High pH Solutions Research Articles

Wettability Alteration of Heavy-Oil-Bitumen-Containing Carbonates by Use of Solvents, High-pH Solutions, and Nano/Ionic Liquids

Summary Capillary imbibition tests are commonly applied to measure wettability-alteration potential of chemicals. However, these tests are exhaustive, time-consuming, and expensive, and the underlying physics of the alteration process from a surface-chemistry point of view is often limited and/or unexplained. Contact-angle measurement is a quicker and more-feasible screening tool to assess the emerging wettability modifiers. It also provides visual data on the mechanics of the wettability-alteration process. This paper focuses on contact-angle measurements as a means to evaluate the wettability alteration on mineral plates and porous-rock samples. Imidazolium ionic liquids were tested at different concentrations. To study the effect of pH on the wettability, sodium chloride and sodium borate were used at different concentrations. The composition of divalent ions was varied because of their possible use with low-/high-salinity water as wettability-alteration agents. Unmodified and surface-modified silica, zirconium, and alumina nanoparticles were also tested. Contact-angle measurements were performed initially on mica, marble, and calcite plates. Experiments were repeated on polished surfaces of Berea sandstone, Indiana limestone, and cleaned Grosmont carbonate cores. Oils (pure and solvent-mixed crude oils) with different viscosities and densities were used to test the effect of oil type on the process. The images were obtained by an single-lens reflex (SLR) camera at different temperatures ranging from 25 to 80°C. By testing with different concentrations, the optimum chemicals were found for different mineral-plate/porous-rock systems. Then, the results were cross checked with the imbibition tests performed on the same samples to validate the contact-angle-measurement observations. Thermal-stability tests were also performed in case of their use during or after a thermal method. For the thermal-stability tests, contact-angle experiments were conducted in a high-pressure and high-temperature (up to 200°C) cell. It was shown that certain ionic liquids and nanofluids are stable at high temperatures and can be efficiently used at low concentrations.

The electrostatic self‐assembly of microgels on polymer brushes and its effects on interfacial friction

ABSTRACTIn this article, a series of monodisperse poly(N‐isopropylacrylamide‐co‐acrylic acid) [P(NIPAm‐AA)] microgels were prepared with different content of acrylic acid (AA) by surfactant‐free emulsion polymerization, and their electrostatic self‐assemble and tribological behavior on polymer brushes were investigated. The ζ‐potential of microgels became more negative with the increase content of AA, which means a stronger hydration capability. For cationic poly[2‐(methacryloyloxy)ethyltrimethylammonium chloride] (PMETAC) brushes, negative P(NIPAm‐AA) microgels adsorbed on the surfaces of brushes as a result of the electrostatic interaction, and more AA content means stronger absorption ability. However, compared to the polymer brushes, P(NIPAm‐AA)2:1 and P(NIPAm‐AA)5:1 microgels possessed the weaker hydration capability, which led to a concomitant increase in friction of interface. In terms of P(NIPAm‐AA)10:1 microgels, due to the weak adsorption, they could be sheared off easily, leading to the PMETAC brushes swell again, and thus, a lower friction of interface was obtained. Moreover, the tribological behavior of microgels was significantly affected by the pH, especially the P(NIPAm‐AA)2:1 microgels exhibited good lubrication property in high pH solution due to high hydration of deprotonated carboxylic acid groups. © 2016 Wiley Periodicals, Inc. J. Appl. Polym. Sci. 2016, 133, 44215.

Bitumen Recovery from Carbonates by a Modified SOS-FR (Steam-Over-Solvent Injection in Fractured Reservoir) Method Using Wettability Alteration Chemicals

This study investigates the applicability of the modified version of the previously proposed SOS-FR (steam-over-solvent injection in fractured reservoir) method to recover bitumen from the Grosmont formation in Canada. Three phases were applied on a total of 13 preserved core samples. In Phase 1, the cores taken from three different parts of the Grosmont formation were soaked in a liquid solvent (heptane or distillate) at ambient conditions. The objective of the first phase was to reduce the viscosity of the bitumen in preparation for the second phase which is wettability alteration. In Phase 2, we soaked the samples in water with chemicals. Wettability modifiers tested include high pH solution, cationic surfactants, and ionic liquids because the screening process indicated they are the most useful wettability alteration chemicals for oil-wet carbonates. One of the key benefits of the ionic liquids is that they are environmentally friendly as they are chemically stable with low level of toxicity and flamm...

Experimental Investigation of Wettability Alteration in Oil-Wet Reservoirs Containing Heavy Oil

Summary Solvent injection is an effective way to lower the viscosity of heavy oil and is considered when thermal techniques are not practically applicable. However, for the economic success of the method, large fractions of the injected solvent must be recovered. This requires further treatments of the reservoir, including water injection with chemicals to penetrate into the oil-wet matrix by changing the wettability. In this paper, we investigate the effect of wettability alteration of the oil-wet rock on solvent as well as oil recovery. Different wettability-alteration agents were tested, including cationic and anionic surfactants, ionic liquids, nanofluids, high-pH solutions, and low-salinity water. The potential of these materials to modify the wettability of aged sandstone and limestone samples was evaluated by use of imbibition tests. After conducting a total of 35 experiments, the most-promising wettability-alteration agents were identified to be anionic surfactants and high-pH solutions in addition to low-salinity water for the sandstone cases. Ion-pair interaction in sandstone and the dissolution of mixed-wet clay particles in carbonate are the main mechanisms of wettability alteration by those chemicals. Cationic surfactants and high-pH solutions were identified as the best wettability modifiers for the limestone samples. Although cationic surfactant changes the wettability by the ion-pair-interaction mechanism, the pH solution is believed to restore the water-wetness by decreasing the attraction forces between calcite and organic components. Ionic liquid at low concentration is able to alter the wettability of carbonate better than other conventional wettability modifiers. One important finding of this work is that solvent injection in heavy-oil-containing reservoirs is essential to condition the reservoir (i.e., to dilute the heavy oil before any wettability-alteration treatment can take place).

Influence of pH on green synthesis of Ag nanoparticles

Ag nanoparticles are synthesized by a biological process using algae Parachlorella kessleri. The effect of changes in the solutions pH on the green synthesis is investigated. The formation of Ag nanoparticles (AgNPs) was monitored using a UV–vis spectrophotometer and verified by TEM. The results confirmed formation of polyhedron and/or near polyhedron AgNPs, ranging between 5 and 60nm in diameter. UV–vis analysis and TEM observation revealed that the size and stability of AgNPs depend on the pH of solution. AgNPs formed in solutions of higher pH (8 and 10) are polyhedron, fine, with narrow size interval and stabile with average size 15nm. Nanoparticles formed in solutions of low pH (2, 4 and 6) started to lose their stability on 10th day of experiment, and the particle size interval was wide.

Composition–rheology relationships in alkali–silica reaction gels and the impact on the gel's deleterious behavior

Alkali–silica reaction (ASR) continues to be a major challenge to the durability of concrete structures. This is in part because the relationships between the composition, properties, and behavior of ASR gels in concrete are poorly understood. Gels with high pore solution pH, osmotic pressure, and rheological (e.g., yield stress) and swelling properties are the most deleterious. In this paper, the effects of the composition (primarily Ca/Si and Na/Si) of synthetic ASR gels on these characteristics are investigated, and regression analyses are done on the data. The pessimum combination of osmotic and rheological properties was found in the case of gels having intermediate calcium and high sodium contents (i.e., Ca/Si=0.2 and Na/Si≈0.85), leading to the highest estimated swelling pressures. These gels also developed the most alkaline pore solutions. While highest yield stresses were observed in the gels with low calcium and low sodium, they showed negligible osmotic and swelling pressures.

Novel anticorrosive zinc phosphate coating for corrosion prevention of reinforced concrete

Deterioration of reinforcing concrete structures is a common problem among all the coast countries. Every year, several billion dollars are spent to repair and maintain reinforced concrete structures. Over time, the metal reinforcing bars used to improve the properties of concrete become susceptible to corrosion due to factors such as the presence of chloride and carbonation. Present work includes the use of novel anticorrosive coating. The use of zinc phosphate (ZP) coating has advantage of the low solubility of phosphates in medium- or high-pH solutions; also the resulting coating remains adhered to the metal surface even under extreme deformation. This study presents the efficiency of a new inhibitive pigment ZP containing zirconium compound obtained by chemical conversion (CC) method and cathodic protection to protect the steel rebars against localised corrosion in concrete. The corrosion behaviour of coated steel was assessed by open circuit potential, potentiodynamic polarisation and electrochemical impedance spectroscopy. Firstly, results demonstrated that the new coating show an adsorption on steel surface and provides an effective corrosion resistance compared to carbon steel rebar. Secondly, results showed that the increased weight of coating made by CC is consistent with the development of the polarisation resistance and corrosion potential of samples studied. Thirdly, a reduction in the corrosion rate is obtained once the coating covers the surface of the metal.

The effect of simulated concrete pore solution composition and chlorides on the electronic properties of passive films on carbon steel rebar

Effects of simulated concrete pore solution composition, pH, and added chlorides on electronic properties of passive films on carbon steel rebar were investigated using Mott–Schottky (M–S) analysis. Passive films showed n-type semiconductive behavior with two discrete donor species and high donor densities. Deep donor densities increased with increasing passivation time. Less protective films resulted in lower space charge capacitances and lower flatband potentials. Sulfates had little influence on electronic properties. Chlorides caused a loss of linearity of M–S plots. This loss of linearity required higher chloride levels and longer exposure times to occur in higher pH solutions.

Mesoporous silicon carbide nanofibers with in situ embedded carbon for co-catalyst free photocatalytic hydrogen production

Silicon carbide (SiC) has been considered a promising metal-free photocatalyst due to its unique photoelectrical properties and thermal/chemical stability. However, its performance suffers from the fast recombination of charge carriers. Herein, we report mesoporous SiC nanofibers with in situ embedded graphitic carbon (SiC NFs-Cx) synthesized via a one-step carbothermal reduction between electrospun carbon nanofibers and Si powders. In the absence of a noble metal co-catalyst, the hydrogen evolution efficiency of SiC NFs-Cx is significantly improved under both simulated solar light (180.2 μmol·g–1·h–1) and visible light irradiation (31.0 μmol·g–1·h–1) in high-pH solution. The efficient simultaneous separation of charge carriers plays a critical role in the high photocatalytic activity. The embedded carbon can swiftly transfer the photogenerated electrons and improve light absorption, whereas the additional hydroxyl anions (OH–) in highpH solution can accelerate the trapping of holes. Our results demonstrate that the production of SiC NFs-Cx, which contains exclusively earth-abundant elements, scaled up, and is environmentally friendly, has great potential for practical applications. This work may provide a new pathway for designing stable, lowcost, high efficiency, and co-catalyst-free photocatalysts.

Cost-effective copper removal by electrosorption powered by microbial fuel cells.

This work studied a cost-effective electrosorption that driven by microbial fuel cells (MFC-sorption) to remove Cu(2+) from wastewater without an external energy supply. The impact factors, adsorption isotherms and kinetics of the novel process were investigated. It indicated that a low electrolyte concentration and a high solution pH could enhance the Cu(2+) removal efficiency, while the adsorption capacity increased with the increase of numbers of MFCs in series and the initial Cu(2+) concentration. The adsorption isotherms study indicated that the monolayer adsorption in MFC-sorption was dominant. The kinetics study suggested the increase of initial Cu(2+) concentration could enhance the initial adsorption rate. The electrode characterizations verified the existence of Cu2O and Cu on the electrode surface of active carbon fibers (ACFs), suggesting that MFC-sorption was not only an adsorption process, but also a redox reaction process.

Influence of AC waveforms on stress corrosion cracking behaviour of pipeline steel in high pH solution

The effect of various waveforms AC on stress corrosion cracking (SCC) behaviour and mechanism of X80 pipeline steel was investigated in high pH carbonate/bicarbonate solution by polarisation curves and slow strain rate tensile tests. Under various waveforms AC, the passivity of the steel degrades severely, and pitting corrosion easily forms on the electrode surface. With or without AC application, the SCC behaviour and mechanism of the steels in the solution are distinctly different. Without the presence of AC, the cracks propagation are intergranular, and the mechanism is anodic dissolution. AC significantly increases the SCC susceptibility of pipeline steel. The order of the SCC susceptibility of the steel at various waveforms AC is: sine wave < square wave < triangular wave. Under a long term AC interference, the fracture mode is transgranular, and the mechanism of the steel in high pH solution is controlled by anodic dissolution and hydrogen embrittlement.

Two-dimensional reactive transport modeling of the alteration of a fractured limestone by hyperalkaline solutions at Maqarin (Jordan)

Two-dimensional reactive transport modeling of the Maqarin Eastern Springs site, a natural analogue for the alteration of a fractured limestone by high-pH Portland cement waters, has been performed using the CrunchFlow code. These 2D calculations included transport by advection–dispersion–diffusion along a single fracture and diffusion in the wall rock. Solute transport was coupled to mineral dissolution and precipitation. A limited sensitivity analysis evaluated the effect of different values of primary mineral surface areas, flow velocity and sulfate concentration of the inflowing high-pH solution.Major secondary minerals include ettringite–thaumasite, C–S–H/C–A–S–H and calcite. C–S–H/C–A–S–H precipitation is controlled by the dissolution of primary silicates. Ettringite precipitation is controlled by diffusion of sulfate and aluminum from the wall rock to the fracture, with aluminum provided by the dissolution of albite. Calcite precipitation is controlled by diffusion of carbonate from the wall rock. Extents of porosity sealing along the fracture and in the fracture-wall rock interface depend on assumptions regarding flow velocity and composition of the high-pH solution. The multiple episodes of fracture sealing and reactivation evidenced in the fracture infills were not included in the simulations. Results can qualitatively reproduce the reported decrease in porosity in the fractures and in the wall rock next to the fractures. Instances of porosity increase next to fractures caused by carbonate dissolution were not reproduced by the calculations.

Acid-Activatable Michael-Type Fluorescent Probes for Thiols and for Labeling Lysosomes in Live Cells.

A Michael addition is usually taken as a base-catalyzed reaction. Most fluorescent probes have been designed to detect thiols in slightly alkaline solutions (pH 7-9). The sensing reactions of almost all Michael-type fluorescent probes for thiols are faster in a high pH solution than in a low pH solution. In this work, we synthesized a series of 7-substituted 2-(quinolin-2-ylmethylene)malonic acids (QMAs, substituents: NEt2, OH, H, Cl, or NO2) and their ethyl esters (QMEs) as Michael-type fluorescent probes for thiols. The sensing reactions of QMAs and QMEs occur in distinct pH ranges, pH < 7 for QMAs and pH > 7 for QMEs. On the basis of experimental and theoretic studies, we have clarified the distinct pH effects on the sensing reactivity between QMAs and QMEs and demonstrated that two QMAs (NEt2, OH) are highly sensitive and selective fluorescent probes for thiols in acidic solutions (pH < 7) and promising dyes that can label lysosomes in live cells.

Investigation on the side effects of municipal solid waste incineration ashes when used as mineral addition in cement-based material

The main focus of this study is the characterisation of the municipal solid waste incineration (MSWI) ashes and their influence on engineering properties of cement paste when part of Portland cement is replaced with ground MSWI ashes. Petrographic examinations were performed in order to identify chemical composition of ashes and to determine their contents. To evaluate the main side effect of ashes when used in cement, the creation of network of bubbles due to the presence of aluminium, ashes, and aluminium powder were submerged in high pH solution and the evolution of hydrogen gas was measured. Cement paste cylinders were cast with various amounts of mineral additions and their strength and durability were investigated. Analysis on the measured data demonstrated that the use of ashes as cement replacement has both beneficial and detrimental effects on the strength and durability caused by the filler effect and hydrogen gas development, respectively.

Potato Virus M-Like Nanoparticles: Construction and Characterization.

Virus-like particles (VLPs) are multisubunit self-assembly competent protein structures with identical or highly related overall structure to their corresponding native viruses. To construct a new filamentous VLP carrier, the coat protein (CP) gene from potato virus M (PVM) was amplified from infected potato plants, cloned, and expressed in Escherichia coli cells. As demonstrated by electron microscopy analysis, the PVM CP self-assembles into filamentous PVM-like particles, which are mostly 100-300nm in length. Adding short Gly-Ser peptide at the C-terminus of the PVM, CP formed short VLPs, whereas peptide and protein A Z-domain fusions at the CP N-terminus retained its ability to form typical PVM VLPs. The PVM-derived VLP carrier accommodates up to 78 amino acid-long foreign sequences on its surface and can be produced in technologically significant amounts. PVM-like particles are stable at physiological conditions and also, apparently do not become disassembled in high salt and high pH solutions as well as in the presence of EDTA or reducing agents. Despite partial proteolytic processing of doubled Z-domain fused to PVM VLPs, the rabbit IgGs specifically bind to the particles, which demonstrates the functional activity and surface location of the Z-domain in the PVM VLP structure. Therefore, PVM VLPs may be recognized as powerful structural blocks for new human-made nanomaterials.

Layered Double Hydroxide Assemblies with Controllable Drug Loading Capacity and Release Behavior as well as Stabilized Layer-by-Layer Polymer Multilayers.

A stable drug release system with magnetic targeting is essential in a drug delivery system. In the present work, layered double hydroxide assemblies stabilized by layer-by-layer polymer multilayers were prepared by alternative deposition of poly(allylamine hydrochloride) and poly(acrylic acid) species on composite particles of Fe3O4 and ZnAl-LDH and then covalent cross-linkage of the polymer multilayers by photosensitive cross-linker. The successful fabrication was recorded by Zeta potential and Fourier transform infrared spectrum measurements. The formed assemblies were stable in high pH solutions (pH > 7). The drug loading capacity and release behavior of the assemblies could be controlled by treatment with appropriate acidic solution, and were confirmed by loading and release of a simulated drug, methylene blue. The formed assemblies possessed enough saturated magnetic strength and were sensitive to external magnetic field which was essential for targeting drug delivery. The formed assemblies were multifunctional assemblies with great potential as drug delivery system.

Crop physiological response to nutrient solution electrical conductivity and pH in an ebb-and-flow hydroponic system

Small-scale hydroponic and aquaponic crop production is increasingly common in urban areas of the US and growers have questions about which system and crops to use. Hydroponic nutrient solution contains water soluble nutrients, electrical conductivity (EC) is maintained between 1 and 3dSm−1, and target pH is between 5.5 and 6. In contrast, plants in aquaponic systems are fertilized by aquaculture effluent, which is characterized by lower EC (less than 1dSm−1) and a target pH near 7.2. Duplicate greenhouse trials were conducted between 2013 and 2015 to assess the growth, yield, quality, and potential gross returns of four crops – basil (Ocimum basilicum L.), kale (Brassica oleracea L.), chipotle pepper (Capsicum annuum L.), and cherry tomato (Solanum lycopersicum L.) – grown in a recirculating ebb-and-flow system with nutrient solution EC and pH levels commonly observed in hydroponic (high EC–low pH) and small-scale aquaponic (low EC–high pH) systems. Solution pH and EC, plant height, and leaf greenness data were collected regularly throughout crop growth, and yield and percent soluble solids (°Brix) data were collected at harvest. Crops grown in the high EC–low pH solution approached a greater final height, but relative growth rate was not different from the low EC–high pH solution. Leaf chlorophyll content, estimated from leaf greenness, was up to 37% lower in the low EC–high pH solution. Marketable yield of basil and kale was reduced by 44% and 76% in the low EC–high pH solution, respectively. Yield loss in tomato and pepper was less severe (<32%), but still significant. Observed yield reductions were greater than previous comparisons of floating-raft aquaponic and hydroponic systems, which demonstrates the importance of root to nutrient solution contact area and fertigation frequency when using low EC–high pH nutrient solution (e.g., aquaculture effluent). Differences may also suggest there are components of aquaponic solution not tested in this mechanistic study (e.g., organic metabolites and alternative nutrient forms or ratios) that may contribute to crop growth and yield in aquaponics. On a per plant basis, kale ($10.62) and cherry tomato ($9.16) grown in the high EC–low pH solution provided the greatest potential gross returns, but farm-scale net profit potential will depend on many factors including plant spacing and input costs.

Tuning the emission of aqueous Cu:ZnSe quantum dots to yellow light window

Synthesis of internally doped Cu:ZnSe QDs in an aqueous solution still suffers from narrow tunable emissions from the blue to green light window. In this work, we extended the emission window of aqueous Cu:ZnSe QDs to the yellow light window. Our results show that high solution pH, multiple injections of Zn precursors, and nucleation doping strategy are three key factors for preparing yellow emitted Cu:ZnSe QDs. All these factors can depress the reactivity of CuSe nuclei and Zn monomers, promoting ZnSe growth outside CuSe nuclei rather than form ZnSe nuclei separately. With increased ZnSe QD size, the conduction band and nearby trap state energy levels shift to higher energy sites, causing Cu:ZnSe QDs to have a much longer emission.

Photovoltaic Properties of CdSe/CdS and CdS/CdSe Core–Shell Particles Synthesized by Use of Uninterrupted Precipitation Procedures

Cadmium Selenide (CdSe) and cadmium sulfide (CdS) are good electron acceptors for hybrid solar cells. CdSe and CdS nanoparticles can be prepared at low temperatures (60–80°C) from alkaline aqueous solutions of a cadmium salt, sodium citrate, and thiourea, as sulfur source, or sodium selenosulfate, as selenium source. Under the same experimental conditions, the reaction kinetics for CdS were faster than for CdSe. Formation of CdSe/CdS core–shell particles (type I: CdSe as core and CdS as shell) could be achieved by use of an uninterrupted one-step process by setting high and low solution temperatures for the core and shell compounds, respectively. The yield of the CdSe product was higher at a pH 8.5–9.5 whereas that of the CdS product was higher at higher pH (10–11). Therefore, formation of the “inverse” CdS/CdSe structure (type II: CdS as core and CdSe as shell) was possible in a one-step solution process by choosing a high solution pH for the core and a lower pH for the shell. Photoluminescence spectra and electron micrographs confirmed formation of the two types of core–shell particle. The photovoltaic performance of heterojunctions prepared with core–shell particles and poly(3-hexylthiophene) (P3HT), also suggested formation of core–shell particles. Both the photovoltage and photocurrent density of hybrid solar cells depended on the shell compound and not on the core. It was shown that the interface of the heterojunctions plays is important in solar cell applications, and its modification could be realized by incorporating different shell compounds on core particles.

Silicate species of water glass and insights for alkali-activated green cement

Despite that sodium silicate solutions of high pH are commonly used in industrial applications, most investigations are focused on low to medium values of pH. Therefore we have investigated such solutions in a broad modulus range and up to high pH values (∼14) by use of infrared (IR) spectroscopy and silicon nuclear magnetic resonance (29Si-NMR). The results show that the modulus dependent pH value leads to more or less charged species, which affects the configurations of the silicate units. This in turn, influences the alkali-activation process of low CO2 footprint cements, i.e. materials based on industrial waste or by-products.