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Currently, palladium represents an expensive and scarce element in the Earth's crust, with the mineral resources of platinum group metals (PGMs) predominately localized in South Africa and Russia. The growing demand for this material necessitates the development of suitable strategies to recover it from end-of-life devices. The recovery of palladium by combining leaching and sacrificial photocatalytic deposition in a low-waste process was proposed here as a possible alternative to the current technologies. The effect of the species involved in the single processes in the recirculated stream was evaluated, where a negligible influence of the sacrificial species (ethanol) in the leaching unit was noticed. Different home-prepared ZnO photocatalysts were tested, and the best performance in terms of recovery of palladium was obtained in the presence of ZnO nanoparticles prepared through sol–gel synthesis. The proposed procedure is a viable route for the recovery of Pd from spent catalysts: by combining the processes, the complete oxidation of palladium was observed in about 15 minutes, while the recovery of Pd through photodeposition on ZnO occurred within 120 minutes of irradiation.

Silver is extensively used in electronics, industrial catalysis, and biomedical sector owing to its enhanced physicochemical properties. E-waste recycling may contribute significantly to enhance silver recovery in the view of a circular economy and limit the depletion of mineral sources. In this scenario, hydrometallurgical routes represent the most widely used techniques for silver extraction/recovery and require strong acidic solutions, high temperatures, and multiple operating units. An alternative sustainable route for silver recovery from leaching solutions used for silver extraction in industrial applications is herein proposed for the first time. The novel green process of silver recovery is based on the UV/vis light-driven photocatalytic deposition of pure metallic silver over low-cost and non-toxic ZnO photocatalyst. In the second step, ZnO is dissolved by slight acidification and pure metallic silver is easily recovered. Low environmental impact, mild operating conditions, and economic viability are among the major perks of the new silver recovery process developed. In the view of a full-scale implementation, several operating conditions of the recovery process (i.e., photocatalyst load, starting silver concentration, type of hole scavenger and irradiation) were thoroughly investigated. A mathematical model capable of describing the system behaviour under different operating conditions was also developed and allowed to estimate unknown kinetic parameters for the Ag-photodeposition process.

Photocatalytic hydrogen production from alkanol-amines as sacrificial agents by using Cu-modified TiO2–P25 prepared via in situ photodeposition of cupric ions under UV-A light irradiation was investigated. A direct comparison among different sacrificial agents (monoethanolamine, diethanolamine, and triethanolamine) was preliminarily performed. Diethanolamine was selected for further investigation, due to its higher hydrogen production rate with respect to other alkanol-amines. Effect of pH, starting concentration of sacrificial agent, and catalyst/co-catalyst loads were studied. Solution pH exerts major impact on the photoefficiency for hydrogen generation: reaction mechanisms at different pH values were extensively examined. For the first time, a validated kinetic model estimated the unknown rate constants of (i) reaction between diethanolamine and photogenerated holes, (ii) proton reduction, and (iii) diethanolamine adsorption on the photocatalyst surface.

Pd, Rh, Pt are employed in a wide range of applications, such as catalytic converters, fuel cells and electronic devices. In the last years, an increasing pressure on their market was recorded due to a growing demand and limited resources. Therefore, the recovery of these materials from wastes represents an interesting goal to be achieved. The most widely proposed techniques for recovering the palladium from wastes are leaching and ion exchange. Strong oxidizers, acids and high temperature (343–363 K) are used for leaching, leading problems for the environment and the safety. In this work the attention was focused on a system containing zero-valent palladium nanoparticles in which the leaching is performed in mild acidic conditions, by using chloride solutions containing cupric ions (NaCl/CuCl2). The process was studied at varying temperature, pH, chloride and cupric ion concentrations. Good results were obtained at pH 5.0 and temperatures between 288 K and 333 K. The process is more acceptable than the traditional ones from a safety point of view being characterized by less severe conditions (pH and temperatures). A shrinking spherical particles model was adopted to analyse the experimental data from which a development under a kinetic control was demonstrated.

A shortage of market supplies is nowadays recorded for precious metals such as palladium, due to a wide range of applications in which they are used. The development of efficient and inexpensive recovery methodologies of precious metals from waste materials is thus necessary and urgent. In the present study a zinc oxide based photocatalytic system under UV/Visible-light radiation was chosen for palladium (II) deposition from solutions containing it. The effect of ethanol as sacrificial agent was investigated at varying catalyst load, irradiation conditions (UV+visible/visible/dark), metal starting concentration as well as the presence of cupric and chloride ions in solution. Moreover, ZnO dissolution at pH under 6.0 was proposed for the recovery of pure metallic palladium. A network of reactions and a kinetic model were proposed.

Pd, Rh, Pt are employed in a wide range of applications, such as catalytic converters, fuel cells and electronic devices. In the last years, an increasing pressure on their market was recorded due to a growing demand and limited resources. Therefore, the recovery of these materials from wastes represents an interesting goal to be achieved. The most widely proposed techniques for recovering the palladium from wastes are leaching and ion exchange. Strong oxidizers, acids and high temperature (343-363 K) are used for leaching, leading problems for the environment and the safety. In this work the attention was focused on a system containing zero-valent palladium nanoparticles in which the leaching is performed in mild acidic conditions, by using chloride solutions containing cupric ions (NaCl/CuCl

Solar energy exploitation is one of the most challenging applications for sustainable energy production. In this work a photoactivated fuel cell was developed, using visible light and the Fe(III)/Fe(II) redox couple for the simultaneous production of electrical energy and oxidation of polluting organics (alcohols) contained in synthetic and real wastewaters. WO3 was selected as a cheap and environmentally friendly photocatalyst more efficient than TiO2 (i) under visible light irradiation and (ii) in the presence of in-situ photodeposited Pd. Pd photodeposition was found to reduce the band gap of bare WO3, thus increasing visible light capture and limiting the occurrence of photogenerated hole/electron recombination. Higher photocatalytic performances were recorded over WO3–Pd compared to TiO2 and bare WO3, despite the low BET superficial area of WO3–Pd (2.34 m2 g−1). Optimal conditions were identified at pH = 2.0 with 2% w/w Pd load. The results also evidenced the influence of the selected sacrificial organics and water matrices. A quantum yield of 84.89% and an energy efficiency of 4.15% were the best results achieved so far for the proposed system. The present photoelectrochemical cell offers a very promising system for electrical energy production by using wastewater from wine manufacturing industry and solar light radiation.

The depletion of fossil chemicals and energy sources led to develop processes allowing the conversion of renewable feedstocks into useful products. Bioethanol production is a typical case of biomass conversion into chemical species with attractive uses, such as fuel, fuel additives, or chemical intermediates. In the present work, the possibility to produce acetaldehyde through Cu/TiO2 photocatalytic oxidation in liquid phase with aqueous mixtures at ethanol concentrations comparable to those of biorefinery outlet streams was assessed for the first time. The effect of cupric ion concentration on acetaldehyde selectivity was investigated. A nearly unit value of acetaldehyde selectivity was observed for a starting cupric ion concentration of 120 mM. The recovery and purification of acetaldehyde were performed by removing acetaldehyde from the solution through an inert gas bubbling and feeding the outgoing gaseous mixture to an absorber, in which acetaldehyde was captured by an aqueous stream. The possibility to regenerate the photocatalytic system in situ via zerovalent copper reoxidation was evaluated. In view of full-scale implementations, a careful flammability analysis of the resulting ternary mixture (ethanol/oxygen/nitrogen) along with a feasible process flow sheet were proposed. The possibility to employ bioethanol streams from biorefinery, sunlight irradiation as energy source, water as solvent, mild operating conditions, and low-cost, non-toxic, and reusable photocatalyst, makes the process investigated an attractive example of the eco-green synthesis of valuable commodity chemicals.

The enzymatic hydrolysis of cellulose from biomass feedstock in the sugar-based biorefinery chain is penalized by enzyme cost and difficulty to approach the theoretical maximum cellulose conversion degree. As a consequence, the process is currently investigated to identify the best operating conditions with reference to each biomass feedstock. The present work reports an investigation regarding the enzymatic hydrolysis of apple pomace (AP). AP is an agro-food waste largely available in Europe that might be exploited as a sugar source for biorefinery purposes. A biomass pre-treatment step was required before the enzymatic hydrolysis to make available polysaccharides chains to the biocatalyst. The AP samples were pre-treated through alkaline (NaOH), acid (HCl), and enzymatic (laccase) delignification processes to investigate the effect of lignin content and polysaccharides composition on enzymatic hydrolysis. Enzymatic hydrolysis tests were carried out using a commercial cocktail (Cellic®CTec2) of cellulolytic enzymes. The effect of mixing speed and biomass concentration on the experimental overall glucose production rate was assessed. The characterization of the glucose production rate by the assessment of pseudo-homogeneous kinetic models was proposed. Data were analysed to assess kinetic parameters of pseudo-mechanistic models able to describe the glucose production rate during AP enzymatic hydrolysis. In particular, pseudo-homogeneous Michaelis and Menten, as well as Chrastil’s models were used. The effect of lignin content on the enzymatic hydrolysis rate was evaluated. Chrastil’s model provided the best description of the glucose production rate.

The photocatalytic reduction of nitrate to nitrogen and the simultaneous production of hydrogen was investigated over copper loaded titania (P25) nanoparticles using glycerol as sacrificial agent and UV-A/Vis radiation. The experiments demonstrated that total nitrogen (i.e., nitrate, nitrite, and ammonia) removal efficiencies over 93% were achieved for initial nitrate concentrations up to 150 mg/I. A parallel hydrogen production up to 14 mu M was recorded. Hydrogen generation was affected by nitrate reduction. The reaction rates were dependent on pH and both glycerol and nitrate starting concentrations in the mixture. However, a linear model can be used to describe the process for low concentration of nitrate and constant pH. The system showed a remarkable photoefficiency in decontamination of nitrate-containing solutions and concomitant hydrogen evolution. This study lays the foundation for the future development of numerical models able to predict the chemical behavior of simultaneous proton and nitrate reduction over solar photocatalytic reforming of organics. (C) 2016 Elsevier B.V. All rights reserved.

Biorefinery processes for the production of second generation biofuels and bio-commodities are based on the use of waste lignocellulosic biomasses as a renewable feedstock. The sugar-based biorefinery platform includes biomass pretreatment and hydrolysis of structural polysaccharides as the first steps of the feedstock transformation. Hydrolysis of cellulose and hemicellulose in real biomass can be catalyzed by cellulase enzymes cocktails. The process has been developed up to industrial scale even though the scientific community is still active in investigating several critical issues in order to reduce costs of the process. The process allows obtaining a concentrated sugar aqueous solution (hydrolysate) from the heterogeneous conversion of the complex substrate (biomass) by the catalytic action of cellulases and beta-glucosidase dissolved in the liquid phase. The issues related to the reactor design include multi-scale phenomena affecting reaction kinetics, hydrodynamics as well as mass transfer of the biphasic system. The recent literature has been reviewed in order to highlight the state of the art about modelling of enzyme-catalyzed cellulose hydrolysis kinetics[1, 2], modelling of hydrolysis reactors[3], and optimization of process strategies[4]. Moreover, in the framework of the project Waste2Fuels (H2020-LCE-11-2015 g.a. n°654623), semi-mechanistic models of agro-food waste enzymatic hydrolysis have been assessed in order to obtain quantitative tools for bioreactor modelling. The effect of biomass pretreatment in terms of delignification degree has been quantified through the assessment of kinetic parameters of two agro-food wastes (apple pomace and coffe silverskin). References [1] Jeoh T., Cardona M., Karuna N., Mudinoor A.R., Nill J. (2017) Mechanistic Kinetic Models of Enzymatic Cellulose Hydrolysis--A Review, Biotechnology and Bioengineering, 114 (7), 1369-1385 [2] Bansal P., Hall M., Realff M.J., Lee J.H., Bommarius A.S. (2009) Modeling cellulase kinetics on lignocellulosic substrates, Biotechnology Advances 27, 833-848

The selective oxidation of ethanol to acetaldehyde and acetic acid in aqueous solution, through sacrificial TiO2 photocatalysis in the presence of cupric ions at ambient temperature, under acidic conditions and artificial sunlight, has been investigated. Different commercial TiO2 photocatalyst samples and loads have been tested. The influence of starting cupric ion and ethanol concentrations has been investigated. Ethanol conversion, overall product selectivity, and product yield have been calculated and compared with the aim of maximizing the recovery of valuable commodity chemicals. For the run corresponding to optimal values of ethanol conversion, overall product selectivity and yields, a value of process photoefficiency equal to 33% has been calculated. Based on the experimental results, the main focus of the study has been the development of a photo-oxidation mechanism and a new kinetic model constituted by a set of mass balance equations for the main species involved in the photocatalytic oxidation process. The model has been employed for analyzing data collected at different starting substrates and cupric ion concentrations. A reliable prediction of the concentrations of cupric ions and organic species during selective photo-oxidation runs has been achieved. The modeling investigation has allowed to estimate for the first time the kinetic parameters not available in the literature review, such as the equilibrium adsorption constants and the rate constants for the hole-capture by sacrificial agents. A new alternative strategy to convert ethanol from biorefinery wastewaters into valuable fine chemicals, by using water as solvent, a low-cost catalyst, solar radiation and ambient temperature, has been proposed and kinetically characterized. The model presented can be easily applied to other photocatalytic systems for the oxidation of organic species over metal doped photocatalysts.

In order to support the future hydrogen economy, photocatalytic water splitting technology, based on nanosized semiconductors, has significant potential for the production of hydrogen using solar energy with a low environmental impact. Despite the numerous attempts to prepare materials able to efficiently use solar energy during the past decades, the solar-to-hydrogen energy conversion efficiency is currently far too low for the technology to be economically profitable. This chapter depicts the basics of photocatalytic water splitting and organic photoreforming and surveys metal-based semiconductor nanomaterials (i.e., metal oxides, metal (oxy)sulfides and metal (oxy)nitrides, etc.) used as photocatalysts for hydrogen production in aqueous solution under UVA or visible radiation. Special attention is paid to recent developments for enhancing the effectiveness of the most common metal-based semiconductors. The main experimental factors affecting performance and design of photocatalytic materials are critically discussed.

Concentrated ternary mixture of nitric acid, sulfuric acid, and water are often used in the chemical industry for a wide range of applications. Among these, nitrations of organic substrates are the most common. Nevertheless, there is still a poor understanding of speciation of the acids in the mixtures, and different simplified or semiempirical approaches have been found in the literature to model nitration kinetics by mixed acids. Most of the found investigations are relevant in restricted ranges of experimental conditions, resulting in a fragmentary vision. In this work, most of the approaches found in the literature were reviewed in order to define their limits of validity, and new empirical equations for the estimation of nitronium ion concentration are proposed. Moreover, on the basis of original experimental data, a simplified model is proposed to calculate the dissociation of acids at varying experimental conditions, and the main assumptions reported in the literature were verified. Adopted simplifying assumptions were verified at sulfuric acid concentrations higher than 2.1 mol·L–1 and nitric acid concentrations ranging from 2.0 to 11 mol·L–1.

Within the framework of lignocellulose biorefinery, main issues related to the upstream processes include the drastic temperature and pressure usually required for efficient delignification of the biomass and the cost of the cellulase enzymes used to obtain monomeric sugars from cellulose hydrolysis. Several studies address the optimization of lignin removal with novel pretreatment (e.g. green solvents) with respect to the resulting sugar yields from enzymatic hydrolysis of the pretreated biomass performed at fixed conditions [1]. Among studies related to characterization of enzymatic hydrolysis, the use of semi-mechanistic models have been adopted to describe the kinetics of heterogeneous conversion of cellulose from lignocellulosic biomass into glucose [2, 3]. To investigate the effect of biomass composition resulting from different chemical and enzymatic delignification pretreatments, kinetic characterization of commercial cocktail Cellic CTec2 (Novozymes) has been carried out adopting apple industrial residues pretreated with NaOH, HCl and laccases.

The production of hydrogen by photocatalytic reforming of methanol and glycerol was investigated using metal copper-modified TiO2 nanoparticles, prepared “in situ” by reduction of cupric ions. A modeling investigation was performed through the development of a simplified kinetic model taking into account the mass balance equations for the main reactive species involved in the photocatalytic system. The kinetic model was tested to predict hydrogen generation rates for experimental runs carried out at different initial concentrations of sacrificial agent (methanol and glycerol) and at varying photocatalyst load. The modeling investigation allowed to estimate for the first time the equilibrium adsorption constants and the kinetic constant for the hole-capture by sacrificial agents, as well as the quantum yield and the rate constant of electron-hole recombination for the copper modified-TiO2 nano-photocatalyst. This study provide a reliable approach to model photocatalytic reforming of alcohols over metal modified-TiO2 catalyst for hydrogen generation.

The aim of the present study is the application of integrated solar nano-TiO2 based photocatalytic processes for the removal of copper, iron, zinc and (S, S)-ethylenediamine-N, N'-disuccinic acid (EDDS), used as chelating agent, from soil washing effluents produced by the remediation of samples of potentially polluted soils taken in the "Land of Fires" (Italy). Removal efficiencies of 93.5% (copper), 99.6% (iron), 99.4% (zinc), 97.2% (EDDS) and 80.7% (TOC) were reached through sunlight driven photocatalytic treatments carried out in parabolic trough collectors located in Naples (Italy). The removal degrees were achieved for an incident UVA solar energy per unit volume (Qj, n) of 580 kJ L-1, estimated by taking into account both the effective irradiated surface area of the photoreactor (9.79 × 10-2 m2) and the local solar irradiances collected during the experiments. The combined nano-TiO2-photocatalytic processes applied were shown to sufficiently decontaminate the soil washing effluents to permit the recycling in the soil washing treatment or discharging to public sewers. The study suggests that the two-step solar photocatalytic process investigated can be really adopted as a useful solution for the decontamination of soil washing streams from some heavy metals and chelating organic agents.

[object OThe photocatalytic removal of nitrate with simultaneous hydrogen generation was demonstrated using zero-valent nano-copper-modified titania (P25) as photocatalyst in the presence of UV-A-Vis radiation. Glycerol, a by-product in biodiesel production, was chosen as a hole scavenger. Under the adopted experimental conditions, a nitrate removal efficiency up to 100% and a simultaneous hydrogen production up to 14 ?mol/L of H2 were achieved (catalyst load = 150 mg/L, initial concentration of nitrate = 50 mg/L, initial concentration of glycerol = 0.8 mol/L). The reaction rates were independent of the starting glycerol concentration. This process allows accomplishing nitrate removal, with the additional benefit of producing hydrogen under artificial UV-A radiation. A kinetic model was also developed and it may represent a benchmark for a detailed understanding of the process kinetics. A set of acute and chronic bioassays (Vibrio fischeri, Raphidocelis subcapitata, and Daphnia magna) was performed to evaluate the potential ecotoxicity of the nitrate/by-product mixture formed during the photocatalytic process. The ecotoxicological assessment indicated an ecotoxic effect of oxidation intermediates and by-products produced during the process. © 2017, Springer-Verlag Berlin Heidelberg.bject]

2-Nitrobenzaldehyde and 3-nitrobenzaldehyde are important isomers involved in the synthesis of a variety of products for the bulk and fine chemicals industry. They can be both obtained by direct nitration of benzaldehyde in mixed acid. The meta substituted isomer is the main reaction product even though it has been recently pointed out that the yields of the two compounds (ortho and meta isomers) are affected by the mixed acid composition. In this work, a reaction network consisting of equilibrium and irreversible reactions and a mathematical model are proposed. For each of the reactions the kinetic and thermodynamic parameters were estimated in order to explain and predict the changes in the reactivity and selectivity at varying conditions. Moreover, a simplified approach was successfully used to describe the kinetics of the secondary oxidation pathways of the organics in the nitrating mixtures leading to benzoic and nitrobenzoic acids. The parameter estimation suggested that the ortho-oriented nitration is mainly due to the rearrangement of the complex of benzaldehyde with the nitronium ion rather than to the direct nitration of the organic substrate. On the other hand, the nitration of benzaldehyde and of the complex are both relevant for the meta-oriented isomer formation.

Photocatalytic water splitting and organic reforming based on nano-sized composites are gaining increasing interest due to the possibility of generating hydrogen by employing solar energy with low environmental impact. Although great efforts in developing materials ensuring high specific photoactivity have been recently recorded in the literature survey, the solar-to-hydrogen energy conversion efficiencies are currently still far from meeting the minimum requirements for real solar applications. This review aims at reporting the most significant results recently collected in the field of hydrogen generation through photocatalytic water splitting and organic reforming, with specific focus on metal-based semiconductor nanomaterials (e.g., metal oxides, metal (oxy)nitrides and metal (oxy)sulfides) used as photocatalysts under UVA or visible light irradiation. Recent developments for improving the photoefficiency for hydrogen generation of most used metal-based composites are pointed out. The main synthesis and operating variables affecting photocatalytic water splitting and organic reforming over metal-based nanocomposites are critically evaluated.

The mechanism of selective oxidation of benzyl alcohol to benzaldehyde and of benzaldehyde to benzoic acid by means of ferric ions in water under simulated UV-solar radiation is investigated through the development of a new kinetic model, also based on the results of Electron Spin Resonance (ESR) experiments, not previously reported in the literature. A value of pH = 0.5 is chosen with the aim to minimize the contribution of the undesired hydroxylation reactions. The mathematical model is constituted by of a set of mass balance equations for the chemical species involved in the homogeneous photocatalytic oxidation process. The experimental concentration-time profiles, collected at different starting substrates concentrations, are satisfactorily predicted by the model under deaerated and aerated conditions. The values of different rate constants of the reactions, taken into account for the adopted mechanism, not available in the literature, are estimated by a proper optimizing procedure. The model may be used for the prediction of the performance of the homogeneous Fe(III)-photo-catalytic partial conversion of aromatic alcohols to the corresponding aldehydes in water at room temperature and very acidic pH. © 2014 Elsevier B.V. All rights reserved.

A new photocatalytic system consisting of two subsystems – Cu 0 /Cl − /H + /UV ssr and Cu II /H + /TiO 2 /formic acid/UV ssr – is proposed as a tool to produce hydrogen by reforming an organic species. Formic acid is used as hole scavenger during the experimental runs. An experimental campaign is carried out to demonstrate that the systems can generate hydrogen and to assess how the generation rate depends upon experimental conditions such as copper and TiO 2 loads, chloride and proton ions, and formic acid concentrations. A strong dependence of the Cu 0 /Cl − /H + /UV ssr subsystem reactivity upon copper load, chloride concentration and pH is observed. The investigation on the complete system, starting from zero-valent copper, indicates that the addition of TiO 2 and formic acid to the Cu 0 /Cl − /H + /UV ssr subsystem does not result into any gain in terms of hydrogen produced and, renders the system totally unreactive under some conditions. On the other hand, when a complete system, starting from cupric ions, is adopted, hydrogen production is observed also for prolonged reaction times with a surplus of hydrogen production with respect to that generated by the Cu 0 /Cl − /H + /UV ssr subsystem with the same Cu 0 starting load and in absence of TiO 2 and sacrificial agent.

The characterization of thermal decomposition of cumene hydroperoxide (CHP) in cumene from kinetic point of view is of great interest for industrial applications. However, the efforts done so far by the researchers lead only to the availability of single kinetic laws (first order, autocatalytic, etc.) whose usefulness is strongly limited by the presence in the starting solutions of some impurities. A detailed model aiming at simulating both, thermal and kinetic behavior of the system, is now presented. In other words, the proposed model tries to simulate CHP thermal decomposition process at varying reaction conditions (different initial temperature, in the range 120-160 °C, different initial CHP concentrations, addition of ?-methylstyrene to CHP solutions in cumene) and during isothermal, scanning and adiabatic runs. A good capability of the model is observed to simulate the system behavior by using data collected under isothermal and adiabatic conditions and during scanning calorimetric runs. It is important to stress that the use of the model proposed in the present investigation does not require the adoption of adjustable parameters. © 2012 The Institution of Chemical Engineers. Published by Elsevier B.V. All rights reserved.

Hydrogen is the ideal candidate to fulfill the growing energy demand in a sustainable manner becauseof its high energy content and no emission of greenhouse gases from its combustion. Currently most ofhydrogen generation techniques involve the employment of fossil fuels, with consequent production oftoxic greenhouse gases. The possibility to produce hydrogen by means of photocatalytic processes usingthe solar radiation as energy source fits in perfectly with the switch to a more sustainable energy pro-duction. The solar photocatalytic hydrogen generation can be achieved by reforming organic substancescontained in civil or industrial wastewaters. This could allow to combine water decontamination withproduction of an energy carrier starting from a renewable source, the solar radiation.Within this perspective, a novel nano-TiO2photocatalytic system based on the solar reforming of formicacid in presence of cupric ions and chlorides has been investigated. The effect on hydrogen generationrate of the initial concentrations of formic acid, chloride and cupric ion, and pH values has been evaluated.For both formic acid and chloride ions, at least up to a starting concentration of 103mM, the higher theinitial concentration, the higher the rate of hydrogen generation. Hydrogen production has turned outto be noticeably dependent on cupric ion concentration. An almost opposite behavior has been foundvarying the starting cupric ion concentration in the range 2.5–20 mM, with the highest value of hydrogenproduction rate recorded for Cu(II) initial concentration equal to 5.0 mM. The pH value has been identifiedto be a crucial parameter of the system. A decrease in hydrogen production has been also observed risingpH of the solution from 1.0 to 4.0. A characterization of the solid samples recovered at the end of theruns has been performed by X-ray Diffractometry. These experimental outcomes have been rationalizedwithin a consistent reaction mechanism able to predict the system behavior under different operatingconditions. This work opens the way to the development of new competitive processes able to use wasteorganic streams for hydrogen generation through photacatalytic system based on solar energy.© 2015 Elsevier B.V. All rights reserved.

BACKGROUND: The conversion of hydroxybenzyl alcohols, nitro-benzyl alcohol and methoxybenzyl alcohols into the corresponding aldehydes is attempted in aqueous solution by Cu(II) (which reduces to Cu(0)), at room temperature, under acidic and deaerated conditions, using TiO2 solar simulated light photocatalysis. RESULTS: Under the experimental conditions adopted, the yields of the corresponding hydroxyaldehydes, when Cu(II) was completely reduced to Cu(0), were 21.6% for 4-hydroxybenzaldehyde, 11.5% for 3-hydroxybenzaldehyde and 20.2% for 2-hydroxybenzaldehyde. Higher conversions of 2-methoxybenzyl alcohol and 4-methoxybenzyl alcohol were recorded relative to unsubstituted benzyl alcohol. A selectivity of 5.2%, at 50% conversion of the substrate, was observed for the oxidation of 4-nitrobenzyl alcohol to 4-nitrobenzaldehyde. For high degrees of aromatic alcohols conversion, oxidation of the generated aldehydes to the corresponding benzoic acid derivatives is observed. CONCLUSION: The introduction of substituents into the aromatic alcohols structure changes the photocatalytic oxidation rate and product selectivities with respect to that previously observed for unsubstituted benzyl alcohol. In particular, the presence of both electron donating (hydroxy, methoxy groups) and electron withdrawing (nitrogroup) groups on the aromatic ring of the substrate causes a detrimental effect on the selectivity of the process with respect to the case of benzyl alcohol. © 2012 Society of Chemical Industry

In the future, solar energy, along with other renewable resources, could play a key role in mass production of fine chemicals. It could also potentially solve environmental problems, as demonstrated by recent developments in the use of solar energy, such as solar photocatalysis. The solar photocatalytic technology has been demonstrated to be effective for: • Treating groundwater, drinking water, industrial wastewater, and air and soil pollution, • Water disinfection, and • Industrial production of fine chemicals. This report summarizes the current status of solar photocatalysis and identifies future opportunities for research and industry in this field, including recent relevant bibliography. The main commercial solar photocatalytic applications are described, included the technologies based on sunlight for antifogging and self-cleaning of coating materials, glass, and concrete. An overview of several different solar photoreactors and the main operating process parameters are also provided. For the estimation of capital costs, it is suggested the use of appropriate “figures of merit”. The present review would be of interest for researchers, technologists, engineers, and industrialists.

The conversion of pyridinemethanol isomers into their respective aldehydes and carboxylic acids has been attempted in aqueous solution through sacrificial TiO2 photocatalysis in the presence of cupric ions, at ambient temperature, under acidic and deaerated conditions, using artificial sunlight. The presence of a nitrogen atom in the aromatic ring, with respect to benzylic alcohol and its derivatives, affects the photocatalytic behavior of the substrate. The influence of both pH and temperature has also been investigated. The position of the methanolic group on the aromatic ring leads to slight changes in the selectivities, yields and the oxidation rates. Under the adopted conditions, the yields and selectivities to aldehydes are always higher than those of the respective carboxylic acids. The photocatalytic process can be carried out in consecutive copper reduction/oxidation steps in order to reuse the catalyst. In this way greater yields and selectivities to the desired product than 60% can be achieved. The process can be considered interesting as it concerns the eco-green production of valuable fine chemicals, using water as a solvent at ambient conditions, a cheap heterogeneous catalyst and solar radiation.

In the future, solar energy, along with other renewable resources, could play a key role in mass production of fine chemicals. It could also potentially solve environmental problems, as demonstrated by recent developments in the use of solar energy, such as solar photocatalysis. The solar photocatalytic technology has been demonstrated to be effective for: • Treating groundwater, drinking water, industrial wastewater, and air and soil pollution, • Water disinfection, and • Industrial production of fine chemicals. This report summarizes the current status of solar photocatalysis and identifies future opportunities for research and industry in this field, including recent relevant bibliography. The main commercial solar photocatalytic applications are described, included the technologies based on sunlight for antifogging and self-cleaning of coating materials, glass, and concrete. An overview of several different solar photoreactors and the main operating process parameters are also provided. For the estimation of capital costs, it is suggested the use of appropriate “figures of merit”. The present review would be of interest for researchers, technologists, engineers, and industrialists.

An intense scientific activity was recorded during the last several years in the field of preparation, characterization and use of copper-based TiO 2 photocatalysts for hydrogen generation through photocatalytic reforming of organics. Different copper species were used dissolved in aqueous solution or incorporated on the TiO 2 surface as single co-catalyst or in the presence of a second catalyst (e.g., graphene, carbon fibers) to (1) effectively separate the electron–hole pairs, thus reducing the occurrence of the recombination reaction, and (2) extend the light absorption to the visible range of the solar spectrum. Many organic species (e.g., methanol, glycerol, formic acid) were proposed as sacrificial agents for hydrogen generation, although the prevailing idea is that of using organic compounds currently found in industrial wastewaters. The pH value was recognized as a fundamental variable in photocatalytic H 2 generation via copper modified-TiO 2 catalysts. A positive effect to promote hydrogen generation was associated to an increase in pH until moderate alkaline values. On the other hand, a release in the solution of cupric ions and a consequent decrease in photocatalytic activity were observed when decreasing pH. A relevant lack of information was recorded about the efficiencies of hydrogen generation which were reported only in few papers. Therefore, this critical literature review has been performed with the aim of providing a complete background to select the most efficient approaches and eventually promote new competitive systems for hydrogen generation via photoreforming for industrial applications.

The TiO2 photocatalytic oxidation of the N,N'-ethylenediamine-disuccinic acid and Cu(II) ions photoreduction were investigated in acidic solutions. The experimental results indicated a conversion of 100% for both EEDS and Cu(II) species whereas the mineralization degree was quite small (24%). The influence of several experimental variables, like purging gas, counter ion nature, pH, TiO2 type, photocatalyst load, initial concentration of cupric ions, radiation source (natural or artificial), was investigated. For almost equimolar feed ratios of reactants, EDDS was not totally removed whereas Cu(II) species were completely reduced. An analysis of the data collected indicated a Cu(II)/EDDS molar consumption ratio close to two. The presence of oxygen decreased the photoreduction process of Cu(II) species, whereas the initial concentration of Cu(II) ions and the counter ion (excepted for the chloride ions) did not affect the photocatalytic process. Ecotoxicity tests (Pseudokirchneriella subcapitata and Lemna minor) on treated samples indicated a marked decrease of the ecotoxicity for very prolonged reaction times. (C) 2014 Elsevier B.V. All rights reserved.

A kinetic model is developed to simulate the thermal decomposition of dicumyl peroxide (DCP) in cumene with and without oxygen in the reacting system, based on a reaction network that is comprised of a set of 51 reactions. An optimization procedure is adopted to obtain the best estimates for most of the related kinetic parameters, few of which are available in the literature. The model is successfully validated by simulating the concentration profiles of all the species participating in the decomposition of DCP in cumene, under varying initial conditions, using previously best-estimated values of the kinetic parameters. © 2011 American Chemical Society.

Selective oxidation of benzyl alcohol to benzaldehyde in aqueous solution, under acidic conditions, through the TiO 2 /Cu(II)/solar UV photocatalytic system, was investigated. Different commercial TiO 2 samples were tested. The best result found, in terms of yield, was of 35% for benzaldehyde with respect to the initial benzyl alcohol concentration. During a single run, a partial conversion of benzaldehyde to benzoic acid was also observed. By-products, present at trace level, were 2-hydroxy-benzyl-alcohol, 4-hydroxy-benzyl-alcohol, 2-hydroxy-benzaldehyde and 4-hydroxy-benzaldehyde. On the basis of the formation of these species a production of HO radicals could be thus inferred. The study suggested that different operative parameters, such as the composition and amount of photocatalyst, pH, ionic components in water and the initial concentration of Cu(II) ions, played an important role in the photocatalytic selective oxidation of benzyl alcohol. Moreover, the results of the present investigation indicated that, at the end of the process, Cu(II) could be regenerated and reused, through a re-oxidation of Cu(0), produced during the photolytic run, with air in the dark. A general mechanism of oxidation, supported by the experimental results was proposed.

The knowledge of the substances which form when a molecule undergoes chemical reactions under unusual conditions is required by European legislation to evaluate the risks associated with an industrial chemical process. A thermal decomposition is often the result of a loss of control of the process which leads to the formation of many substances in some cases not easily predictable. The evaluation of the change of an overall toxicity passing from the parent compound to the mixture of its thermal decomposition products has been already proposed as a practical approach to this problem when preliminary indications about the temperature range in which the molecule decomposes are available. A new procedure is proposed in this work for the obtainment of the mixtures of thermal decomposition products also when there is no previous information about the thermal behaviour of investigated molecules. A scanning calorimetric run that is aimed to identify the onset temperature of the decomposition process is coupled to an isoperibolic one in order to obtain and collect the products. An algal strain is adopted for toxicological assessments of chemical compounds and mixtures. An extension of toxicological investigations to human cells is also attempted. © 2009 Elsevier B.V. All rights reserved.

The ozonation of glycerol and its main oxygenated derivatives is studied aiming at evaluating the possibility to convert them into valuable products. The direct ozonation of glycerol results into a mixture of its oxygenated derivatives. In some cases the use of ozone to convert them into valuable products proceeds with good selectivity. A kinetic study to estimate the kinetic constants of ozone attack to the main glycerol oxygenated intermediates is carried out. The data found are in keeping with the few values found in the literature for alcoholic groups by ozone. © 2009 International Ozone Association.

The photoreduction of Cu(II) in presence of an organic species as sacrificial agent has been investigated by many research groups but some controversial results are reported in literature. In this work, the photoreduction process of Cu(II) in presence of formic acid is investigated aiming at clarifying the reaction mechanism and assess the reaction kinetics. The effect of operating conditions such as TiO 2 load, initial concentration of sacrificial agent, pH and ionic strength was studied. The results of the work are: (1) the system reactivity does not depend neither on pH (in the range 2.0–3.5) nor on ionic strength of the solution; (2) formic acid is adsorbed on TiO 2 surface; (3) the nature of anionic species can influence the Cu(II) photoreduction (e.g. the addition of sulphate or phosphates reduces the reaction rates); and (4) FA can be completely mineralized during this photoxidation process; for example, this is observed for a TiO 2 load of 0.1 g/L after a reaction time of about 240 min. A simplified kinetic model is developed to describe the behavior of the system and validated by analysing the data collected during the experimental work.

A pool of laboratory experiments is planned with the aim of evaluating the possibility to reduce the phytotoxicity of olive mill wastewater (OMW) with combined physico-chemical processes (centrifugation-ozonation, centrifugation-solar photolysis, centrifugation-solar modified photoFenton, centrifugation-solar modified photoFenton-ozonation). A moderate COD removal of an OMW is reached by using ozonation or solar modified photoFenton separately or solar modified photoFenton/O(3) combined process even for prolonged treatment times. The O(3)-treated OMWs are still toxic towards algal growth (Pseudokirchneriella subcapitata) and only for dilutions equal to or higher than 1:160 a stimulation of algal growth is observed. The sole ozonation does not reduce significantly the phytotoxicity of tested OMW measured through the GI calculation of Raphanus sativus L., Cucumis sativus L. and Lactuca sativa L. A marked reduction of OMW inhibition, higher than 50%, is evidenced for 1:8 dilution OMW samples ozonated for 2h. The long-term storage of OMW associated with solar irradiation without or with Fe(III) ions under continuous aeration is less efficient than ozonation, and the combined action of the two former treatments does not significantly contribute to enhance both COD removal and germination index. Better results are obtained on seed germination and root elongation of plantlets of the three selected species, which germinated on OMW-free solidified medium and were then transferred on a solidified culture medium containing O(3)-treated OMW diluted 1:2 and 1:4. The operating costs are estimated for the solar modified photoFenton-ozonation process.

The abatement of ferulic acid (FA), a polyphenolic constituent of olive mill wastewater, is studied in the pH range 5.0-7.0 by using hydrogen peroxide and an amorphous iron oxide as catalyst. The effect of pH, catalyst load, hydrogen peroxide and substrate starting concentrations is assessed during the investigation. A suitable reaction scheme is developed and used to build a mathematical model which satisfactorily describes the system's behavior. Kinetic constants for the proposed scheme as well as the total active site concentration of the catalyst in the studied pH range are estimated. The occurrence of internal mass-transfer limitation for the adopted granulometric fraction of the catalyst is demonstrated. © 2007 Elsevier B.V. All rights reserved.

To better understand the batch production of 5-nitrosalicylic acid by means of the nitration of salicylic acid through the mixture nitric acid/acetic acid, the solubility of the two main mononitro derivatives of salicylic acid is investigated. For this purpose, the behavior of the two mononitro compounds in the ternary system organic/ acetic acid/nitric acid is separately studied at different temperatures (288 to 303) K and nitric acid concentrations [(0 to 2) molâL-1 for 5-nitrosalicylic acid, (0 to 1) molâL-1 for 3-nitrosalicylic acid]. The solubility of these compounds increases with a rise in temperature, whereas only the solubility of 5-nitrosalicylic acid is dependent upon the nitric acid concentration. The mutual effect of each organic acid on the solubility of the other is also investigated. The observed dependencies are explained through simple thermodynamic relationships.

The nitration of salicylic acid by means of HNO3/AcOH is investigated, and the results are compared with those obtained using different nitrating systems: HNO3/H2SO4/H2O ( mixed acid), HNO3/Ac2O/AcOH, aqueous HNO3 (70% by weight) at 343 K. Little differences are found in terms of yield of the desired product (5-nitrosalicylic acid) among HNO3/AcOH mixture, mixed acid, and HNO3/Ac2O/AcOH systems, aqueous HNO3 giving the poorest results. However according to the data collected during the present investigation the use of the system HNO3/AcOH presents some advantages with respect to the others for the separation and purity of desired product, waste minimization, and safety improvements. The reaction kinetics for the nitration of salicylic acid with this system is also investigated. A global second-order kinetic law (one for the substrate, one for nitric acid) is used in the analysis of the data collected for the formation of the two mononitroderivatives (3-nitro- and 5-nitrosalicylic acids) and of the side product 2-nitrophenol

BACKGROUND: The conversion of hydroxybenzyl alcohols, nitro-benzyl alcohol and methoxybenzyl alcohols into the corresponding aldehydes is attempted in aqueous solution by Cu(II) (which reduces to Cu(0)), at room temperature, under acidic and deaerated conditions, using TiO2 solar simulated light photocatalysis. RESULTS: Under the experimental conditions adopted, the yields of the corresponding hydroxyaldehydes, when Cu(II) was completely reduced to Cu(0), were 21.6% for 4-hydroxybenzaldehyde, 11.5% for 3-hydroxybenzaldehyde and 20.2% for 2-hydroxybenzaldehyde. Higher conversions of 2-methoxybenzyl alcohol and 4-methoxybenzyl alcohol were recorded relative to unsubstituted benzyl alcohol. A selectivity of 5.2%, at 50% conversion of the substrate, was observed for the oxidation of 4-nitrobenzyl alcohol to 4-nitrobenzaldehyde. For high degrees of aromatic alcohols conversion, oxidation of the generated aldehydes to the corresponding benzoic acid derivatives is observed. CONCLUSION: The introduction of substituents into the aromatic alcohols structure changes the photocatalytic oxidation rate and product selectivities with respect to that previously observed for unsubstituted benzyl alcohol. In particular, the presence of both electron donating (hydroxy, methoxy groups) and electron withdrawing (nitrogroup) groups on the aromatic ring of the substrate causes a detrimental effect on the selectivity of the process with respect to the case of benzyl alcohol.