Electrokinetic Zeta Potential Research Articles

Effect of nanomaterials functionality on the acidic crude oil: Wettability and oil recovery studies

Chemical enhanced oil recovery often involves the injection of chemicals, such as surfactants, polymers, nanoparticles, and macromolecules. These chemicals are to alter the rock-oil-water interactions and mobilize the oil towards the production well. However, they often pose considerable challenges in the harsh environment of the oil-wet reservoirs, such as chemical instability, and high retention/adsorption of chemicals in the near-wellbore. Herein, we investigated the effect of functionalized silica nanofluids on improving oil recovery in the carbonate reservoir as a function of the oil acidity. To do so, we synthesized two types of silica nanofluids functionalized with sulfonate and carboxylate groups. We used two crude oils with different total acid numbers (TAN) of 0.4 and 5.7 mg/KOH. All experiments were ran at 100 °C and salinity of 67–240 kppm to simulate the harsh reservoir conditions of the Saudi Arabia. Spontaneous imbibition oil recovery studies were conducted to assess their effects on oil recovery. Contact angle and interfacial tension were performed at different conditions to examine the oil recovery mechanism. Further, in order to corroborate the previous research and comprehend the principles underlying the oil recovery, we also examined the electrokinetic zeta potential in parallel. Also, to better understand how oil and nanofluid functional groups interact, we conducted a surface complexation model study. In addition, molecular simulation (density functional theory and molecular dynamics) are employed to gain atomistic insights on the implicated molecular interactions between nanosilica particles with calcite surface in seawater brine. DFT simulations predicted that both functionalized nanosilica can form thermodynamically stable complexes with a dry and hydrated calcite surface. Further, MD simulations reveal that a good amount of both functionalized nanosilica are interacting with calcite surface in the diffuse electric double layer of the calcite-brine interface. However, the carboxylated functionalized nanosilica particles interact with rock stronger than sulfonated ones. Further, the carboxylated nanosilica could form stable complexes with naphthenic acids mediated by calcium ions, which supports the synergy effect observed experimentally. The results shed light on much more complex mechanisms behind the oil recovery rather than the common peripheral understanding. This work provides a good insight into the applicability of nanofluids for enhanced oil recovery for further research and field trials.

Adsorptive Recovery of Cd(II) Ions with the Use of Post-Production Waste Generated in the Brewing Industry

Post-production waste generated in the brewing industry was used to analyze the possibility of Cd(II) ion recovery in biosorption processes. Brewer’s grains (BG), which are waste products from beer manufacturing processes, are a promising material that can be reused for biosorption. The biomass contains appropriate functional groups from fats, proteins, raw fibers, amino acids, carbohydrates and starch, showing a strong affinity for binding metal ions and their removal from wastewater. The biosorbent material was characterized by several research methods, such as particle size distribution, elemental composition and mapping using SEM-EDX analysis, specific surface area and pore volume (BET, BJH), thermogravimetry, electrokinetic zeta potential, SEM morphology and FT-IR spectrometry. Initial and equilibrium pH, adsorbent dosage, initial metal concentration and contact time were parameters examined in the research. The highest biosorption efficiency was obtained at a level of 93.9%. Kinetics analysis of the processes and sorption isotherms were also carried out. Based on the conducted experiments, it was found that this material has binding properties in relation to Cd(II) ions and can be used for wastewater treatment purposes, being a low-cost biosorbent. This research studies are in line with current global trends of circular and sustainable economies.

Effective bioremoval of Fe(III) ions using paprika (Capsicum annuum L.) pomace generated in the food industry

In these studies, removal of Fe(III) ions by biosorption processes from aqueous solutions was carried out using paprika (Capsicum annuum L.) pomace generated during processing in the food industry. The biosorbent material was characterized using several analytical methods, including particle size distribution, XRD, SEM–EDS, electrokinetic zeta potential, surface area analysis (BET, BJH), thermogravimetry, morphology (SEM), spectrophotometry FT-IR. Several factors, such as biosorbent dosage, initial concentration, contact time and initial pH were analyzed to show an effect on the bioremoval process, efficiency and adsorption capacity. As a result, the maximum adsorption efficiency and capacity were determined to be 99.1% and 7.92 mg/g, respectively. Based on the kinetics analysis, the bioremoval process is better described by the Langmuir isotherm model and the pseudo-second order equation model. In conclusion, the achieved research results suggest that paprika biomass can be an effective material for efficiently removing iron(III) from wastewater and improving water quality. These studies on the recovery of iron metal from the environment fit in the latest trends in the concept of the global circular economy.

Molecular dynamics and continuum analyses of the electrokinetic zeta potential in nanostructured slit channels

This work presents a theoretical and numerical study of electrokinetic flow and the zeta potential for the case of slit channels with nanoscale surface features of dimensions comparable to the Debye length, by employing molecular dynamics simulations and continuum-level analyses. A simple analytical model for considering the average effect of such surface features producing nanoscale roughness is proposed by employing matched asymptotic solutions for the charge density and fluid flow field, and matching conditions that satisfy electroneutrality and the Onsager reciprocal relation between the electroosmotic flow rate and streaming current. The proposed analytical model quantitatively accounts for results from molecular dynamics simulations that consider the presence of ion solvation shells and surface hydration layers. Our analysis indicates that a simultaneous knowledge of the electroosmotic and pressure-driven flow rate or streaming current can be instrumental to unambiguously determine the zeta potential in the presence of nanoscale surface features .

Ionization Properties of Phospholipids Determined by Zeta Potential Measurements.

Biological membranes are vital for diverse cellular functions such as maintaining cell and organelle structure, selective permeability, active transport, and signaling. The surface charge of the membrane bilayer plays a critical role in these myriad processes. For most biomembranes, the surface charge of anionic phospholipids contributes to the negative surface charge density within the interfacial region of the bilayer. To quantify surface charge, it is essential to understand the proton dissociation behavior of the titratable headgroups within such lipids. We describe a protocol that uses model membranes for electrokinetic zeta potential measurements coupled with data analysis using Gouy-Chapman-Stern formalism to determine the pKa value of the component lipids. A detailed example is provided for homogeneous bilayers composed of the monoanionic lipid phosphatidylglycerol. This approach can be adapted for the measurement of bilayers with a heterogeneous lipid combination, as well as for lipids with multiple titratable sites in the headgroup (e.g., cardiolipin).

The influence of phyllosilicate mineralogy on the rheology of mineral slurries

Phyllosilicate minerals have been shown to present some rheological challenges during ore beneficiation, with difficulties such as reduced flotation rates and complex tailings treatment arising. This study focuses on two phyllosilicate minerals which commonly exist as major gangue components in many industrial ores: muscovite with its thin platy structure and vermiculite which exhibits concertina-like swelling behaviour. The surface charge distribution of the minerals is evaluated using electrokinetic zeta potential measurements and potentiometric titrations. Rheology tests give the plastic viscosities and Bingham yield stresses of the suspensions. The results show that muscovite and vermiculite particles have an apparent negative charge due to the high aspect ratio of the negatively charged tetrahedral faces to the edges within a tetrahedral-octahedral-tetrahedral (T–O–T) layer configuration. The charge separation between the edges and faces results in the non-typical stacking behaviour of muscovite and vermiculite particles, forming suspensions with higher Bingham yield stresses than quartz, a non-phyllosilicate isotropic mineral with a regular non-platy morphology. However, upon yielding, these structures are destroyed and the resultant suspensions are characterised by low Bingham viscosities similar to isotropic minerals. This study provides a preliminary understanding of the flow behaviour of muscovite and vermiculite.

Theory of transport in nanofluidic channels with moderately thin electrical double layers: Effect of the wall potential modulation on solutions of symmetric and asymmetric electrolytes

Electrokinetic phenomena play an important role for the transport in submicrometer-size channels since the electric double layers formed at the walls can occupy a substantial part of the channel volume. This presents a theoretical difficulty and specific problems are usually treated numerically or not comprehensively. In our work we present a theoretical model that allows one to obtain analytical expressions for the transport of fluid (electro-osmotic flow), ions (electric current), and dissolved charged molecules (analytes). The model is based on the weak double layer approximation and has a wide range of validity. An important feature of this theoretical approach is that it is applicable not only to symmetric but also to asymmetric 2:1 and 1:2 electrolytes which exhibit very interesting properties in nanoscale channels. The possibility of affecting the wall electrokinetic zeta potential by applying a transverse voltage bias is analyzed. This transverse bias is used in an attempt to control the transport in the channel and such devices are often called "fluidic field-effect transistors." Our model quantifies the effect of the voltage bias on the zeta potential of the channel wall and therefore can be used for prediction of transport and optimization of separations in such fluidic devices.

Chemical Behavior and Corrosion Resistance of Medical Grade Titanium after Surface Modification by Means of Ion Implantation Techniques

AbstractThis work presents data on topographical structure, chemical surface composition, physicochemical properties and corrosion resistance of medical grade titanium after ion implantation. Pure commercial titanium has been implanted with 30 keV Na-, Ca- and P-ions at fluences of 2.0 × 1017 cm-2 and 1.5 × 1017 cm-2, respectively. Some of the samples were heat treated at 600 °C for 40 min. Atomic force microscopy (AFM) was used for surface analysis. The chemical composition was investigated using Rutherford backscattering spectrometry (RBS). Physicochemical investigations were carried out using contact angle measurements to determine the polarity of the modified titanium surfaces. Moreover, the electrokinetic zeta potentials on a physiological pH value have been determined. Finally, the corrosion resistance was examined in simulated body fluid (SBF) containing 4 g/l bovine serum albumin (BSA) using cyclic voltametry.Considering the P-implantations, the measured depth distribution of phosphorus agrees well with calculations. For the implantation of Na and Ca, the concentration of implanted atoms in the maximum of the depth distribution is noticeably lower and the distribution extends to larger depths compared to the predictions. This finding is associated with a strong incorporation of oxygen over the whole penetration depth of the implanted ions. According to topographical and chemical changes different contact angles as well as zeta potentials have been detected for the ion implanted surfaces compared to pure titanium. The electrochemical examinations indicate that the implantation has no negative influence on the corrosion resistance in comparison to unmodified medical grade titanium. The results show that ion implantation using certain ions can be used to design tailor-made titanium surfaces from a physicochemical point of view.

Interfacial chemistry and particle interactions and their impact upon the dewatering behaviour of iron oxide dispersions

The influence of interfacial chemistry and particle interactions on sedimentation and electroosmosis (EO) of coagulated iron oxide dispersions has been investigated. Both pH and ionic strength of NH 4Cl electrolyte had a profound effect on the particle electrokinetic zeta potential and dispersion rheological behaviour (shear yield stress), impacting strongly on the dewatering behaviour. In the absence of NH 4Cl, the zeta potential decreased with increasing dispersion pH, with an isoelectric point (iep) observed at pH 5.6. Upon NH 4Cl addition, specific adsorption of NH 4 + ions onto particles at pH>6 occurred and led to a significant reduction in particle zeta potential, accompanied by a shift in iep to higher pH (>7.5) and/or charge reversal. The shear yield stress was large where the zeta potential was low and small where the zeta potential was high. Fast dewatering rate was achieved by pH modification and NH 4Cl addition, however, these had no substantial impact upon the dispersion consolidation behaviour. Dewatering rates correlated strongly with both particle zeta potential and shear yield stress, the latter being highest at pH where the zeta potential was low and, hence, interparticle attraction was at a maximum (repulsion minimized). The consolidation of concentrated dispersions (60 wt.% solid) to a “spadeable” paste consistency (85 wt.% solid) by electroosmosis was achieved for moderately charged particles at 5×10 −3 M NH 4Cl and pH values away from the iep using moderate power consumption. The results exemplify clear links existing between interfacial chemistry, particle interactions and dewaterability of iron oxide tailings, which may be optimized to facilitate tails compaction.

Interfacial chemistry, particle interactions and improved dewatering behaviour of smectite clay dispersions

In this work, the influence of hydrolysable metal ions, Mn(II) and Ca(II), on the interfacial chemistry, particle interactions and dewatering behaviour of smectite clay dispersions has been investigated at the pH range 3–12. Metal ion specific adsorption, accompanied by a marked reduction in particle zeta potential, was observed to have a profound influence on the colloid stability, rheology and dewatering behaviour of unflocculated and flocculated smectite dispersions. The performance of anionic polyacrylamide-acrylate copolymer (PAM) used for flocculation strongly depended upon the initial degree of dispersion, the metal ion type and its concentration and the pulp pH. Prior addition of Mn(II) ion species significantly enhanced flocculant adsorption at pH 7.5 but not at higher pH (e.g. 10.5). A similar improved flocculation effect was observed in the presence of Ca(II) ions at pH 10.5 than at lower pH (e.g. 7.5). This observation is consistent with metal ion hydrolysis and specific adsorption occurring at these pH values and had a significant impact on slurry settling rate and extent of consolidation. An optimum flocculation and dewatering conditions of 0.05 M metal ion and flocculant dosage of 500 g/ton solid which induced partial (∼50%) rather than complete particle surface coverage by a monolayer, was determined. The flocculant adsorption mechanism appears to involve hydrogen bonding between the amide functional group (–CONH 2) of the polymer and the hydroxyl groups of the smectite particle surface as shown by spectroscopic analysis. Metal ion and flocculant adsorption, which synergistically acted to reduce the electrokinetic zeta potential and the high yield stress between particles, produced faster clarification rates and greater dispersion consolidation. The results demonstrate clear links existing between surface chemistry, particle interactions and pulp dewatering and enable some of the physicochemical treatment issues towards improving smectite clay tails dewatering behaviour, beyond what is currently observed in plant practice, to be addressed.

非分極性電極を用いた矩形電気泳動速度測定装置

This paper reports a modified electrophoresis apparatus by the microscopic method in the surface electrochemical study of flotation.After examining the apparatus with platinum electrodes in all its aspects, an acrylite new apparatus with non-polarizable calomel electrodes as the working electrodes so as to avoid polarization was designed and was proved satisfactory for use. Cell dimension was 2.108mm in depth, 19.87mm in width and 200mm in length, and electrophoresis was measured at the stationary level so that electroosmotic flow was zero. Field strength was measured by the vacuum tube voltmeter by putting the small calomel electrodes in the cell.By considering the theoretical equation on the electroosmotic flow in the cell, derived by Komagata, it was found that ratio of width to depth of the cell must be more than 5, and the deviation in the focusing point is discussed. Effects of the settling of particles during the mobility measurement and of particle size were also considered, and it was concluded that the former is negligible small when measured under the condition in which particles are observed within the focusing depth, and that the most suitable particle size is less than about 2μ in diameter.A mobility of -1.07μ/sec/V/cm in distilled water at 25°C was observed on the sphalerite sample and the calculated electrokinetic zeta potential was -14mV.