Alkaline Solvent Research Articles

A novel polyether polyol contains repeating cyclohexane units and its application on reactive polyurethane adhesive

A novel polyether polyol was successfully synthesized from cyclohexene oxide (CO), propylene oxide (PO), and poly(propylene glycol) 400 through ring‐opening polymerization, catalyzed by double metal cyanide catalyst for the first time. Then, the obtained cyclohexane‐based polyether polyol (CPOL) further reacted with 4,4′‐diphenylmethane diisocyanate to form reactive polyurethane adhesive (RPUA). The thermal properties and mechanical strength of the RPUA were characterized by differential scanning calorimetry, dynamic mechanical analysis, thermogravimetric analysis, and lap shear strength test. It was found that with the introduction of cyclohexane units, the glass transition temperature (Tg) and thermal stability of the RPUA increased about 122.3% and 3.32%, respectively. Besides, the lap shear strength of the RPUA prepared with the synthesized CPOL was 130.67% higher than the counterpart derived from conventional polyether polyol 2000. Furthermore, compared with RPUA‐PPG, RPUA‐CPOL also exhibited excellent lap shear strength on polycarbonate substrate even when the adhesion joints were immersed into hot water or alkaline solvent. All the above results suggest that the cyclohexane units in polyether polyol have great improvements in the thermal stability and lap shear strength of RPUA.

Depolymerization of Lignin from Extracted Solid Waste of Cupressus lusitanica Mill. Biomass Using Imidazole

Implementation of green chemistry and biorefinery concept are needed to boost production of biomass-derived fuels, chemicals, and materials with cost-effective processing of sustainable feedstock. The use of imidazole as a novel solvent for biomass pretreatment creates an approach that helps accomplish this concept. The present work is dedicated to study the pretreatment of residual lignocellulosic biomass, namely, extracted solid waste of Cupressus lusitanica, by application of the alkaline solvent—imidazole. The pretreatment allowed obtaining cellulose- and hemicellulose-rich fractions, whereas lignin was depolymerized. Both cellulose and hemicellulose recovery were highly dependent on the reaction conditions. The highest cellulose content was obtained at 160 °C for 4 h and was 40.7 ± 0.6 wt% with a delignification yield of 65.2 ± 0.4 wt%. The effect of biomass delignification on the efficiency of enzymatic digestibility was also analyzed and it was observed a good linear relationship between the delignification yield and the glucan to glucose yield. The presence of added-value phenolic compounds from depolymerized lignin in recovered imidazole was analyzed by capillary electrophoresis and determination of total phenolic content and antioxidant activity was also performed. These compounds were tentatively identified and their structures proposed on the basis of the HPLC–MS analyzes.

How alkaline solvents in viscosity measurements affect data for oxidatively damaged celluloses. Cuoxam and Cadoxen

The effect of the degradation induced by the solvents for cellulose cuoxam and cadoxen and its dependency on the nature of the carbonyls in oxidatively-damaged cellulosics was investigated by combining a novel approach of sample regeneration and gel permeation chromatography coupled with carbonyl-selective labelling for reliable molecular characterization. The type of cellulosic pulp, degree and mode of oxidation and dissolution time were considered. Results show that the main discriminating factors in determining the degradation of oxidatively-damaged celluloses in alkaline dissolving media are: (1) the type of pulp, i.e. hemicellulose-containing pulps are more severely compromised; (2) of particular relevance, the prior oxidation mechanism, meaning not only the amount of oxidized moieties (greater oxidation, greater solvent-induced damage) but also their position on the chains (i.e. peroxide-oxidized cellulose is more unstable than hypochlorite-oxidized cellulose).

Ultrasound-assisted processing of Chlorella vulgaris for enhanced protein extraction

The green microalga Chlorella vulgaris is a promising source of proteins of high nutritional value for the food industry. The present study aims to improve the recovery of proteins and umami free amino acids from C. vulgaris by exploring the use of ultrasound following multiple approaches including ultrasound-assisted single solvent extraction, ultrasound-assisted sequential solvent extraction and ultrasound-assisted enzymatic extraction. Ultrasound-assisted single solvent extraction using an alkaline solvent during 10 min provided equivalent protein recoveries to those obtained in control experiments macerating the biomass during 18 and 24 h. Ultrasound-assisted sequential solvent extraction using 0.4 M NaOH followed by 0.4 M HCl achieved a protein recovery of 79.1 ± 5.3%, 1.32-fold higher than the control experiments without ultrasound for 1 h. Ultrasound-assisted enzymatic extraction using lysozyme resulted in protein recoveries ranging from 33 to 42%, and these extracts also contained a high percentage of umami free amino acids. Ultrasound-assisted enzymatic extraction with protease enhanced the recovery of proteins (58–82%), although the extracts had low percentage of umami free amino acids. The scanning electron microscopy imaging revealed that ultrasound-assisted solvent extraction and ultrasound-assisted enzymatic extraction significantly changed the morphology of the cell surface.

New Cysteine Protease Inhibitors: Electrophilic (Het)arenes and Unexpected Prodrug Identification for the Trypanosoma Protease Rhodesain.

Electrophilic (het)arenes can undergo reactions with nucleophiles yielding π- or Meisenheimer (σ-) complexes or the products of the SNAr addition/elimination reactions. Such building blocks have only rarely been employed for the design of enzyme inhibitors. Herein, we demonstrate the combination of a peptidic recognition sequence with such electrophilic (het)arenes to generate highly active inhibitors of disease-relevant proteases. We further elucidate an unexpected mode of action for the trypanosomal protease rhodesain using NMR spectroscopy and mass spectrometry, enzyme kinetics and various types of simulations. After hydrolysis of an ester function in the recognition sequence of a weakly active prodrug inhibitor, the liberated carboxylic acid represents a highly potent inhibitor of rhodesain (Ki = 4.0 nM). The simulations indicate that, after the cleavage of the ester, the carboxylic acid leaves the active site and re-binds to the enzyme in an orientation that allows the formation of a very stable π-complex between the catalytic dyad (Cys-25/His-162) of rhodesain and the electrophilic aromatic moiety. The reversible inhibition mode results because the SNAr reaction, which is found in an alkaline solvent containing a low molecular weight thiol, is hindered within the enzyme due to the presence of the positively charged imidazolium ring of His-162. Comparisons between measured and calculated NMR shifts support this interpretation.

Spiro N-oxidized pyrrolidone-appended hemicyanine: Synthesis, lower pH-sensing and colormetric temperature sensing

Three novel spiro N-oxidized pyrrolidone-appended hemicyanine derivatives have been synthesized and characterized by 1H NMR, 13C NMR, UV–Vis and HRMS. The molecular structures of spirocyclic dye 2a and its opening-ring product 2aa have been determined by single-crystal X-ray diffraction analysis. The UV–vis spectra show significant solvatochromic behavior of three spirocyclic derivatives, especially in acidic and alkaline solvents. Spirocyclic dye 2a displays an excellent pH dependent behavior and responds linearly to extreme acidic conditions in the pH ranges of 1-4. The absorption spectra studies on opening-ring reaction reveal that acid and heat dual stimulation can induce opening-ring of 2a, which exhibits temperature-responsive linear in the range of 25–45 °C, behaving a colorimetric thermometer sensing. These properties provide the possibility for 2a-c to be used as stimulating response molecule switch.

PERBANDINGAN PENGGUNAAN PELARUT ALKALI (KOH DAN NaOH) TERHADAP HASIL EKSTRAKSI RUMPUT LAUT MERAH (Eucheuma cottonii, sp) ASAL ACEH JAYA

Indonesia is an archipelago that is rich in natural marine potential. One of the provinces in Indonesia that is rich in natural marine potential is Aceh. Aceh, which is rich in seaweed, has good prospects to improve the economy of its people. One of the seaweed cultivated in Aceh is Eucheuma cottonii, which has carrageenan content. In the process of carrageenan processing from seaweed alkali is needed which aims to produce carrageenan granules. Precipitation of carrageenan was carried out by heat extraction method which varied alkaline solvents namely NaOH and KOH and than do FTIR and SEM analysis. From the results of FTIR in the absorption area of ​​1010-1080 cm-1 showed the absorption of glycosidik bonds and at 849-850 cm-1 uptake was absorption from galactose-4-phosphate bonds. In wavelength is a type of carrageenan kappa. SEM results show different and uneven carrageenan surfaces.

Accelerated wound healing ability of Jatropha sap by iota carrageenan-poly (vinyl alcohol) hydrogel film.

Jatropha sap (JTS), an important fluid carried in xylem and phloem tubes of Jatropha multifida L. plant, has good wound healing property. However, physicochemical stability of JTS needs to be improved in order for it to be useful as a topical wound-healing agent. In this study, we developed an iota carrageenan-polyvinyl alcohol (IC-PVA) hydrogel film (HF) as a carrier of JTS and evaluated its wound-healing ability. The characterization of JTS secondary metabolites by ultraviolet-Vis spectrophotometry suggested presence of flavonoid, saponin, and alkaloids in the sap. We successfully extracted IC from Euchima spinosum using alkaline solvent at 80°C–90°C with calcium chloride as the precipitator. The result of computer simulation using Discovery Studio software and Autodock Tools showed the presence of hydrogen bonding interaction of IC-PVA. IC-PVA/JTS HF with excellent physical properties including high swelling ratio (246.32%) and high gel fraction (16.75%). In addition, irritation test in mice confirmed the absence of hypersensitivity reaction, redness, and allergic reactions. Interestingly, IC-PVA/JTS HF significantly accelerated wound healing when compared to the nontreated group/control with 98% wound closure by 10 days. These results suggest that IC-PVA HF has improves wound-healing ability of JTS.

Selective removal of SO2 from coal-fired flue gas by alkaline solvents using a membrane contactor

The presence of SO2 in coal-fired flue gas has adverse effects on the amine solutions used for CO2 capture. In addition, SO2 emissions in the atmosphere are also a primary source of pollution. In this study, the SO2 removal efficiency of three aqueous alkaline absorbents NaOH, Na2SO3, and CaO was studied using a membrane contactor. The morphology of the used membrane was examined using SEM and contact angle characterization techniques. Gas removal efficiency was studied within a feed gas flow rate of 0.5–5 m3/h, absorbent flow rate of 5–100 mL/min, and absorbent concentration of 0–0.01 mol/L. The gathered results showed that aqueous CaO has superior gas removal performance. It achieved a SO2 removal efficiency of 99.99 % at a concentration of 0.0025 mol/L, while the aqueous NaOH and Na2SO3 absorbents achieved 99.99 % removal efficiency at concentrations of 0.001 mol/L. Through comprehensive experimental work, the optimum operating parameters needed to achieve maximum SO2 removal efficiency were also determined. Furthermore, the durability of the membrane was tested in a four week continuous gas removal test and SEM images were recorded weekly to observe module morphology. The obtained results indicated that the membrane was quite durable and did not deteriorate noticeably.

Acidic and alkaline deep eutectic solvents in delignification and nanofibrillation of corn stalk, wheat straw, and rapeseed stem residues

In this work, six different deep eutectic solvent (DES) treatments—five acidic (natural organic acid–choline chloride) and one alkaline (K2CO3–glycerol)—were used and compared in delignification and nanofibrillation of agricultural by-products from wheat straw, corn stalk, and rapeseed stem. The DES treatments were performed at 100 °C for 8 h, at 100 °C for 16 h, and at 80 °C for 24 h. The yield of cellulose and lignin fractions was obtained gravimetrically, and a more detailed composition of fractions was obtained for the 16 h treatment. All the samples were further nanofibrillated, and the properties of nanocelluloses and their nanopapers were measured. Acidic lactic acid–choline chloride and alkaline K2CO3–glycerol DESs resulted in the highest delignification yields (11.8–5.7 wt-%), nanocellulose viscosity (1360–555 Pa s), and crystallinity index (54–38 %), but the strength properties of nanopapers from alkaline DES treatment (170–132 MPa) were better compared to acidic DESs (132–24 MPa). A plausible explanation for this difference may be that the alkaline DES also dissolved waxes and proteins, which can mitigate the adhesion and network formation between the nanofibers. It was also observed that the separated lignin fractions from acidic and alkaline DES treatments had different characteristics as determined by FTIR.

An Experimental Study of Emulsion Flow in Alkaline/Solvent Coinjection with Steam for Heavy-Oil/Bitumen Recovery

SummaryWater is the dominant component in steam-injection processes, such as steam-assisted gravity drainage (SAGD). The central hypothesis in this research is that in-situ oil transport can be enhanced by generating oil-in-water emulsion, where the water-continuous phase acts as an effective oil carrier. As part of the research project, this paper presents an experimental study of how oil-in-water emulsion can improve oil transport in porous media at elevated temperatures.Diethylamine (DEA) was selected as the organic alkali that generates oil-in-water emulsions with Athabasca bitumen at a 1,000-ppm NaCl brine and a 0.5-wt% alkali concentration. This aqueous composition had been confirmed to be an optimum in terms of oil content in the water-external emulsion phase at a wide range of temperatures. Then, flow experiments with a glass-bead pack were conducted to measure the effective viscosities of emulsion samples at shear rates from 5 to 29 seconds−1 at 35 bar and temperatures from 373 to 443 K.Results show that the oil-in-water emulsions were more than 15 times less viscous than the original bitumen at temperatures from 373 to 443 K. At the shear rate of 5 seconds−1, for example, the emulsion viscosity was 12 cp at 373 K, at which the bitumen viscosity was 206 cp. The efficiency of in-situ bitumen transport was evaluated by calculating the bitumen molar flow rate under gravity drainage with the new experimental data. Results show that oil-in-water emulsion can enhance the in-situ molar flow of bitumen by a factor of 273 at 403 K and 345 at 373 K, in comparison with the two-phase flow of oil and water in conventional SAGD. At 443 K, only a fraction of bitumen is emulsified in water, but the bitumen transport by both oil-in-water emulsion and an excess oil phase in DEA-SAGD can enhance the molar flow of bitumen by a factor of 19 in comparison to SAGD. This is mainly because the mobility of the bitumen-containing phase is enhanced by the reduced viscosity and increased effective permeability. A marked difference between alkaline solvents and conventional hydrocarbon solvents is that only a small amount of an alkaline solvent enables enhancing the in-situ transport of bitumen.

Cross-flow deposited hydroxyethyl cellulose (HEC)/polypropylene (PP) thin-film composite membrane for aqueous and non-aqueous nanofiltration

In this study, hydroxyethyl cellulose (HEC) was cross-flow deposited on flat-sheet polypropylene (PP) porous support and insolubilized by cross-linking using glutaraldehyde (GA) to fabricate cost-effective thin-film composite membrane for aqueous and non-aqueous nanofiltration. Membrane physico-chemical property, permeation performance, as well as tolerance to acid, alkaline and organic solvents were systematically characterized. The obtained HEC/PP composite membrane was found to be effectively modulated in pore size via changing HEC and GA contents and possessed good fabrication reproducibility. The desired HEC/PP composite membrane with an average pore diameter of around 2.21nm exhibited high fluxes of 41.0 and 8.2L/m2h to pure water and ethanol, respectively, and removals of 99.9%, 99.9% and 96.7% to 50mg/L dye aqueous solutions of methyl blue, Congo red and sunset yellow, respectively. Soaking tests revealed that the HEC/PP composite membrane possessed good tolerance to acid, alkali and organic solvents of tetrahydrofuran, ethyl acetate and ethanol. Continuous filtration of dye/ethanol solution demonstrated that the HEC/PP membrane possessed excellent long-term durability in ethanol solution, maintaining a stable flux higher than 4.6L/m2h and removals of 95.4% and 84.2% to methyl blue and Congo red, respectively, during the whole filtration of 110h.

Single-chain conformation of carboxylated schizophyllan, a triple helical polysaccharide, in dilute alkaline aqueous solution

Synchrotron-radiation small-angle X-ray scattering measurements were carried out for a schizophyllan (SPG) sample with the weight-average molar mass Mw of 340 kg mol−1 and five carboxylated SPG (sclerox) samples with different degrees of substitution (DS) ranging from 0.18 to 0.45 in 200 mM aqueous NaOH including 10 mM NaCl to determine Mw, the second virial coefficient A2, the particle scattering function P(q), and the radius of gyration ⟨S2⟩. Positive A2 values indicated that this alkaline solvent was a good solvent for all polysaccharide samples investigated. The resultant Mw values (~100 kg mol−1) were much smaller than that for the trimer in aqueous NaCl at neutral pH, indicating all SPG and sclerox samples dissolved as single chains in the alkaline solvent. Both P(q) and ⟨S2⟩ were consistently explained by the wormlike chain model. The obtained parameters were almost independent of DS. While the chain stiffness (12–18 nm) in terms of the Kuhn segment length or twice the persistence length was similar to those for the other single chain polysaccharides, the helix pitch per residue (0.1 nm) was quite smaller than the trimer state (0.3 nm). This shrunken main-chain helical structure is most likely due to hydrophobic interactions between helical main chain and side groups.

How Alkaline Solvents in Viscosity Measurements Affect Data for Oxidatively Damaged Celluloses: Cupri-Ethylenediamine.

Although efficient and inexpensive, conventional viscometry to determine the average degree of polymerization (DP) of cellulose may mislead the final DP because cellulose degradation occurs in the used solvents, which consist of alkaline amino complexes of transition metals, such as cupri-ethylenediamine (CED). For oxidatively damaged pulps or celluloses, viscosity-DP determinations may be more inaccurate because alkali-induced β-elimination reactions render such oxidized celluloses even more vulnerable. Despite the risk identified in many studies, a systematic investigation of the parameters affecting the viscosity-DP assessed by reliable analytics is still required. Here, a new approach evaluating the effects of CED on oxidized cellulosics was used (i.e., immediate pulp regeneration after dissolution in CED). In-depth molecular feature characterization (e.g., absolute molar masses and oxidized groups' profiling related to molecular weight distribution) by gel permeation chromatography coupled with fluorescence and multiangle laser light scattering clarified the behavior of oxidized celluloses and the influencing parameters upon dissolution in CED.

Simple extraction of silica nanoparticles from rice husk using technical grade solvent: effect of volume and concentration

One of the main components of rice husk ash (RHA) is silica, which can be used as raw material for fertilizer. The study examined influences of various volume and concentration on silica extraction. The silica was extracted using a technical alkaline grade solvent (NaOH) with a variation in volume/the ratio of RHA to the amount of solvents (1: 4, 1: 5, and 1: 6) and the solvent concentration (0.50, 0.75 and 1 N). The highest average yield was found in the concentration of 1 N solvent with the ratio of RHA to the number of solvents 1: 6 is 62.83%. Based on the physical characteristics of silica from RHA which include whiteness (93.2496.66%), moisture content (0.49-2.81%), and density (0.56-0.95 g / mL) indicates that the use of technical alkaline solvents tends to decrease the purity of the proven silica also with the presence of major contaminants such as Na and Cl and other elements through SEM-EDX, XRF, and XRD test. In saline soils, the presence of contaminants in silica with an amorphous phase (2θ = 22.29°) especially Na and Cl may have a negative effect if used as raw material for fertilizers.

Natural colorant extraction from Cinnamomum camphora tree leaves of different maturities and its ultrasonic‐assisted extraction process

AbstractThis study investigated natural colorant extraction from camphor tree leaves using a green and effective process. Ethanol, acetic acid, aqueous sodium carbonate and an aqueous solution of cellulase enzyme were used to examine the extraction performance, with and without the assistance of ultrasonics. Results showed that when subjected to changes in frequency and extraction time, ultrasonics is able to accelerate the extraction process and achieve a better yield for chlorophyll and anthocyanin extraction from fresh leaves compared with a traditional heating bath at similar temperatures. However, when an alkaline solvent was used to extract dark brown colorant from the old leaves, a traditional heating bath was found to be more effective than ultrasonic extraction. Cellulase enzyme failed to show its effectiveness in this study when serving as a colorant‐extracting solvent, regardless of the use of ultrasonics.

CO2 absorption from simulated flue gas in a bubble column

ABSTRACTCarbon dioxide (CO2) absorption from power plant generated flue gas is investigated for CO2 emissions reduction. Amino acid alkaline solvents have the potential to reduce the energy required for solvent regeneration. This project is focused on CO2 absorption by amino acid alkaline solvents in a bubble column. Important parameters characterizing the reactor, e.g., bubble size, liquid-phase dispersion coefficient, and gas holdup, are experimentally determined. A theoretical model based upon transient mass and energy balances for the chemical species involved is presented. Simulation results are compared to experimental data. The model can be used to predict, optimize, and control CO2 absorption in industrial-scale applications.

Synthesis and characterization of epoxy resins containing imine group and their curing processes with aromatic diamine

The epoxy resins containing imine bonding were prepared from hydroxyl substituted Schiff base monomers in two steps. At the first step, hydroxyl substituted Schiff base monomers were synthesized via condensation reaction. At the second step, epoxy resins were synthesized from the reaction between Schiff base monomers and epichlorohydrine (EPC). Then curing processes of epoxy resins were achieved by p-phenylenediamine compound. The structures of resulting compounds were confirmed by FT-IR, UV-Vis and 1H-NMR. TG-DTA and DSC measurements were performed for thermal characterizations of the compounds. Chemical resistances of the cured epoxy-amine systems were determined for coating applications in acidic, alkaline and organic solvents. HCl (10%, aqueous solution), NaOH (10%, aqueous solution), DMSO, DMF, N-methylpyrrolidone, ethanol, THF and acetone were used for corrosion tests. Chemical resistance data of the synthesized epoxy resins demonstrated that they have good chemical resistance against various acid, alkaline and common organic solvents. Surface morphologies of epoxy resin and the cured epoxy resin were determined with scanning electron microscopy (SEM) measurements. Also, optical band gap (Eg) values of Schiff base monomers and epoxy resins were calculated from UV-Vis measurements.

Reconstructing Dual‐Induced {0 0 1} Facets Bismuth Oxychloride Nanosheets Heterostructures: An Effective Strategy to Promote Photocatalytic Oxygen Evolution

Sunlight‐driven photocatalytic water splitting to generate oxygen (O2) is a promising approach for utilizing solar energy. Herein, direct Z‐scheme heterostructure photocatalysts composed of ultrathin Bi3O4Cl and BiOCl nanosheets are rationally fabricated via alkaline chemical etching and solvent exfoliation for O2 evolution under visible light. With AgNO3 and FeCl3 as the electron scavenger, the optimized ultrathin Bi3O4Cl/BiOCl exhibits prominent photocatalytic activity for O2 production under visible‐light illumination and the production rate (Fe3+: 58.6 µmol g−1 h−1) is much higher than the nanocrystal heterostructure (Fe3+: 28.5 µmol g−1 h−1). This ultrathin heterostructure system can efficiently transfer the electrons, which leads to a considerable improvement in the photocatalytic performance. Due to the suitable band edge potentials and the intense electronic interaction between two‐dimensional (2D) Bi3O4Cl and 2D BiOCl, as confirmed by theoretical computations, photoluminescence, and photoelectricity tests, the ultrathin heterojunction with an internal electric field has a highly remarkable charge transfer. The intimate interface contact and {0 0 1} facets effect promote the high photocatalytic performance of the ultrathin Bi3O4Cl/BiOCl heterostructure.

Comparison of deep eutectic solvents (DES) on pretreatment of oil palm empty fruit bunch (OPEFB): Cellulose digestibility, structural and morphology changes

In this work, a novel solvent, deep eutectic solvent (DES) was applied to examine its effectiveness in pretreating OPEFB. Three types of DESs, i.e. choline chloride-lactic acid (ChCl-LA), choline chloride-urea (ChCl-U) and choline chloride-glycerol (ChCl-G) were investigated. The pretreatment performance was based on cellulose digestibility, structural and morphology changes. At molar ratio of 1:2, ChCl-LA attained the highest reducing sugars yield of 20.7%, followed by ChCl-G (20.0%) and ChCl-U (16.9%). FT-IR and SEM results further confirmed the outstanding ability of ChCl-LA due of its ability in cellulose, hemicellulose and lignin disruption, exposing its cellulose fraction to enzymatic hydrolysis. ChCl-LA is also more favorable compare to acid and alkaline solvents as it could prevent sugars loss, use of expensive corrosion resistant equipment and ease products separation.