In this work, an eco-friendly sol-gel synthesis of pure and doped TiO2, previously developed at lab-scale, is applied in three different environmental applications at lab-scale and then, upscaled towards industrial applications. For each application, the TiO2 is used as a coating deposited mainly on steel substrates. The three applications are: (i) the development of a photocatalytic reactor made of a UV lamp, an ozonation part and a TiO2 photocatalytic coating to treat water from swimming pools, (ii) the development of a new generation of low energy sterilizers by an advanced oxidation process using a photocatalytic coating illuminated by a blue LED, and (iii) an easy-to-clean coating for outdoor steel. In each application, the up-scale results were similar to those obtained in the laboratory with respect to the crystallinity, the visual aspect, the hydrophilicity, and the photocatalytic properties of the produced coatings. These developments showed the possibility to bring sol-gel TiO2 products outside the laboratory towards pilot and industrial applications, and opens the way for many possible up-scaled sol-gel based environmental applications.

A new functionalization method was developed with the aim of producing stable TiO2-based colloids starting from commercial Evonik Aeroxide P25 powder. The stability of P25 colloids was efficiently increased by grafting 4-hydroxybenzoic acid (4-HBA) on the P25 surface. Results highlighted that 4-HBA interacted with the surface of P25 through its carboxylic group. The key parameter for an optimized stability is the 4-HBA/P25 ratio. If the amount of 4-HBA is too high compared to the TiO2 available surface, 4-HBA molecules preferentially interact with each other, therefore reducing their adsorption on P25. Eight different amounts of 4-HBA were grafted on P25, producing stable colloids in both ethanol and water medium. In both media, the optimal properties and highest stability were obtained for a 4-HBA/TiO2 mass ratio equal to 0.333. This optimal sample was further tested and compared to pure P25 (used as reference material) for p-nitrophenol (PNP) degradation under UV-visible light without any stirring to highlight the beneficial effect of the powder stability. The photocatalytic results showed that the grafted sample reached a degradation up to 8 times higher than pure P25. This functionalization method is easy to implement and stabilizes colloids starting from any pre-synthesized powder. This versatility widens the field of applications, and opens the door for further developments in areas such as coatings.

An eco-friendly photocatalytic coating, active under a cost-effective near-visible LED system, was synthesized without any calcination step for the removal of organic pollutants. Three types of doping (Fe, N and Fe + N), with different dopant/Ti molar ratios, were investigated and compared with undoped TiO(2)and the commercial P25 photocatalyst. Nano-crystalline anatase-brookite particles were successfully produced with the aqueous sol-gel process, also at a larger scale. All samples displayed a higher visible absorption and specific surface area than P25. Photoactivity of the catalyst powders was evaluated through the degradation ofp-nitrophenol in water under visible light (>400 nm). As intended, all samples were more performant than P25. The N-doping, the Fe-doping and their combination promoted the activity under visible light. Films, coated on three different substrates, were then compared. Finally, the photoactivity of a film, produced from the optimal N-Fe co-doped colloid, was evaluated on the degradation of (i)p-nitrophenol under UV-A light (365 nm) and (ii) rhodamine B under LED visible light (395 nm), and compared to undoped TiO(2)film. The higher enhancement is obtained under the longer wavelength (395 nm). The possibility of producing photocatalytic films without any calcination step and active under low-energy LED light constitutes a step forward for an industrial development.

Last decades, the valorization of biomass became a topic of interest, and especially the production of syngas by the catalytic reforming of biomass. But one drawback for a large-scale development is the associated production of tars. This work focuses on the catalytic reforming of tars present in bio-syngas reactors. Efficient Ni-based/gamma-Al2O3 catalysts were developed in previous studies by an aqueous sol-gel process. Here, four of those catalysts, exhibiting promising catalytic properties for toluene reforming (used as tar model molecule), were further evaluated on long-term experiments and under H2S. Indeed, long-term performance and resistance to poisoning are two key properties of catalysts for industrial applications. One commercial catalyst, Hifuel (TM), was also evaluated for comparison. The results showed that the pure Ni/gamma-Al2O3 catalyst presented a low deactivation throughout 30 h of experiment with neither Ni particle size nor support crystallinity alteration. All co-doped Ni/gamma-Al2O3 catalysts were more resistant against deactivation than the pure Ni/gamma-Al2O3 catalyst. As only amorphous carbon was deposited, an easy regeneration was performed by heating the catalysts 2 h at 650 degrees C under air. The catalytic activity remained unchanged in similar 30 h-experiment. Contrarily, the commercial Hifuel (TM) catalyst underwent a strong and quick deactivation by the formation of filamentous carbon. The regeneration under air was not sufficient to regenerate the catalyst. The Ni/gamma-Al2O3 catalyst activity was assessed in the presence of H2S. The results showed that the toluene conversion was only slightly affected by the presence of H2S in the syngas mixture, highlighting its very good resistance to poisoning.

The pseudo-second-order (PSO) kinetic model has become among the most popular ways to fit rate data for adsorption of metal ions, dyes, and other compounds from aqueous solution onto cellulose-based materials. This review first considers published evidence regarding the validity of the mechanistic assumptions underlying application of the PSO model to adsorption kinetics. A literal interpretation of the model requires an assumption that different adsorption sites on a solid substrate randomly collide with each other during a rate-limiting mechanistic step. Because of problems revealed by the literature regarding the usual assumptions associated with the PSO model, this review also considers how else to account for good fits of adsorption data to the PSO model. Studies have shown that adsorption behavior that fits the PSO model well often can be explained by diffusion-based mechanisms. Hypothetical data generated using the assumption of pseudo-first-order rate behavior has been shown to fit the PSO model very well. In light of published evidence, adsorption kinetics of cellulosic materials is expected to mainly depend on diffusion-limited processes, as affected by heterogeneous distributions of pore sizes and continual partitioning of solute species between a dissolved state and a fixed state of adsorption.

In this paper, several TiO2 materials doped with zirconia precursor (0.7, 1.4, 1.6 and 2.0 mol%) were synthesized by an easy aqueous sol-gel synthesis at ambient temperature. This method consists in the peptization of the TiO2 colloid in presence of HNO3. The corresponding pure TiO2 material was also synthesized for comparison. The performances and the physico-chemical properties of these materials were compared to the well-known Evonik P25 photocatalyst. The physico-chemical characterizations showed that nano-crystalline anatase-brookite particles were produced with the sol-gel process, with higher specific surface area than P25 (-200 m(2)g(-1) vs. 47 m(2)g(-1)). All samples presented a higher visible absorption than P25. The XPS spectra showed that all the samples were doped with nitrogen and that mixed TiO2-ZrO2 oxide materials were obtained when doping with zirconia precursor. Photoactivity was evaluated through the degradation of p-nitrophenol in water. On the one hand, under UV/visible light, the ZrO2 doping increased the degradation efficiency of the pure TiO2 catalyst due to a better charge separation in the mixed TiO2-ZrO2 oxides. The activity of the sample with the highest dopant content was even higher than the one of P25. On the other hand, under visible light, all samples were much more efficient than P25. This activity shift towards visible range was due to the N-doping of the catalysts, with a slight improvement for the doped ones. Finally, the feasibility of producing films starting from an aqueous suspension of the photocatalyst was assessed on P25, pure TiO2 and the best doped material. The photoactivity of these films, evaluated on the degradation of methylene blue under UV-A light, showed that the sample with the highest dopant concentration had an efficiency 4 times higher than pure TiO2 and 20 times higher than P25. (C) 2019 Elsevier Ltd. All rights reserved.

In this work, TiO2 nanoparticles were modified with different Cu and Pt species: metallic nanoparticles and ions. The photocatalysts were prepared via a sol-gel process by peptization with HNO3 at low temperature (i.e. < 100 degrees C). The metallic nanoparticles were prepared by NaBH4 reduction from the corresponding metallic salts. For the ion modification, metallic salts were just added during the synthesis of the TiO2. The materials were characterized by X-ray diffraction (XRD), nitrogen adsorption-desorption, diffuse reflectance, and X-ray photoelectron spectroscopy (XPS). The results showed that the TiO2 materials were mainly composed of anatase phase with a small amount of brookite phase. The nanoparticle size was in the range of 4-8 nm leading to high specific surface area (i.e. >200 m(2) g(-1)). The absorption property of these materials showed a visible sensitization for all samples even the pure TiO2 compared to the Evonik P25 due to N-doping confirmed by XPS analysis. The photocatalytic activity on the degradation of p-nitrophenol (PNP) showed an increase in the efficiency for nearly all catalysts compared to the pure one. Some mechanisms were proposed to explain these modifications of activity with doping. Under visible light, the photocatalysts were up to 5 times more efficient than P25 (for the best sample composed of Cu metallic nanoparticles).

This article reports the different steps of the design, development and validation of a process for continuous production of carbon nanotubes (CNTs) via catalytic chemical vapor deposition from the laboratory scale to the industrial production. This process is based on a continuous inclined mobile-bed rotating reactor and very active catalysts using methane or ethylene as carbon source. The importance of modeling taking into account the hydrodynamic, physicochemical and physical phenomena that occur during CNT production in the process analysis is emphasized. The impact of this invention on the environment and human health is taken into consideration too.

Several hundred papers are published yearly reporting liquid-phase adsorption kinetics data. In general the data is analyzed using a variety of standard models such as the pseudo first- and second-order models and the Intraparticle-Diffusion model. The validity of these models is often assessed empirically via their ability to fit the data, independently of their physicochemical soundness.The aim of the present paper is to rationalize the analysis of liquid-phase adsorption kinetics data, and to investigate experimental factors that influence the adsorption kinetics, in addition to the characteristics of the adsorbent material itself. For that purpose we use a simple Langmuir adsorption-diffusion model, which enables us to identify three dimensionless numbers that characterize the working regime of any batch adsorption experiment: an adsorption Thiele modulus, a saturation modulus, and a loading modulus.The standard models are found to be particular cases of the general adsorption-diffusion model for specific values of the dimensionless numbers. This provides sound physicochemical criteria for the validity of the models. Based on our modeling, we also propose a general yet simple data analysis procedure to practically estimate the diffusion coefficient in adsorbent pellets starting from adsorption half-times. (C) 2015 Elsevier Inc. All rights reserved.

An environmentally-friendly aqueous sol–gel process for producing undoped and Cu2+, Ni2+, Zn2+ or Pb2+-doped TiO2 photocatalysts exhibiting a remarkably high photocatalytic activity without requiring any calcination step has been developed. The physicochemical properties of the catalysts were characterized by ICP-AES, XRD, UV–Vis spectroscopy and nitrogen adsorption–desorption. It has been found that the catalysts are composed of nanocrystallites of anatase with a size of 6–7 nm and a specific surface area varying from 184 to 275 m2 g−1. A screening of the photocatalytic activity of the undoped and doped photocatalysts has been performed by evaluating the degradation of 4-nitrophenol under artificial light (330 nm < λ < 800 nm) after 7 h of illumination using a custom-designed multisample photoreactor. The activity measured for the TiO2-Undoped catalyst was found to be five times higher than the activity measured for uncalcined TiO2 catalysts produced by other sol–gel methods. We propose that this interesting result is due to the particular morphology of the xerogels obtained. It has also been demonstrated that the presence of the dopant leads to an enhancement of the photocatalytic activity in all cases. The role of particular dopants in modulating the photocatalytic activity will be discussed. Finally, the possibility of producing undoped and Zn2+-doped films presenting a higher activity than the commercial photocatalytic coating (Saint Gobain Glass Bioclean®) without requiring any calcination step has been demonstrated. These preliminary results constitute an important step forward in the development of photocatalytic films using a sol–gel process compatible with the constraints associated with large-scale industrial processing.

Multi-walled carbon nanotubes (CNTs) were produced in a continuous inclined mobile-bed rotating reactor by the catalytic chemical vapour deposition of methane on a bimetallic Ni–Mo/MgO catalyst whose activity remains constant in the course of time. Measurements performed on the continuous reactor were validated to ensure that the installation worked correctly and that measurements were precise enough. The performance of the reactor was simulated using a model based on the chemical reactor engineering approach. Hypotheses of the model were verified, and a kinetic study was performed to obtain a kinetic rate expression and to determine the catalytic activity as a function of time. The purity level of produced CNTs depends on the desired properties of the product, so the operating conditions are linked to the purity level that is required. A minimal purity level corresponds to high carbon production, and a maximal purity level corresponds to high specific productivity. It was shown that operating conditions had to be fixed to reach a given specific productivity or a given carbon production, and the optimized operating conditions leading to those two opposite purity level objectives were established.