Three-dimensional simulation of acidizing process in carbonate rocks using the Darcy–Forchheimer framework

Acidizing is an economical and effective practice to remove the near wellbore damage, which is performed by injecting acid into the formation through the wellbore. The injected acid dissolves the rock, by which the permeability nearby the wellbore can be improved. For a carbonate reservoir, the injected acid dissolves some of the minerals and some narrow and long channels, named wormholes, are formed then. These wormholes can bypass the damaged zone and hence improve the productivity of the well. The process for acid dissolving rocks involves complex physicochemical change, including the chemical reactions at the pore scale and the fluid flow at Darcy scale. In this paper, a 3-D reactive flow model with non-Darcy framework is developed based on the two-scale continuum model, and is solved by using the finite volume method. Five types of dissolution patterns, named face dissolution, conical wormhole, wormhole, ramified wormhole, and uniform dissolution, are obtained as the injection velocity increases. The effect of non-Darcy flow on dissolution pattern and breakthrough volume is analyzed. It is found that there is no effect of non-Darcy on dissolution structure and breakthrough volume when the injection velocity is very low. However, when the injection velocity is very high, the generated wormhole has more branches when using the Forchheimer equation than using the Darcy equation. Moreover, the optimal injection velocity is found to be the same whether considering the non-Darcy flow or not.

Novel MIPs-Parabens based SPE Stationary Phases Characterization and Application

In this work, the synthesis, characterization, and application of novel parabens imprinted polymers as highly selective solid-phase extraction (SPE) sorbents have been reported. The imprinted polymers were created using sol–gel molecular imprinting process. All the seven parabens were considered herein in order to check the phase selectivity. By means of a validated HPLC-photodiode array detector (PDA) method all seven parabens were resolved in a single chromatographic run of 25 min. These SPE sorbents, in-house packed in SPE empty cartridges, were first characterized in terms of extraction capability, breakthrough volume, retention volume, hold-up volume, number of theoretical plates, and retention factor. Finally, the device was applied to a real urine sample to check the method feasibility on a very complex matrix. The new paraben imprinted SPE sorbents, not yet present in the literature, potentially encourage the development of novel molecularly imprinted polymers (MIPs) to enhance the extraction efficiency, and consequently the overall analytical performances, when the trace quantification is required.

Application of Lecithin-templated Mesoporous Silica Microparticles for the Specific and Selective Removal of Phospholipids

Phospholipids are among the many components of algae bio oil, and they harbor the trans-esterification process by poisoning the catalyst, hence the need for they removal prior to this process is crucial. Mesoporous silica materials are feasible and viable candidates for the selective removal of phospholipids by tailoring their surface morphology using different surfactants (templates) for specific and selective adsorption. In this study, the adsorption of phospholipids using lecithin template mesoporous silica microparticles (Leci-MSM) was investigated. Comparative studies using cetyltriammoniumbromide mesoporous microparticles (CTAB-MSM) were also carried out. Both Leci-MSM and CTAB-MSM were synthesized via sol-gel process, packed into mini columns and used for column breakthrough adsorption studies. Scanning electron micrographs revealed a particle size of 5.0 µm for Leci-MSM and 2.95 µm for CTAB-MSM. Textural analysis by BET and BJH exhibited a surface area of 425 and 1210 m2/g for Leci-MSM and CTAB-MSM, respectively. A pore volume of 1.59 and 2.77 cc/g for Leci-MSM and CTAB-MSM, respectively, were also obtained. In addition, Leci-MSM revealed a column breakthrough volume of 28 mL at 41 min, while for the CTAB-MSM was 46 mL at 53 min. The actual adsorption capacity recorded by Leci-MSM was 11.34 mg/g and 8.71 mg/g for CTAB-MSM.

Development of Membrane Hollow Fiber for Determination of Maleic Anhydride in Ambient Air as a Field Sampler

This research develops a rapid method for sampling and analysis of maleic anhydride (MA) in air using a one-step hollow fiber (HF) membrane in the liquid phase followed by high-performance liquid chromatography. A sampling chamber was prepared for sampling of MA with HF-supported de-ionized water absorbency. Several important parameters, such as sampling flow rate, sampling time, and breakthrough volume (BTV), were optimized at different concentrations using a central composite design. The results showed that sampling could be performed at the maximum period of 4 h with a flow rate of 1 mL min–1 for different concentrations (in the range of 0.05–2 mg m–3). The BTV was 240 mL. The relative standard deviations for the repeatability of interday and intraday were 7–10%, 10%, respectively, and the pooled standard deviation was 0.088. The limit of detection and limit of quantitation values were 0.033 and 0.060 mg m–3, respectively. Moreover, our findings revealed that the samples could be stored in sealed HF flexible plastic tubes in a cover at refrigerator temperature (4°C) for up to 7 days. The HF method was compared with method number 3512 National Institute Occupational Safety and Health for determination of MA. There was a good correlation (R2 = 0.99) between the two methods at a concentration of 0.05 to 2 mg m–3 in the laboratory and the average concentration of MA for both methods was 0.11 mg m–3 in the ambient air at an adhesive manufacturer. Our findings indicated that the proposed HF can act as a reliable, rapid, and effective approach for sampling of MA in workplaces.

Comparison between Exhaustive and Equilibrium Extraction Using Different SPE Sorbents and Sol-Gel Carbowax 20M Coated FPSE Media

This paper reports the performance comparison between the exhaustive and equilibrium extraction using classical Avantor C18 solid phase extraction (SPE) sorbent, hydrophilic-lipophilic balance (HLB) SPE sorbent, Sep-Pak C18 SPE sorbent, novel sol-gel Carbowax 20M (sol-gel CW 20M) SPE sorbent, and sol-gel CW 20M coated fabric phase sorptive extraction (FPSE) media for the simultaneous extraction and analysis of three inflammatory bowel disease (IBD) drugs that possess logP values (polarity) ranging from 1.66 for cortisone, 2.30 for ciprofloxacin, and 2.92 for sulfasalazine. Both the commercial SPE phases and in-house synthesized sol-gel CW 20M SPE phases were loaded in SPE cartridges and the extractions were carried out under an exhaustive extraction mode. FPSE was carried out under an equilibrium extraction mode. The drug compounds were resolved using a Luna C18 column (250 mm × 4.6 mm; 5 m particle size) in gradient elution mode within 20 min and the method was validated in compliance with international guidelines for the bioanalytical method validation. Novel in-house synthesized and loaded sol-gel CW 20M SPE sorbent cartridges were characterized in terms of their extraction capability, breakthrough volume, retention volume, hold-up volume, number of the theoretical plate, and the retention factor.

Preconcentration of ultra-traces of Cu(II) in water samples using SBA-15 sorbent modified with a thiocarbohydrazide ligand prior to determination by flame atomic absorption spectrometry

A simple, reliable and rapid method for the extraction of ultra-trace copper(II) using nanoporous SBA-15 sorbent modified with a thiocarbohydrazide ligand, and determination by flame atomic absorption spectrometry is presented. The optimum parameters of the method were obtained as pH of aqueous solution 5, sorbent amount 2 mg, stirring time 20 min and 0.4 M HCl solution as the eluent solvent. This method has a breakthrough volume greater than 1500 mL with a concentration factor of more than 300, linear range 0.8?2500.0 ?g L-1, limit of detection 0.253 ?g L-1 and limit of quantification 0.844 ?g L-1 for copper(II). The capacity of 2 mg of modified SBA-15was found to be 123.00?0.04 mg g-1. Standard deviations were 3.3, 2.3 and 2.1 % for 1, 2 and 4 ?g mL-1, respectively (n = 5). This method was successfully applied for the determination of copper(II) in different real samples, especially in the food samples.

Reuse of Electrocoagulated Metal Hydroxide Sludge to Fluoride and Arsenic Removal by a Fixed-Bed Column in Continuous Operation

In the present study, Electrocoagulated Metal Hydroxide Sludge (EMHS) was analyzed as adsorbent material to remove both fluoride ion (F-) and arsenic V (As(V)) from aqueous effluents. This material was generated during an electrocoagulation process using Aluminum anode. It was characterized by using specific surface areas and the surface morphology was studied by scanning electron microscopy (SEM). Adsorbent fixed-beds are generally studied to remove different class of contaminants. EMHS was evaluated using a continuous flow rate column test with an experimental design. The effect of initial concentration of F- (2.5–10 mg L−1) and the Empty Bed Contact Time (EBCT (0.4–0.8 min)) was studied following a central composite design methodology. The experimented parameters had a significant influence on saturation time, breakthrough volume, and breakthrough time. A response surface analysis was a tool for analyzing the adsorption study, showing interactions that are complicated to identify by others methods. The results, here reported, revealed that EMHS is an efficient and promising adsorbent material in order to remove F- and As(V) from water contaminated by these pollutants.

TREATMENT OF NATURAL GAS BY ADSORPTION OF CO2

Apart from burning, one of the possible uses of natural gas is as a fuel for motor vehicles. There are two types of fuel from natural gas — CNG (Compressed Natural Gas) or LNG (Liquefied Natural Gas). Liquefaction of natural gas is carried out for transport by tankers, which are an alternative to long-distance gas pipelines, as well as for transport over short distance, using LNG as a fuel for motor vehicles. A gas adjustment is necessary to get LNG. As an important part of the necessary adjustment of natural gas to get LNG, a reduction of CO₂ is needed. There is a danger of the carbon dioxide freezing during the gas cooling. This work deals with the testing of adsorption removal of CO2 from natural gas. The aim of these measurements was to find a suitable adsorbent for CO₂ removal from natural gas. Two different types of adsorbents were tested: activated carbon and molecular sieve. The adsorption properties of the selected adsorbents were tested and compared. The breakthrough curves for CO₂ for both adsorbents were measured. The conditions of the testing were estimated according to conditions at a gas regulation station — 4.0MPa pressure and 8 °C temperature. Natural gas was simulated by model gas mixture during the tests. The breakthrough volume was set as the gas volume passing through the adsorber up to the CO₂ concentration of 300 ml/m3 in the exhaust gas. The thermal and pressure desorption of CO₂ from saturated adsorbents were also tested after the adsorption.