Mechanochemical transformation of an organic ligand on mineral surfaces: the efficiency of birnessite in catechol degradation

Synthesis of modified amorphous manganese oxide using low-cost sugars and biochars: Material characterization and metal(loid) sorption properties

In this study, amorphous Mn oxides (AMOs) and their composites with biochar (BC) were synthesized using different sugars (glucose, sucrose, and molasses), and their sorption efficiency toward Zn(II), Cd(II), and As(V) was tested. Additionally, detailed characterization of synthesized materials using various solid-state analysis methods (e.g. XRD, FTIR-ATR, and/or SEM-EDX) was also performed. Despite glucose-based AMOs presented higher sorption efficiency for As(V), i.e., 0.73 mmol g^-1 (glucose) > 0.27 mmol g^-1 (sucrose and molasses), similar sorption efficiency toward Zn(II), i.e., 0.80 mmol g^-1 (glucose and molasses) > 0.66 (sucrose) and Cd(II) (0.71-0.74 mmol g^-1 (sucrose and molasses) > 0.36 mmol g^-1 (glucose), was observed for sucrose- and molasses-based AMOs under the given conditions. Next, the sorption efficiency of all AMO/BC composites was proportional to their AMO content. Finally, Mn(II) leaching from the structure of the new AMOs was negligible compared to that observed for the glucose-based AMOs, in this study as well as in other similar studies. Moreover, using molasses as reducing agent during AMO synthesis dramatically decreased the total cost of the final materials, which suggested that these new AMOs could represent interesting alternatives for standard remediation technologies. The AMOs synthesized using low-cost sugars could, therefore, be promising materials for real field applications, since the main disadvantages of using standard AMOs are mitigated. Nevertheless, the efficiency and stability of these composites under real-life conditions must be tested prior to their direct application for remediation technologies.

A sandwich-type catalytic composite reassembled with a birnessite layer and metalloporphyrin as a water oxidation catalyst

Sandwich-type MnTAPP@bir was synthesized by re-assembly of exfoliated birnessite and MnTAPP, and exhibited superior OER performance.

Mechanochemical removal of carbamazepine

Carbamazepine (CBZ) is a drug used for treating epilepsy, neuropathic pain, schizophrenia and bipolar disorder. Its widespread use is indicated by its listing in the WHO's Model List of Essential Medicines. The accumulation of CBZ in various environmental compartments, specifically in crops irrigated with treated effluent or grown on soils containing biosolids, is often reported. Being a persistent PPCP (a pharmaceutical and personal care product), developing procedures to remove CBZ is of great importance. In the present study, the breakdown of CBZ by surface reactions in contact with various minerals was attempted. While Al-montmorillonite enhanced CBZ disappearance without the need to apply mechanical force, the efficiency of magnetite in enhancing the disappearance increased considerably upon applying such force. Ball milling with magnetite generated a virtually complete disappearance of CBZ (∼94% of the applied CBZ disappeared after milling for 30 min). HPLC, LC/MS and FTIR were employed in an attempt to elucidate the rate of disappearance and degradation mechanisms of CBZ. A small amount of the hydrolysis product iminostilbene was identified by LC/MS and the breaking off of carbamic acid from the fused rings skeleton of CBZ was indicated by FTIR spectroscopy, confirming the formation of iminostilbene.

Mechanochemical destruction of halogenated organic pollutants: A critical review

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.

Preparation of ultrafine magnetic biochar and activated carbon for pharmaceutical adsorption and subsequent degradation by ball milling

Ball milling was used to prepare two ultrafine magnetic biochar/Fe3O4 and activated carbon (AC)/Fe3O4 hybrid materials targeted for use in pharmaceutical removal by adsorption and mechanochemical degradation of pharmaceutical compounds. Both hybrid adsorbents prepared after 2h milling exhibited high removal of carbamazepine (CBZ), and were easily separated magnetically. These adsorbents exhibited fast adsorption of CBZ and tetracycline (TC) in the initial 1h. The biochar/Fe3O4 had a maximum adsorption capacity of 62.7mg/g for CBZ and 94.2mg/g for TC, while values obtained for AC/Fe3O4 were 135.1mg/g for CBZ and 45.3mg/g for TC respectively when data were fitted using the Langmuir expression. Solution pH values slightly affected the sorption of TC on the adsorbents, while CBZ sorption was almost pH-independent. The spent adsorbents with adsorbed CBZ and TC were milled to degrade the adsorbed pollutants. The adsorbed TC itself was over 97% degraded after 3h of milling, while about half of adsorbed CBZ were remained. The addition of quartz sand was found to improve the mechanochemical degradation of CBZ on biochar/Fe3O4, and its degradation percent was up to 98.4% at the dose of 0.3g quarts sand/g adsorbent. This research provided an easy method to prepare ultrafine magnetic adsorbents for the effective removal of typical pharmaceuticals from water or wastewater and degrade them using ball milling.

A facile one-pot synthesis of three-dimensional microflower birnessite (δ-MnO2) and its efficient oxidative degradation of rhodamine B

A facile synthesis of high purity microflower birnessite and its efficient oxidative degradation of RhB.

Mechanochemically enhanced degradation of pyrene and phenanthrene loaded on magnetite

The enhancement of the degradation of polycyclic aromatic hydrocarbons (PAHs), exemplified by pyrene and phenanthrene, using mild grinding in the presence of common minerals was investigated. Magnetite, birnessite, and Na- and Cu-montmorillonite samples were loaded with pyrene or phenanthrene and ground manually or in a ball mill for short periods of time. The ground samples were analyzed for PAHs and for their metabolites, using high-performance liquid chromatography and liquid chromatography-mass spectrometry. No degradation of pyrene occurred when it was in contact with Na-montmorillonite or birnessite. Sorption of pyrene on Cu-montmorillonite enhanced its degradation, but grinding of the loaded clay actually inhibited pyrene's degradation. Phenanthrene hardly degraded on Cu-montmorillonite. Grinding magnetite loaded with either PAH resulted in a significant degradation of both (∼50% after grinding for 5 min), while in the nonground samples, negligible degradation was detected. The extent of degradation increased with the duration of grinding. The degradation of either PAH loaded on magnetite yielded oxidized products. In soil samples contaminated with PAHs and mixed with magnetite, a similar grinding-induced degradation pattern was observed, but with a lower rate. A liquid phase was required to initiate degradation in the soil. The liquid phase apparently served as the medium through which the pollutants reached the surface of the degradation-enhancing mineral.

Mechanochemical degradation of pentachlorophenol onto birnessite

The existence of a lot of worldwide pentachlorophenol-contaminated sites has induced scientists to concentrate their effort in finding ways to degrade it. Therefore, an effective tool to decompose it from soil mixtures is needed. In this work the efficiency of the phyllomanganate birnessite (KBi) in degrading pentachlorophenol (PCP) through mechanochemical treatments was investigated. To this purpose, a synthesized birnessite and the pollutant were ground together in a high energy mill. The ground KBi-PCP mixtures and the liquid extracts were analyzed to demonstrate that mechanochemical treatments are more efficient in removing PCP than a simple contact between the synthesized birnessite and the pollutant, both in terms of time and extent. The mechanochemically induced PCP degradation mainly occurs through the formation of a surface monodentate inner-sphere complex between the phenolic group of the organic molecules and the structural Mn(IV). This is indicated by the changes induced in birnessite MnO(6) layers as a consequence of the prolonged milling with the pollutant. This mechanism includes the Mn(IV) reduction, the consequent formation of Mn(III) and new vacancies, and free Mn(2+) ions release. The PCP degradation extent is limited by the presence of chloro-substituents on the aromatic ring.