Search

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 C8 chain compounds have been demonstrated to be toxic, persistent, and bioaccumulative, thus inducing their phase-out. Currently, C6 telomer based fluorocarbon surfactants are considered better alternatives to C8 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 C6 fluorotelomers in solid waste. In the present study, 6:2 fluorotelomer sulfonate is effectively destroyed (~100%) in rapid manner (2 “flake-off” process through radical mechanism.

The destruction of persistent organic pollutants (POPs) is a large challenge in particular in developing and emerging economies. To date, a detailed assessment of non-combustion technologies with respect to formation of dioxins is lacking. In this study, an assessment of mechanochemical (MC) destruction technology for polychlorinated biphenyls (PCBs) and polybrominated diphenyl ethers (PBDEs) in contaminated soil remediation was conducted. Actual applied conditions of pilot-scale MC POPs destruction process indicates that the temperature increase inside the ball mills has the potential to form high levels of toxic polybrominated and polychlorinated dibenzo-p-dioxins and dibenzofurans (PXDD/Fs) when dioxin precursors are present. Therefore, the MC technology was modified for treatment of the PCB and PBDE containing soil including an efficient cooling system which could prevent the formation of PXDD/F during the destruction of PCBs and PBDEs. This is likely relevant for all contaminated soils containing relevant dioxin precursor and need to be considered for treatment of soils with MC and probably other non-combustion technologies. Graphical abstract ᅟ.

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.

A novel mechano-synthesis method has been elaborated in this work for the design of efficient cobalt-based Fischer–Tropsch catalysts. The process aims to reduce the total number of steps involved in the synthesis of solid catalysts and thus to avoid relevant toxic solutions generated during the catalyst preparation. The mechano-synthesis of the Co/Al2O3 catalyst was processed in a low-energy vibratory micro mill and high energy planetary ball mill. Porous spherical γ-aluminas (1860 µm and 71 µm mean particle diameter) were used in this work as host compounds. Co3O4 (3 µm mean particle diameter) has provided guest particles for mechano-synthesis. The catalysts were characterized by textural (surface area, porosity and particle size) and structural analyses (X-ray diffraction, TPR, SEM-EDX and microprobe). The microprobe images show deposition of Co3O4 on the surface of the alumina and indicated no Co3O4 diffusion inside the alumina pores. SEM-EDX mapping illustrated that cobalt coating tended to occur on surface of rounded shape of cracked alumina fragments. After milling, the crystallite size of Co3O4 decreased to 15 nm from 30 to 50 nm. The TPR profiles indicated very low concentrations of inactive cobalt aluminate mixed compounds which are usually produced during the catalyst preparation by impregnation. In Fischer–Tropsch synthesis, the catalysts prepared using mechano-synthesis methods showed catalytic performance comparable to the catalysts prepared by impregnation.

Mechanochemical activation of metal oxides is studied by a novel methodology based on solid state reaction with a stable radical specie. Such approach corroborates that vacancy formation by high energy ball milling, also in nonreducible oxides, is responsible for electron release on particles’ surfaces. This finding suggests a new defect engineering strategy to improve effectiveness of metal oxides as co-milling reagent for halogenated organic pollutant destruction. Results prove that high valent metal doping of a commonly employed co-milling reagent such as CaO determines 2.5 times faster pollutant degradation rate. This enhancement is due to electron-rich defects generated by the dopant; electrons are transferred to the organic pollutant thus causing its mineralization. The proposed strategy can be easily applied to other reagents.

In this work, alumina-supported cobalt (Co/Al2O3) catalysts were prepared using new solvent-free mechanochemical synthesis methods: low-energy vibratory ball milling (Fritsch, Pulverisette 0) and high-energy planetary ball milling (Retsch, PM 100). γ-Al2O3 supports and Co/Al2O3 catalysts after mechanochemical treatments were characterized using a combination of techniques. The study of solid particles revealed the abrasion and fragmentation phenomena of porous γ-Al2O3 particles and pore filling under milling. Functional cobalt particles introduced by the mechanochemical synthesis were observed to be preferentially localized on the outer surface of the alumina supports. High Fischer–Tropsch reaction rates were obtained with the catalysts prepared by optimized mechanochemical synthesis conditions. The enhanced catalytic performance can be attributed to the relatively high dispersion of cobalt and the absence of inert cobalt aluminates which are usually present in the catalysts synthesized by the conventional impregnation.