Effect of Synthesis Method on Reaction Mechanism for Hydrogen Evolution over CuxOy/TiO2 Photocatalysts: A Kinetic Analysis.

The existing literature survey reports rare and conflicting studies on the effect of the preparation method of metal-based semiconductor photocatalysts on structural/morphological features, electronic properties, and kinetics regulating the photocatalytic H2 generation reaction. In this investigation, we compare the different copper/titania-based photocatalysts for H2 generation synthesized via distinct methods (i.e., photodeposition and impregnation). Our study aims to establish a stringent correlation between physicochemical/electronic properties and photocatalytic performances for H2 generation based on material characterization and kinetic modeling of the experimental outcomes. Estimating unknown kinetic parameters, such as charge recombination rate and quantum yield, suggests a mechanism regulating charge carrier lifetime depending on copper distribution on the TiO2 surface. We demonstrate that H2 generation photoefficiency recorded over impregnated CuxOy/TiO2 is related to an even distribution of Cu(0)/Cu(I) on TiO2, and the formation of an Ohmic junction concertedly extended charge carrier lifetime and separation. The outcomes of the kinetic analysis and the related modeling investigation underpin photocatalyst physicochemical and electronic properties. Overall, the present study lays the groundwork for the future design of metal-based semiconductor photocatalysts with high photoefficiencies for H2 evolution.

A novel green approach for silver recovery from chloride leaching solutions through photodeposition on zinc oxide.

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.

Zero-valent palladium dissolution using NaCl/CuCl2 solutions.

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.

Osteosíntesis en fracturas oblicuas o espiroideas largas de metacarpianos: comparación entre tratamiento con tornillos interfragmentarios solos y placa con tornillos / Osteosynthesis in long oblique and spiral metacarpal fractures: Comparison between interfragmentary screws and plating

Objetivos: Comparar el tratamiento de pacientes con fracturas oblicuas o espiroideas largas de metacarpianos, mediante reducción abierta y fijación interna con tornillos interfragmentarios solos o placas y tornillos. Materiales y métodos: Se realizó un estudio retrospectivo comparativo entre 2 grupos de pacientes: uno con 24 pacientes tratados con tornillos interfragmentarios solos y otro con 17 pacientes tratados mediante osteosíntesis con placas y tornillos. En ambos, se utilizó un abordaje longitudinal dorsal, y se les indicó inmovilización posoperatoria con valva de yeso y rehabilitación con el mismo equipo de terapistas ocupacionales. Tras un seguimiento mínimo de 12 meses, se evaluaron los resultados con el puntaje DASH, la movilidad activa total, la distancia pulpejo-palma y la fuerza con dinamometría comparativa. Se consideró significativo un valor p <0,05. Resultados: El tiempo promedio de seguimiento fue de 24.5 meses (rango 12-43).No se hallaron diferencias estadísticamente significativas en el puntaje DASH, la movilidad activa total, la distancia pulpejo-palma y la fuerza. El tiempo hasta el reingreso laboral fue inferior en el grupo tratado con placas y tornillos, aunque se registraron dos casos de retiro de material, sumado, en uno de ellos, a adherencia tendinosa (tenólisis). Conclusiones: El tratamiento de pacientes con fracturas oblicuas o espiroideas largas de metacarpianos, mediante tornillos interfragmentarios solos o placas y tornillos logró resultados similares, se destaca el menor tiempo hasta la reincorporación laboral y la mayor cantidad de complicaciones con placas y tornillos. Nivel de Evidencia: III

Objective: To compare open reduction and internal fixation with interfragmentary screws and with plates and screws for the treatment of long oblique or spiral metacarpal fractures. Materials and methods: A comparative retrospective study was carried out between 2 groups of patients treated surgically. In the first group, 24 patients were treated with interfragmentary screws and in the second group, 17 patients were treated with plate and screw osteosynthesis. A dorsal longitudinal approach was used. Postoperatively, immobilization was performed using a plaster splint; both groups followed rehabilitation with same occupational therapist team. After a minimum follow-up of 12 months, they were evaluated with the DASH score, total active motion (TAM), pulp-to-palm distance, and comparative contralateral dynamometry. A p value < 0.05 was considered significant. Results: The average follow-up was 24.5 months (range 12-43 months). There were no statistically significant differences in DASH, TAM, pulp-to-palm distance, and strength. The group treated with plate and screw fixation returned to work earlier, although there were two cases of implant removal, in addition to tendon adherence (tenolysis) in one of them. Conclusions: The treatment of patients with long oblique or spiral metacarpal fractures with interfragmentary screws or plates and screws showed similar outcomes; the treatment with plate and screws allowed an earlier return to work but had a greater number of complications. Level of Evidence: III

Ultrafast photodegradation of isoxazole and isothiazolinones by UV254 and UV254/H2O2 photolysis in a microcapillary reactor.

The photodegradation process of methylisothiazolinone (MIT), benzisothiazolinone (BIT), and isoxazole (ISOX) in ultrapure water and synthetic wastewater by means of UV254 photolysis and by UV254/H2O2 advanced oxidation process were investigated in a microcapillary photoreactor designed for ultrafast photochemical transformation of microcontaminants. For the first time, we estimated key photo-kinetic parameters, i.e. quantum yields (35.4 mmol·ein-1 for MIT, and 13.5 and 55.8 mmol·ein-1 for BIT at pH = 4-6 and 8, respectively) and rate constants of the reaction of photo-generated OH radicals with MIT and BIT (2.09·109 and 5.9·109 L mol-1·s-1 for MIT and BIT). The rate constants of the reaction of photo-generated OH radicals with ISOX in MilliQ water was also estimated (2.15·109 L mol-1·s-1) and it was in good agreement with literature indications obtained in different aqueous matrices. The models were extended and validated to the case of simultaneous degradation of mixtures of these compounds and using synthetic wastewater as an aqueous matrix. High resolution-accurate mass spectrometry analysis enabled identification of the main intermediates (BIT200, B200, saccharin, BIT166) and enabled proposal of a novel degradation pathway for BIT under UV254/H2O2 treatment. This study demonstrates an ultrafast method to determine key photo-kinetic parameters of contaminants of emerging concern in water and wastewater, which are needed for design and validation of photochemical water treatment processes of municipal and industrial wastewaters.

Assessment of optimal conditions for the restoration and recovery of agricultural soil.

We assessed whether soil with high Cr contamination could be reclaimed by alkali, mineral, and organic acid-based ligands (OABLs) washing. We tested HNO3, H2SO4, HCl, NaOH, H2O2, lactic acid (LA), malic acid (MA), oxalic acid (OA), and citric acid (CA), together with EDTA, obtaining the highest efficiencies in presence of 1 M sulfuric acid (98%). Nonetheless we noted that using OABLs, we obtained a Cr(III) removal efficiency similar to the one obtained using mineral acids. Indeed 1 M of LA and MA and 0.8 M of OA allowed obtaining, respectively, 88%, 75%, and 67% removal percentage. The extraction process with OABLs was strongly dependent on intraparticle diffusion of Cr-LA, Cr-MA, and Cr-OA complexes. We also determined the apparent diffusion coefficients. Residual toxicity of treated soils was tested with the nematode, Caenorhabditis elegans. The OABL washing generally allowed getting a soil without Cr and with reduced toxicity. However, the washing process also removed other cations that acted as nutrients. Consequently, we conducted toxicity tests on enriched soil and found that the mortality index improved. In some cases (LA and MA), mortality was comparable to that observed with uncontaminated control samples. In contrast, when contaminated soils were washed with sulfuric acid, in all conditions, we observed significant ecotoxicity. Therefore, we concluded that only the OABL treatment provided a non-toxic soil that could be reused for anthropic activities.

Fractura de clavícula: Técnica mínimamente invasiva / Minimally invasive approach for clavicular fractures

Objetivo: Describir la técnica quirúrgica mínimamente invasiva con placa regional bloqueada para fracturas mediodiafisarias de clavícula y mostrar nuestros resultados clínicos y radiográficos. Materiales y Métodos: Se evaluó, en forma retrospectiva, a 15 pacientes (12 hombres y 3 mujeres, media de la edad, 32.4 años [rango 17-51]) con fractura de clavícula, tratados con reducción y osteosíntesis con placa superior bloqueada anatómica mediante una técnica mínimamente invasiva. Según la clasificación de Allman, 12 pacientes tenían fractura de clavícula tipo I y tres, tipo II. Resultados: El tiempo promedio de cirugía fue de 53 minutos (rango 51-65). Se logró la consolidación de todas las fracturas en un promedio de 13.3 semanas (rango 12-15). No hubo seudoartrosis ni consolidaciones viciosas. El puntaje promedio de Constant fue de 98 (rango 95-100). Todos los pacientes se manifestaron satisfechos con los resultados estéticos y funcionales. Conclusiones: Este estudio demuestra que la técnica mínimamente invasiva para las fracturas mediodiafisarias de clavícula, utilizando placas regionales anatómicas bloqueadas superiores, puede ser un procedimiento reproducible y una alternativa a las técnicas quirúrgicas convencionales. Además, los resultados clínicos y radiográficos satisfactorios se obtuvieron sin complicaciones mayores y sin disestesias en la zona de la herida. Nivel de Evidencia: IV

Objectives: To describe the minimally invasive locking plate approach for midshaft clavicular fractures, and report our radiographic and clinical results. Methods: We retrospectively evaluated fifteen patients (12 men and 3 women, mean age: 32.4 years [range 17-51]) with clavicular fractures who underwent minimally invasive superior locking plate osteosynthesis and reduction. According to Allman classification of clavicular fractures, 12 patients had a type I fracture, while 3 had a type II fracture. Results: The average operating time was 53 minutes (range 51-65). Union was achieved in all patients in an average of 13.3 weeks (range 12-15). Patients were satisfied with cosmetic and functional results. Conclusions: This study shows that minimally invasive superior locking plate approach for midshaft clavicular fractures can be a reproducible procedure and an alternative to conventional surgical approaches. Clinical and radiological results were achieved without major complications and wound dysesthesia. Level of Evidence: IV

Removal of antiretroviral drugs stavudine and zidovudine in water under UV254 and UV254/H2O2 processes: Quantum yields, kinetics and ecotoxicology assessment.

The concentration of antiretroviral drugs in wastewater treatment plants (WWTP) effluents and surface waters of many countries has increased significantly due to their widespread use for HIV treatment. In this study, the removal of stavudine and zidovudine under UV254 photolysis or UV254/H2O2 was investigated in a microcapillary film (MCF) photoreactor, using minimal water samples quantities. The UV254 quantum yield of zidovudine, (2.357 ±â€¯0.0589)·10-2 mol ein-1 (pH 4.0-8.0), was 28-fold higher that the yield of stavudine (8.34 ±â€¯0.334)·10-4 mol ein-1 (pH 6.0-8.0). The second-order rate constant kOH,iof reaction of hydroxyl radical with the antiretrovirals (UV254/H2O2 process) were determined by kinetics modeling: (9.98 ±â€¯0.68)·108 M-1 s-1 (pH 4.0-8.0) for zidovudine and (2.03 ±â€¯0.18)·109 M-1 s-1 (pH 6.0-8.0) for stavudine. A battery of ecotoxicological tests (i.e. inhibition growth, bioluminescence, mutagenic and genotoxic activity) using bacteria (Aliivibrio fischeri, Salmonella typhimurium), crustacean (Daphnia magna) and algae (Raphidocelis subcapitata) revealed a marked influence of the UV dose on the ecotoxicological activity. The UV254/H2O2 treatment process reduced the ecotoxicological risk associated to direct photolysis of the antiretrovirals aqueous solutions, but required significantly higher UV254 doses (≥2000 mJ cm-2) in comparison to common water UV disinfection processes.

Photodegradation and ecotoxicology of acyclovir in water under UV254 and UV254/H2O2 processes.

The photochemical and ecotoxicological fate of acyclovir (ACY) through UV254 direct photolysis and in the presence of hydroxyl radicals (UV254/H2O2 process) were investigated in a microcapillary film (MCF) array photoreactor, which provided ultrarapid and accurate photochemical reaction kinetics. The UVC phototransformation of ACY was found to be unaffected by pH in the range from 4.5 to 8.0 and resembled an apparent autocatalytic reaction. The proposed mechanism included the formation of a photochemical intermediate (ϕACY = (1.62 ± 0.07)·10-3 mol ein-1) that further reacted with ACY to form by-products (k' = (5.64 ± 0.03)·10-3 M-1 s-1). The photolysis of ACY in the presence of hydrogen peroxide accelerated the removal of ACY as a result of formation of hydroxyl radicals. The kinetic constant for the reaction of OH radicals with ACY (kOH/ACY) determined with the kinetic modeling method was (1.23 ± 0.07)·109 M-1 s-1 and with the competition kinetics method was (2.30 ± 0.11)·109 M-1 s-1 with competition kinetics. The acute and chronic effects of the treated aqueous mixtures on different living organisms (Vibrio fischeri, Raphidocelis subcapitata, D. magna) revealed significantly lower toxicity for the samples treated with UV254/H2O2 in comparison to those collected during UV254 treatment. This result suggests that the addition of moderate quantity of hydrogen peroxide (30-150 mg L-1) might be a useful strategy to reduce the ecotoxicity of UV254 based sanitary engineered systems for water reclamation.

Sacrificial photocatalysis: removal of nitrate and hydrogen production by nano-copper-loaded P25 titania. A kinetic and ecotoxicological assessment.

The 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 µmol/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.

Alkaline direct transesterification of different species of Stichococcus for bio-oil production.

The cost of bio-oil refining from microalgal biomass can be significantly reduced by combining extraction and transesterification. The characterisation and optimisation of the combined steps have been carried out on strains of Stichococcus bacillaris, focusing on catalyst type and concentration, reaction time and temperature, methanol/biomass ratio, pre-mixing time and water content in the biomass. The bio-oil yield has been referenced as production of fatty acid methyl esters (FAMEs). The maximum yield (∼17%) was achieved using dried biomass with alkaline catalyst at 60°C and methanol/biomass weight ratio of 79:1. Alkaline catalyst conditions gave faster reaction rates and higher bio-oil yields than acid catalyst. Yield was also strongly affected by water content in the biomass. A mechanistic interpretation has been proposed to elucidate the effect of the different operating conditions. However, the structural characteristics of the Chlorophyta cell wall can be very different, leading to different bio-oil yields when the same protocol is applied. Therefore, the optimised protocol of direct transesterification for Stichococcus bacillaris strains was tested on other Stichococcus strains and several other Chlorophyta species characterised by a different cell wall structure. It was clearly demonstrated that different results for bio-oil yield were obtained within the same microalgal species and much more within different microalgal genera.

Investigation on the removal of the major cocaine metabolite (benzoylecgonine) in water matrices by UV254/H2O2 process by using a flow microcapillary film array photoreactor as an efficient experimental tool.

A microcapillary film reactor (MCF) was adopted to evaluate and compare the removal efficiency of benzoylecgonine (BE), an emerging micropollutant deriving from illicit drug abuse (cocaine), in different aqueous matrices: milliQ water, synthetic and real wastewater and surface water. The removal processes investigated were the direct photolysis with UV radiation at 254 nm, and the advanced oxidation process (AOP) with the same UV radiation and hydrogen peroxide. As a result of the microfluidics approach developed through an innovative experimental apparatus, full conversion of BE was reached within a few seconds or minutes of residence time in the MCF depending on the process conditions adopted. The radiation dose was estimated to be approximately 5.5 J cm(-2). The innovative MCF reactor was found to be an effective tool for photochemical studies, especially when using highly priced, uncommon, or regulated substances. The removal efficiency was affected by the nature of the aqueous matrix, due to the presence of different xenobiotics and natural compounds that act primarily as HO(•) radical scavengers and secondly as inner UV254 filters. Moreover, nano-liquid chromatography (LC)-high resolution-mass spectrometry analysis was utilized to identify the main reaction transformation products, showing the formation of hydroxylated aromatics during the photochemical treatment.

Kinetic characterization of the photosynthetic reaction centres in microalgae by means of fluorescence methodology.

The kinetic characterization of the photosynthetic activity in autotrophic microalgae plays a key role in the design of optimized photobioreactors. This paper presents a procedure to assess kinetic parameters of a three-state photosynthetic reaction centres model. Four kinetic parameters of the model were assessed by processing the time-series measurements of pulse-amplitude modulation fluorimetry. The kinetic parameters were assessed for several microalgal strains (Stichococcus bacillaris, Scenedesmus vacuolatus, Chlamydomonas reinhardtii, Chlorella vulgaris) growth in vertical and inclined bubble columns and irradiated by white-light or red/blue light. The procedure was successfully applied to the investigated strains. The assessed parameters allow identifying the irradiance range under which: the photochemical process is controlled by the photons capture; the photoinhibition competes with the photochemical quenching. The analysis of the time-scale of the photosynthetic reaction centres as a function of the irradiance allows interpreting the performances of photobioreactors characterized by non-homogeneous irradiance.

Fe(III)-photocatalytic partial oxidation of benzyl alcohol to benzaldehyde under UV-solar simulated radiation.

A great deal of interest is recorded among researchers in the identification of new catalytic systems that make possible the selective oxidation of organic species in the presence of non-toxic solvents, primarily water, through the use of inexpensive catalysts. The possibility to selectively oxidize benzyl alcohol to benzaldehyde is studied in the present work by using ferric ions as homogeneous catalysts and oxygen as an oxidant under UV-solar simulated radiation. Due to the possibility that Fe(III) aquo-complex photolysis could generate undesired reactive OH radicals with the consequent occurrence of side reactions, most of the runs are carried out at pH = 0.5 at which these events have a reduced incidence. The results indicate that benzyl alcohol can be partially converted into benzaldehyde with yield and selectivity values higher than 40% and 80% respectively for the conditions adopted, with a minor occurrence of benzoic acid formation. Reaction schemes to account for the experimental observations are provided.

Photodegradation of naproxen and its photoproducts in aqueous solution at 254 nm: a kinetic investigation.

The kinetics of photodegradation of the non steroidal anti-inflammatory drug naproxen (+)-S-2-(6-methoxynaphthalen-2-yl)propanoic acid, an emerging organic pollutant, was studied in aqueous solutions under deaerated and aerated conditions. The photolysis experiments were carried out under monochromatic irradiation (λ = 254 nm) at pH = 7.0 and T = 25 °C. Simplified reaction schemes of photodegradation of naproxen are proposed in absence and in presence of oxygen respectively. The schemes take into account the photolysis of naproxen and its photoproducts and the reactions of the measured species with oxygen dissolved in the liquid bulk. According to these schemes, two kinetic models were developed which correlate the experimental data, for runs performed in absence and in presence of oxygen, with a fair accuracy and allowed to estimate the best values for the unknown kinetic parameters. The calculated quantum yield of direct photolysis of naproxen under deaerated media is in good agreement with the one previously reported. Under aerated conditions, the generation of singlet oxygen has also been taken into account. The obtained results, under the adopted conditions, indicated a marked influence of dissolved oxygen on the photodegradation rates of naproxen and the relative distribution of the major reaction intermediates.

Kinetic and chemical characterization of thermal decomposition of dicumylperoxide in cumene.

Dicumylperoxide (DCP) is one of the most used peroxides in the polymer industry. It has been reported that its thermal decomposition can result in runaway phenomena and thermal explosions with significant economic losses and injuries to people. In the present paper thermal behaviour of dicumylperoxide in cumene was investigated over the temperature range of 393-433 K under aerated and de-aerated conditions. The results indicated that when oxygen was present, the decomposition rate did not follow a simple pseudo-first order kinetic as previously reported in literature. A satisfactory fit of the experimental data was, in this case, achieved by means of kinetic expression derived under the assumption of an autocatalytic scheme of reaction. The reaction rate was, on the contrary, correctly described by a pseudo-first order kinetic in absence of oxygen. Under both aerated and de-aerated conditions, chemical analysis showed that the decomposition mainly resulted in the formation of acetophenone and dimethylphenylcarbinol with minor occurrence of 2,3-dimethyl-2,3-diphenylbutane. The formation of methane and ethane was also invariably observed while the appearance of cumylhydroperoxide as a reaction intermediate was detected under only aerated conditions. Therefore, two reaction schemes were proposed to explain system behaviour in the presence of oxygen and after its purging.

Oxidation of 2,4-dichlorophenol and 3,4-dichlorophenol by means of Fe(III)-homogeneous photocatalysis and algal toxicity assessment of the treated solutions.

Chlorophenols are used worldwide as broad-spectrum biocides and fungicides. They have half-life times in water from 0.6 to 550 h and in sediments up to 1700 h and, due to their numerous origins, they can be found in wastewaters, groundwaters or soils. Moreover, chlorophenols are not readily biodegradable. Recently, classic Advanced Oxidation Processes (AOP) have been proposed for their abatement in an aqueous solution. This paper investigates the oxidation of 2,4-dichlorophenol and 3,4-dichlorophenol, at starting concentrations of 6.1 · 10(-5) mol L(-1), in aqueous solutions through Fe(III)/O(2) homogeneous photocatalysis under UV light (303 ÷ 366 nm). The Fe(III)/O(2) homogeneous photocatalysis is less expensive than using H(2)O(2) due to the capability of Fe(III) to produce OH radicals, if irradiated with an UVA radiation, and of oxygen to re-oxidize ferrous ions to ferric ones when dissolved in solution. The results show that the best working conditions, for both compounds, are found for pH=3.0 and initial Fe(III) concentration equal to 1.5 · 10(-4) mol L(-1) although the investigated oxidizing system can be used even at pH close to 4.0 but with slower abatement kinetics. Toxicity assessment on algae indicates that treated solutions of 2,4-dichlorophenol are less toxic on algae Pseudokirchneriella subcapitata if compared to not treated solutions whereas in the case of 3,4-dichlorophenol only the samples collected during the runs at 20 and 60 min are capable of inhibiting the growth of the adopted organism. The values of the kinetic constant for the photochemical re-oxidation of iron (II) to iron (III) and for HO attack to intermediates are evaluated by a mathematical model for pH range of 2.0-3.0 and initial Fe(III) concentrations range of 1.5 · 10(-5)-5.2 · 10(-4) mol L(-1).

A procedure for the assessment of the toxicity of intermediates and products formed during the accidental thermal decomposition of a chemical species.

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.

Kinetic investigation of Cu(II) ions photoreduction in presence of titanium dioxide and formic acid.

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 0.1g/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.

Effect of combined physico-chemical processes on the phytotoxicity of olive mill wastewaters.

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.