsher testing conditions with pH in the range of 0 ~ 1. Figure 1

Effect of Commercial Protective Cultures and Bacterial Fermentates on Listeria monocytogenes Growth in a Refrigerated High-Moisture Model Cheese

Biopreservatives are clean-label ingredients used to control pathogenic and spoilage microorganisms in ready-to-eat foods, including cheese. In a first set of experiments, the efficacies of six commercial biopreservatives in controlling Listeria monocytogenes growth at 4°C were tested in a high-moisture model cheese (pH 6.00, 56% moisture, and 1.25% salt) made of cream, micellar casein, water, salt, lactose, lactic acid, and a single protective culture (PC-1, PC-2, or PC-3 at 106 CFU/g [target]) or bacterial fermentate (CM-1 or CM-2 [cultured milk] or CSV-1 [cultured sugar-vinegar blend], 0.5 or 1.0% target level). Cheeses were inoculated with 3 log CFU/g L. monocytogenes (5-strain cocktail), after which 25-g samples were vacuum sealed and stored at 4°C for 8 weeks. L. monocytogenes populations from triplicate samples were enumerated weekly on modified Oxford agar in duplicate trials. L. monocytogenes growth (≥1-log increase) was observed in approximately 1 week in control cheese and those formulated with 106 CFU of PC-1 or PC-2 per g. Growth was delayed to 2.5 weeks in model cheeses formulated with 106 CFU of PC-3 per g or 0.5% CM-2 and to 3 weeks with 0.5% CM-1 or CSV-1. Growth was further delayed to 6.5 to 7.5 weeks in model cheeses formulated with 1.0% CM-1 or CM-2, while formulation with 1.0% CSV-1 inhibited L. monocytogenes growth for 8 weeks. In a second set of experiments, the combined effects of pH and 0.5% CSV-1 on L. monocytogenes inhibition were investigated. Incorporation of 0.5% CSV-1 delayed L. monocytogenes growth to 3, 6, and >10 weeks in cheeses of pH 6.00, 5.75, and 5.50, respectively, versus growth observed in 1, 1, and 3.5 weeks in control cheeses. These data suggest that certain fermentates have greater antilisterial activity than protective cultures in directly acidified cheeses with direct biopreservative incorporation and refrigerated storage. Further research is needed to optimize the conditions to prevent listerial growth by utilizing protective cultures in fresh, soft cheeses.

Investigation of the adsorption performance of acid treated lignite coal for Cr (VI) removal from aqueous solution

Several methods have been used to reduce the negative contribution of heavy metal contaminants effluents in the environment. The method studied in this research was the use of activated carbon derived from Ethiopian lignite for hexavalent chromium adsorption from aqueous solution. The adsorption study was evaluated as the function of initial Cr (VI) concentration, adsorbent dosage and pH. All the batches' tests were conducted by using synthetic wastewater in this study. General Factorial Design (GFD) of Response surface methodology (RSM) was used in this batch test for analysis of experimental. The effects of independent variables on various initial Cr (VI) concentrations between 20 ppm and 100 ppm were evaluated. According to ANOVA analysis, each and combined term is statistically significant. A Cr (VI) removal efficiency of 98 % was achieved at pH 1 with 3.5 g of LAC in 200 ml of solution at 4 h of contact time using initial Cr (VI) concentration of 20 ppm. Removal increased up to 96.54% when Cr (VI) concentration decreased to 20.5 ppm, and adsorbent dose increased to 3.01 g at pH 1. 49.94% chrome removal was achieved at Cr (VI) concentration of 100 ppm and pH 5 with an adsorbent dose of 3.5 g for the combined effect of initial Cr (VI) concentration and pH, which was decreased with increased both initial Cr (VI) concentrations and pH value. With the combined effect of pH and adsorbent dosage the maximum percentage removal of Cr (VI) ion was obtained at lower pH and higher adsorbent dosage (96.5%). The adsorption of Cr (VI) was evaluated using batch adsorption equilibrium isotherms (Langmuir and Frendlich) and kinetics reaction rate (first and second order). The Frendlich isotherm model was the best one for the description of adsorption of Cr (VI) onto LAC heterogeneous surface energy. The adsorption kinetics of Cr (VI) onto LAC followed the second order kinetic model, suggesting that the adsorption reaction rate depends on two parameters, which might be the Cr (VI) concentration and adsorbent dosage. These results support similar conclusions mentioned by several authors in the literature.

Natural Organic Matter, Orthophosphate, pH, and Growth Phase Can Limit Copper Antimicrobial Efficacy for Legionella in Drinking Water.

Copper (Cu) is a promising antimicrobial for premise plumbing, where ions can be dosed directly via copper silver ionization or released naturally via corrosion of Cu pipes, but Cu sometimes inhibits and other times stimulates Legionella growth. Our overarching hypothesis was that water chemistry and growth phase control the net effect of Cu on Legionella. The combined effects of pH, phosphate concentration, and natural organic matter (NOM) were comprehensively examined over a range of conditions relevant to drinking water in bench-scale pure culture experiments, illuminating the effects of Cu speciation and precipitation. It was found that cupric ions (Cu2+) were drastically reduced at pH > 7.0 or in the presence of ligand-forming phosphates or NOM. Further, exponential phase L. pneumophila were 2.5× more susceptible to Cu toxicity relative to early stationary phase cultures. While Cu2+ ion was the most effective biocidal form of Cu, other inorganic ligands also had some biocidal impacts. A comparison of 33 large drinking water utilities' field-data from 1990 and 2018 showed that Cu2+ levels likely decreased more dramatically (>10×) than did the total or soluble Cu (2×) over recent decades. The overall findings aid in improving the efficacy of Cu as an actively dosed or passively released antimicrobial against L. pneumophila.

Antioxidant responses of the mussel Mytilus coruscus co-exposed to ocean acidification, hypoxia and warming

In the present study, the combined effects of pH, dissolved oxygen (DO) and temperature levels on the antioxidant responses of the mussel Mytilus coruscus were evaluated. Mussels were exposed to two pH (8.1, 7.7-acidification), two DO (6 mg L−1, 2 mg L−1-hypoxia) and two temperature levels (20 °C, 30 °C-warming) for 30 days. SOD, CAT, MDA, GPx, GSH, GST, TAOC, AKP, ACP, GPT, AST levels were measured in the gills of mussels. All tested biochemical parameters were altered by these three environmental stressors. Values for all the test parameters except GSH first increased and then decreased at various experimental treatments during days 15 and 30 as a result of acidification, hypoxia and warming. GSH content always increased with decreased pH, decreased DO and increased temperature. PCA showed a positive correlation among all the measured biochemical indexes. IBR results showed that M. coruscus were adversely affected by reduced pH, low DO and elevated temperature.

Feasibility of electro coagulation using iron electrodes in treating paper industry wastewater

The paper-making process generates a large quantum of wastewater (ww); due to its squat biodegradability index, electro-coagulation (EC) method of treatment is gaining the significance as compared to biochemical and other conventional techniques. Electro-oxidation of anodes produces the coagulant, and eases the treatment with no external coagulant usage. This study is aimed in determining the efficacy of EC using iron electrodes in treating paper industry ww. The combined influence of treatment time (T), pH and applied voltage (V) is examined by conducting a series of experiments of ww treatment designed based on the response surface method (RSM); subsequently, the influence on TDS, turbidity, TOC and COD was also assessed individually. The respective experimental outcomes have been statically validated for their effectiveness by carrying the regression, parametric tests, analysis of variance (ANOVA), distribution and residual analysis. The pilot study effectively reduced the TDS, turbidity, TOC and COD, respectively, to 51%, 65% 68%, and 70% at the optimum pH 8, T −60 min. and 20 V, with the individual regressions (R2) of 0.95, 0.87, 0.92 and 0.78 with the P value < 0.001. Similarly, the combined effect of pH, T and V on ww developed the regression of 0.88 with the P value < 0.001. The empirical model reveals a good correlation between experimental and predicted data.

Combined effects of pH and thermal treatments on IgE-binding capacity and conformational structures of lectin from black kidney bean (Phaseolus vulgaris L.).

Combined effects of pH and thermal treatments on black kidney bean lectin (BKBL) were investigated by response surface methodology (RSM). Low-pH (1.0, 2.0, 3.0) incubation decreased hemagglutination activity (HA) and IgE-binding capacity, but the activities would be restored when the lectin was treated by pH shifting to 7.2. Conformational structure analyses indicated that low-pH induced protein unfolding and pH-shifting treatment resulted in a limited structural rearrangement. Mild heating, such as 60°C for 3min, slightly increased the HA and IgE-binding activities of pH shifted BKBL, but no obvious effects in the pH 1.0 incubated BKBL. High-temperature and long-time treatment might induce the protein aggregation, further decreased HA and IgE-binding capacities. RSM results showed both IgE-binding capacity and HA were the lowest under the combination of pH 1.0 incubation with 80°C heating for 15min or pH shifting from 1.0 to 7.2 with 100°C heating for 10min.

Wheat Straw Biochar as a Specific Sorbent of Cobalt in Soil.

There is an urgent need to search for new sorbents of pollutants presently delivered to the environment. Recently biochar has received much attention as a low-cost, highly effective heavy metal adsorbent. Biochar has been identified as an efficient material for cobalt (Co) immobilization from waters; however, little is known about the role of Co immobilization in soil. Hence, in this study, a batch experiment and a long-term incubation experiment with biochar application to multi-contaminated soil with distinct properties (sand, loam) were conducted to provide a brief explanation of the potential mechanisms of Co (II) sorption on wheat straw biochar and to describe additional processes that modify material efficiency for metal sorption in soil. The soil treatments with 5% (v/w) wheat straw biochar proved to be efficient in reducing Co mobility and bioavailability. The mechanism of these processes could be related to direct and indirect effects of biochar incorporation into soil. The FT-IR analysis confirmed that hydroxyl and carboxyl groups present on the biochar surface played a dominant role in Co (II) surface complexation. The combined effect of pH, metal complexation capacity, and the presence of Fe and Mn oxides added to wheat straw biochar resulted in an effective reduction of soluble Co (II), showing high efficiency of this material for cobalt sorption in contaminated soils.

Microplastic pollution reduction by a carbon and nitrogen-doped TiO2: Effect of pH and temperature in the photocatalytic degradation process

Microplastics (MPs) are pollutants formed by plastics ≤ 5 mm and are present in marine and terrestrial environments. Due to their large surface to volume ratio and chemical surface properties, MPs adsorb hazardous chemicals from their surrounding environment. When MPs are consumed by fauna, they transfer those substances through the trophic chain. An essential issue of MPs is their disposal. Due to their size, the disposal methods commonly used for plastic items are not suited for MPs. Here, photocatalysis in an aqueous medium is proposed as an alternative to fight MPs pollution. Although the photocatalysis of MPs has been reported, the effect of operating variables in the process has not been investigated. To fill this gap, the impact of pH and temperature on the degradation process of HDPE MPs was investigated using C,N-TiO2 and visible light. Degradation was followed by mass loss, carbonyl index calculation and microscopy. It was found that photocatalysis at low temperature (0 °C) increases MPs’ surface area by fragmentation, and low pH value (pH 3) favours hydroperoxide formation during photooxidation. By using the design of experiments tool, it was demonstrated that there is a combined effect of pH and temperature in the photocatalysis of HDPE MPs.

Effects of ionic and reductive atmosphere on the conformational rearrangement in hen egg white lysozyme prior to amyloid formation

In this study, the combined effects of pH and salt concentration on the aggregation and amyloid formation of a charge-bearing protein (hen egg white lysozyme, HEWL) were investigated, as well as the inhibition of amyloid formation by using dithiothreitol (DTT) as a denaturing agent. Amyloid formation was found to depend on the ion strength and pH of the sample solution. Rather than the total charge, the partial charge of the amyloid related residues contributes to amyloid formation at pH < isoelectric point (pI). On the other hand, at pH> pI HEWL only undergoes alkaline denaturation regardless of the ionic strength. The effect of adding different amounts of DTT at different times on amyloid formation was also investigated. These results suggested that the positions of charges on a protein and the protein secondary structure are critical for protein aggregation and amyloid formation.

Active control of salinity-based power generation in nanopores using thermal and pH effects.

Harvesting blue energy from saline solutions has attracted much attention recently. Salinity-based power generation in nanopores is governed by both passive factors (e.g., the nanopore diameter, nanopore length, nanopore material, and pore density) and active factors (e.g., the concentration gradient, temperature, and pH environment). The present study performs COMSOL multiphysics numerical simulations based on the Poisson–Nernst–Planck equations, Navier–Stokes equations and heat transfer equation to examine the combined effects of the temperature gradient and pH level on the diffusion voltage and maximum power generation in single silica nanopores with lengths of 100 nm and 500 nm, respectively. In performing the simulations, the pH value is adjusted in the range of pH 5–11, the salinity concentration gradient is 100-fold and 1000-fold, respectively. Three different thermal conditions are considered, namely (1) isothermal-room temperature (298 K); (2) asymmetric thermal (temperature of low-concentration reservoir and high-concentration reservoir are 323 K and 298 K, respectively); and (3) isothermal-high temperature (323 K). The results show that the generated power varies significantly with both the pH level and the temperature conditions. In particular, the asymmetric thermal condition yields an effective improvement in the power generation performance since it reduces the surface charge density on the surface of the nanopore near the low-concentration end and therefore suppresses the ion concentration polarization (ICP) effect. The improvement in the energy harvesting performance is particularly apparent at pH levels in the range of 9–10 (about 100% higher than that of pH 7). Overall, the results confirm the feasibility of using active factors to enhance the power generation performance of salinity gradient-based nanopore systems.

Effect of soil pH and organic matter content on heavy metals availability in maize (Zea mays L.) rhizospheric soil of non-ferrous metals smelting area.

Maize plant tissues and rhizosphere soil were collected from an agricultural area around the Huludao Zinc Plant in Liaoning Province, China, to investigate the effects of soil pH and organic matter content on heavy metal concentration and accumulation in different types of maize tissues. The mean pH of the soil samples was 7.02 (range 5.74-7.86), and the mean organic matter content was 31.03gkg-1 (range 18.80-52.20gkg-1). The average Cu, Zn, Pb, and Cd contents in soil were 2.92, 6.72, 7.95, and 16.28 times greater than the corresponding background values, respectively. The geo-accumulation index indicated that the soils were uncontaminated to moderately contaminated by Cu, moderately to strongly contaminated by Pb and Zn, and strongly contaminated by Cd. The average available Cu, Pb, Zn, and Cd contents in the soil samples were 16.34, 6.997, 69.77, and 0.190mgkg-1, respectively, while their bioavailability coefficients were 28.53%, 1.65%, 40.44%, and 10.83%, respectively. The respective mean Pb and Cd concentrations in grain samples were 0.341 and 0.342mgkg-1, which exceeded the maximum concentrations permitted by the Chinese National Standard. Thus, the maize grain is not safe for consumption and poses potential risks to human health. With the exception of Cu, the combined effect of pH and organic matter content had a stronger influence on the availability of heavy metals in soil compared with either factor alone. Cd uptake in maize plant tissues was affected by the combination of soil pH, organic matter content, and bioavailable Cd content in soil; however, the combination of these three factors had only slight effects on Cu, Zn, and Pb absorption in maize tissues.