Ferroelectric solid solution Li1-xTa1-xWxO3 as potential photocatalysts in microbial fuel cells:Effect of the W content

Microbial fuel cells(MFCs)are bio-electrochemical systems that can directly convert the chemical energy contained in an effluent into bioelectricity by the action of microorganisms.The performance of these devices is heavily impacted by the choice of the material that forms the cathode.This work focuses on the assessment of ferroelectric and photocatalytic materials as a new class of non-precious catalysts for MFC cathode construction.A series of cathodes based on mixed oxide solid solution of LiTaO_3with WO_3formulated as Li_(1-x)Ta_(1-x)W_xO_3(x=0,0.10,0.20 and0.25),were prepared and investigated in MFCs.The catalyst phases were synthesized,identified and characterized by DRX,PSD,MET and UV–Vis absorption spectroscopy.The cathodes were tested as photoelectrocatalysts in the presence and in the absence of visible light in devices fed with industrial wastewater.The results revealed that the catalytic activity of the cathodes strongly depends on the ratio of substitution of W^(6+)in the LiTaO_3matrix.The maximum power densities generated by the MFC working with this series of cathodes increased from60.45 mW·m^(-3)for x=0.00(LiTaO_3)to 107.2 mW·m^(-3)for x=0.10,showing that insertion of W^(6+)in the tantalate matrix can improve the photocatalytic activity of this material.Moreover,MFCs operating under optimal conditions were capable of reducing the load of chemical oxygen demand by 79%(COD_(initial)=1030 mg·L^(-1)).

Valorization of a Good Bioceramic from Moroccan Waste Fish Bone by a Heat Treatment Method

A tricalcium phosphate(TCP)material was produced from sardine and mackerel waste using a heat treatment method after a Soxhlet extraction to obtain the non-soluble portion of fish waste.The bones were annealed at temperatures between 400℃ and 1200℃.The thermal analysis(TG-DTA)was carried out to investigate the thermal stability of TCP and to confirm the removal of organic matter from the raw fish.The calcined bones were characterized by Fourier transform infrared spectroscopy(FT-IR),X-ray diffraction(XRD),and field emission scanning electron microscopy(FESEM).The calcium to phosphorous weight ratio was determined by ICP-AES.FT-IR and XRD confirmed the similarities to syntheticβ-TCP(JCPDS-09-169),FE-SEM results revealed the formation of nanostructured TCP.These results suggest that varying the isolation temperature between 600-1200℃ has tremendous impact on the production of TCP from fish bone waste with the required properties.

Implication of sewage sludge increased application rates on soil fertility and heavy metals contamination risk

This paper aims to assess soil fertility and risk contamination parameters in response to increased amendment rates of sewage sludge application,under semi-arid climatic conditions of Morocco,using two soil textures:soil A(clay-silty)and soil B(sandy-clay)over two years.To this end,sewage sludge and soils treatments physicochemical parameters,heavy metals content,degree of pollution and associated risks were evaluated and compared to controlled soils.The results showed that all studied parameters changed significantly(p<0.05)in a dose-dependent manner for both soils compared to the untreated control soils.Indeed,there were significant increase in organic matter(OM),total organic carbon(TOC)and nutrients content(N,P and K)of both sols as a response to increased sewage sludge amendment rates.Overall,sewage sludge application showed a positive agronomic potential for both soil and plant.However,there were concern about some heavy metals contamination risks,the results showed a gradual increase of heavy metals concentration in this order:Cu>Pb>Zn>Ni>Cd>Cr.Nevertheless,their concentrations were below the critical values established by the European Union for the agronomic use of soil.The obtained results of assessed parameters indicating SS degree of pollution and associated risks showed a low to a moderate contamination risks of heavy metals.Accordingly,environmental risks of sewage sludge application will be related to increase of heavy metals mainly in a long-term agricultural reuse.Thus,optimal management of sewage sludge application is recommended to ensure sustainability and benefits at the same time to master the contamination risks.