Solvent Treatment Research Articles

Tribological properties of novel palygorskite nanoplatelets used as oil-based lubricant additives

Layered palygorskite (PAL), commonly called attapulgite, is a natural inorganic clay mineral composed of magnesium silicate. In this study, an aqueous miscible organic solvent treatment method is adopted to prepare molybdenum-dotted palygorskite (Amo-PMo) nanoplatelets, which greatly improved the specific surface area of PAL and the dispersion effect in an oil-based lubricant system. Their layered structure and size were confirmed using transmission electron microscopy (TEM) and atomic force microscopy. Following a tribological test lubricated with three additives (PAL, organic molybdenum (SN-Mo), and Amo-PMo), it was found that the sample of 0.5 wt% Amo-PMo exhibited the best tribological properties with a coefficient of friction of 0.09. Moreover, the resulting wear scar diameter and wear volume of the sliding ball surface were 63% and 49.6% of those lubricated with base oil, respectively. Its excellent lubricating performance and self-repairing ability were mainly attributed to the generated MoS2 adsorbed on the contact surfaces during the tribochemical reaction, thereby effectively preventing the direct collision between asperities on sliding solid surfaces. Thus, as-prepared Amo-PMo nanoplatelets show great potential as oil-based lubricant additives, and this study enriches the existing application of PAL in industry.

PENGARUH JENIS PELARUT TERHADAP AKTIVITAS ANTIOKSIDAN EKSTRAK ECENG PADI (Monochoria vaginalis Burm F. C. Presel.)

This study was conducted to determine the effect of different solvents on the antioxidant activity of rice hyacinth extract and to find out the right type of solvent used to extract rice hyacinth with the highest antioxidant activity. The experimental design used in this study was a completely randomized design with various types of solvents as a treatment using maceration method. The treatment consisting of four type of solvents i.e water, ethanol, methanol, and acetone. All treatments were repeated four times to obtained 16 experimental units. The data obtained were analyzed by variance and if the treatment had significant effect then followed by Duncan test. The results showed that the various types of solvent treatments had a very significant effect (P<0.01) on antioxidant activity. The results showed that ethanol solvent had the best treatment which produced an antioxidant activity based on IC50 of 0,49 mg/mL, yield of 26.17%, total phenol content of 11.12 mg GAE/g, total flavonoid content of 8.26 mg QE/g, total tannin content of 5.18 mg TAE/g.
 Keywords: rice hyacinth, maceration, anioxidant activity

Flexible metal-free hybrid hydrogel thermoelectric fibers

Highly conductive poly(3,4-ethylenedioxythiophene):poly(styrenesulfonate) (PEDOT:PSS) fiber has been developed as a more promising candidate compared with bulk and film to achieve wearable thermoelectric energy harvesting. Single-walled carbon nanotubes (SWCNTs) with nanostructures are considered as an effective conductive filter for the further improvement in the thermoelectric (TE) performance of PEDOT:PSS fibers. However, the previous research primarily focused on PEDOT:PSS/SWCNT films instead of fibers. In this study, PEDOT:PSS/SWCNT hybrid fibers were synthesized via gelation process, which presents a 30% enhancement of the electrical conductivity with negligible changes in Seebeck coefficient. Moreover, there was a significant increase in the Young’s modulus in accordance with the addition of an appropriate amount of SWCNTs. Thereafter, the as-prepared hybrid fibers were treated using ethylene glycol (EG) to further optimize the TE performance. Moreover, the influence of the treatment time and temperature was systematically investigated. The EG treatment resulted in a significant improvement in the electrical conductivity without a significant decrease in the Seebeck coefficient. Furthermore, the hybrid fibers were subject to EG treatment at elevated temperature, whose optimal power factor was approximately 30% higher than that of the EG-treated PEDOT:PSS/SWCNT fibers at 25 °C. This indicates that the solvent treatment at higher temperature improves the TE performance of hybrid fibers. The findings of this study can serve as a guide for the preparation of flexible and metal-free hybrid fiber with enhanced TE performance and Young’s modulus.

PEDOT: PSS hydrogel film for supercapacitors via AlCl3-induced cross-linking and subsequent organic solvent treatments

An ionically crosslinked conducting polymer poly (3, 4-ethylenedioxythiophene): poly (4-styrenesulfonate) (PEDOT: PSS) hydrogel was synthesized by fast gelation of PEDOT: PSS dispersion (PH1000) using a high concentration of Al3+ (2 M) with a high water content of 94.4 wt% and three-dimensional interconnected networks. The highly conductive PEDOT: PSS hydrogel film was achieved by soaking it in ethylene glycol (EG) for a certain time. It was found for the first time that the conductivity of the PEDOT: PSS hydrogel film can be further improved with the vapors of m-cresol. It delivers 158 F g−1 at a scan rate of 50 mV s−1 with an outstanding rate capability and good cycling stability with 84.9% capacitance retention after 2000 cycles.

Reversible Interlayer Sliding and Conductivity Changes in Adaptive Tetrathiafulvalene-Based Covalent Organic Frameworks.

Ordered interlayer stacking is intrinsic in two-dimensional covalent organic frameworks (2D COFs) and has strong implications on COF's optoelectronic properties. Reversible interlayer sliding, corresponding to shearing of 2D layers along their basal plane, is an appealing dynamic control of both structures and properties, yet it remains unexplored in the 2D COF field. Herein, we demonstrate that the reversible interlayer sliding can be realized in an imine-linked tetrathiafulvalene (TTF)-based COF TTF-DMTA. The solvent treatment induces crystalline phase changes between the proposed staircase-like sql net structure and a slightly slipped eclipsed sql net structure. The solvation-induced crystallinity changes correlate well with reversible spectroscopic and electrical conductivity changes as demonstrated in oriented COF thin films. In contrast, no reversible switching is observed in a related TTF-TA COF, which differs from TTF-DMTA in terms of the absence of methoxy groups on the phenylene linkers. This work represents the first 2D COF example of which eclipsed and staircase-like aggregated states are interchangeably accessed via interlayer sliding, an uncharted structural feature that may enable applications such as chemiresistive sensors.

Surface Ligands Management for Efficient CsPbBrI2 Perovskite Nanocrystal Solar Cells

CsPbX3 (X = Cl, Br, I) inorganic perovskite nanocrystals (PNCs) not only maintain the excellent optical and electronic properties of bulk material but also possess the features of nano‐materials, such as tunable bandgap and easily processable colloidal ink, and enable them to be suitable for incorporation into various electronic devices and compatible with printing techniques. In contrast to the traditional II‐VI and III‐V semiconductor nanocrystals, the unique defect‐tolerance effect makes the CsPbX3 PNCs promising materials for optoelectronic applications. The ligands around the PNCs play a critical role in the optoelectronic devices performance. Herein, through a facile hexane/ethyl acetate (MeOAc) solvent treatment method to control the ligand amount around CsPbBrI2 PNCs, the impact of ligand amount on the performance of solar cell is systematically demonstrated and the ligand amount is quantified precisely via the nuclear magnetic resonance internal standard method. Through controlling the ligand amount, the film quality, charge transfer, and transport properties are largely improved. In addition, a simple annealing process is applied to improve the interface properties by partial crystal fusion. As a consequence, the photovoltaic power conversion efficiency of 12.2% is achieved, which is the highest performance reported for mixed‐halide CsPbX3 PNCs solar cells.

Solvent treatment inducing ultralong cycle stability poly(3,4‐ethylenedioxythiophene):poly(styrenesulfonic acid) fibers as binding‐free electrodes for supercapacitors

As one kind of conducting polymer composite, poly(3,4-ethylenedioxythiophene):poly(styrenesulfonic acid) (PEDOT:PSS) has been widely used as an electrode for energy storage and conversion devices because of its optical transmittance, flexibility, and high electrical conductivity etc. Here, we prepared binding-free PEDOT:PSS fibers (PFs) electrodes with high capacitive performance for supercapacitors via a facile method followed by various solvent treatments. Dimethyl sulfoxide (DMSO)-treated electrodes displayed a better specific capacitance (Cs) of 202 F/g at 0.5 A/g with higher elongation at break, flexibility, and conductivity of 140.7 S/cm, compared to those of pristine PEDOT:PSS materials. More importantly, the DMSO-treated fibers possessed improved stability, which retained 105% of the initial Cs after 22 000 long cycles at 10 A/g. It is believed that the fabricated PFs will be promising organic electrodes for portable supercapacitors and other flexible electronic devices in the near future.

Chemical recycling of waste tire in high-temperature organic fluid

The inadequate treatment of waste tire is currently a major environmental and economical issue. In this study, the effective solubilization of waste tire into diethyl ether was attained by the thermal treatment in organic solvent at 200–300 °C. Not only aromatic, but also aliphatic alcohols were effective on the solubilization. Among aliphatic alcohols, 1-heptanol was the most effective solvent on the solubilization and reached near 70% in the thermal treatment at 200 °C under inert atmosphere. Model compound study containing sulfur–sulfur bond suggests the disulfide–alcohol exchange reaction leading devulcanization of the waste tire.

Sulfonated functionalization of carbon derived corncob residue via hydrothermal synthesis route for esterification of palm fatty acid distillate

Low-cost biodiesel was successfully produced through esterification of palm fatty acid distillate over corncob residue-derived heterogeneous solid acid catalyst. The sulfonated functionalized carbon derived from corncob was synthesized via hydrothermal carbonization followed by chemical activation using concentrated sulfuric acid. This technique allows efficient carbonization process and able to maintain active polar species of the catalyst hence effectively improves the acid strength of prepared catalyst. The esterification of palm fatty acid distillate over HTC-S catalyst was optimized via the one-variable-at-a-time technique, and 92% free fatty acid conversion with a biodiesel yield of 85% was achieved at optimum conditions of 2 h reaction time, 70 °C reaction temperature, 3 wt% catalyst loading, and 15:1 methanol-to-oil molar ratio. Various of catalyst regeneration techniques have been studied and sulfuric acid treatment is found to be the most effective approach for restoring the active sites for spent HTC-S catalyst in comparison to washing solvent and thermal treatment. The HTC-S catalyst regenerated via sulfuric acid treatment is capable to convert PFAD to biodiesel with free fatty acid conversion >90% for two consecutive cycles. The synthesized PFAD-derived biodiesel has complied with the international biodiesel standard ASTM D6751.

Chemical and non-chemical pre-treatment techniques for bio ethanol production from biomass

The present work is focused on the yield of bioethanol using chemical and non-chemical pre-treatment techniques. Textile cotton waste is taken as the biomass for the present work. The acid and ultrasonication pre-treatment has been chosen as chemical and non-chemical method respectively. Experiments were carried out with acid and ultrasonication pre-treatment techniques by varying different parameters. The compositional analysis was done using the Soxhlet extraction method to find the cellulose, hemicellulose and lignin content. The functional group changes were confirmed by FT-IR analysis. The sugar yield is measured using Di Nitro Salicylic acid method. The increase in sugar yield is confirmed after pre-treatment and the samples were taken into fermentation process. The fermentation is done by using Saccharomyces cerevisiae. The yeast is initially inoculated in the YPD medium. The grown yeast is used in the fermentation process for the production of bioethanol. The presence of bioethanol is confirmed using GC analysis and yield of bioethanol produced using acid, ultrasonic pre-treatment and solvent treatment is compared. It is also noticed that acid, ultrasonicated and solvent pre-treatment biomass shows 0.58 g/l, 0.543 ml/g and 0.334 ml/g of bioethanol respectively.

Integrative strategy to determine residual proteins in cefaclor produced by immobilized penicillin G acylase

There is a growing trend in the pharmaceutical industry towards substituting conventional chemical synthesis routes of semi-synthetic β-lactam antibiotics (SSBAs) through environmentally sustainable enzymatic processes. These have advantages such as cost reduction in terms of solvent and waste treatment and time saving owing to fewer reaction steps. Penicillin G acylase (PGA) is an industrially important enzyme that is mainly used to catalyze the synthesis of SSBAs. In this study, we established an integrative strategy using three different analytical methods for determining the PGA-associated residual protein content, which is a critical quality issue in the end product. Cefaclor was taken as representative example of SSBAs. High-performance liquid chromatography coupled with fluorescence detection (HPLC-FD) allowed the routine analysis of PGA residual proteins and other low molecular weight (MW) impurities with high detection specificity and sensitivity, comparable to those of the Bradford assay and microfluidic protein chip electrophoresis. However, these latter two methods were superior for quantitative and qualitative analysis, respectively, and should be regarded as necessary adjuncts to the HPLC-FD method. By combining the three methods, trace levels of residual proteins were detected in four (out of 13) cefaclor bulk samples from two different manufacturers, with a major protein MW of ∼63 kDa. This suggests that the higher MW PGA subunit tends to persist in the end product. The integrative determination strategy described here can be used to evaluate SSBA bulk samples and monitor the process of SSBA manufacturing by enzymatic methods, especially in terms of inter-batch consistency and process stability.

H-aggregate triggered mechanochromic luminescence property of 7-(diethylamino)-coumarin-3-carbaldehyde oxime derivative

For the organic luminogens, the packing structure and fluorescent emission of H-aggregate could be affected by mechanical stimuli. According to the finding, here a new coumarin oxime derivative 4-chloro-7-(diethylamino)-coumarin-3-carbaldehyde oxime A1 showing reversible mechanochromic luminescence (MCL) property was developed. Optical properties study in the solution and DFT calculation revealed that A1 had ICT nature. The emission wavelength in solid state of A1 changed reversibly from 515 nm to 540 nm upon mechanical stimuli and solvent treatment. To demonstrate the relationship between MCL property and molecular structure, another three relative coumarin oxime compounds were synthesized. The results showed that the formation of H-aggregate in solid state observed by X-ray diffraction analysis was considered to be responsible for MCL property of A1, and the intermolecular H-bonding caused by oxime hydroxyl group played a key role in the formation of H-aggregate. Furthermore, the potential application in rewritable data storage based on the MCL behavior of A1 was studied.

Preparation of Natural Multicompatible Silk Nanofibers by Green Deep Eutectic Solvent Treatment

Natural silk fibers consist of well-organized, sophisticated hierarchical architectures that contribute to the robust mechanical performance and functions of the fibers; thus, the direct extraction of silk nanofibers (SNFs) at a single level is a major challenge. Herein, a novel simple, environmentally friendly, and recyclable route was developed to directly downsize natural silks into SNFs via a green deep eutectic solvent (DES) system assisted by mild mechanical disintegration. SNFs with diameters ranging from 2.3 to 28 nm and lengths of 598 ± 308 nm were isolated at a high yield (over 70%) under optimal DES pretreatment conditions. On the basis of the inherent amphoteric properties of SNFs, the pH sensitivity and reversibility were explored to lighten the weight of SNF dispersions for storage and transport, and furthermore, the double adsorption properties of the SNFs might functionalize them for transparent anticounterfeiting devices. In addition, the nanodispersibility of the SNFs in organic solvents and the subsequent nanofiber-containing composite materials with hydrophobic polymer matrixes provide new prospects for wound dressing and porous scaffold materials in biomedical applications.

Impact of alcohol washing on the flavour profiles, functionality and protein quality of air classified pea protein enriched flour

In this study the potential of aqueous solvent washing on removing off-flavours in air classified pea protein-enriched flour (PPEF) was investigated. Unpleasant flavour compounds are one of the main deterrents to the application of pulses. PPEF was treated with ethanol or isopropanol at three different concentrations (20%, 50%, and 80%) to remove the volatiles related to unpleasant beany, earthy and astringent flavours. Headspace solid phase microextraction followed by GC-MS was used to identify the flavour compounds in untreated and treated PPEF. Besides the flavour profile, changes to their proximate composition, colour, functionality and protein quality were compared among untreated and treated samples. Higher concentrations of ethanol and isopropanol (50% and 80%) showed greater effectiveness in removing flavour compounds by reducing the total peak area by 82%–94%. Protein content in all treated samples (58.2%–64.3% d.b.) increased compared to untreated PPEF (55.5%) as a result of purification due to the decrease in ash, lipid and carbohydrate content. However, alcohol treatment reduced the protein solubility and oil holding capacity in all samples by 38.3%-75.9%, and 16.7%-30.2%, respectively. Although in vitro protein digestibility was improved with the solvent treatments, the amino acid scores of those samples became lower (i.e., reduced levels of methionine, cysteine or tryptophan) resulting in up to a 27.8% reduction in in vitro protein digestibility correct amino acid scores. Both ethanol and isopropanol at 50% and 80% concentration proved to be effective in removing flavour compounds in PPEF with some modifications on the chemical compositions, protein functionalities and quality.

Lithium-selenium sulfide batteries with long cycle life and high energy density via solvent washing treatment

SeS2 is a promising cathode material that has both advantages of S and Se. In a carbonate-based electrolyte, Li-SeS2 batteries show good cycle performance but work at low discharge voltage due to slow Li-ion diffusion. Here, we report a simple solvent treatment method for synthesizing cathode composite materials to overcome the disadvantage of carbonate-based electrolytes. The solvent washing treatment can effectively remove excess SeS2 that blocks carbon pores, which act as an electrolyte pathway. Additionally, the SeS2/OMC composite (w-SeS2/OMC) maintains the SeS2 configuration, thus leading to both the advantages of S and Se. As a result, enhanced Li-ion diffusion helps to reduce polarization and elevate the discharge voltage to ~2 V. In addition, it shows excellent capacity retention (360 mAh g−1) for 2,000 cycles at a 1C rate.

Enhanced Efficiency of Halide Perovskite Solar Cells by Solvent Engineering

During the process of the low-temperature solution fabrication, it always leads to high defects density at the grain boundaries and the interfaces, which are great barriers toward excellent solar cells. Different polar molecules of solvents are brought in to modify the surface composition by tuning the nucleation densities to obtain perovskite films with high crystallization quality. In this work, with efficiently exchanging intramolecular mechanism, high-quality MAPbI3-based perovskite films had been conveniently fabricated. Two kinds of polar molecules of dimethyl sulfoxide (DMSO) and N-methyl-2-pyrrolidone (NMP) were added to the dimethylformamide (DMF) solvent to result in perovskite films with high quality. As a result, the device with NMP solvent treatment outputs improved efficiency of 18.5% at the short-circuit current (Jsc) of 23.3 mA cm–2, with an open-circuit voltage (Voc) of 1.075 V and a fill factor of 77.1% under standard AM 1.5 solar illumination. This method of solvent engineering might provide a convenient way for the application of perovskite-based photovoltaic devices.

The Influence of Solid/Solvent Interfacial Interactions on Physicochemical and Mechanical Properties of Ofloxacin

To investigate the potentials of a simple solvent treatment technique for improving the physicochemical and mechanical properties of ofloxacin. Ofloxacin was treated with 5% aqueous ammonia solution at a solid to solvent ratio of 1:3 and treatment time of 4 h in stoppered flasks, then filtered under vacuum. Changes in ofloxacin powder characteristics were monitored using SEM, particle size analysis, IR, DSC, XRD, hydrophilicity, equilibrium solubility, dissolution rate, flowability, and compressibility tests. The effect of PVP K90 and Tween 80 used in two concentrations (0.2% and 2%) was investigated. Crystals of ofloxacin having particle size < 160 μm were included whenever appropriate for comparison. The treated ofloxacin showed bundles of elongated prisms with a wide particle size range (2 to 39 μm). Average size was reduced from 9.8 to 6.4 and 4.6 μm with 2% Tween 80 and PVP, respectively. Different analytical techniques confirmed that neither structure modification nor additive molecule incorporation in crystal lattice occurred during treatment. The treated powder showed repose angle 39°, bulk density 0.282 g/cm3, tap density 0.319 g/cm3, Hausner ratio 1.13, Carr’s index 11.6%, compact hardness 5–6.45 kg, porosity 13–6.38%, and elastic recovery 4.5–8.8%. The corresponding values for untreated ofloxacin were 59.5°, 0.221 g/cm3, 0.314 g/cm3, 1.42, 29.6%, 3.74–5.27 kg, 15.38–7.22%, and 4.57–8.83%, respectively. Values were further improved by PVP addition. Treating ofloxacin powder with 5% aqueous ammonia solution in the presence of 2% PVP improves the dissolution, flowability, and compressibility of the drug. The treated powder is suitable for the preparation of tablets with few excipients.

Aqueous miscible organic-layered double hydroxides with improved CO2 adsorption capacity

Potassium-promoted layered double hydroxide (LDH)-derived materials are suitable elevated temperature CO2 adsorbents for pre-combustion CO2 capture. A challenge for the commercialization of LDHs as efficient CO2 adsorbents is their low capacities (ca. 0.5–0.6 mmol/g@400 °C) due to their hydrogen-bonded stacked structure. In this study, the aqueous miscible organic solvent treatment (AMOST) was used to exfoliate Mg3Al–CO3 LDH into nanosheets with a flower-like morphology, resulting in high surface areas of 287 and 212 m2/g for CC1 (washed with ethanol) and CC2 (washed with acetone), respectively. The exfoliated LDH structure exposed more interlayered CO2 active sites and promoters for alkali metal modification. Six impregnation solvents, water, acetone, ethanediol, ethanol, DMAC, and methanol were screened to optimize the CO2 uptake of 20 wt% K2CO3-promoted CC1. K2CO3/CC1(ed) using ethanediol as the impregnation solvent reached a CO2 working capacity of 1.46 mmol/g at 400 °C in the first cycle and 1.23 mmol/g after 10 cycles, twice the capacity of the commercial K2CO3/MG70. Material characterization indicated that the unexpectedly high performance of K2CO3/CC1(ed) could be attributed to the uniform K+ dispersion on the surface of K2CO3/CC1(ed) rather than bulk phase formation and the release of the residual solvent during calcination that could generate more paths for CO2 diffusion.

Evaluation of the Environmental Impact and Efficiency of N-Doping Strategies in the Synthesis of Carbon Dots.

The efficiency and associated environmental impacts of different N-doping strategies of carbon dots (CDs) were evaluated. More specifically, N-doped CDs were prepared from citric acid via two main synthesis routes: Microwave-assisted hydrothermal treatment with addition of N-containing small organic molecules (urea and ethylenediamine (EDA)); and microwave-assisted solvothermal treatment in N-containing organic solvents (n,n-dimethylformamide (DMF), acetonitrile and pyridine). These syntheses produced CDs with similar blue emission. However, XPS analysis revealed that CDs synthesized via both hydrothermal routes presented a better N-doping efficiency (~15 at.%) than all three solvothermal-based strategies (0.6–7 at.%). However, from the former two hydrothermal strategies, only the one involving EDA as a nitrogen-source provided a non-negligible synthesis yield, which indicates that this should be the preferred strategy. This conclusion was supported by a subsequent life cycle assessment (LCA) study, which revealed that this strategy is clearly the most sustainable one from all five studied synthesis routes.

Functionalized Amphiphilic Diblock Fullerene Derivatives as a Cathode Buffer Layer for Efficient Inverted Organic Solar Cells.

The amphipathic interface layer sandwiched between cathode and active layers had always played a role to balance interface compatibility and interfacial energy barriers in inverted organic solar cell (OSC) devices. Two functionalized amphiphilic diblock fullerene derivatives named C60-2DPE and C60-4HTPB were synthesized and applied as an interface layer in modifying zinc oxide (ZnO). Based on their amphipathic characteristics, the solvent treatment was introduced to cause an obvious self-assembly of the two materials on ZnO. The introduced cathode buffer layer could improve the interface compatibility between ZnO and the organic active layer effectively with its amphipathic blocks. Based on the PTB7-Th:PC71BM system, the OSC devices with a functionalized fullerene derivative layer could reach a power conversion efficiency of 9.21 and 8.86% for C60-2DPE and C60-4HTPB , respectively.