Citric Acid Coated Magnetite Nanoparticles Research Articles

Conformance Control in Oil Reservoirs by Citric Acid-Coated Magnetite Nanoparticles.

Reservoir conformance control methods may significantly improve enhanced oil recovery technologies through reduced water production and profile correction. Excessive water production in oil and gas reservoirs leads to severe problems. Water shutoff and conformance control are, therefore, financially and environmentally advantageous for the petroleum industry. In this paper, water shutoff performance of citric acid-coated magnetite (CACM) and hematite nanoparticles (NPs) as well as polyacrylamide polymer solution in a heterogeneous and homogeneous two-dimensional micromodel is compared. A facile one-step technique is used to synthesize the CACM NPs. The NPs, which are reusable, easily prepared, and environmentally friendly, are characterized using Fourier-transform infrared spectroscopy, field emission scanning electron microscopy, dynamic light scattering, and X-ray diffraction. The results confirm uniform spherical Fe3O4 NPs of an average diameter of 40 nm, well coated with citric acid. CACM NPs provide a high pressure drop coupled with an acceptable resistance factor and residual resistance factor owing to NP arrangement into a solid-/gel-like structure in the presence of a magnetic field. A resistance factor and a residual resistance factor of 3.5 and 2.14, respectively, were achieved for heavy oil and the heterogeneous micromodel. This structure contributed to an appreciable plugging efficiency. CACM NPs respond to ∼1000 G of magnetic field intensity and display a constant resistance factor at intensities between 4500 and 6000 G. CACM NPs act as a gel, forming a solid-/gel-like structure, which moves toward the magnetic field and thereby shuts off the produced water and increases the oil fraction. The findings of this study suggest the ability to shut off water production using specially designed magnetic field-responsive smart fluids. The application would require innovative design of field equipment.

Development of an analytical method based on citric acid coated magnetite nanoparticles assisted dispersive magnetic solid-phase extraction for the enrichment and extraction of sildenafil, tadalafil, vardenafil and avanafil in human plasma and urine prior to determination by LC-MS/MS

A new analytical method based on dispersive magnetic solid-phase extraction (DMSPE) was introduced for the preconcentration of phosphodiesterase-5 (PDE-5) inhibitors in human urine and blood samples. For this purpose, citric acid coated magnetic iron nanoparticle was synthesized and characterized. The assay involved the extraction of sildenafil, tadalafil, vardenafil and avanafil as PDE-5 inhibitors using magnetic sorbent material. Effects of experimental variables in the extraction procedure were optimized using two techniques; one-variable-at-a-time and response surface methodology. Under the optimum conditions, the limits of detection and quantification values were obtained in the range of 0.06 to 0.94 ng g−1 and 0.19 to 3.13 ng g−1, respectively. The proposed method showed good linearity (R2 > 0.9968) and satisfactory repeatability (%RSD < 9.57%) even at very low concentrations. The proposed method was applied to human urine and plasma samples by spiking experiments. High percent recoveries indicated that the method is applicable for the accurate determination of selected PDE-5 analytes.

Integrating synthesized citric acid-coated magnetite nanoparticles with magnetic fields for enhanced oil recovery: Experimental study and mechanistic understanding

Nanofluid injection has emerged as an attractive enhanced oil recovery (EOR) process in the past decade. These fluids improve oil recovery by reducing interfacial tension (IFT), modifying wettability, and reducing mobility ratio. In this communication, magnetite citric acid-coated nanoparticles (NPs) were synthesized by an affordable, facile and one step method and then characterized using Field emission scanning electron microscopy (FE-SEM), X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), and Dynamic light scattering (DLS). Afterward, the microscopic and macroscopic efficiencies of oil recovery in heterogeneous and homogeneous 2D micromodels were investigated in the presence of magnetic field. Citric acid-coated magnetite NPs started to respond to the magnetic field around the intensity of 800 Gauss and also showed the maximum ultimate recovery factor at the intensity of 2750 Gauss. In addition, citric acid coated magnetite NPs provided more enhanced oil recovery factor compared to hematite NPs, because of reducing interfacial tension (IFT) between the oil and injection fluid, altering surface wettability from oil-wet to water-wet, promoting the NPs distribution in porous media, and generating column-like structure in the presence of magnetic field. In fact, magnetite NPs act as piston toward the magnetic field by creating a column which sweeps the oil and increases production. Furthermore, citric acid-coated magnetite NPs flooding increased ultimate recovery factor more than polymer and hematite NPs flooding.

Aqueous aggregation behavior of citric acid coated magnetite nanoparticles: Effects of pH, cations, anions, and humic acid

Improving the colloidal stability of magnetite nanoparticles (MNPs) is essential for their successful applications. In this study, the surface zeta potential and particle size evolutions of citric acid coated magnetite nanoparticles (CA-MNPs) were measured under varied aqueous conditions using dynamic light scattering (DLS). The effects of pH (5.0–9.0), ionic strength (IS), cations (Na+ and Ca2+), anions (phosphate, sulfate, and chloride) and humic acid on the aggregation behaviors of CA-MNPs were explored. Compared with bare MNPs, the stability of CA-MNPs were greatly improved over the typical pH range of natural aquatic environments (pH = 5.0–9.0), as the coated CA-MNPs were highly negatively charged over the pH range due to the low pKa1 value (3.13) of citrate acid. CA-MNPs were more stable in the presence of monovalent cation (Na+) compared with divalent cation (Ca2+), as Ca2+ could neutralize the surface charge of MNPs more significantly than Na+. In the presence of anions, the surface charges of CA-MNPs became more negative, and the stability of CA-MNPs followed the order: in phosphate > sulfate > chloride. The observed aggregation trend could be explained by the differences in the valences of the anions and their adsorption behaviors onto CA-MNPs, which altered the surface charges of CA-MNPs. The measured critical coagulation concentrations (CCC) values of CA-MNPs in these electrolyte solutions agreed well with Derjaguin–Landau–Verwey–Overbeek (DLVO) calculations. With the addition of Humic acid (HA), the aggregation of CA-MNPs was inhibited in all electrolyte solutions even with the critical coagulation concentrations. This is due to the adsorption of HA onto CA-MNPs, which enhanced the electrostatic and steric repulsive forces between CA-MNPs. Considering the good stability of CA-MNPs in solutions with varied pH and electrolyte compositions, as well as with the easy synthesis of CA-MNPs and their non-toxicity, this study suggested CA coating as a good strategy to increase the stability of MNPs.

Hydrophilic Magnetite Nanoparticles Enhance Anticancer Activity of Anthracyclines In Vitro

A novel method for enhancing the anticancer activity of anthracyclines in vitro was proposed by using hydrophilic magnetic nanoparticles. Citric acid-coated magnetite nanoparticles Fe3O4 (nano-Fe3O4-CA) interacted with anthracyclines by electrostatic and hydrophobic forces, resulting in the formation of aggregates (nano-Fe3O4-CA-drug). The aggregate was studied by resonance light scattering and fluorescence spectroscopy. The results indicated that in comparison with anthracyclines, the nano-Fe3O4-CA-drug showed high activity towards incorporation in the DNA chain. Furthermore, the cytotoxicity of nano-Fe3O4-CA-drug was investigated by cytotoxicity experiment and cell morphology study. The results confirmed that the nano-Fe3O4-CA-drug could inhibit the growth of cells more effectively than the drug alone. In conclusion, usage of nano-Fe3O4-CA affords reduction of the dosage of anthracyclines in vitro.

Citric acid coated magnetite nanoparticles to overcome intrinsic rifampicin resistance in Mycobacterium smegmatis

Methods We have studied the effect of rifampicin on growth of cells, with and without the nanoparticles. Further, cellular uptake of nanoparticles was studied by transmission electron microscopy. Since, permeability barrier and drug efflux are responsible for intrinsic drug resistance, we have performed accumulation and efflux studies on common efflux pump substrate ethidium bromide (EtBr) by semi automated fluorometric method in the presence and absence of nanoparticles.

Stability and Relaxation Mechanisms of Citric Acid Coated Magnetite Nanoparticles for Magnetic Hyperthermia

Magnetite (Fe3O4) nanoparticles are proper materials for Magnetic Fluid Hyperthermia applications whenever these conjugate stability at physiological (neutral pH) medium and high specific dissipation power. Here, magnetite nanoparticles 9–12 nm in size, electrostatically stabilized by citric acid coating, with hydrodynamic sizes in the range 17–30 nm, and well dispersed in aqueous solution were prepared using a chemical route. The influence of media acidity during the adsorption of citric acid (CA) on the suspension’s long-term stability was systematically investigated. The highest content of nanoparticles in a stable suspension at neutral pH is obtained for coating performed at pH = 4.58, corresponding to the larger amount of CA molecules adsorbed by one carboxylate link. Specific absorption rates (SARs) of various magnetite colloids, determined calorimetrically at a radio frequency field of 265 kHz and field amplitude of 40.1 kA/m, are analyzed in terms of structural and magnetic colloid properties. Larger dipolar interactions lead to larger Néel relaxation times, in some cases larger than Brown relaxation times, which in the present case enhanced magnetic radio frequency heating. The improvement of suspension stability results in a decrease of SAR values, and this decrease is even large in comparison with uncoated magnetite nanoparticles. This fact is related to interactions between particles.

Enhancing remote controlled heating characteristics in hydrophilic magnetite nanoparticles via facile co-precipitation

Citric acid coated magnetite nanoparticles were synthesized using a one-step and two-step co-precipitation method at different temperatures. The stability of the nanoparticles in aqueous media was compared. The magnetic heating characteristics in an alternating magnetic field were examined and specific absorption rates were determined. The nanoparticles were characterized by various techniques (Fourier transform infrared, UV spectrophotometry, thermogravimetric analysis, dynamic light scattering, transmission electron microscopy, X-ray diffraction and vibrating sample magnetometry). The temperature of synthesis and mode of functionalizing the particles affected their physical and magnetic properties. Higher temperatures led to increased specific absorption rates for both methods but more stable hydrophilic superparamagnetic nanoparticles were obtained in the one-step method.