THE USE OF NATURAL MATERIALS FOR THE TREATMENT OF LEACHATES OF THE AGADIR DUMP

Within the perspective of adopting effective solutions to the problems related to the burial of urban waste and its resulting harmful effects on both the environment and the human health, suitable actions should be taken to remedy the shortcomings of this somehow primitive method of waste disposal, namely those of the generated leachates. Because of their high pollutant load, leachates have to undergo a treatment of purification before being discharged into the environment.The focus of our study is to develop a simple technique to reduce the pollutant load of leachates in the technical burying center (TBC) of solid waste in Tamellast, Grand Agadir. This technique is based on the treatment of leachates through aeration followed by a percolation-infiltration on sand. The sand used is raw titaniferous sand (RTS) which is very abundant in the region of Agadir. Young leachate samples issued from fresh urban waste were collected at TBC, Tamellast. The physicochemical analyses of the young leachates show that their pH is very acidic, the values of conductivity are very important and greatly exceed the normal limit value specified for the discharges (2.7 mS / cm). The levels of biodegradable organic matter are important (the COD and BOD5 values are 17800 mg of O2 / L and 9100 mg of O2 / L, respectively). The aeration of leachate by injecting air has increased electrical conductivity due to the different chemical and biological reactions involved in the treatment. However, the values of COD and BOD5 have decreased. This decrease shows the significant effect of aeration on the reduction of polluting organic matter. The ratio BOD5 / COD is greater than 0.5 and shows that the treated leachate is of a very good biodegradability. After aeration, the young leachate was infiltrated by percolation on a sand column. The BOD5 value reached 280 mg of O2 / L (the BOD5 limit value of direct discharge = 300 mg of O2 / L) and the COD value is 540 mg of O2 / L (the limit value of direct release COD = 600 mg of O2 / L). The technique developed in this study led to high abatement rates (96.96% for COD and 97% for BOD5) in organic matter and lower COD and BOD5 values

Half a century of amyloids: past, present and future

Amyloid diseases are global epidemics with profound health, social and economic implications and yet remain without a cure. This dire situation calls for research into the origin and pathological manifestations of amyloidosis to stimulate continued development of new therapeutics. In basic science and engineering, the cross-ß architecture has been a constant thread underlying the structural characteristics of pathological and functional amyloids, and realizing that amyloid structures can be both pathological and functional in nature has fuelled innovations in artificial amyloids, whose use today ranges from water purification to 3D printing. At the conclusion of a half century since Eanes and Glenner's seminal study of amyloids in humans, this review commemorates the occasion by documenting the major milestones in amyloid research to date, from the perspectives of structural biology, biophysics, medicine, microbiology, engineering and nanotechnology. We also discuss new challenges and opportunities to drive this interdisciplinary field moving forward. This journal i

A Theoretical Study of the Relationship between the Electrophilicity ω Index and Hammett Constant σp in [3+2] Cycloaddition Reactions of Aryl Azide/Alkyne Derivatives

The relationship between the electrophilicity ω index and the Hammett constant σp has been studied for the [2+3] cycloaddition reactions of a series of para-substituted phenyl azides towards para-substituted phenyl alkynes. The electrophilicity ω index—a reactivity density functional theory (DFT) descriptor evaluated at the ground state of the molecules—shows a good linear relationship with the Hammett substituent constants σp. The theoretical scale of reactivity correctly explains the electrophilic activation/deactivation effects promoted by electron-withdrawing and electron-releasing substituents in both azide and alkyne components

Luminescence and Faraday rotation properties of Tb2O3 and Tb:Y2O3 single crystals

International audienceHeavily-doped and fully concentrated 2.78% Tb:Y2O3 and Tb2O3 single crystals with high optical quality and very low levels of impurities have been grown and studied for their luminescence and Faraday rotation properties. Absorption, emission and fluorescence decay measurements performed vs excitation wavelength and temperature and their confrontation with Judd-Ofelt and crystal-field calculations show the contributions of two types of luminescent centers: dominant ones with a 5D4 emission lifetime of 23 µs corresponding to coupled near-neighbor Tb3+ ions, all in C2 symmetry sites, and minority ones with a 5D4 emission lifetime of about 2 ms corresponding to coupled Tb3+ ions in C2 and C3i near-neighbor symmetry sites. Faraday rotation measurements confirm Tb2O3 as the Tb-based Faraday crystalline material with the largest ever measured Verdet constant, at all temperatures and from the visible to the near-infrared. They also show that the dominant luminescent centers contribute more particularly to this large Verdet constant thanks to a favorable crystal-field splitting of their 7F6 ground multiplet and also to the contributions of both types of spin-allowed and spinforbidden 4f-5d absorption bands

Catalytic abatement of dichloromethane over transition metal oxide catalysts:thermodynamic modelling and experimental studies

Abstract Dichloromethane (DCM) is a noxious chemical that is widely used in industry. The current work focuses on the catalytic abatement of DCM from industrial effluents to minimize its harmful effects to the environment and human wellbeing. Three transition metal oxide catalysts (V, Cu and Mn) supported on γ-Al₂O₃ were synthetized for total oxidation of DCM in presence of steam. Thermodynamic modelling was used to reveal information related to the stability of the used transition metal oxides in the abatement conditions. The results showed that with 10 wt-% CuO and 10 wt-% V₂O₅ containing catalysts 100% conversion of DCM together with 90% HCl yield and insignificant by-product formation can be achieved at temperature around 500 °C. According to modelling, V₂O₅ should be stable at the conditions of DCM oxidation, while CuO would be more stable at higher temperature level (decomposition of CuCl₂ starts at 300 °C). MnCl₂ remains stable until 800 °C, which leads to deactivation of MnO₂ catalyst. Presence of steam inhibits the poisoning of the materials by chlorine based on thermodynamic calculation. XRF analysis supports the results of thermodynamic modelling — used MnO₂ and CuO catalysts contain chlorine, which was not detected in case of V₂O₅/Al₂O₃. CuO/γ-Al₂O₃ seems to be a good alternative to noble metal catalysts for the total oxidation of dichloromethane when used in the presence of steam and the temperatures above 300 °C to minimize Cl-poisoning. The outcomes of this study showed that the prepared metal oxides are promising catalysts to minimize pollution caused by chlorinated volatile organic compounds