Mechanochemistry

Mechanochemical synthesis emerged as the most advantageous, environmentally sound alternative to
traditional routes for nanomaterials preparation with outstanding properties for advanced applications.
Featuring simplicity, high reproducibility, mild/short reaction conditions and often solvent-free condition
(dry milling), mechanochemistry can offer remarkable possibilities in the development of advanced
catalytically active materials. The proposed contribution has been aimed to provide a brief account of
remarkable recent findings and advances in the mechanochemical synthesis of solid phase advanced
catalysts as opposed to conventional systems. The role of mechanical energy in the synthesis of solid
catalysts and their application is critically discussed as well as the influence of the synthesis procedure
on the physicochemical properties and the efficiency of synthesized catalysts is studied. The main
purpose of this feature article is to highlight the possibilities of mechanochemical protocols in
(nano)materials engineering for catalytic applications.

Mechanochemical modifi cation of the structure of brown coal humic acids with classical base (NaOH)
and oxidizing base (Na2CO3·1.5H2O2) reagents was studied. Treatment of brown coal under these conditions leads
to an increase in the degree of recovery of humic acids without breaking the macrostructure of the molecules.
The reaction with the base reagent leads to an increase in the content of carboxy groups at hydrocarbon chains,
whereas the action of the oxidizing base reagent leads to an increase in the content of phenolic and carboxy groups
at aromatic rings, with the formation of chelating structures. The samples obtained show high performance as
sorbents for heavy metals.

The ability of the bulky H-shaped pentiptycene scaffold in promoting the mechanochromic and vapochromic luminescence properties for organometallic materials has been demonstrated with the N^C^N cyclometalated platinum(II) complexes [X-NCNPtY], where X = Br or Pa, the substituent on the terdentate dipyridylbenzene N^C^N ligand, and Y = Cl or Pa, the ancillary ligand, in which Pa = pentiptycene acetylene. Intermolecular interactions between the planar NCNPt cores are described by π−π and d−π interactions with negligible Pt II ···Pt II bonding, corresponding to ligand-centered excimer rather than metal−metal-to-ligand charge-transfer emission, for these platinum(II) complexes in aggregates and in the solid state. Interplay of the relative excimer-to-monomer emission intensity in response to external force and/or vapor stimuli accounts for the luminescence mechanochromism and vapochromism of the pentiptycene-incorporated platinum(II) complexes [Pa-NCNPtCl], [Br-NCNPtPa], and [Pa-NCNPtPa], whereas the pentiptycene-free counterpart [Br-NCNPtCl] undergoes little or no emission color response. In particular, the complex [Pa-NCNPtCl] displays a distinct response to aromatic versus nonaromatic organic vapors: namely, aromatic vapors such as benzene convert the excimer emission to monomer emission, but the opposite is true with nonaromatic vapors. A two-stage emission color change from red to orange and then to yellow could thus be achieved by grinding and by subsequent benzene-vapor fuming. Another feature associated with [Pa-NCNPtCl] is an aggregation-induced green → magenta luminescence color change in water/tetrahydrofuran mixed solutions. The structure− luminescence property relationship is discussed in relation to intermolecular interactions and packing modes that depend on the number and positions of pentiptycene groups.

Many tons of intentionally produced obsolete halogenated persistent organic pollutants (POPs), are stored worldwide in stockpiles, often in an unsafe manner. These are a serious threat to the environment and to human health due to their ability to migrate and accumulate in the biosphere. New technologies , alternatives to combustion, are required to destroy these substances, hopefully to their complete mineralization. In the last 20 years mechanochemical destruction has shown potential to achieve pollutant degradation , both of the pure substances and in contaminated soils. This capability has been tested for many halogenated pollutants, with various reagents, and under different milling conditions. In the present paper, a review of the published work in this field is followed by a critique of the state of the art of POPs mechanochemical destruction and its applicability to full-scale halogenated waste treatment.

Comprising 20–30% of the shells of crustaceans, α-chitin has been shown to provide a wide range of valuable products such as therapeutic substances, platform molecules and functional materials. However, the polysaccharide’s crystallinity has been poorly studied, and this has limited its widespread utilization thus far.

Filling that research gap, this thesis reports a new mechanochemical method of ball milling which amorphizes α-chitin in a controlled way. Using powder XRD to measure the polysaccharide’s crystallinity index (CrI%), a low balls-to-chitin (BtC) steel system was found to reduce CrI by an average of 6.0 units in regular milling times with good precision (±2.5 CrI units). That data set was correlated for the first time with FT-IR intensity ratios showing an unaffected degree of acetylation (DA), a steady decrease of glycosidic linkage content and α-chitin’s characteristic amide I split. The behaviour of the latter was rationalized as an experimental indicator for the weakening of the polysaccharide’s intermolecular hydrogen bonding network which is hypothesized to arise from the distribution of the average collision force within the nanofibril structure.

The combination of increased collision frequency along with the presence of a solid acid catalyst (kaolinite) provided optimum mechanochemical conditions for efficient conversion of α-chitin into water-soluble products. The latter were analysed with a MALDI-TOF MS method developed in Memorial University revealing oligomers of N-acetyl-D-glucosamine (NAG) with degrees of polymerization (DP) of 1 to 5. The monomer and dimer reached yields of 5.1 and 3.9 wt.%, respectively, within 6 h, which compare well with yields of glucose and cellobiose from literature cellulose ball milling. The products of this solvent-free oligomerization process were complemented by colorimetric approximations of reducing ends as well as size exclusion chromatography observations. This analysis is expected to stimulate future research for the sustainable production of these likely biologically active chitooligosaccharides.

In parallel, the inevitable fraction of higher MW chitin resulting from the ball milling process has been shown to conveniently solubilize in cold NaOH. An optimum concentration of 19 wt.% of the alkali was found to dissolve ~5 wt.% high MW/crystallinity α-chitin via a freeze-thaw process at −28 °C and give films of acceptable mechanical properties after a simple casting treatment with HCl. Practically, this method avoids some of the disadvantages of organic salt solution solvents like the need for a costly recycling/purification treatment, their life cycle issues, the high temperatures, and the long stirring times. At the same time, it can quickly create homogeneous solutions of predictable viscosities in the 1–10 wt.% range allowing for more efficient and controlled chitin deacetylation.

The crystallization of ciprofloxacinan antibacterial fluoroquinolone compoundwith salicylic acid resulted in the isolation of five distinct solid forms of the drug, namely, an anhydrous salt, two polymorphic forms of the salt monohydrate, methanol and acetonitrile solvates, and the salt-cocrystal hydrate. The salicylate salts were investigated by different analytical techniques ranging from powder and single crystal X-ray diffractometry, differential scanning calorimetry, thermogravimetric analysis, variable temperature powder X-ray diffraction, dynamic vapor sorption analysis, dissolution, and solubility investigations. Real-time in situ Raman spectroscopy was used to investigate the mechanochemical formation pathways of the different solid polymorphs of ciprofloxacin salicylate. The mechanism of the phase transformation between the crystalline forms was evaluated under mechanochemical conditions. It was found that the formation pathway and kinetics of the grinding process depend on the form of the starting material and reaction conditions. The analysis of the solid-state thermal evolution of the hydrated salts revealed the two-step mechanism of dehydration process, which proceeds through a formation of the distinct intermediate crystalline products.

Ethionamide (ETH), a Biopharmaceutics Classification System class II drug, is a second-line drug manufactured as an oral dosage form by Pfizer to treat tuberculosis. Since its discovery in 1956, only one reformulation was proposed in 2005 as part of the efforts to improve its solubility. Due to the limited scientific research on active pharmaceutical ingredients (APIs) for the treatment of neglected diseases, we focused on the development of an approachable and green supramolecular synthesis protocol for the production of novel solid forms of ETH. Initially, three salts were crystal engineered and supramolecular synthesized via slow evaporation of the solvent: a saccharinate, a maleate and an oxalate. The crystal structures of all salts were determined by single crystal X-ray diffraction. In sequence, mechanochemical protocols for them were developed, being the scale-up production of the maleate salt successfully reproducible and confirmed by powder X-ray diffraction. Finally, a more complete solid-state characterization was carried out for the ETH maleate salt, including thermal analysis, infrared spectroscopy, scanning electron microscopy and equilibrium solubility at different dissolution media. Although ETH maleate is thermodynamically less stable than ETH, the equilibrium solubility results revealed that this novel salt is much more soluble in purified water than ETH, thus being a suitable new candidate for future formulations.

Fisetin, luteolin and genistein, natural polyphenolic compounds of pharmaceutical interest, were combined with nicotinamide and isonicotinamide with an aim to obtain their cocrystals. A screening experiment utilizing solvent-drop grinding was conducted for those combinations. Cocrystalline phases were identified by XRPD and, as far as possible, obtained as single crystals in solution evaporation approach. Five new cocrystals were isolated, characterized by X-ray single-crystal diffraction, FT-Raman spectroscopy, thermal analysis (DSC and TG–DTA), 1H NMR in solution and compared in terms of supramolecular motifs. Reported herein fisetin–nicotinamide (1 : 2) ethanol hemisolvate (FisNam), fisetin–isonicotinamide (1 : 1) (FisInam), two polymorphic forms of luteolin–isonicotinamide (1 : 1) (LutInam, LutInam2) and genistein–nicotinamide (1 : 1) monohydrate (GenNam) cocrystals reveal the presence of an O–HNarom heterosynthon between an O7 hydroxyl moiety of a flavonoid and the pyridyl ring of a coformer. Within those species, mutual orientations of molecules as well as flavonoid–coformer stoichiometry and solvent presence in crystal lattice are factors that imply resulting motif formation and crystal packing.

Combination of two active pharmaceutical ingredients, myricetin and piracetam, yields a 1:1 cocrystal characterized by X-ray single-crystal and powder diffraction, Raman spectroscopy, 1H NMR, thermal analysis (DSC & TG-DTA) methods. Constituents of the cocrystalline phase were also investigated in terms of Hirshfeld surfaces. Compounds in their neutral forms cocrystallize in the Pna21 space group of orthorhombic system. Notably, piracetam adopts an uncommon conformation, not encountered in its cocrystals previously described. In the crystal lattice, a three-dimensional hydrogen-bonded network is observed, including formation of a 2D molecular scaffolding motif. A scale-up procedure is readily available with use of solvent-drop grinding method, in which application of a variety of common solvents leads to formation of the cocrystal, as confirmed by XRPD and Raman spectroscopy.

Chemical recycling technologies are the most promising for a waste-to-energy/material recovery of plastic waste. However, 30% of such waste cannot be treated in this way due to the presence of halogenated organic compounds, which are often utilized as flame retardants. In fact, high quantities of hydrogen halides and dioxin would form. In order to enabling such huge amount of plastic waste as viable feed-stock for recycling, an investigation on mechanochemical pre-treatment by high energy ball milling is carried out on polypropylene containing decabromodiphenyl ether. Results demonstrate that co-milling with zero valent iron and quartz sand ensures complete debromination and mineralization of the flame retardant. Furthermore, a comparative experiment demonstrates that the mechanochemical debromination kinetics is roughly proportional to the polymer-to-haloorganics mass ratio.

Mechanochemical transduction enables an extraordinary range of physiological processes such as the sense of touch, hearing, balance, muscle contraction, and the growth and remodelling of tissue and bone 1-6 . Although biology is replete with materials systems that actively and functionally respond to mechanical stimuli, the default mechanochemical reaction of bulk polymers to large external stress is the unselective scission of covalent bonds, resulting in damage or failure 7 . An alternative to this degradation process is the rational molecular design of synthetic materials such that mechanical stress favourably alters material properties. A few mechanosensitive polymers with this property have been developed 8-14 ; but their active response is mediated through non-covalent processes, which may limit the extent to which properties can be modified and the longterm stability in structural materials. Previously, we have shown with dissolved polymer strands incorporating mechanically sensitive chemical groups-so-called mechanophores-that the directional nature of mechanical forces can selectively break and re-form covalent bonds . We now demonstrate that such forceinduced covalent-bond activation can also be realized with mechanophore-linked elastomeric and glassy polymers, by using a mechanophore that changes colour as it undergoes a reversible electrocyclic ring-opening reaction under tensile stress and thus allows us to directly and locally visualize the mechanochemical reaction. We find that pronounced changes in colour and fluorescence emerge with the accumulation of plastic deformation, indicating that in these polymeric materials the transduction of mechanical force into the ring-opening reaction is an activated process. We anticipate that force activation of covalent bonds can serve as a general strategy for the development of new mechanophore building blocks that impart polymeric materials with desirable functionalities ranging from damage sensing to fully regenerative self-healing.

Combination of genistein and caffeine leads to a 1:1 cocrystalline phase, which was identified by means of a solvent-drop grinding experiment and isolated afterwards in a solution-evaporation approach. Obtained cocrystal was characterized by X-ray single-crystal and powder diffraction as well as investigated in terms of thermal stability and Hirshfeld surfaces. A scale-up procedure was provided by slurry technique, enabling solubility determination. Neutral forms of both compounds cocrystallize in a common P21/c space group of the monoclinic crystal system. Analysis of packing and interactions in the crystal lattice reveals formation of molecular layers, formed by O–H...O, O–H...N and C–H...O-type contacts between genistein and caffeine molecules, whereas stabilization of the three-dimensional crystal lattice is provided by pi...pi interactions. Dissolution studies in a 50:50 v/v ethanol–water medium revealed that the maximum solubility of the cocrystalline phase reached 0.861 mg/mL after 8 h, revealing some degree of enhancement as compared to parent genistein, maximum solubility of which was also reached after 8 h and equalled 0.588 mg/mL.

h i g h l i g h t s g r a p h i c a l a b s t r a c t Solid state reaction with a stable radical was developed to study metal oxide MC activation. Electron release under ball milling is due to vacancy formation, even in nonreducible oxides. High valent metal doping is effective to produce electron-rich defects in metal oxide. Defect engineered metal oxide boosts POP MC destruction rate under ball milling.

Mechanochemical transduction enables an extraordinary range of physiological processes such as the sense of touch, hearing, balance, muscle contraction, and the growth and remodelling of tissue and bone 1-6 . Although biology is replete with materials systems that actively and functionally respond to mechanical stimuli, the default mechanochemical reaction of bulk polymers to large external stress is the unselective scission of covalent bonds, resulting in damage or failure 7 . An alternative to this degradation process is the rational molecular design of synthetic materials such that mechanical stress favourably alters material properties. A few mechanosensitive polymers with this property have been developed 8-14 ; but their active response is mediated through non-covalent processes, which may limit the extent to which properties can be modified and the longterm stability in structural materials. Previously, we have shown with dissolved polymer strands incorporating mechanically sensitive chemical groups-so-called mechanophores-that the directional nature of mechanical forces can selectively break and re-form covalent bonds . We now demonstrate that such forceinduced covalent-bond activation can also be realized with mechanophore-linked elastomeric and glassy polymers, by using a mechanophore that changes colour as it undergoes a reversible electrocyclic ring-opening reaction under tensile stress and thus allows us to directly and locally visualize the mechanochemical reaction. We find that pronounced changes in colour and fluorescence emerge with the accumulation of plastic deformation, indicating that in these polymeric materials the transduction of mechanical force into the ring-opening reaction is an activated process. We anticipate that force activation of covalent bonds can serve as a general strategy for the development of new mechanophore building blocks that impart polymeric materials with desirable functionalities ranging from damage sensing to fully regenerative self-healing.

Secondary copper recovery is attracting increasing interest because of the growth of copper containing waste including e-waste. The pyrometallurgical treatment in smelters is widely utilized, but it is known to produce waste fluxes containing a number of toxic pollutants due to the large amount of copper involved, which catalyses the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (" dioxins "). Dioxins are generated in secondary copper smelters on fly ash as their major source, resulting in highly contaminated residues. In order to assess the toxicity of this waste, an analysis of dioxin-like compounds was carried out. High levels were detected (79,090 ng TEQ kg −1) in the ash, above the Basel Convention low POPs content (15,000 ng TEQ kg −1) highlighting the hazardousness of this waste. Experimental tests of high energy ball milling with calcium oxide and silica were executed to assess its effectiveness to detoxify such fly ash. Mechanochemical treatment obtained 76% dioxins reduction in 4 h, but longer milling time induced a partial de novo formation of dioxins catalysed by copper. Nevertheless, after 12 h treatment the dioxin content was substantially decreased (85% reduction) and the copper, thanks to the phenomena of incorporation and amorphization that occur during milling, was almost inactivated.

Fluorinated organic chemicals have a wide variety of industrial and consumer applications. For long time perfluorooctane sulfonate and perfluorooctanoic acid have been used as precursors for manufacture of such chemicals. However, these C 8 chain compounds have been demonstrated to be toxic, persistent, and bioaccumulative, thus inducing their phase-out. Currently, C 6 telomer based fluorocarbon surfactants are considered better alternatives to C 8 products because of their low bioaccumulability. But, their high persistency suggests that in the near future their concentrations will increase in the environment and in industrial waste. Being a solid state non-thermal technology, mechanochemical treatment is a good candidate for the destruction of emerging C 6 fluorotelomers in solid waste. In the present study, 6:2 fluorotelomer sulfonate is effectively destroyed (~100%) in rapid manner (<1 h) by high energy ball milling with KOH. Stoichiometric fluoride formation confirms its entire mineralization, assuring that no toxic by-products are generated. Reaction mechanism and kinetics indicate that effective mineralization of the perfluorinated moiety is obtained thanks to a rapid CF 2 " flake-off " process through radical mechanism.

Zero-valent iron (ZVI) is a valuable material for environmental remediation, because of its safeness, large availability, and inexpensiveness. Moreover, its reactivity can be improved by addition of (nano-) particles of other elements such as noble metals. However, common preparation methods for this kind of iron-based composites involve wet precipitation of noble metal salt precursors, so they are often expensive and not green. Mechanochemical procedures can provide a solvent-free alternative, even at a large scale. The present study demonstrates that it is possible to tailor functional properties of ZVI-based materials, utilizing high-energy ball milling. All main preparation parameters are investigated and discussed. Specifically, a copper-carbon-iron ternary composite was prepared for fast degradation of 4-nitrophenol (utilized as model pollutant) to 4-aminophenol and other phenolic compounds. Copper and carbon are purposely chosen to insert specific properties to the composite: Copper acts as efficient nano-cathode that enhances electron transfer from iron to 4-nitrophenol, while carbon protects the iron surface from fast oxidation in open air. In this way, the reactive material can rapidly reduce high concentration of nitrophenols in water, it does not require acid washing to be activated, and can be stored in open air for one week without any significant activity loss.

High-energy ball-milling of powder mixtures of zincite (ZnO) and iron (α-Fe) at different weight ratios was performed in air using a planetary ball mill with a stainless steel milling assembly. Structural and microstructural changes during the ball-milling (up to 30 h) were monitored using X-ray powder diffraction, field emission scanning electron microscopy (FE-SEM) and UV-Vis diffuse reflectance spectroscopy. The mechanism of iron oxidation was determined from the results of Mössbauer spectroscopy. It was found that an early phase of ball-milling caused the oxidation of iron from Fe0 to Fe2+ followed by the formation of a solid solution structurally similar to wüstite. The wüstite-type phase rapidly disappeared upon prolonged milling, which was accompanied by further oxidation of iron from Fe2+ to Fe3+ and the formation of spinel-type ferrite structurally similar to franklinite (ZnFe2O4) in the products with a high zinc content, or magnetite (Fe3O4) in the products with a high iron content. Further milling or annealing had a low impact on the franklinite-type phase, but caused the transition of the magnetite-type phase to the phase structurally similar to hematite (α-Fe2O3). The results of energy dispersive X-ray spectrometry (EDS) showed a dramatic increase in the degree of contamination with the increase in the proportion of the starting iron (∼9 times higher contamination during the milling of pure iron compared with pure zincite). It was shown that the source of contamination (balls or vial) strongly depends on the type of milled sample. Ball-milling of relatively big and heavy grains (starting iron) caused preferential contamination from the vial whereas ball-milling of smaller and lighter grains (products obtained after prolonged milling) caused preferential contamination from the balls. After prolonged milling the contamination due to wear of the balls was dominant in all the products. An explanation for the observed impact of grain size on the source and the degree of contamination was proposed.

High-energy ball-milling in an oxidative atmosphere caused gradual transition of pure zincite into zinc ferrite due to the oxidation of steel contamination. The rate of contamination increased dramatically (>3×) in an inert atmosphere due to the abrasion of milling tools by the steel chips coming from it.

Purpose

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).
Materials and methods

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).
Results and discussion

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.
Conclusions

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.

We demonstrate the reversibility and thermodynamic control in covalent mechanosynthesis, by using the base-catalysed metathesis of aromatic disulfides as a model reaction. The mechanochemical formation of thermodynamic equilibrium mixtures is observed for both neat and liquid-assisted grinding methodologies. Different methodologies lead to mutually different equilibrium compositions, which also differ from those obtained by solution equilibration. The differences can be explained in terms of crystal packing effects superimposed onto the inherent reactivity of isolated molecules. Calculations indicate that the differences in relative energies of reactants and products in their respective crystal structures can bias the mechanochemical reaction equilibrium towards the complete conversion of reactants into the product, in that way opening the doors for the development of dynamic combinatorial synthesis in the solid state and for the rational design of solid-state synthesis using mechanochemistry.

It is demonstrated that processing flow affects the kinetics of the interfacial coupling reaction between functional groups that are grafted to polymer chains. At melt temperatures the amine group on the end of nylon 6 chains reacts with maleic anhydride grafted polyethylene (PE-MA) and forms graft copolymers. Bilayers were made by lamination and coextrusion and adhesion was measured using asymmetric dual cantilever beam (ADCB). The amount of graft copolymer in the interface was quantified by X-ray photon spectroscopy (XPS). With quiescent lamination, adhesion increased with temperature and the concentration of PE-MA. The adhesion metric, G c (critical energy release rate), plotted as a function of R (interfacial copolymer density) fell on the same master curve, unifying reaction process, temperature and time. G c was a linear function of R for low-copolymer coverage and weak adhesion. For relatively high coverage and strong adhesion, G c scaled with R. 2 Coextrusion with compressive flow resulted in a reaction rate strikingly two-orders of magnitude faster than that without compressive flow. The rate in the noncompressive die was close to quiescent lamination. Even for lamination, when compressive flow was applied normal to the interface, the coupling reaction rate was also greatly accelerated. Several mechanisms are speculated for this remarkable acceleration in polymer chain coupling.

Among the different techniques proposed for preparing cyclodextrin inclusion complex in the solid state, mechanochemical activation by grinding appears as a fast, highly efficient, convenient, versatile, sustainable, and eco-friendly solvent-free method. This review is intended to give a systematic overview of the currently available data in this field, highlighting both the advantages as well as the shortcomings of such an approach. The possible mechanisms involved in the inclusion complex formation in the solid state, by grinding, have been illustrated. For each type of applied milling device, the respective process variables have been examined and discussed, together with the characteristics of the obtained products, also in relation with the physicochemical characteristics of both the drug and cyclodextrin subjected to grinding. The critical process parameters were evidenced in order to provide a useful guide for a rational selection of the most suitable conditions for an effici...

ABSTRACT Abstract Combination of genistein and caffeine leads to a 1:1 cocrystalline phase, which was identified by means of a solvent-drop grinding experiment and isolated afterwards in a solution-evaporation approach. Obtained cocrystal was characterized by X-ray single-crystal and powder diffraction as well as investigated in terms of thermal stability and Hirshfeld surfaces. A scale-up procedure was provided by slurry technique, enabling solubility determination. Neutral forms of both compounds cocrystallize in a common P21/c space group of the monoclinic crystal system. Analysis of packing and interactions in the crystal lattice reveals formation of molecular layers, formed by O—H···O, O—H···N and C—H···O-type contacts between genistein and caffeine molecules, whereas stabilization of the three-dimensional crystal lattice is provided by π···π interactions. Dissolution studies in a 50 : 50 v/v ethanol-water medium revealed that the maximum solubility of the cocrystalline phase reached 0.861 mg/mL after 8 hours, revealing some degree of enhancement as compared to parent genistein, maximum solubility of which was also reached after 8 hours and equalled 0.588 mg/mL.

Secondary copper recovery is attracting increasing interest because of the growth of copper containing waste including e-waste. The pyrometallurgical treatment in smelters is widely utilized, but it is known to produce waste fluxes containing a number of toxic pollutants due to the large amount of copper involved, which catalyses the formation of polychlorinated dibenzo-p-dioxins and dibenzofurans (&quot; dioxins &quot;). Dioxins are generated in secondary copper smelters on fly ash as their major source, resulting in highly contaminated residues. In order to assess the toxicity of this waste, an analysis of dioxin-like compounds was carried out. High levels were detected (79,090 ng TEQ kg −1) in the ash, above the Basel Convention low POPs content (15,000 ng TEQ kg −1) highlighting the hazardousness of this waste. Experimental tests of high energy ball milling with calcium oxide and silica were executed to assess its effectiveness to detoxify such fly ash. Mechanochemical treatment...

The mechanochemical preparation of highly functionalized 3,5-disubstituted hydantoins was investigated in the presence of various poly(ethylene) glycols (PEGs), as safe grinding assisting agents (liquid-assisted grinding, LAG). A comparative study under dry-grinding conditions was also performed. The results showed that the cyclization reaction was influenced by the amount of the PEG grinding agents. In general, cleaner reaction profiles were observed in the presence of PEGs, compared to dry-grinding procedures.

Perfluorinated chemicals (PFCs) are attracting increasing concern due to their chemical stability and toxicity, which make them classifiable as persistent organic pollutants. However, such compounds are employed for the manufacture of many industrial and consumer products, hence their substitution is not possible in the near future. Suitable technologies for PFCs environmentally sound management are necessary. High energy ball milling with KOH has been proved to obtain PFCs safe destruction, but with excessive reagent. In the present study, a Waste-to-Materials solution is proposed: PFCs are co-milled with stoichiometric amounts of La2O3 and thus are fully converted into LaOF, a noteworthy luminescent material with many potential industrial applications. Reaction mechanism is also investigated: Ball milling process activates La2O3; this latter provokes oxidation to CO2 and carbonization of PFCs; fluorides are incorporated into the La2O3’s lattice to form the oxyfluoride. Interestingly, kinetic analysis suggests that the mechanical activation of La2O3 might follow a zeroth-order reaction rate.

of mechanochemical degradation of imidazolium bis(trifluoromethanesulfonyl)imide ionic liquid with alkyl and mPEG side groups were studied using 2 novel technique of Mechanically Stimulated Gas Emission Spectroscopy. Mechanical stimulus caused degradation of both anionic and the cationic moieties. On the latter, the degradation was concentrated on the alkyl and ether chains rather than on the imidazole. For the anionic moiety various degradation steps associated with the emission of CH x F y volatile products followed by the SO 2 and SO 3 emission were identified. Simulation of frictional heat dissipation revealed that tribochemical reactivity was induced by mechanical energy supply rather than the temperature increase. Thermal degradation of the same ionic liquids studied using Thermogravimetric Analysis and Fourier Transform Infrared Spectroscopy was concentrated mainly on the cationic moiety. Thermal stability significantly depended on the side chains.

The mechanochemical preparation of highly functionalized 3,5-disubstituted hydantoins was investigated in the presence of various poly(ethylene) glycols (PEGs), as safe grinding assisting agents (liquid-assisted grinding, LAG). A comparative study under dry-grinding conditions was also performed. The results showed that the cyclization reaction was influenced by the amount of the PEG grinding agents. In general, cleaner reaction profiles were observed in the presence of PEGs, compared to dry-grinding procedures.

Polyethylene glycol-functionalized nanographene oxide (PEGylated n-GO) was synthesized from alkyne-modified n-GO, using solvent-free click-mechanochemistry, i.e., copper(I)-catalyzed azide-alkyne cycloaddition (CuAAC). The modified n-GO was subsequently conjugated to a mucin 1 receptor immunoglobulin G antibody (anti-MUC1 IgG) via thiol-ene coupling reaction. n-GO derivatives were characterized with Fourier-transformed infrared (FT-IR) spectroscopy, thermogravimetric analysis (TGA), Bradford assay, sodium dodecyl sulfate polyacrylamide gel electrophoresis (SDS-PAGE), and atomic force microscopy (AFM). Cell targeting was confirmed in vitro in MDA-MB-231 cells, either expressing or lacking MUC1 receptors, using flow cytometry, confocal laser scanning microscopy (CLSM) and multiphoton (MP) fluorescence microscopy. Biocompatibility was assessed using the modified lactate dehydrongenase (mLDH) assay.

The mechanochemical preparation of highly functionalized 3,5-disubstituted hydantoins was investigated in the presence of various poly(ethylene) glycols (PEGs), as safe grinding assisting agents (liquid-assisted grinding, LAG). A comparative study under dry-grinding conditions was also performed. The results showed that the cyclization reaction was influenced by the amount of the PEG grinding agents. In general, cleaner reaction profiles were observed in the presence of PEGs, compared to dry-grinding procedures.

In the present study, an adsorbent material for removal of organic contaminants in wastewater is synthetized by a green and facile mechanochemical method. It is composed of Ti 3 C 2 T x MXene layers (obtained by mechanochemical etching of MAX phase with concentrated HF) pillared with terephthalate by rapid direct reaction. Such material shows high specific surface area (135.7 m 2 g −1) and excellent adsorption capability of methylene blue (209 mg g −1) because of the larger interlayer space among MXene sheets and free carboxylate groups of terephthalate. The spent adsorbent is reutilized (with addition of sole aluminum) to synthetize the MAX phase by mechanochemical procedure, where the terephthalate and the pollutant are carbonized into the carbide. In this way, new MXene-based adsorbent can be re-synthetized for further use.

Brominated organic pollutants are considered of great concern for their adverse effect on human health and the environment, so an increasing number of such compounds are being classified as persistent organic pollutants (POPs). Mechanochemical destruction is a promising technology for POPs safe disposal because it can achieve their complete carbonization by solvent-free high energy ball milling at room temperature. However, a large amount of co-milling reagent usually is necessary, so a considerable volume of residue is produced. In the present study a different approach to POPs mechanochemical destruction is proposed. Employing stoichiometric quantities of Bi 2 O 3 or La 2 O 3 as co-milling reagent, brominated POPs are selectively and completely converted into their corresponding oxybromides (i.e. BiOBr and LaOBr), which possess very peculiar properties and can be used for some actual and many more potential applications. In this way, bromine is beneficially reused in the final product, while POPs carbon skeleton is safely destroyed to amorphous carbon. Moreover, mechanochemical destruction is employed in a greener and more sustainable manner.

The ability of computational methods to predict the structures and energetics that determine the equilibrium of solid state mechanochemical reactions has been assessed. Two previously characterised base catalysed metathesis reactions between aromatic disulfides are studied using crystal structure prediction methods and lattice energy calculations that combine molecular electronic structure methods with anisotropic atom-atom potentials. We find that lattice energy searches locate three of the six crystal structures as global minima on their respective crystal energy landscapes. The remaining structures are less successfully predicted, due to problems modelling relative conformational energies due to limitations of the density functional theory method for calculating intramolecular energies. Prediction of the overall reaction energies proves challenging for current methods, but the results show promise as a base on which to build more accurate and reliable approaches.

Interaction of mineral talc as an inert carrier with bioactive species (salicylic acid, glycerol, olive oil) in a mechanochemical process was studied by FTIR spectroscopy. Reaction of the talc silicate hydroxyls with carboxyl or alcohol moieties was observed for all the species studied. Dispersed layered composites, built from the silicate (talc) matrix, to which a bioactive component is bound, are formed in this interaction on the time scale of 1–5 min. The formation of new materials viz. layered dispersed mechano-composites proceeds due to etherification or esterification of the active sites on the silicate surface with acids or alcohols.

... PbO + TiO2 PbTiO3 perovskite 19, 20 Pb3O4+ 3 TiO2 PbTiO3 &quot; 19, 20 1.5 PbO + Nb2O5 Pb1.5Nb2O6.5 pyrochlore 21 PbO + MoO3 PbMoO4 scheelite 19 Pb3O4 +3 MoO3 PbMoO4 &quot; 19 PbO + WO3 PbWO4 &quot; 19 Pb3O4 +3 WO3 PbWO4 &quot; 19 BaO2 + MoO3 BaMoO4 &quot; 19 ...

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.

The paper presents the effects of the mechanochemical activation of ThO 2 -UO 3 and ThO 2 -CeO 2 mixtures in air and (for ThO 2 -UO 3 ) in suspension in H 2 O or CHCl 3 . Planetary ball mill (Pulverisette 5, Fritch) with stainless steel triboreactors and milling balls from the same materials are used. Milling for 5 h of the ThO 2 -UO 3 mixture does not affect significantly the crystal structure of the ThO 2 but leads to amorphization of UO 3 , sharp decrease of its crystallites size and increase of the ionic character of the U-O bond. Storage of the activated product (2 months at room temperature) or heating (3 h, 165 o C) leads to partial relaxation of the UO 3 crystal structure. The X-ray diffraction data does not give proves for formation of ThO 2 -UO 3 solid solution. Formation of solid solution Ce 0.6 Th 0.4 O 2 accompanied with some amount of amorphisized ThO 2 , is established as a result of co-milling at the same conditions of the mixture ThO 2 -CeO 2 with a mole ratio 1. XRD-determined lattice parameter (5.