The contamination of water and soil with heavy metals such as lead is a major global problem. Heavy metals affect the physiological functions of living organisms, cause cancer, and damage the immune system. Hydroxyapatite (Ca10(PO4)6(OH)2) is one of the most effective materials for the removal of heavy metals from contaminated water and soil. This study focuses on the structural characterization of lead-doped hydroxyapatite synthesized using two different methods: incipient wetness impregnation (IWI) and ion exchange under varying concentrations of Pb(II). Characterization methods such as X-ray diffraction (XRD), Fourier transform infrared spectroscopy (FTIR), scanning electron microscope (SEM), and thermogravimetric analysis (TGA) were used to understand the incorporation and/or the deposition of lead on the surface of calcined or uncalcined lead-doped hydroxyapatite. The XRD spectra show that for powders doped with more than 0.6

The aim of this research was the study of the centrifugation effect on olive mill wastewater (OMW) treatment by coagulation-flocculation using the Ca(OH)(2)-pectin system. To separate the treated OMW from the residual sludge, two methods were used: gravity decantation and centrifugation. Efficiency of the treatment was evaluated following the evolution of the OMW treated volumes and the reduction rates of dry matter (DM) and phenolic compounds (PC) and other parameters related to residual toxicity. Compared to gravity decantation, centrifugal separation significantly enhances the treatment of the OMW studied. Additionally, this separation method reduces considerably the treatment duration compared to gravity decantation i.e. 10 min instead of 4 h. The lime-pectin system improved OMW purification. Optimal doses of lime and pectin were respectively 10 g/L and 0.2 g/L. Under these conditions, centrifugal separation allowed to obtain a volume of treated OMW about 78.2% of the raw effluent volume and reduced the rates of DM by 38% and of PC by 79%. The COD was also reduced by 60.0%. These results show that the resulting sludge may be used for production of fertilizers or land augmentation, thus avoiding costly disposal.

Up-to-date, solar salt (a mixture of 60 mass% NaNO 3 and 40 mass% KNO 3 ) is practically the only media for thermal energy storage (TES) in concentrated solar power (CSP). This commercial product’s utilization is limited below 550 °C to avoid an irreversible thermal decomposition. The development of new performing TES materials is decisive for the deployment of CSP technology. Our recent work reported promising results obtained with mono-alkali polyphosphate (M-PO 3 ) as TES materials. These materials can work up to around 900 °C, but their melting point is still high, which is at least 628 °C. In order to lower their melting point, binary and ternary mixtures of alkali polyphosphates are investigated in this work. Different mixtures made of two or three alkali polyphosphates were prepared and studied using thermal analysis methods. The most promising mixture found in this work was the ternary Li-Na-K-PO 3 , which contained 33.3% (mol%) of each alkali metal. This mixture can be used as a liquid TES material in the temperature range of 398 to 900 °C. The results open new prospects for the development of the thermal energy storage field.

Permeable reactive barrier (PRB) containing zero valent iron (ZVI), plaster and additives to make a porous composite structure was tested to remove an organic nitro compound as model pollutant. An aqueous solution of 4-nitroaniline (PNA) was passed through a porous plaster composite column and chemical degradation quantified by UV-Vis spectroscopy. PNA was reduced to p-phenylenediamine and the rate of the reduction was strongly related to ZVI amount, pollutant volume, and the contact rate with metal particles. The parameters could be controlled by reactor design and operation. The columns were made to test the materials for making precast plaster blocks containing ZVI. The results showed that such porous plaster blocks could be efficient as retaining walls for environmental applications.

Permeable reactive barrier (PRB) containing zero valent iron (ZVI), plaster and additives to make a porous composite structure, was tested to remove an organic nitro compound as model pollutant. An aqueous solution of 4-nitroaniline (PNA) was passed through a porous plaster column and chemical degradation quantified by UV-Vis spectroscopy. PNA was reduced to p-phenylenediamine and the rate of the reduction was strongly related to ZVI amount, pollutant volume, and the contact rate with the metal particles. The PBR could be controlled by design and operation. Test columns were made to evaluate the materials for making precast plaster blocks containing ZVI. The results showed that such porous plaster blocks could be efficient as retaining funneling walls for environmental applications. Thus economical Calcium sulphate solids can be used for making remediation columns for depolution with reactive products such as iron metal with capacity for treating unwanted toxic nitrates, or chlorinatedsolvents present in waterways. A reactive permeable barrier containing zero valent iron will last as long as some iron particles remain to react.

Wood waste containing halogenated compounds such as polyvinyl chloride (PVC) is in abundant supply, although the pyrolysis of such waste feedstock for energy production may cause corrosion and environmental problems due to the release of HCl gas. Hence, there is a need to understand the pyrolysis behaviour of chlorine-contaminated wood in order to develop methods that minimise the impact of chloride species on pyrolysis equipment and product quality. In literature, few studies exist on the kinetic analysis of wood and PVC co-pyrolysis. The existing models assume a single-step reaction with an n-order reaction mechanism for the entire process, which may lead to large errors in the kinetic parameters estimated. Therefore, in this paper, we develop and validate a multi-step kinetic model that predicts the pyrolysis behaviour and reaction mechanism of poplar wood (PW) pellet with different contents of PVC (0, 1, 5, 10, 100 wt%). Using data from thermogravimetric analysis of the pellets at heating rates of 5, 10 and 20 °C/min, we determined the apparent kinetic parameters by combining Fraser-Suzuki deconvolution, isoconversional methods and master plot procedures. Our model fitted the experimental data well with a deviation of less than 4.5%. Our results show that the addition of 1 wt% PVC to PW decreases the activation energy of hemicellulose and cellulose pyrolysis in PW from 136.3 to 101.6 kJ/mol and from 216.7 to 108.2 kJ/mol, respectively. This demonstrates the importance of acid hydrolysis reactions between the cellulosic fibres of PW and HCl released from PVC dehydrochlorination. Furthermore, we found that a nucleation and growth mechanism best represents the rate-limiting interactions between PVC and PW, which we linked to the formation of metal chloride crystals from acid-base reactions between HCl and PW minerals. Our kinetic model is an improvement of current models for the co-pyrolysis of wood and PVC, and can be readily used in a reactor-scale model of a pyrolyser or gasifier due to its relative simplicity.

The dry reforming of methane over hydroxyapatite- and alumina/magnesia (commercial Pural MG 30)-supported nickel catalysts was investigated. The catalytic performance of the catalysts prepared with fresh supports highly depended on the basicity, the metal-support interaction, and the metal particle size. Calcination of the supports at 1200 degrees C for 5 h made the catalysts less active because of specific surface area reduction and basicity destruction. However, this treatment allowed avoiding any further catalyst deactivation by thermal sintering and maintained excellent catalytic stability over 300 h of time-on-stream. These tests under simulated industrial conditions (high contact time and long time-on-stream) showed the competitiveness of the prepared catalysts in this important catalytic process.

This work is devoted to the removal of H2S from the gas phase using a suspension of calcium carbonate-based residues, recovered from the production of sodium bicarbonate. A 145 L (1.6 m height and 0.34 m internal diameter) slurry bubble column (SBC) reactor was used. The gaseous effluent was bed from the bottom and get out from the top of the column. The suspension (2-20 wt%) was recirculated from the bottom to the top by a pump. This created a counter-current regime between the gas phase (from the bottom to the top) and the liquid phase (from the top to the bottom) which favor the gas/liquid exchange inside the reactor. The influence of different parameters including solid concentration in the suspension (w(s)), recirculating rate of the suspension (Q(R)), inlet gas flow rate (Q(G)), and volume of the suspension, was investigated. The results obtained with this confirmed those at the lab scale, for both synthetic gaseous effluent (H2S diluted in compressed air) and real gaseous effluent emitted by the buffer tank of a wastewater treatment plant. This allows validating the technology before its deployment at the large industrial scale for H2S removal from the gas phase.

The aim of this study was to compare the technique sensitivity of an adhesive system to the moisture conditions of the dentinal substrate by measuring the dentin permeability variation. Infrared spectroscopy allows analysis of dentin components and in particular the remaining dentin water, depending on application of the adhesive on dry or humid dentin. Thermal studies help determining whether the water is free or bound. Within the limitations of this study the adhesive didn’t yield unfavourable results, whether the technique was moist or overdry. The results point to the use of isopropanol as a solvent with favourable solubilities and vapour pressure compatible with adhesive resins.

In this study the spectrophotometric behaviour of gelatin-based hydrogels, in the presence and absence of dyes, was studied. The aim was to formulate equivalent-tissue phantoms to be used as 3D-dosimeter, suitable for Optical Computed Tomography (OCT). The hydrogels show good transparency and good stability of baseline optical density and, in the presence of dye, the response of optical density as a function of concentration was higher than in aqueous solution. The hydrogels were formulated in order to reduce the diffusion of the image of the irradiated field over time and to have stable fantoms as a function of time. To this purpose, the diffusion coefficients of two dyes, Bromophenol Blue (BPB) and Bromocresol Green (BCG), were determined as a function of the hydrogel chemical composition. As comparison, in some experiments Xylenol Orange (XO) was used. In particular, the presence of sucrose, as thickener, can reduce to almost half BPB mobility. In conclusion, it was shown that optical properties and controlled dye diffusion in gelatin-based hydrogels could allow using them as 3D-dosimeter for optical detection.

A new absorption spectroscopy method which enables rapid measurement of the diffusion coefficient of Fe3+ in gelatin gel used in dosimetry was investigated. The physical approach, the preparation and the experimental application of this new method were tested on the EasyDosit dosimetry gel and the results were validated by MRI measurement. The diffusion coefficients measured on this gel were then compared with those of the other gels presented in the literature. This gel, which is considered stable, has a small post-irradiation ion diffusion, despite the absence of a complexing or crosslinking agent. The diffusion coefficients of a range of dosimetry gels containing different proportions of gelatin were also measured and the results show diffusion coefficients D from 3.21.10−10 m2.s−1 to 2.41.10−10 m2.s−1.

The carbonation of residual brines generates large volumes of carbonate-based solid wastes. Physicochemical properties of these solids are adequate for acid-gas removal. This work studies the valorization of calcium carbonated-based solid wastes for efficient H2S removal from air at low concentrations (<= 200 ppmv) in a threephase semi-continuous reactor. Synthetic air polluted with H2S was bubbled into the slurry of two different wastes in a stirred tank to evaluate their effect for H2S removal. The efficiency of H2S removal was kept constant and could reach up to 98% during 8 h of reaction. Adequate physico-chemical characterization of used sorbents allowed understanding the interaction of sulfide species with sorbent particles. Thus, the reaction pathway for H2S removal was determined. It has been demonstrated that the dissolution of H2S gas at the gas-liquid interface was then accelerated by high basicity of calcium carbonate-based wastes, followed by the oxidation of dissolved sulfide species. This last was catalyzed by metals and metals oxides which were initially present in the solid wastes. The results obtained demonstrate the possibility to valorize the carbonates which have been precipitated during the carbonation of industrial brines to develop a low cost H2S removal process.

The long-term survival of aesthetic restorations remains a challenge dependant on successful and reliable bonding of ceramics to dental substrate. In order to improve resin cement bonding to ceramics, various surface treatments favoring micromechanical retention and chemical bonding were recommended [1,2]. According to CekikNagas, the composition of the ceramic determines the best surface treatment to be applied [3].

Ni-based catalysts were prepared using two hydroxyapatites (Ca-HA1, S-BET = 7 m(2)/g and Ca-HA2, S-BET = 60 m(2)/g) with different physico-chemical properties. The objective of the study was to evaluate the performance of these two materials as promising supports for dry reforming reaction (DRM) as well as to investigate the influence of different process parameters, such as temperature, pressure, time and catalyst pretreatment on the performance of these two catalysts. Thermodynamic calculations were performed to determine the conditions that would limit solid carbon deposit and favor the reactants conversion. Then, an experimental parametric study was carried out to investigate the impact of the temperature, pressure, catalyst pretreatment and support thermal treatment on the catalysts performance. The results showed that the catalyst pretreatment allowed the reduction of the nickel particles in a higher extent, which resulted in better catalytic performance when compared to the catalysts without pretreatment. High temperatures around 700 degrees C and low pressures around 1.6 bar were required to attain high CH4 and CO2 conversions around 70-80% as well as high H-2 and CO selectivity around 90% for 90 h of time on stream. In all cases, Ni/Ca-HA2 catalyst presented better catalytic performance than Ni/Ca-HA1 due to the presence of smaller nickel particles (10-20 nm), stronger basicity, higher density of basic sites (0.23 mmol g(-1)) as well as higher specific surface area (S-BET = 60 m(2)/g) of the Ca-HA2 support. Ni/Ca-HA2 catalyst was highly active (initial methane conversion: 75%) and relatively stable during 90 h of TOS and its catalytic behavior was comparable with the performance of Ni-based catalysts prepared with conventional supports reported in the literature. (C) 2019 Hydrogen Energy Publications LLC. Published by Elsevier Ltd. All rights reserved.

Hydroxyapatite (HAP, Ca-10(PO4)(6)(OH)(2)) has all the criteria of a catalyst support, in particular its high thermal stability. However it is still less studied in the heterogeneous catalysis. For the first time, hydroxyapatite supported bimetallic Co-Ni catalysts were prepared and evaluated in the dry reforming of methane (DRM) process. Nanoparticles containing both nickel and cobalt were well formed on the surface of HAP by conventional impregnation methods. No modification of HAP structure was observed after metals deposition. DRM reaction was carried out at 700-750 degrees C and around 1.6 bar, using a fixed-bed reactor which was fed with a mixture of 20%vol CH4, 20%vol CO2 and 60%vol N-2. CH4 and CO2 conversion reached up to 60 and 68% at 700 degrees C, respectively, and 73 and 79% at 750 degrees C, respectively during long reaction times of 50-160 h. Water as a by-product could be quantified along the catalytic reaction indicating the implication of reverse water-gas-shift reaction. TEM-EDX analysis of the used catalysts recovered after catalytic tests showed that coke deposition was limited and there was slight modification of metals particle size. The results obtained were very promising for the design of an efficient catalytic system for DRM process.