Mechanochemical Pretreatment Research Articles

Bismuth preoxidation for preparing solutions of salts

The oxidation of metal bismuth after the introduction of bismuth oxide, ammonium nitrate, sodium chloride or carbonate into its melt, as well as the effect of mechanochemical preactivation on the oxidation process have been studied by X-ray diffraction analysis and thermogravimetry. It has been established that the oxidation of metal bismuth occurs at the dispersion stage, and the mechanochemical pretreatment of metallic bismuth mixed with 10–30% of its oxide leads to a decrease in the temperature of the onset of bismuth oxidation from 350 to 200°C. An ecologically pure method for obtaining concentrated solutions of various bismuth salts from metal by its preconversion to oxide and dissolution in mineral acids has been shown to be useful.

Highly crystalline poly(heptazine imides) by mechanochemical synthesis for photooxidation of various organic substrates using an intriguing electron acceptor – Elemental sulfur

Low-defect potassium poly(heptazine imide) (PHIK-BM) was engineered for application in photocatalytic oxidation of organic substrates. Mechanochemical pretreatment of a mixture of 5-aminotetrazole in LiCl/KCl eutectics using high-energy ball milling afforded a highly homogeneous mixture that, upon sequential thermolysis at 600°C, gave nanosized particles of PHIK–BM. The photocatalytic activity of the free-standing PHIK–BM plates was assessed in the oxidation of benzyl alcohol to benzaldehyde under visible light irradiation using elemental sulfur as an electron acceptor. Both quantitative conversion (>99%) of benzyl alcohol and selectivity (>98%) with respect to benzaldehyde were achieved. The developed method was extended to aliphatic alcohol oxidation coupled with multicomponent Hantzsch 1,4-dihydropyridine synthesis. These 1,4-dihydropyridines were also photocatalytically oxidized by PHIK–BM to the corresponding substituted pyridines, with very good yields and under mild metal-free conditions.

Solventless synthesis of AEL-type aluminophosphate molecular sieve from mechanochemically pretreated low-templated reactants

One of the main obstacles that hamper the application of zeolites is the high consumption of expensive structure-directing agent. Herein, we reported the mechanochemisty-mediated solventless synthesis of AlPO4-11 aluminophosphate molecular sieve with low dosage of diisopropylamine (DIPA) as the structure-directing agent. The influences of DIPA/Al2O3 ratio, fluoride ions, seed crystals and high-energy mechanochemical pretreatment on the synthesis of AEL-type zeolite were investigated in detail. Both DIPA and fluoride ions are indispensable for the successful synthesis of AEL phase. The resultant AEL molecular sieves were characterized by XRD, SEM, TG-DTA, CHN elements analysis, and N2 physisorption. The results indicate that the introduction of seed crystals cannot improve the phase purity and crystallinity of the resulting products. On the other hand, high-energy mechanochemical pretreatment not only can affect the morphology of AEL zeolite, but more importantly, can also reduce the consumption of structure-directing agent.

Ultrasonically-enhanced mechanochemical synthesis of CaAl-layered double hydroxides intercalated by a variety of inorganic anions

CaAl-layered double hydroxides (CaAl-LDHs) were synthesised with various interlayer anions (CO32−, F−, Cl−, Br− and I−) by mechanochemical pre-treatment followed by ultrasonic irradiation in aqueous media. The parameters of the syntheses (duration of pre-milling and sonication, quality of the aqueous media, temperature) were altered in order to optimise the procedure and to understand the formation of LDH and other secondary products. The products were characterised by X-ray diffractometry (XRD) and scanning electron microscopy (SEM). The optimisation resulted in close-to-phase-pure CaAl-LDHs, not only with carbonate and chloride interlayer anions, but the hard-to-intercalate bromide and iodide as well.

Preparation and characterization of Silicalite-1 zeolites with high manganese contents from mechanochemically pretreated reactants

Silicalite-1 zeolites with high manganese contents isomorphously incorporated within the framework were synthesized by using mechanochemical pretreatment.

Effect of the addition of calcium hydroxide on the hydrothermal–mechanochemical treatment of Eucalyptus

The effect of Ca(OH)2 addition on optimization of hydrothermal–mechanochemical pretreatment, which combines hydrothermal and milling treatments, was examined. The highest glucose yield of 90% was achieved in the ball-milled specimen previously treated at 170°C in the presence of 20% Ca(OH)2 per substrate weight. The specific surface area of the substrate was closely correlated with glucose yield, and a larger specific surface area was obtained when treating the specimen at 170°C in the presence of Ca(OH)2 compared to treatment at 170°C without Ca(OH)2. Although the Ca(OH)2-treated specimen was relatively unaffected by delignification, the cleavage of the ester bonds between lignin and hemicellulose was confirmed by FT-IR. This suggests that Ca(OH)2 weakens the substrate structure by loosening the bonds between lignin and hemicellulose as the mechanism to increase the specific surface area regardless of the high lignin content, facilitating the fibrillation of fibers with mechanical milling.

The Biomec process for mechanochemically assisted biodegradation of PCBs in marine sediments

The Biomec process, a two-stage treatment based on a short mechanochemical (MC) pretreatment and then followed by an aerobic biological degradation, was developed and tested for detoxifying marine sediments that were largely contaminated by polychlorobiphenyls (PCBs). Clean marine sediment spiked with PCBs (Aroclor 1260) and, alternatively, with decachlorobiphenyl in slurry conditions was ultramilled for 1 min in a nutational high energy ball mill, then was treated aerobically in a bioreactor with a purposely selected commercial bacterium (Burkholderia xenovorans). With ∼66 % overall PCB biodegradation achieved in less than 3 months, laboratory experiments confirmed the remarkable effectiveness of Biomec process when compared to direct bioremediation. The investigation showed in particular that the MC pretreatment decreased the chlorination degree of high-chlorinated PCB congeners, and consequently their biorecalcitrance, through the substitution of some chlorine atoms with hydroxyl groups. This reaction eases the aerobic degradation of the hydroxyl-substituted PCBs by B. xenovorans, allowing bacteria to skip the cell stressing step of aromatic ring bi-hydroxylation along the biodegradation pathway. After short MC treatment of the sediments, a common biological aerobic treatment can degrade PCB congeners, the highly chlorinated ones were included, in a fast, effective and cheap manner.

Synthesis of MCM-41 with High Manganese Content by Mechanochemical Pretreatment of the Starting Materials

Abstract Manganese-incorporated MCM-41 with high manganese content of Mn/(Mn + Si) = 9.2 mol % and BET specific surface area of 750 m2 g−1 was obtained by utilizing mechanochemical treatment. Clear differences in the state of manganese throughout the synthetic conditions were confirmed by various spectroscopic analyses.

Preparation and Properties of Chemical Resistant Conductive Composites with Restrained Negative Temperature Coefficient Behaviour Based on Mechanochemically Devulcanised Waste Fluoroelastomers

The presence of negative temperature coefficient (NTC) effect is harmful to temperature auto-control and also hinders the application of self-regulating heater materials. Mechanochemically devulcanised waste fluoroelastomer (FKM) can hinder the aggregation of conducting fillers and inhibit the NTC effect. Herein, we report for the first time that the devulcanised FKM can be used as low cost but effective functional filler for making chemical resistant conductive composites with restrained NTC effect. The NTC effect was notably restrained via introducing devulcanised FKM into the carbon black-filled poly(vinylidene fluoride) composites. A platform with a volume resistivity higher than 106 Ω•cm was observed at temperature range of 167–180°C. The crystallization imperfection and limited mobility of carbon black induced by the well dispersed FKM powders are responsible for the delay of NTC effect. Furthermore, the mechanical properties of the composites were significantly improved through the mechanochemical pretreatment of FKM. Meanwhile, the devulcanised FKM-filled composites have excellent chemical resistance. The stable resistivity in a wide temperature range of the prepared low cost composites gives them attractive prospects as over current and temperature sensor materials.

Morphology and physical properties of composite foams based on low‐density polyethylene and ground tire rubber

Low‐density polyethylene (LDPE)/(ground tire rubber) (GTR) composite foams with an average cell size smaller than 100 µm were produced by compression molding. The effects of the mechanochemical pretreatment of the LDPE/GTR blends and their GTR content on the cell morphology and physical properties were investigated. The results indicated that the pretreatment of LDPE/GTR blends by using a pan‐mill type of mechanochemical reactor made in our laboratory improved the dispersion state and thereby enhanced the foamability of the blends. The average cell size of the composite foams decreased from 64.0 to 42.3 µm with an increase in GTR content from 0 to 50 phr (parts by weight per hundred parts of resin). Moreover, the addition of 20–40 phr of GTR into the LDPE foams increased their rebound resistance and decreased their compression set. J. VINYL ADDIT. TECHNOL., 19:105–112, 2013. © 2013 Society of Plastics Engineers

Application of Mechanochemical Pretreatment Prior to Aqueous Extraction of Eleutheroside B from Eleutherococcus senticosus

A mechanochemical pretreatment was used prior to aqueous extraction of eleutheroside B from Eleutherococcus senticosus. The effects of the mechanochemical assisted extraction parameters hydroxypropyl-β-cyclodextrin (HP-β-CD) content, particle size, and circulating water temperature on the extraction yield of eleutheroside B were investigated. The mechanochemical assisted extraction process was optimized based on an orthogonal experimental design. The optimum process conditions were a HP-β-CD content of 23% (w/w), a particle size of D95 ≤ 44 μm and circulating water temperature of 40 °C. The mechanochemical assisted extraction process produced a higher eleutheroside B extraction yield, using a shorter extraction time and a greatly simplified process compared with traditional heat-reflux extraction, which makes mechanochemical assisted extraction a potential tool for eleutheroside B extraction from Eleutherococcus senticosus. Moreover, this technique used water as the solvent, making mechanochemical assisted extraction a less expensive and eco-friendly technique compared with traditional heat-reflux extraction.

Mechanochemical devulcanization of ground tire rubber and its application in acoustic absorbent polyurethane foamed composites

AbstractThe use of recycled rubber in preparation of acoustic absorbent materials will help to combat the existing environmental problems of both waste disposal and noise pollution. The focus of this work is to investigate the influence of mechanochemical pretreatment of ground tire rubber (GTR) on the acoustic absorption properties of polyurethane (PU)/GTR foamed composites. GTR subjected to pan‐milling could be mechanochemically devulcanized by breaking up the crosslinked structures through inducing fairly strong shearing and compressing forces. The significant increase in sol fraction of GTR confirmed the partial devulcanization during pan‐milling. Moreover, thermal gravimetric analysis indicated that rubber content in the soluble part of GTR was also remarkably increased. The devulcanization increased flexible chains of the GTR particles, which could help to improve damping properties as well as acoustic absorption ability of the PU/GTR foamed composites. Dynamic mechanical analysis and acoustic absorption measurements well confirmed this hypothesis. The loss modulus and sound absorption coefficient of PU/GTR foamed composites were remarkably increased through the mechanochemical pretreatment of GTR. The mechanochemical pretreatment also enhanced foamability of the composites as revealed by cell morphology. © 2012 Wiley Periodicals, Inc. J. Appl. Polym. Sci., 2013

Enhancement of thermal aging performance and oil resistance of acrylic rubber vulcanisates by adding devulcanised ground fluoroelastomer ultrafine powder as functional filler

In this study, devulcanised ground fluoroelastomer (FKM) ultrafine powder with the sol fraction of 19·8% and the average particle size of ∼1 μm or less was successfully prepared by solid state mechanochemical milling at ambient temperature. This reclaimed FKM can be used as a low cost but effective functional additive for enhancing the thermal aging performance and oil resistance of acrylic rubber (ACM) vulcanisates. The mechanical properties of the ACM–ground FKM blends were significantly improved through the mechanochemical pretreatment of FKM. The ACM–devulcanised FKM blends showed similar curing behaviours and enhanced mechanical properties as compared to pure ACM compound. As devulcanised FKM content increased, the tensile strength of thermal aged (150°C×72 h) ACM vulcanisates increased from 3·9 to 6·4 MPa, by ∼65%; while elongation at break increased from 42·8 to 106·1%, by ∼1·5 times. The ACM–devulcanised FKM blends also exhibited better oil resistance than pure ACM. Dynamic mechanical analysis and scanning electron microscopy–energy dispersive spectroscopy confirmed the well miscibility and superior dispersion of devulcanised FKM in ACM matrix.

Comparative evaluation of tensile bond strength of a polyvinyl acetate-based resilient liner following various denture base surface pre-treatment methods and immersion in artificial salivary medium: An in vitro study.

Background and Aim:This study was formulated to evaluate and estimate the influence of various denture base resin surface pre-treatments (chemical and mechanical and combinations) upon tensile bond strength between a poly vinyl acetate-based denture liner and a denture base resin.Materials and Methods:A universal testing machine was used for determining the bond strength of the liner to surface pre-treated acrylic resin blocks. The data was analyzed by one-way analysis of variance and the t-test (α =.05).Results:This study infers that denture base surface pre-treatment can improve the adhesive tensile bond strength between the liner and denture base specimens. The results of this study infer that chemical, mechanical, and mechano-chemical pre-treatments will have different effects on the bond strength of the acrylic soft resilient liner to the denture base.Conclusion:Among the various methods of pre-treatment of denture base resins, it was inferred that the mechano-chemical pre-treatment method with air-borne particle abrasion followed by monomer application exhibited superior bond strength than other methods with the resilient liner. Hence, this method could be effectively used to improve bond strength between liner and denture base and thus could minimize delamination of liner from the denture base during function.

Antioxidant Activity of Saururus chinensis Pretreated by Mechanochemical Technology - Nitrite Scavenging and Electron Donating Ability -

Saururus chinensis is used as a raw material of an anti-rheumatic, poultice, sedative and stomachic. The tea of dried Saururus chinensis leaves has a function of relaxing pains in back and breast and of treating stomach ailments. The plant has the functions of anti-inflammatory, depurative, diuretic, febrifuge and refrigerant. The extraction of functional material is carried out by methanol and ethanol solvents. Mechanochemical grinding is applied as a pretreatment process before extraction to enhance the extraction efficiency by increasing the surface area of the materials while changing the chemical properties of the materials. Extraction of functional materials from the Saururus chinensis after grinding as a pretreatment using the mechanochemical technology was accomplished in this study to investigate the effect of grinding on the antioxidant activities of the extract. Saururus chinensis was ground by the planetary ball mill and the morphology was analyzed by SEM. Mechanochemical pretreatment increased the yields of functional materials from 5.9 g to 6.4, 7.0, and 8.1 g after grinding of 30 minutes, 1 hour and 2 hours, respectively. Nitrite scavenging ability increased from 53.0-71.0% to 61.0-79.0% for the methanol extraction in the solution of pH 1.2. Also, Electron donating abilities were increased from 7.90-33.51% to 11.97-38.51% for the methanol extraction. The extract concentration for the half inhibition of DPPH radicals was reduced from 278μg/mL in the original sample to 263μg/mL in the sample after grinding for the methanol extraction.

Effects of Mechanochemical Pretreatment on the Extraction of Functional Materials from Houttuynia cordata

Houttuynia cordata is used as a raw material of oriental medicine to acquire antioxidant and anti cancer effect and to cure a heart disease. Mechanochemical technology not only reduces the size of the object but also changes the chemical properties of the object. Extraction of functional materials from the Houttuynia cordata after grinding as a pretreatment using the mechanochemical technology was conducted in this study to investigate the effect of grinding on the yields and antioxidant activities of the extract. Houttuynia cordata was ground by the planetary ball mill and the morphology was analyzed by SEM. Yields of functional materials were increased from 6.2 g in the sample without grinding to 7.0, 7.8, 8.8 g after grinding of 30 minutes, 1 hour and 2 hours, respectively. Nitrite scavenging abilities were increased from 57-77% to 69-86% as a result of mechanochemical pretreatment. Also, DPPH scavenging abilities for the methanol extraction were increased from 10.01-40.29% to 11.01-49.29% as a result of mechanochemical grinding.

Mechanochemical methods of activating processes of biomass pretreatment

This work deals with the fundamental problems of searching for and attaining synergetic effects manifested upon the mechanochemical pretreatment of plant material. Laws relating the intense physicomechanical effects on the raw material during its preprocessing to the deep hydrolytic reactions of hemicelluloses in the bulk of the structural units of plant biomass are established. It was shown earlier on models that mechanical effects are able to dramatically influence the reactivity of macromolecules by changing the hybridization of bonds. To discover similar regularities for plant structures, we performed experiments on the grinding of biomaterials. The best results were obtained in an extruder in the presence of catalysts for polysaccharide hydrolytic cleavage (acids, alkalies, and enzymes). Using birch wood, it was shown that the hydrolytic processes are accelerated by several orders of magnitude in the extruder force fields; the working temperature was considerably reduced (relative to thermohydrolysis) and neither furfural nor any other harmful side product was detected. Our results suggest that the use of mechanochemical methods allows processing time to be reduced by an order and of magnitude along with the formation of side products, testifying to the utility of this technique’s practical application.

Mechanochemical-assisted efficient extraction of rutin from Hibiscus mutabilis L.

Abstract Mechanochemical-assisted extraction (MCAE) technique was developed for the efficient extraction of rutin from Hibiscus mutabilis L. This process was carried out via mechanochemical pretreatment in AGO-2 high intensity planetary mill. Highest yield of rutin was obtained by grinding H. mutabilis with Na2CO3 (15.0 wt.%) and Na2B4O7·10H2O (1.5 wt.%) for 4 min, extraction temperature at 25 °C, total extraction time of 15 min (two cycles of 10 min and 5 min), acidification pH 5.0 and solvent/material ratio of 25 mL/g. Scanning electron microscopy, X-ray powder diffraction and diffuse-reflectance UV–Vis spectrum were applied to identify the physicochemical property changes. These changes mainly included the enhanced diffusivity and water solubility of rutin resulting from the breakage of cell walls and its transformation into a water-soluble salt form by the mechanochemical pretreatment. Compared with heat reflux and superfine grinding extraction, MCAE showed the advantages of efficiency, no organic solvent consumption and much lower extraction temperature. Industrial relevance In this study, mechanochemical-assisted extraction of rutin from H. mutabilis was developed and the physicochemical changes in this process were supervised. Owing to its great potential to transform the target compounds into water-soluble forms, MCAE provided a good alternative for efficient aqueous extraction of bioactive compounds, especially some poorly water-soluble natural products.

The effect of calcination on reactive milling of anthracite as potential precursor for graphite production

The effect of a pretreatment using reactive ball milling and calcination on the graphitizability of an anthracite coal is explored. A thermal anneal of Buck Mountain anthracite at 1400 °C in argon increased the L c crystallite dimension (from 12 to 20 Å) and led to an increase in the oxidation temperature of the product. Ball milling of the coal reduced particle size with a nominal effect on carbon order and the degree of graphitization after the 1400 °C thermal anneal ( L c from 18 to 29 Å). Ball milling in cyclohexene led to a substantial increase in the graphitizability at 1400 °C ( L c from 12 to 50 Å). The enhanced reactivity was due to both carbon structure and introduced metal. The products of the mechano-chemical pretreatment and thermal anneal consisted of nanographene ribbons and multi-walled nanopolyhedral particles. It oxidized at moderate temperatures and had a high (74.3%) degree of graphitization based on X-ray diffraction analysis; the derived material has potential as filler for production of graphite.

Application of mechanochemical pretreatment (MCPT) to aqueous extraction of eleutheroside b from Eleutherococcus senticosus

Application of mechanochemical pretreatment (MCPT) to aqueous extraction of eleutheroside b from Eleutherococcus senticosus