Ammonium Persulfate Research Articles

Efficient co-production of glucose and carboxylated cellulose nanocrystals from cellulose-rich biomass waste residues via low enzymatic pre-hydrolysis and persulfate oxidation

Carboxylated cellulose nanocrystals (cCNCs) can be prepared directly from biomass in a one-step ammonium persulfate (APS) oxidation. However, the cellulose in the biomass is not fully utilized because APS oxidation degrades the cellulose amorphous regions. In this paper, to improve cellulose utilization rate, a two-step method (enzymatic pre-hydrolysis and APS oxidation) was developed to co-produce fermentable sugar and cCNCs from xylooligosaccharides manufacturing waste residue (XOR) of corncob. Enzymatic pre-hydrolysis produced 26.1 g of glucose per 100 g of XOR with a cellulase loading of 5 FPU/g cellulose in 24 h. Subsequent oxidation produced 22.9 g cCNCs with 0.5 M APS in 8 h. In contrast, the one-step APS method only produced 28.3 g cCNCs per 100 g of XOR. The total cellulose utilization rate by the two-step method increased by 73 % compared to the one-step APS method. Structural characteristics of cCNCs prepared by the two-step method were slightly different from those of the one-step method, but good properties were maintained. Therefore, the co-production method could prepare glucose and cCNCs with stable properties from XOR with a greatly improved cellulose utilization rate.

Intensification of Cr(VI) adsorption using activated carbon adsorbent modified with ammonium persulfate

Granular activated carbon has been modified by ammonium persulfate as a new adsorbent for Cr(VI) adsorption from aqueous solutions. The adsorbent was characterized by nitrogen adsorption–desorption isotherm data and infrared spectroscopy. The impact of different factors, such as the initial pH level of the solution, time, temperature, ionic strength, and initial concentration of the Cr(VI) ion, on the adsorption efficiencies of the adsorbent has been studied by batch experiments. Kinetic studies and the adsorption thermodynamics of Cr(VI) with ammonium persulfate-modified activated carbon adsorbent were carefully studied. The results showed that the Cr(VI) adsorption follows a pseudo-second-order kinetic model and the adsorption reaction is endothermic and spontaneous. The adsorption isotherm was scrutinized, and the fitting results showed that the Langmuir model could well represent the adsorption process. The maximum adsorption capacity of Cr(VI) onto persulfate-modified activated carbon was 108.69 mg g−1. The research results showed that using persulfate-modified activated carbon adsorbent can greatly remove Cr(VI) from aqueous solutions.

A smart capecitabine imprinted nanocontainer with the dual-responsive performance to pH/NIR light

Capecitabine (CAP) is a kind of prodrug that can be metabolized into 5-fluorouracil (5-FU) in vivo, so it is usually classified as the antimetabolite fluoropyrimidine deoxynucleoside analog. In this paper, CAP, upconversion nanoparticles (UCNPs), 3,5-dicarboxy-4-methacrylate-based azobenzene (MAPDIA)/acrylic acid-functionalized gelatin, N,N′-methylene bisacrylamide (MBA), and ammonium persulfate (APS) were used as template, light trigger, bifunctional monomers, cross-linking agent and initiator, respectively. By using the free-radical polymerization and the molecular imprinting technique, the potential drug delivery nanocontainer CAP-MIP with the dual-responsive performance to pH/near infrared light (NIR) was successfully prepared. Furthermore, the characterization of CAP-MIP was also carried out by the modern instrumental analysis such as FTIR, XRD, TGA, BET and so on. The stimulus-responsive release experiment in vitro indicated the maximum cumulative release rate of CAP changed from 1.71 % to 89.54 % when the pH value in medium varied from 1.2 to 8.3, and the equilibrium release time point also greatly prolonged to 420 min from 40 min, respectively. When irradiated by 980 nm monochromatic NIR light in the same solution of pH 6.8, the maximum release rate of the sample could reach 96.21 % at 180 min, which respectively corresponded to the data of 41.84 % at 420 min under the condition of the absence of additional NIR light. In addition, CAP-MIP also had the excellent specific adsorption for CAP with the selectivity factor of 2.904 and the maximum CAP-loaded capacity of 7 mg•g−1. The above information denoted the target material should be of some potential in drug delivery system application.

Introduction of a spectrophotometric method for salivary iodine determination on microplate based on Sandell-Kolthoff reaction.

Iodine is an essential element for the synthesis of thyroid hormones. Therefore, a reliable marker of iodine supply is important. Iodine is predominantly excreted via kidneys, but also via salivary glands. Our aim was to introduce a new and simple method for determination of salivary iodine concentration (SLIC). Self-prepared chemicals and standards for Sandell-Kolthoff reaction on microplate with ammonium peroxydisulfate (AP) in the range 0-400 µg/L were used. Suitability of water-based standards (WBS) and artificial saliva-based standards (ASS) for standard curve were tested. We followed standards for method validation, defined concentration of used AP and compared our results with Inductively Coupled Plasma Mass Spectrometry (ICP-MS). WBS gave more reliable results than ASS as an underestimation of iodine concentration was found for ASS. LoB was 6.5 µg/L, LoD 12.0 µg/L, therefore analytical range was 12-400 µg/L. Intra- and inter-assay imprecisions at iodine concentrations, namely 20, 100, 165, and 350 µg/L were 18.4, 5.1, 5.7, and 2.8%, respectively, and 20.7, 6.7, 5.1, and 4.3%, respectively. Suitable molarity of AP was 1.0 mol/L and showed no difference to 1.5 mol/L (P values for samples with concentration 40, 100, and 150 µg/L, were 0.761, 0.085, and 0.275, respectively), whereas there was a significant change using 0.5 mol/L (P<0.001). Saliva samples could be diluted up to 1:8. There was no interference of thiocyanate and caffeine up to 193.5 mg/L. Our original method was comparable to ICP-MS. Spaerman coefficient was 0.989 (95% CI: 0.984-0.993). The new method for SLIC determination is in excellent agreement with ICP-MS and easy-to-use.

Synthesis of CuO nanosheets on Cu foil via one-step wet chemical process at different reaction temperatures and their photoelectrochemical performance

Cupric oxide (CuO) nanostructures were directly grown on copper substrate via a simple one step solution-immersion process. The films were formed by the direct oxidation of copper in aqueous solution containing sodium hydroxide (NaOH) and ammonium persulfate (NH4)2S2O8. The influence of the reaction temperature on the structural, morphological, optical and photoelectrochemical (PEC) properties of the formed copper compounds nanostructures was investigated. The XRD and Raman spectroscopy results revealed the formation of Cu(OH)2/CuO composite for the samples prepared at 3 and 25 °C, and pure CuO was obtained for the samples prepared at 45 and 55 °C. The SEM micrographs showed that the formed Cu(OH)2 and CuO present a nanowire bundles and nanosheet morphology, respectively. The increase of the reaction temperature enhanced the absorbance of the CuO samples in the entire visible region. According to the photoelectrochemical measurements, the increase of the reaction temperature resulted in an improvement of the PEC response. The CuO nanosheets synthesized at 55 °C presents the highest and the most stable PEC response. A reasonable mechanism describing the formation of nanostructured copper compounds at different reaction temperatures is discussed in this paper.

Super Stable Silk Nanofibrils Prepared by an Improved Exfoliation Method and Their Related Applications

AbstractThe high crystallinity and sophisticated hierarchical architecture of native animal silk endow it with comprehensive mechanical properties that are superior to those of most synthetic fibers. However, these features also make the direct exfoliation of silk nanofibrils (SNFs) highly challenging. On the other hand, silk‐based materials prepared by conventional method (i.e., through silk fibroin aqueous solution) are usually weak, so the preparation methods based on SNFs have attracted much attention in recent years. Herein, a facile and environmentally friendly route is developed to directly exfoliate SNFs from natural Bombyx mori silkworm silk via ammonium persulfate oxidation followed by ultrasonication. The obtained SNFs have a high yield (nearly 40%) and are well dispersed in water in a wide pH range, so they can act as a good starting material to prepare subsequent silk‐based materials. The main application of the SNFs demonstrated in this article is a curcumin (Cur)/SNFs hydrogel as wound dressing. In vivo experimental results show that the Cur/SNFs hydrogel significantly enhanced the healing rate of wounds on diabetic mice. Therefore, the preparation method developed in this study provides an efficient way to produce SNFs, which have great potential for a wide range of applications, including as wound dressings for diabetics.

A new inhibitor of quaternary copolymer against calcium carbonate scaling in high-temperature geothermal fluids

An effective quaternary copolymer inhibitor against calcium carbonate scaling in 120 °C geothermal fluids, with an inhibition ratio of over 95 %, was synthesized through aqueous free radical polymerization of itaconic acid (IA), acrylic acid (AA), hydroxy ethyl methacrylate (HEMA), and sodium allylsulfonate (SAS). The synthesis process involved using ammonium persulfate as an initiator and tert-butanol as the molecular weight regulator. A four-factor, three-level orthogonal experiment was conducted to optimize the synthesis process, resulting in a monomer ratio of m(IA):m(AA) = 1:7, 15 % initiator concentration, a reaction temperature of 90 °C, and a reaction time of 2.5 h. Fourier transform infrared spectroscopy (FT-IR) analysis revealed the presence of carboxyl, sulfonic acid, hydroxyl, and ester groups in the copolymer, while thermogravimetric analysis (TGA) confirmed its thermal stability. Scanning electron microscopy (SEM) and X-ray diffraction (XRD) examinations of calcium carbonate crystals indicated that the copolymer scale inhibitor caused significant damage to the surface morphology and crystal structure. This scaling inhibitor is useful for efficient geothermal energy utilization.

Recovery of valuable metal elements from spent lithium-ion battery via a low temperature ammonium persulfate roasting approach

A low-cost and eco-friendly recycling method is crucial for recovering valuable elements from end-of-life lithium-ion batteries (LIBs), which plays a vital role in addressing resource scarcity and reducing the environmental impact. This study aims to develop a low-temperature pyro-metallurgical combined process to recycle spent LiNi0.5Co0.2Mn0.3O2 (NCM523). Unlike traditional pyrometallurgy methods that generate liquid alloys and slags at temperatures exceeding 1000 °C, the (NH4)2S2O8 roasting approach operates at 350 °C and converts NCM523 to water-soluble sulfates, exhibiting remarkable leaching efficiencies of Li, Ni, Co, and Mn, with values of 99.43 %, 99.87 %, 98.88 %, and 99.19 %, respectively. Systematic studies were conducted to investigate the influence of roasting temperature, (NH4)2S2O8-to-NCM mass ratio, and roasting time on the sulfation process. Furthermore, the mechanism of sulfation reaction was identified by combining experiments with thermodynamic calculation. At temperatures above 160 °C, (NH4)2S2O8 decomposes into (NH4)2S2O7, which reacts with NCM. Lithium in a layered structure forms Li2SO4, while transition elements form MnSO4, Li2Co (SO4)2, and NiSO4. At around 350 °C, (NH4)2S2O8 further decomposes into NH4HSO4, releasing SO2 and NH3. SO2 reacts with remaining NCM or unsulfated transition metal oxides, converting them into MnSO4, Li2Co (SO4)2, and NiSO4. Above 800 °C, the metal sulfates decompose into stable oxides. This study presents a low-temperature sulfation method that effectively disintegrates the crystal structure of lithium metal oxides without the need for acids or reducing agents.

Sequential Electrochemical and Chemical Multi-Polymerization of Catechol for Abatement of Environmental Pollutants

Catechol is a substance that is commonly found in wastewaters from a variety of sectors including paper, paint, petroleum, dyes, antioxidants, pesticides, iron and steel, solvents, nylon, detergent, textile, plastic, rubber, cosmetics, and medicine. In this study, sequential electrochemical and chemical multi-polymerization of catechol was investigated for environmental pollution abatement. The effect of operating parameters like catechol concentration (2–10 g/L), ammonium persulphate (APS) concentration (2–10 g/L) and reaction temperature (20–60 °C) were evaluated using response surface methodology. Catechol concentration was determined using HPLC in a gradient mobile phase. The electrochemical behavior of the polymer was investigated by cyclic voltammetry (CV). The structural and morphological properties of polycatechol were characterized by Fourier transform infrared spectroscopy (FTIR), and scanning electron microscopy with energy dispersive X-ray (SEM–EDX) analysis. It was observed from the SEM images a polymeric structure developed from a crystalline and heterogeneous structure when the APS concentration increased. Similarly, it was seen in SEM images that the polymers transitioned from a bulk and heterogeneous structure to a homogeneous structure as the temperature increased, and back to a heterogeneous structure as the catechol concentration increased. It was also found that catechol removal increased and reaction selectivity decreased by increasing the reaction temperature. The optimum operating conditions were found as 4 g/L catechol concentration, 9.5 g/L APS concentration, 30 °C reaction temperature with 100 cycles at 50 mV/s of electrochemical polymerization and 72 h of chemical polymerization. The results of this study show the potential of challenging new routes not only facile polymerization of organic monomers but also to decrease the undesirable pollutant concentration in the wastewater.

Hyperbranched aromatic poly(amidoamine) mediated interfacial polymerization for high-performance thin film composite membranes

The escalating global demand for clean water has driven a growing interest in developing thin-film composite (TFC) membranes with high permeability and selectivity for wastewater treatment and desalination processes. Engineering polymer materials with precisely tunable properties for selective molecular separation remains a challenging step toward achieving this goal. Herein, we have fabricated a highly permselective asymmetric polyamide nanofilm with a dual-layer structure in which the bottom layer is a porous hyperbranched aromatic polyamide (HBPA) interlayer, and the top layer is a dense polyamide layer with a nanostrip structure. The HBPA porous layer was covalently assembled in situ via oxidative coupling reaction with ammonium persulfate on a polysulfone (PSF) substrate. The hydrophilic porous HBPA interlayer forms nanosized cavities that may enhance the storage and confine amine monomer diffusion, leading to the construction of a striped pattern PA nanofilm. The resulting asymmetric PA membrane exhibits excellent water permeability of 18.39 ± 1 L m−2 h−1 bar−1 (3.98 times that of control membranes) and improved divalent salt (Na2SO4) rejection (≥98 %), surpassing most of the commercial and reported nanofiltration membranes. The HBPA-regulated interfacial polymerization provides a groundbreaking framework for developing high-performance membranes for precisely controlled nanofiltration.

Quaternization-based graft modification of straw fibers for conditioning the sludge dewatering performance.

Extracellular polymeric substances (EPS) are a critical influencing factor in sludge dewatering. Disrupting such EPS contributes to the release of bound water in sludge, enhancing the sludge dewatering performance. In This study, quaternized straw fibers that are destructive to the EPS structure and components in active sludge were prepared useing heterogeneous free radical graft polymerization. Straw fibers, dimethyl diallyl ammonium chloride (DMDAAC), ammonium persulfate (APS), and acrylamide (AM) were taken as the substrate, grafting monomer, catalyst, and cross-linking agent, respectively.The optimal processing conditions determined for the DMDAAC-based quaternization and graft modification of straw fibers were as follows: reaction temperature of 60 °C, reaction time of 5 h, 0.100 g of catalyst APS dosage per gram of straw, and 3.000 ml of DMDAAC dosage per gram of straw. The optimal processing conditions yielded 1.335 g of modified straw fibers per gram of straw, 33.67% grafting rate, and 31.70% substitution of the quaternary ammonium groups. The capillary suction time (CST) was conditioned from 243.3 ± 22.6 s in the original sludge to 134.5 ± 34.45 s. The specific resistance to filtration (SRF) was reduced from 8.82 ± 0.51 × 1012 m/kg in the original sludge to 4.59 ± 0.23 × 1012 m/kg.

Phase Separation Derived Anisotropic Adhesive Structural Color Hydrogel Films For Flexible Electronics

AbstractHydrogels hold great promise in the field of flexible electronics. Attempts in this area tend to the microstructure design of hydrogels, giving them specific adhesion and multi‐sensing functions. Here, a novel phase separation‐derived anisotropic adhesive structural color hydrogel film is presented for visually flexible electronics. The hydrogel film is generated by template replicating colloidal crystal by using phase separation emulsions of hydrophilic monomer (acrylic acid, AA), hydrophobic monomer (lauryl methacrylate, LMA), co‐monomer ([2‐(methacryloyloxy) ethyl] dimethyl‐(3‐sulfopropyl) ammonium hydroxide (SBMA)), surfactants (hexadecyl trimethyl ammonium bromide, CTAB) and initiator (ammonium persulphate (APS)). The appearance of phase separation results in asymmetric morphologies of hydrogel film, imparting them with anisotropic adhesive performance. Attributed to the formation of inverse opal scaffold structure, the hydrogel film is featured with vivid structural color, showing superior capability in self‐reporting mechanical behavior. Additionally, benefitting from the presence of abundant ions, the hydrogel film exhibits great conductivity. Thus, the resultant hydrogel film is demonstrated with stable dual‐signal sensing properties involving color‐changing and conductivity feedback ability to respond to human activities. These features make the proposed anisotropic adhesive structural color hydrogel film highly potential in the flexible electronic field.

Comparative analysis of millet bran nanocelluloses with various morphologies: Revealing differences in the formation mechanism and structure characteristics

To investigate the differences of nanocelluloses with various morphologies, ammonium persulphate (APS) oxidation, H3PO4 dissolution and regeneration, and ball milling combined with 1-butyl-3-methylimidazolium chloride ([BMIM]Cl) as a medium were applied to isolate cellulose nanocrystals (MCNCs), cellulose nanospheres (MCNSs) and cellulose fibrils (MCNFs) from millet bran. The structure, properties, and formation mechanism of three nanocelluloses were comparatively investigated by Fourier transform infrared spectroscopy, X-ray diffraction, thermogravimetric analysis, atomic force microscope, scanning electronic microscope, and emulsifying ability evaluation. MCNCs had needle-like structures due to the removal of amorphous regions, MCNFs appeared fibrous structures due to swelling and mechanical force, and MCNSs displayed spherical structures through self-assembly. MCNCs and MCNFs were confirmed to exhibit cellulose I structures with crystallinities of 61.24 % and 50.09 %, respectively. MCNSs showed the highest crystallinity of 68.41 % with a cellulose II structure. MCNFs and MCNSs exhibited higher initial decomposition temperatures, while MCNCs showed the highest residual mass. MCNFs suspension showed the highest apparent viscosity, while MCNSs suspension demonstrated superior dispersion. MCNSs-emulsion displayed the smallest droplet size, and MCNFs-emulsion exhibited the highest viscosity. This study reveals the formation mechanisms and relationship between morphologies and properties of three millet bran nanocelluloses, providing a theoretical basis for their application.

Polyaniline/hollow glass beads/carbon fiber powder composite film for multifunctional military tarpaulins

In this paper, a composite film with a thickness of 0.25 mm was prepared, which has the functions of infrared stealth, ultraviolet protection, sound absorption, and thermal insulation. Firstly, polyaniline was synthesized through chemical oxidative polymerization using aniline as a monomer, acetic acid as a dopant, and ammonium persulfate as an oxidant. Then, the synthesized polyaniline (PANI), hollow glass beads (HGB), and carbon fiber powder (CFP) were sequentially added to waterborne polyurethane, and a film coating machine was used to prepare a multifunctional composite film of PANI/HGB/CFP. Finally, the composite film's infrared properties, ultraviolet protection properties, sound absorption properties, thermal constants, resistance to water penetration properties, bending properties, tensile properties, chemical corrosion resistance, and aging resistance were tested. The results show that the prepared PANI/HGB/CFP composite film has an infrared emissivity of 0.668 and an ultraviolet protection factor (UPF) of 1072, indicating that it can block more than 99 % of ultraviolet rays. Additionally, it has an acoustic absorption coefficient of 0.386. At the same time, the thermal conductivity is 0.04629 W/mK, making it a highly efficient material for heat preservation and thermal insulation. The prepared PANI/HGB/CFP composite film is expected to be a new multifunctional military tarpaulin.

Effect of Ammonium Peroxydisulphate (APS) Addition on Polyaniline Nanofiber Microstructure in Interfacial Polymerization Method

Effect of Ammonium Peroxydisulphate (APS) Addition on Polyaniline Nanofiber Microstructure in Interfacial Polymerization Method

Fabrication of Tailored Membranes with Special Surface Wettability Features for Highly Efficient Crude Oil-in-Water Emulsion Separation.

Treating oily wastewater streams such as produced water has a huge potential to resolve the issue of wastewater disposal and generate useful water for reuse. Among different techniques employed for oily wastewater (oil-in-water; O/W emulsion) treatment, membrane-based separation is advantageous owing to its lower energy consumption, recycling, ease of operation, and wider scope of tuning the active layer chemistry for enhanced performance. In line with the possibilities of enhancing the performance of the membranes for efficient O/W emulsion separation, the current work is designed to yield five different variants of polyaniline (PANI) active layers with special surface wettability features (superhyrophilic and underwater superoleophobic) on a ceramic alumina support. To achieve variants of PANI on ceramic alumina supports, emulsion polymerization was carried out, and different concentrations of initiator ammonium persulfate (APS) were applied to lead to PANI-A@Aluminum Oxide membrane, PANI-B@Aluminum Oxide membrane, PANI-C@Aluminum Oxide membrane, PANI-D@Aluminum Oxide membrane, and PANI-E@Aluminum Oxide membrane corresponding to 0.15, 0.25, 0.35, 0.5, and 1.0 M concentrations of initiator. The variation in initiator concentration resulted in different PANI growth patterns; hence, the resultant membranes showed different structural, physical, and performance features. Different characterization techniques including 1H NMR, SEM, FE-TEM, AFM, water contact angle, XRD, EDX, and ATR-FTIR confirmed a more uniform and continuous growth of PANI (PANI-B) using a 0.25 M initiator concentration. The resultant PANI-B@Aluminum Oxide membrane showed an excellent surfactant stabilized crude O/W emulsion separation reaching >99% with a permeate flux of 2154 L m-2 h-1 (LMH) at 4 bar using a 100 ppm surfactant stabilized crude oil-in-water emulsion. The fouling and cleaning cycles revealed that the membrane can be reused with a 70% recovery of the initial permeate flux.

Gas‐free initiation for free‐radical frontal polymerization through charge transfer complexes

AbstractFrontal polymerization is a process in which a localized reaction zone propagates through the coupling of thermal transport and the Arrhenius kinetics of exothermic polymerization. Most initiators that have been used produce volatile by‐products, which create bubbles and voids. Tetraalkyl ammonium persulfates have been used but these require synthesis and do not have long shelf lives. A charge transfer complex (CTC) composed of an iodonium salt, and a phosphine compound has been identified as a gas‐free initiator for free‐radical thermal frontal polymerization. This CTC has 4‐(dimethylamino)phenyldiphenly phophine (DMAPDP) as the donor and p‐(octyloxyphenyl)phenyliodonium hexafluoroantimonate as the acceptor (IOC‐8). The CTC was tested with several acrylates, and all were found to support bubble‐free fronts. We determined the CTC mole ratio for some monomers at which the front velocity reaches a plateau.

Modeling the Kinetics, Equilibrium and Thermodynamics of Poly(acrylamide)/Sodium-Bentonite for Enhanced Phenol Removal from Aqueous Media

A composite based on polyacrylamide and Na-bentonite, designated as PAAm/Na-bentonite was prepared by in-situ radical polymerization using ammonium persulfate as an initiator and bis-acrylamide as a crosslinker. The structural and morphological features were examined by Fourier transform infrared (FTIR) spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM), and Brunner − Emmet − Teller measurements. The results showed PAAm intercalation in the Na-bentonite layers. Equilibrium, thermodynamics, and kinetic studies were conducted by considering the effects of pH, initial phenol concentration, contact time and temperature. The zeta potential of the PAAm/Na-bentonite composite was calculated to understand the mechanism of phenol adsorption onto our product. The pollutant uptake behavior was determined by UV-Vis spectrophotometry. Adsorption results showed that PAAm/Na-bentonite composite showed a maximum adsorption of 160.3 mg.g−1 of 30 mg.L−1 phenol solution at pH 6 after 15 min of adsorption using 4 g.L−1 of the adsorbent. The presence of acrylamide modified the surface characteristics of the Na-bentonite and offered more adsorption sites as confirmed by XRD and SEM. Equilibrium modeling of the phenol removal process was carried out using Langmuir, Freundlich, Temkin, and Dubinin–Radushkevich (D–R) adsorption isotherms. The equilibrium adsorption data were well fitted with the Langmuir model. In addition, the kinetics of adsorption were best described by a pseudo-second-order expression rather than a first-order model. The interactions between phenol molecules and adsorbent were explained by electrostatic as well as hydrogen bonding interactions, as confirmed by the pseudo-second-order kinetic model. A model for the interactions between the composite and the phenol molecules is proposed. The negative values of Gibb’s free energy (ΔG°) confirmed that the process was spontaneous. The positive value of change in entropy (ΔS° = 0.922 JK−1mol−1) suggests that the randomness was increased at the solution/solid interface. We suggest, the results indicate that PAAm/Na-bentonite presents a significant potential as an adsorbent material for phenol removal from aqueous solutions.

The Influence of the Methylene Blue Dye on the Rate and the Mechanism of the Oxidative Polymerization of Aniline

AbstractIt is shown that one‐electron oxidation of aniline with methylene blue is possible only at low temperatures under UV radiation. The kinetics of aniline polymerization under the action of ammonium persulfate in the presence of catalytic amounts of methylene blue is studied. Kinetic curves are obtained by electron paramagnetic resonance (EPR) spectroscopy at various temperatures and concentrations of methylene blue. The catalytic action of the unassociated form of methylene blue and the deactivation of reactive complexes by the dye dimers are shown to compete. In the context of the obtained results the autocatalysis mechanism of oxidative polymerization is considered, which suggests the formation of complexes of aniline and polyaniline that are subject to subsequent rapid oxidation by the persulfate anion.

Synthesis and Evaluation of Plugging Gel Resistant to 140 °C for Lost Circulation Control: Effective Reduction in Leakage Rate in Drilling Process.

Gel plugging agents have become one of the preferred methods for plugging in complex and severe loss conditions during drilling due to their good adaptability to loss channels. To address the common issue of poor temperature resistance in gel-based plugging agents, high-temperature-resistant gel plugging materials were synthesized through the molecular design of polymers, modifying existing agents. Based on the temperature and salt resistance of the aqueous solution of an acrylamide (AM)/N-vinylpyrrolidone (NVP) binary copolymer, temperature-resistant monomer sodium styrene sulfonate (SSS) was introduced and reacted in a polyvinyl alcohol (PVA) aqueous solution. Using ammonium persulfate (APS) as an initiator and crosslinking with N,N-methylenebisacrylamide (MBA), a gel plugging material resistant to 140 °C was synthesized. The structure, thermal stability, water absorption and expansion, and plugging performance of the gel were studied through hot rolling aging, thermogravimetric analysis, infrared spectroscopy, electron microscopy scanning, sand bed experiments, and drag reduction experiments. The results show that the gel material has good thermal stability and water absorption and expansion at 140 °C, and its temperature-resistant plugging performance is excellent, significantly slowing down the loss rate of drilling fluid. This provides a basis for the further development of gel materials.