Strong Acid Research Articles

RESULTS OF RESEARCH OF THERMOSENSITIVE PROPERTIES OF COMPOSITIONS BASED ON CHITOSAN LACTATE

Introduction. The development of stimulus-sensitive drug delivery systems ("in situ" systems) is one of the actively developing trends in pharmaceutical technology. First of all, such systems provide sustained and controlled release of the active substance due to a special sol-gel transition. "In situ" systems are solutions that under various physiological conditions transition into a hydrogel. The transition of a solution into a hydrogel depends on various factors such as temperature, pH change, UV radiation, presence of certain molecules or ions. Biopolymers such as chitosan are the basis for in situ systems. Chitosan is an economically available, biodegradable and biocompatible polymer, which makes it a promising raw material for hydrogels. Solutions of chitosan salts are claimed to have stimuli-responsive properties such as pH- and thermosensitivity, however, the composition of such systems usually includes crosslinking agents that may have intrinsic pharmacological and/or toxic activities. The aim of this study was to test the hypothesis of the thermosensitivity of chitosan lactate-based hydrogels made without crosslinking agents. Material and Methods. In accordance with the objective, screening experiments were performed to obtain and investigate the properties of chitosan lactate, during which prototypes were obtained to test the ability of hydrogels to thermosensitive transition without auxiliary crosslinking agents and to evaluate the properties of chitosan-based hydrogels at different temperature values. Results. As a result of the experiments carried out, it was found that the solutions studied are not capable of thermosensitive phase transition. However, it should be noted that during the experiments samples of hydrogels based on chitosan and lactic acid were obtained with different organoleptic and physical properties depending on the concentration of lactic acid. Conclusions. Based on the results of the screening study, the hypothesis about the thermosensitive transition ability of chitosan lactate solutions without the addition of crosslinking agents was refuted. This issue requires further study using methods that allow to evaluate the underlying changes in the molecular structure of the polymer during gelation when the solution temperature is changed. The experiments also proved the ability of chitosan to form hydrogels in aqueous solutions with low concentration of weak organic acids with pH in the range from 5 to 6.

Sorbic acid is an efficient preservative in pea-based meat analogues

The popularity of plant-based alternatives to meat has increased due to advancements in important attributes such as taste. Using adequate processing at elevated temperatures combined with aseptic packaging, especially in combination with storage below the freezing point, microbial hazards in these products are negligible. However, for plant-based alternatives to ham, sausages, spreads, or cheese, for example, on sandwiches, the product must withstand microbial growth in the fridge after breaking the seal of the food packaging, as everything is not typically consumed directly. Currently, there are few preservations methods, but one solution is adding weak acid preservatives, with less inherent health concerns compared to sulfites and nitrite, e.g. carcinogenicity and hypersensitivity. To be fully effective an acidic pH is required. In this study, an approach where sausage-resembling meat analogues with different pHs (4.14–5.56) were prepared without preservatives, with potassium sorbate (2000 mg/kg), or sodium disulfite (200 mg/kg), and thereafter subjected to standardised challenge tests to elucidate the efficacy. Sorbate was the only preservative effective to prevent growth of all tested organisms, Penicillium roqueforti, Pichia fermentans and Listeria monocytogenes. The identified superiority of sorbate compared to other tested preservatives is relevant knowledge when developing preservation strategies for other types of meat analogues.

Construction of amine-rich coating utilizing amine curing reaction of triglycidyl isocyanate with triethylenetetramine on the surface of poly(styrene-divinylbenzene) microspheres for preparation of anion exchange stationary phase.

Epoxy resins, as important thermosetting polymers, exhibit excellent adhesion to various substrates. In view of this, reticulate coating of triglycidyl isocyanate with triethylenetetramine was introduced onto the surface of poly(styrene-divinylbenzene) utilizing amine curing reaction to obtain poly(styrene-divinylbenzene)@triglycidyl isocyanate-triethylenetetramine composite microspheres. The amino groups and epoxy groups of triglycidyl isocyanate-triethylenetetramine endowed poly(styrene-divinylbenzene) with good reactivity, which could be quaternized under mild conditions to obtain an anion exchange chromatographic stationary phase. The quaternized poly(styrene-divinylbenzene)@triglycidyl isocyanate-triethylenetetramine was characterized by scanning electron microscope, Fourier-transform infrared spectroscopy, N2 adsorption-desorption experiment, etal. The chromatographic performance of the customized column was evaluated by separating seven conventional anions, organic weak acids, and carbohydrates. Poly(styrene-divinylbenzene)@triglycidyl isocyanate-triethylenetetramine possesses the uniform size of poly(styrene-divinylbenzene) microspheres and good reactivity of triglycidyl isocyanate-triethylenetetramine, which offers a flexible strategy for the preparation of anion exchange stationary phase. The column exhibits excellent chemical and mechanical stability and chromatographic performance. Finally, the column was successfully applied for the determination of nitrite in pickles.

Influence of loading method on the performance of Zn/SAPO-34 catalysts and its catalytic preparation of 5-Hydroxymethylfurfural from fructose dehydration

A diverse suite of Zn-SAPO-34 catalysts was synthesized employing three distinct methodologies for the incorporation of zinc species: thermal ion exchange, wet impregnation, and physical mixing. The catalysts were characterized using various analytical techniques including XRD, FT-IR, BET, SEM, XRF, XPS, NH3-TPD, and Py-IR, to elucidate the crystal structure, morphology, surface acidity, and the presence of zinc species within the catalysts. The study showed that the method of zinc introduction markedly impacts the physicochemical properties of the catalysts. Different approaches to introducing zinc species significantly influence the acid strength and type on the catalyst surface, with variations in the existing states of zinc across the catalysts. Specifically, zinc species introduced via thermal ion exchange coexist as ZnOH+ and ZnO within the catalyst, whereas those from wet impregnation and physical mixing are individually present as either ZnOH+ or ZnO. Furthermore, the study examined the catalytic performance of these Zn-SAPO-34 catalysts in the dehydration of fructose to produce 5-hydroxymethylfurfural (HMF). Catalysts prepared via thermal ion exchange exhinited superior performance, achieving an remarkable HMF yield of 94.6 %. Additionally, in situ infrared technology was used to investigate the effect of zinc species introduction on the fructose dehydration process, indicating suggesting that the introduction of zinc species enhances the transformation of fructose molecules.

The Effect of FDM Parameters on the Mechanical Properties of PLA Printed Parts

The most common method for additive manufacturing of thermoplastics is fused deposition modeling (FDM), which is becoming a growing trend in a variety of engineering applications since it can easily create intricate parts. The appropriate choice of process parameters has a significant impact on the mechanical qualities of 3D-printed parts. This study examined the effect of four crucial process variables on the tensile strength of polylactic acid (PLA) samples: infill density, printing speed, build orientation, and layer thickness. Samples were printed in accordance with ASTM D638 using an FDM 3D printer. The findings of this study show that the tensile strength of the PLA-printed samples is highly influenced by factors such as layer thickness, build orientation, and infill density. The PLA-printed samples' tensile strength and Young's modulus were significantly affected by the 90° orientations, hollow infill, 0.4 mm thickness, and 100 mm/s speed. Therefore, as the FDM 3D printer becomes progressively more significant for manufacturing engineering components, finding the parameter values that may lead to stronger mechanical and physical characteristics would definitely help designers and manufacturers globally.

Fabrication of fluorinated superhydrophobic oil-absorption cabins with controllable movement, elasticity, and wear resistance

Superhydrophobic materials that can withstand harsh environments are critical in oil spills. Here, fluorinated superhydrophobic monoliths were prepared in one step based on a high internal phase emulsion (HIPE) templating method. γ-methacryloyloxypropyltrimethoxysilane (KH570)-modified Fe3O4 nanoparticles were added into the emulsion as co-stabilizers and participated in the composition of micro-nano hierarchical structures. The fluorinated alkyl backbone and rough structure enabled the foam to exhibit excellent superhydrophobicity with a water contact angle (WCA) of 153.5° and a sliding angle (SA) of 5.92°. The unique structure and composition of the foam allowed it to maintain stable superhydrophobicity (153.97°) even after severe sandpaper abrasion tests (Drawn 10 m at 7.1 kPa on P400 grit sandpaper). It also demonstrated exceptional hydrophobicity to strong acids, bases, and UV light. The oil-saturated material can be regenerated through a simple extrusion process, showing outstanding reusability. After ten cycles of oil adsorption, the adsorption capacity remains above 90 % of the initial value. The additional magnetic properties of the material enable it to remove oil in confined or hazardous conditions. More importantly, with the assistance of a vacuum pump, the material permits continuous separation of organic solvents from the water. These excellent properties of the foam make it a potential material for treating wastewater.

Hydro-chemical characterization and irrigation suitability assessment of a tropical decaying river in India

Water pollution is a major concern for a decaying river. Polluted water reduces ecosystem services and human use of rivers. Therefore, the present study aims to assess the irrigation suitability of the Jalangi River water. A total of 34 pre-selected water samples were gathered from the source to the sink of the Jalangi River with an interval of 10 km and one secondary station’s data from February 2012 to January 2022 were used for this purpose. The Piper diagram exhibits that the Jalangi River water is Na+–HCO3− types, and the alkaline earth (Ca2+ + Mg2+) outperforms alkalises (Na+ + K+) and weak acids (HCO3− + CO32−) outperform strong acids (Cl− + SO42−). SAR values ranging from 0.35 to 0.64 show that water is suitable for irrigation and poses no sodicity risks. The %Na results show that 91.18% of water samples are good and acceptable for irrigation. RSC levels indicate a significant alkalinity hazard, with 94.12% of samples considered inappropriate for irrigation. PI findings show that 91.18% of water samples are suitable for irrigation. Apart from the spatial water samples, seasonal water samples exhibit a wide variations as per the nature of irrigation hazards. Gibbs plot demonstrates that the weathering of rocks determined the hydro-chemical evolution of Jalangi River water. This study identifies very little evaporation dominance for pre- and post-monsoon water. The analysis of variance (ANOVA) test illustrates that there are no spatial variations in water quality while seasonal variations are widely noted (p < 0.05). The results also revealed that river water for irrigation during monsoon is suitable compared to the pre-monsoon season. Anthropogenic interventions including riverbed agriculture, and the discharge of untreated sewage from urban areas are playing a crucial role in deteriorating the water quality of the river, which needs substantial attention from the various stakeholders in a participatory, and sustainable manner.

Antilisterial and antioxidant exopolysaccharide from Enterococcus faecium PCH.25 isolated from cow butter: characterization and probiotic potential.

Exopolysaccharides produced by lactic acid bacteria have gained attention for their potential health benefits and applications in functional foods. This study explores the isolation and characterization of a novel exopolysaccharide-producing strain from dairy products. The aim was to evaluate its probiotic potential and investigate the properties of the produced exopolysaccharide. A strain identified as Enterococcus faecium PCH.25, isolated from cow butter, demonstrated exopolysaccharide production. The study's novelty lies in the comprehensive characterization of this strain and its exopolysaccharide, revealing unique properties with potential applications in food, cosmetic, and pharmaceutical industries. The E. faecium PCH.25 strain exhibited strong acid tolerance, with a 92.24% viability rate at pH 2 after 2h of incubation. It also demonstrated notable auto-aggregation (85.27% after 24h) and co-aggregation abilities, antibiotic sensitivity, and absence of hemolytic activity, suggesting its probiotic potential. The exopolysaccharide produced by this strain showed bactericidal activity (MIC and MBC = 1.8mg/ml) against Listeria monocytogenes and antioxidant properties (22.8%). Chemical analysis revealed a heteropolysaccharide composed of glucose and fructose monomers, with various functional groups contributing to its bioactivities. Physical characterization of the exopolysaccharide indicated thermal stability up to 270°C, a negative zeta-potential (-27 mV), and an average particle size of 235nm. Scanning electron microscopy and energy dispersive X-ray analysis revealed a smooth, nonporous structure primarily composed of carbon and oxygen, with an amorphous nature. These findings suggest that the exopolysaccharide from E. faecium PCH.25 has potential as a natural antibacterial and antioxidant polymer for use in functional foods, cosmetics, and pharmaceuticals.

Effect of acidity of solid acid catalysts during non-oxidative thermal decomposition of LDPE

AbstractThermal decomposition of low-density polyethylene (LDPE) was monitored by thermogravimetry under N2 atmosphere in the presence of solid acid catalysts such as alumina (α-Al2O3, γ-Al2O3), crystalline silica-alumina (SA, molar ratio of Si/Al = 0.19) and amorphous silica-alumina catalysts (ASA, molar ratio of Si/Al = 4.9). Crystal structure and surface area of solid acid catalysts were measured by XRD and BET, respectively. The strength and distribution of acid sites of solid acid catalysts were estimated by NH3-TPD. It was observed that total acidity strength is in the order of ASA (1.77 μmmol NH3/g) &gt; AS (1.42 μmol NH3/g) &gt; γ-Al2O3 (1.06 μmol NH3/g) &gt; α-Al2O3 (0.06 μmol NH3/g). Thermal degradation behavior of LDPE with and without solid acid catalyst was monitored by TGA, where heating rates (β) of 5, 10, and 20 °C/min were employed under an inert atmosphere, and their activation energies (Ea), onset temperatures (Tinitial), decomposition temperatures (Tdecomp) were calculated and compared. The activation energy (Ea) was evaluated using the Coats-Redfern method. Solid acid catalysts with stronger acidity and higher surface area showed a decrease in activation energy and onset temperature. Activation energy of LDPE over ASA catalyst is decreased to 97.3 kJ/mol from thermal decomposition of LDPE without catalyst of 117.2 kJ/mol under heating rate of 10 °C/min. The isothermal decomposition of LDPE was monitored at 300 °C for 3 h with a heating rate of 10 °C/min, where 13.1% and 24.2% wt. loss were observed over SA and ASA, respectively, while only 0.7% wt. loss was observed for LDPE without a solid acid catalyst. Graphical abstract Single step decomposition of LDPE Thermal degradation behavior of LDPE monitored by TGA, with different heating rates (β) of 5, 10, 20 °C/min.

Improved Mn4+/Mn2+ Contribution in High‐Voltage Zn–MnO2 Batteries Enabled by an Al3+‐Ion Electrolyte

AbstractRechargeable aqueous Zn–MnO2 batteries are attracting attention as a cost‐effective and safe energy storage solution, but their commercialization faces challenges due to limited stability, output voltage, and energy density. Herein, a hybrid‐ion Zn–MnO2 system with enhanced Mn4+/Mn2+ electrochemical contribution is introduced using an Al3+‐based electrolyte. Compared with conventional Zn2+ electrolytes, the hybrid Al3+/Zn2+ cell offers higher output voltage of 1.75 V, capacities up to 469 mAh g−1, and outstanding energy densities up to ≈730 Wh kg−1 at 0.3 A g−1. Besides, the Al3+‐enabled Zn–MnO2 battery shows 100% capacity and energy density retention after 10,000 cycles at 2 A g−1. Even at a high mass–loading of 6.2 mg cm−2, a capacity of ≈200 mAh g−1 is maintained for over 100 cycles. This outstanding performance is related to the contribution of different intercalation and reaction mechanisms, as proved by the combination of electrochemical analysis and ex‐situ x‐ray diffraction characterization of the cells at different discharge stages. Al3+ ions, as Lewis strong acid, contribute to capacity in two significant ways: through a highly reversible intercalation/de‐intercalation that substantially boosts capacitance at low current rates, and promoting the Mn4+/Mn2+ reaction aided by H+ that dominates the capacitance at higher current rates. Overall, this work demonstrates a practical Zn–MnO2 battery with a high potential for low‐cost stationary energy storage habilitated by multiple ion co‐intercalation.

Exploring the efficient catalytic decomposition behavior of AsH3 over HZSM-5 molecular sieve based on in situ DRIFTS characterization

Existing processes for transforming arsine (AsH3) into toxic arsenic oxides (AsxOy) through catalytic oxidation do not meet economic requirements. In contrast, the catalytic decomposition method stands out due to its ability to both remove AsH3 and obtain elemental arsenic (As0) as a valuable product. A series of blank molecular sieves (HZSM-5, 13X, MCM-41, and TS-1) was applied to the catalytic decomposition performance of AsH3. At a catalytic decomposition temperature of 100 ℃, the HZSM-5 zeolite exhibited exceptional performance, achieving a D90% value (the duration for which the AsH3 removal efficiency remained above 90 %) exceeding 40 h. Moreover, up to 83.1 % of the product was As0. Comprehensive characterization revealed that the surface of the HZSM-5 zeolite contained a large number of strong acid sites, which played a key role in As0 generation. In situ diffuse reflectance infrared spectroscopy further revealed the activation behavior of O2 at the Brønsted acid sites on HZSM-5. To assess its suitability in industrial applications, the AsH3 removal performance of the HZSM-5 molecular sieve was investigated in the presence of actual gas components (CO, H2S, PH3). This study provides new ideas for the effective catalytic decomposition of AsH3 and the recovery of valuable products in industry.

Promoting metal oxides–zeolite electron interaction on MnCeOx/HY catalyst for boosting nitrogen oxides reduction

The MnOx-CeO2 metal oxides are considered as promising alternative catalysts for selective catalytic reduction with NH3 (NH3-SCR) to remove NOx due to its excellent low temperature performance. However, their strong oxidative ability can lead to NH3 over-oxidation, narrowing the active temperature range and reducing N2 selectivity. Moreover, their weak surface acidity hampers medium to high-temperature activity and alkali metal resistance. Hence, in this study, MnCeOx metal oxides were coupled with HY zeolite to create MnCeOx/HY, demonstrating excellent NH3-SCR performance. The high dispersion of metal oxides on the zeolite surface and their close integration promoted strong electron interaction, effectively reducing oxygen vacancies and surface adsorbed oxygen concentrations. Consequently, the oxidative ability of active metal oxides was appropriately weakened, suppressing undesirable side reactions. MnCeOx/HY also notably suppressed NO adsorption and nitrate formation, promoting the catalytic reaction solely through the E-R mechanism and enhancing N2 selectivity. The abundant strong acid sites on the zeolite surface facilitates NH3 adsorption at moderate to high temperatures, notably expanding the active temperature window. Furthermore, the acid sites of HY zeolite serve as sacrificial sites, preferentially reacting with alkali metals, thus exhibiting excellent resistance to alkali metal poisoning on MnCeOx/HY. Combining with the DFT results, the structure-activity relationships in this study also reveal the importance of the effective synergy between acid sites and redox sites for optimal catalytic performance, offering valuable insights into the development of highly active and alkali-resistant denitrification catalysts.

Electrospinning of polyetherketoneketone fibers: The effect of fabrication regime on the morphology, physico-chemical and biological characteristics

Electrospinning is a unique technology based on the fabrication of polymer fibers from the solution under an applied electric field. Electrospun membranes are applied in various fields, starting from filter technologies to tissue engineering. Polyalyletherketones (PAEK) is a family of synthetic bioinert polymers characterized by outstanding mechanical performance, high chemical stability, and biocompatibility. In the present study, the effect of electrospinning parameters (collector-to-tip distance, applied voltage, spinning solution flow rate and polymer concentration in the spinning solution) on the morphology of the fabricated polyetherketoneketone (PEKK) membranes as well as their crystal structure, chemical stability and biocompatibility was investigated. Based on 108 combinations of the electrospinning parameters, it was found that minimum concentration of PEKK in the spinning solution in 1,1,1,3,3,3-hexafluoropropan-2-ol (HFP) required for the fibers’ formation is 4 wt %, while the applied voltage providing fibers without defects was found at 20 kV. It was demonstrated that the tested electrospinning regimes allow to fabricate the membranes with average fiber diameter from 0.76 ± 0.29 to 1.46 ± 0.60 μm and porosity from 87 ± 1 to 92 ± 1 %. It was found that electrospinning process has no effect on the chemical structure of PEKK macromolecules. Electrospinning parameters had no effect on crystal structure of PEKK in the fabricated membranes, which was found to be amorphous. The fabricated membranes demonstrated high Young modulus (above 150 MPa) and elongation over 170 %, were stable in strong alkali and acid solutions and biocompatible towards mouse embryonic fibroblasts.

Electrocatalytic Hydrogen Generation by Ni-PN3P Pincer Complexes: Role of Phosphorus Substituents in Tuning the Reactivity.

Electrocatalytic hydrogen evolution reaction (eHER) is crucial in addressing the growing global energy demand. Although nickel-pincer-based molecular complexes, varying in donor atoms, were studied previously for eHER, the impact of variations in the substituents attached to the donor atoms was not investigated. Herein, three air-stable R1PN3PR2-based NiII-pincer complexes [R1=R2=Ph2 (7); R1=R2=tBu2 (9); R1= tBu2, R2=Ph2 (10)], varying solely in P-substituents, were studied in acetonitrile. While the redox potentials for NiII/I and NiI/0 couples underwent anodic shifts by ~100 mV upon progressively substituting tert-butyl by phenyl groups on each P-atom, the corresponding eHER reactivity with organic acids (acetic acid, p-toluenesulfonic acid and trifluoromethanesulfonic acid) of different strengths followed different trends; likely influenced by the pKa of intermediate metal-hydride (M-H) species [pKa(M-H9) > pKa(M-H10) > pKa(M-H7)]. Depending on the acid strength, different oxidation states of the metal were activated to promote eHER. The catalytic rates for 9, 10, and 7 were calculated to be 85 s-1, 77 s-1 and 95 s-1 with Faradaic efficiencies of 88.5 ± 2%, 66.1 ± 1.4%, and 91.7 ± 1.5% respectively, in acetic acid. Electrochemical data supported by theoretical results reinforce a significant electronic influence of the anchoring P-substituents on the activity of these complexes.

Catalytic recycling of polylactic acid over zirconium phosphate supported WOx active sites

Chemical upcycling of end-of-life plastics is an economically and environmentally feasible way to tackle plastics crisis. Among them, methanol alcoholysis of polylactic acid (PLA) is a promising approach, which can produce methyl lactate (MLA) that can be further converted to lactide to achieve a sustainable development. In this work, a series of WOx/ZrP catalysts with WOx active sites in low coverage and high surface area were synthesized via anchoring WOx species on the surface of zirconium phosphate (ZrP). Characterizations indicated that the strong interaction between WOx and ZrP promoted the formation of WOx active sites in low coverage. In particular, 10 %WOx/ZrP catalyst was highly active and stable for the alcoholysis of PLA plastics under mild conditions due to the abundant WOx active sites and strong acidity. The yield of MLA over 10 %WOx/ZrP catalyst reached 94.5 % within 4 h at 160 °C, which was superior to the performance of traditional solid acids (α-ZrP, HZSM-5, Hβ and Amberlyst-45). In addition, 10 %WOx/ZrP was versatile for the alcoholysis of discarded PLA-based products and could be recycled at least five times. The prominent performance of 10 %WOx/ZrP catalyst and the possible reaction mechanism were discussed.

Selective production of phenol from the end-of-life wind turbine blade through catalytic pyrolysis

This study employed catalytic pyrolysis to enhance the selectivity and yield of phenol in the pyrolysis oil derived from the end-of-life wind turbine blade (WTB). It was confirmed that the NiO(10)/Al2O3 catalyst exhibited the best activity, reaching a phenol selectivity of 28.57 % at 500 °C with a heating rate of 10 °C/min. Furthermore, a competitive phenomenon between the catalytic formation of phenol and that of gaseous products was observed. Characterization results indicated that at lower loading content of NiO on the Al2O3 carrier, NiAl2O4 crystals tended to form preferentially, which reduced catalyst activity by covering surface strong acid sites. With increasing the loading content of NiO, saturation of NiAl2O4 formation occurred, and free NiO crystals became dominant. This resulted in the creation of abundant Lewis acid sites, enhancing the catalytic formation of phenol. Whilst, excessive accumulation of free NiO crystals increased strong acid sites and significantly generated lattice oxygen, promoting the cracking of pyrolysis oil to gaseous products, which was detrimental to phenol enrichment but facilitated the production of H2-rich syngas. The conclusions offered valuable insights for upgrading pyrolysis products derived from epoxy resin polymers during the recovery of end-of-life WTB.

Effects of anions on the electrospray ionization of proteins in strong acids.

The effect of anions on the positive electrospray ionization (ESI) of proteins in different strong acids with varying pH values from 3 to 1 is studied using high-pressure ESI. Reducing the pH from ∼2 to 1 caused a drastic shift in charge state from a high-charge-state distribution (HCSD) to a narrow low-charge-state distribution (LCSD). The shift in charge state was consistent with the circular dichroism result that showed a conformational change due to the "acid-induced folding" of proteins from an unfolding state to a compact molten globule state. Acids of different anions produced noticeable differences in the average charge for HCSD and LCSD. For HCSD, the average charge was lower than the value typically observed using formic and acetic acids. As for LCSD, the average charge was lower than the "native" charge. The high abundance of acid anion that induces the protein compaction was believed to play a role in charge reduction. The effectiveness of anions to "refold" a highly unfolded protein to a compact state and the propensity to reduce the charge of HCSD for proteins appeared to follow the selectivity series of anions towards the stationary phase in ion chromatography. However, the propensity of anions to reduce the charge for LCSD follows quite an opposite trend. The presence of ammonium salt in the acidic solution was found to increase the charge of LCSD. The simple mass spectrum with a narrow distribution of charge state obtained with perchloric acid at pH 1 was demonstrated to facilitate the counting of basic sites.

Effect of acid soak treatment of the precursor on the structure and properties of polypropylene-based carbon fibers

Polyolefin fibers have received wide attention as the precursor for low-cost carbon fiber, and cross-linking of linear polyolefin by strong acid has been proven to be an effective way to stabilize the precursor fiber prior to carbonization. However, the conventional temperature used in sulfonation process is too high and could result in severe decomposition of the linear chain of the polymer, which further deteriorated the mechanical properties of the as-prepared carbon fiber. Thus, reducing the duration of sulfonation process operated at high temperature may alleviate the degradation behavior, conferring the polyolefin-based carbon fibers with better performance. In this paper, polypropylene (PP) fibers were soaked in sulfuric acid at 50 °C–90 °C, before the conventional preparation protocol of PP-based carbon fiber. The structural evolution from PP to carbon fiber were characterized by Differential scanning calorimetry (DSC), Fourier transform infrared spectroscopy (FTIR), X-ray diffraction (XRD), and Raman spectroscopy. The mechanical and conductive properties of carbonized fibers where further measured. The results showed that the soak in sulfuric acid resulted in swelling of PP fibers in diameter direction, as well as reducing the crystallinity of the fibers, both of which were physical transformation, and could be easily controlled by soak temperature. The subsequent sulfonation at conventional temperature was fastened for the soaked PP fibers, and the duration of sufficient sulfonation were almost reduced by half. The obtained carbon fibers exhibited better thermal conductivity and mechanical properties, which were enhanced by 25 % and 40 %, respectively, compared with that without soak pretreatment.

Lignin-MOF hybrid polymetallic composites for selective hydrogenolysis of cellulose derived 5-hydroxymethylfurfural

The development of green, effective and inexpensive catalysts was important for the catalytic transfer hydrogenation of 5-hydroxymethylfurfural (HMF) to prepare 5-methylfurfuryl alcohol (MFA). The assembly of sodium lignosulfonate (LS) with NiCo-MOFs through a simple hydrothermal method was reported, and a series of iron-containing polymetallic hybrid catalysts were investigated. The introduction of iron led to the increase of medium strong acid sites and Lewis acid sites in the catalyst and enhanced the adsorption of furan rings, thus improved the catalytic activity. The effects of calcination temperature, iron content, and reaction parameters (including reaction temperature, pressure, hydrogen donor solvent) were all studied in detail. It was found that HMF could be completely converted over Fe@Ni3Co-MOF-LS, with a MFA yield of 88.75 % under the optimal condition (240 ℃, 2 MPa N2 in 4 h) without the presence of hydrogen. This study provided a new perspective for the utilization of lignin resource as carbon-based catalysts for the production of biomass-derived platform chemicals.

Degradative solvent-catalyzed extraction of sewage sludge

It is necessary for the further development of sludge degradative solvent extraction (DSE) to significantly increase the bio-oil yield and adjust its composition. In this study, the effects of MCM-41, HZSM-5, and SSZ-13 on the physical properties, yield, and composition of bio-oil were compared. Results show that all three catalysts effectively promote the conversion of volatiles in the residue to the heavy component (heavy-s). The addition of MCM-41 improved the yieldof both the light component (light-s) and heavy-s. Their yields increased from 8.11% and 20.47% to 14.39% and 29.18%, respectively. Its all-silicon structure and weak acidity have no significant effect on the composition of the bio-oil. HZSM-5 addition increases the light-s yield to 25.58%. Its MFI structure and proper acidity are beneficial to the formation of aromatic hydrocarbons and olefins, while effectively reducing oxygenates. SSZ-13 increases the heavy-s yield to 27.89%, and promoted the formation of nitrogen-containing compounds significantly.