Scale precipitation on HDPE pipe by degassing of CO2 dissolved in water

In Algeria, high-density polyethylene (HDPE) is widely used in drinking water pipes. This study is focused on the precipitation of calcium carbonate, a major constituent of scale, from calcocarbonically pure (CCP) water in HDPE pipe. Studying scaling in natural conditions is very difficult because it occurs over many years. For this, accelerated scaling is caused by the degassing CO2 dissolved in water. The kinetic study has shown that the germination time and the critical pH decrease with the hardness (30, 40 and 50 °f) and temperature (30, 40 and 50 °C) of water. On the other hand, scaling process efficiency (η) and the supersaturation coefficient (Ωcal) of CaCO3 increase with these parameters. The CaCO3 precipitation occurs both in solution and on walls of HDPE. By the weighing method, it is shown that the deposit mass increases with hardness and temperature. Calcium carbonate precipitates much more in homogeneous phase than in heterogeneous one. The study also showed that heterogeneous nucleation on HDPE is much less important than on PA, PVC, chrome and Inox. These measurements are supported by the characterization of X-ray diffraction deposits and by scanning electron microscopy, which recognizes that the precipitate obtained consists mainly of calcite.

Binary Graft of Poly(N-vinylcaprolactam) and Poly(acrylic acid) onto Chitosan Hydrogels Using Ionizing Radiation for the Retention and Controlled Release of Therapeutic Compounds

In this study, we carried out the synthesis of a thermo- and pH-sensitive binary graft, based on N-vinylcaprolactam (NVCL) and pH sensitive acrylic acid (AAc) monomers, onto chitosan gels (net-CS) by ionizing radiation. Pre-oxidative irradiation and direct methods were examined, and materials obtained were characterized by FTIR-ATR, thermogravimetric analysis (TGA), scanning electron microscopy (SEM), and swelling tests (equilibrium swelling time, critical pH, and temperature). The best synthesis radiation method was the direct method, which resulted in the maximum grafting percentages (~40%) at low doses (10–12 kGy). The main goal of this study was the comparison of the swelling behavior and physicochemical properties of net-CS with those of the binary system (net-CS)-g-NVCL/AAc with the optimum grafting percentage (~30%). This produced a material that showed an upper critical solution temperature (UCST) of 33.5 °C and a critical pH value of 3.8, indicating the system is more hydrophilic at higher temperatures and low pH values. Load and release studies were carried out using diclofenac. The grafted system (32%) was able to load 19.3 mg g−1 of diclofenac and release about 95% within 200 min, in comparison to net-CS, which only released 80% during the same period. When the grafted system was protonated before diclofenac loading, it loaded 27.6 mg g−1. However, the drug was strongly retained in the material by electrostatic interactions and only released about 20%.

Assessment of the Erosive Potential of the Commonly Consumed Fruit-Based Beverages Among Children

Background: Dental erosion, an irreversible loss of dental hard tissue by a chemical process without the involvement of bacteria can be caused by various intrinsic and extrinsic factors. The consumption of foods with a low pH can cause a drop in the pH of the oral cavity below critical pH and its persistence can lead to a potential damage to teeth. As acidic beverages are likely to be a major factor in the etiology of dental erosion, it is important to determine the erosive potential of commonly consumed fruit-based beverages among children and educate the parents of their detrimental effects on teeth. Objectives: To evaluate and compare the pH and titratable acidity of the commonly consumed fruit-based beverages. Methodology: Three commonly consumed flavours (Orange, Apple, Mixed fruit) of fruit-based beverages (Group 1 - fresh fruit juice; Group 2 - packed fruit juice; Group 3 - packed fruit drink) were analyzed for pH and titratable acidity. The pH was determined using digital pH meter and the titratable acidity was measured by adding 1M sodium hydroxide (NaOH) in increments of 0.2 ml to 100 ml of the freshly prepared/ opened fruit-based beverages until the pH reached 5.5 and 7. The pH reading was measured after each increment (0.2 ml) of NaOH, until a stable pH was achieved. All the measurements were repeated in triplicates. Results: The pH of all drinks investigated in the present study ranged between 3.29 - 4.43. On comparison of the titratable acidity, packed fruit drink (Group 3) exhibited highest titratable acidity, followed by packed fruit juices (Group 2) and fresh fruit juices (Group 1). Conclusion: All the fruit-based beverages in the present study exhibited an acidic pH, which was well below the critical pH of 5.5, thereby exhibiting an erosive potential.

Soil pH Responses to Simulated Acid Rain Leaching in Three Agricultural Soils

Soil has the nature of acidity and alkalinity, mostly indicated by soil pH that could greatly affect soil ecological processes and functions. With exogenous inputs of acidic materials (such as acid rain), soils may more or less resist to maintain their pH levels within specific thresholds by various buffering processes. It has been well established that soil properties such as cation exchange capacity (CEC), soil organic matter (SOM), and clay content play important roles in mitigating the effects of acid inputs, but the factors varied across soils. This microcosm experiment was conducted to investigate changes in the soil pH and quantitatively estimate the critical pH threshold of simulated acid rain for three highly weathered soils (red soil, lateritic red soil, and latosol) that are typical soil types widely distributed across the world’s subtropical and tropical climatic zones, as well as important influential factors, after continuously adding different levels of simulated acid rain on the surface of soil cores. The results showed that the change in the soil pH was not significantly different among the three soils, although it was exponentially related to soil CEC and clay content. Resultantly, the latosol that had high soil CEC and clay content was more resistant to simulated acid rain, especially when relatively weak simulated acid rain treatments were applied. The lateritic red soil that contained the lowest soil CEC and clay content showed the greatest decline in the soil pH under the strongest simulated acid rain treatment of pH being 2.5. Furthermore, we estimated the critical pH threshold of simulated acid rain for the three soils and observed that it was considerably different among the soils. Surprisingly, the pH threshold of simulated acid rain was also positively related to the soil CEC and clay content, therefore making the highest pH threshold in the latosol. Our results imply that soil CEC and clay content may play critical roles in the soil acid-buffering processes from two aspects; it could not only contribute to the soil acid-buffering capacity, but also affect the threshold of acidity of acid rain below which abrupt soil acidification may occur.

Solvent Treatment of Wet-Spun PEDOT: PSS Fibers for Fiber-Based Wearable pH Sensing

There is a growing desire for wearable sensors in health applications. Fibers are inherently flexible and as such can be used as the electrodes of flexible sensors. Fiber-based electrodes are an ideal format to allow incorporation into fabrics and clothing and for use in wearable devices. Electrically conducting fibers were produced from a dispersion of poly (3,4-ethylenedioxythiophene)-poly (styrenesulfonate) (PEDOT: PSS). Fibers were wet spun from two PEDOT: PSS sources, in three fiber diameters. The effect of three different chemical treatments on the fibers were investigated and compared. Short 5 min treatment times with dimethyl sulfoxide (DMSO) on 20 μm fibers produced from Clevios PH1000 were found to produce the best overall treatment. Up to a six-fold increase in electrical conductivity was achieved, reaching 800 S cm−1, with no loss of mechanical strength (150 MPa). With a pH-sensitive polyaniline coating, these fibers displayed a Nernstian response across a pH range of 3.0 to 7.0, which covers the physiologically critical pH range for skin. These results provide opportunities for future wearable, fiber-based sensors including real-time, on-body pH sensing to monitor skin disease.

Chemical Potential-Induced Wall State Transitions in Plant Cell Growth

The pH/T duality of acidic pH and temperature (T) action for the growth of grass shoots was examined in order to derive the phenomenological equation of wall properties for living plants. By considering non-meristematic growth as a dynamic series of state transitions (STs) in the extending primary wall, the critical exponents were identified, which exhibit a singular behaviour at a critical temperature, critical pH and critical chemical potential (μ) in the form of four power laws: $$f_{\pi } \left( \tau \right) \propto \left| \tau \right|^{\beta - 1}$$ f π τ ∝ τ β - 1 , $$f_{\tau } (\pi ) \propto \left| \pi \right|^{1 - \alpha }$$ f τ ( π ) ∝ π 1 - α , $$g_{\mu } (\tau ) \propto \left| \tau \right|^{ - 2 - \alpha + 2\beta }$$ g μ ( τ ) ∝ τ - 2 - α + 2 β and $$g_{\tau } (\mu ) \propto \left| \mu \right|^{2 - \alpha }$$ g τ ( μ ) ∝ μ 2 - α . The indices α and β are constants, while π and τ represent a reduced pH and reduced temperature, respectively. The convexity relation α + β ≥ 2 for practical pH-based analysis and β ≡ 2 “mean-field” value in microscopic (μ) representation were derived. In this scenario, the magnitude that is decisive is the chemical potential of the H+ ions, which force subsequent STs and growth. Furthermore, observation that the growth rate is generally proportional to the product of the Euler beta functions of T and pH, allowed to determine the hidden content of the Lockhart constant Ф. It turned out that the pH-dependent time evolution equation explains either the monotonic growth or periodic extension that is usually observed—like the one detected in pollen tubes—in a unified account.

An electrospun fibrous platform for visualizing the critical pH point inducing tooth demineralization

The BCG–PS/PVP electrospun fibrous membrane can rapidly, sensitively and conveniently sense the critical pH point of 5.5 of dental caries.

Acid mobilization of aluminum from minerals and rocks

Leaching of aluminum from minerals (hornblende, biotite, mica, microcline, labradorite, albite) and rocks (granite, tuff sandstone, schist) by the acidified river water was experimentally studied. The relationship between aluminum concentration and solution acidity lg[Al] = A – BpH in which slope coefficient В has roughly the same value for all samples, equal 0.740.09, was established. It was drawn a conclusion on prevailing of polymeric hydroxocomplexes of aluminum into solution. The critical pH value below which concentration of dissolved aluminum exceeds the maximum allowable concentration (MAC) for fishery water bodies makes 6.60.3.