Advanced oxidation processes for food industry wastewater valorization and treatment

2015 - 2016The research of new eco-friendly technologies that enable the production of energy is nowadays one of the topics of greatest interest to the scientific community. The population has chosen to break free from the use of fossil fuels, and this leads to the study and development of processes for the production of clean energy starting from biomass. However, at the same time, the concern of the industry is also the disposal and treatment of wastewater. Starting from these considerations, it is advisable to develop processes that, under mild conditions, allow to obtain interesting hydrogen or methane yields. This objective could be achieved through the use advanced oxidation processes (AOPs), such as heterogeneous photocatalysis, photo-Fenton like reaction and photoelectrocatalysis. So, an interesting approach is to explore, in parallel to wastewater treatment, the possibility to produce also an energy source such as hydrogen and/or methane from the degradation of organic substance present in wastewater by AOPs. Considering the characteristic of food industries wastewaters, it is interesting to evaluate the performances of advanced oxidation processes for their treatment aimed to the valorization, through the conversion of specific substances (sugars), in order to obtain compounds with high energetic value, but also for removing substances hardly biodegradable (such as food dyes) that could be present in these industry wastewaters. In this PhD thesis it has been studied the performances of the photocatalytic process for the hydrogen production from food industries wastewaters. In particular, starting from synthetic solution containing glucose, it was evaluated the effect of the presence of noble metals on the semiconductor surface and the effect of the photoactive support (TiO2). Subsequently, providing for the application of heterogeneous photocatalysis to industrial level, the study has been directed to the formulation of a noble metal free photocatalyst with good performances in the production of hydrogen and in the degradation of the sugars present in the solutions. The final formulation was represented by LaFeO3 (a perovskite with semiconducting properties) prepared by combustion flame method. To improve the performances under visible light, LaFeO3 was modified with Ru (Ru-LaFeO3), whose cost is much lower than those of Pd, Pt or Au. Always perspective of the application of the process to industrial level, it was developed a structured photocatalyst for solving the problems related to the photocatalyst separation after the treatment. In particular it was studied the efficiency of magnetic Fe2O3 as support for Ru-LaFeO3. It was also investigated the photoelectrocatalytic process for the hydrogen production, considering the general aspects of the process, the advantages and in particular the attention has been focused on the electrodeposition process for the synthesis of Fe2O3 based photoanodes. Finally, the aim has been the application of the photocatalytic process on a real wastewater coming from the washing process of the fruit (especially cherries). It was not underestimated the presence of food dyes in these types of wastewater. For this reason it was evaluated the efficiency of photo-Fenton process in the removal of several food dyes (such as Red Allura and Tartrazine) using LaFeO3 deposited on corundum monoliths. In addition, it has been evaluated the possibility to couple the photocatalytic process (used for the valorization of the wastewater through the production of hydrogen) to the optimized photo-Fenton system to completely remove the not-biodegradable substances still present in the wastewaters recovered after the photocatalytic treatment using Ru-LaFeO3 supported on magnetic Fe2O3 particles. [edited by author]XV n.

BHPR research: qualitative1. Complex reasoning determines patients' perception of outcome following foot surgery in rheumatoid arhtritis

Background: Foot surgery is common in patients with RA but research into surgical outcomes is limited and conceptually flawed as current outcome measures lack face validity: to date no one has asked patients what is important to them. This study aimed to determine which factors are important to patients when evaluating the success of foot surgery in RA Methods: Semi structured interviews of RA patients who had undergone foot surgery were conducted and transcribed verbatim. Thematic analysis of interviews was conducted to explore issues that were important to patients. Results: 11 RA patients (9 ♂, mean age 59, dis dur = 22yrs, mean of 3 yrs post op) with mixed experiences of foot surgery were interviewed. Patients interpreted outcome in respect to a multitude of factors, frequently positive change in one aspect contrasted with negative opinions about another. Overall, four major themes emerged. Function: Functional ability & participation in valued activities were very important to patients. Walking ability was a key concern but patients interpreted levels of activity in light of other aspects of their disease, reflecting on change in functional ability more than overall level. Positive feelings of improved mobility were often moderated by negative self perception ("I mean, I still walk like a waddling duck”). Appearance: Appearance was important to almost all patients but perhaps the most complex theme of all. Physical appearance, foot shape, and footwear were closely interlinked, yet patients saw these as distinct separate concepts. Patients need to legitimize these feelings was clear and they frequently entered into a defensive repertoire ("it's not cosmetic surgery; it's something that's more important than that, you know?”). Clinician opinion: Surgeons' post operative evaluation of the procedure was very influential. The impact of this appraisal continued to affect patients' lasting impression irrespective of how the outcome compared to their initial goals ("when he'd done it ... he said that hasn't worked as good as he'd wanted to ... but the pain has gone”). Pain: Whilst pain was important to almost all patients, it appeared to be less important than the other themes. Pain was predominately raised when it influenced other themes, such as function; many still felt the need to legitimize their foot pain in order for health professionals to take it seriously ("in the end I went to my GP because it had happened a few times and I went to an orthopaedic surgeon who was quite dismissive of it, it was like what are you complaining about”). Conclusions: Patients interpret the outcome of foot surgery using a multitude of interrelated factors, particularly functional ability, appearance and surgeons' appraisal of the procedure. While pain was often noted, this appeared less important than other factors in the overall outcome of the surgery. Future research into foot surgery should incorporate the complexity of how patients determine their outcome Disclosure statement: All authors have declared no conflicts of interes

Facile method to immobilize ZnO particles on glass spheres for the photocatalytic treatment of tannery wastewater

In order to apply the photocatalytic processes on a real scale for the treatment of industrial wastewaters, the use of slurry reactors employing suspended photocatalysts is not suitable due to the need for an uncomfortable and expensive separation phase of photocatalyst. To overcome this disadvantage, the photocatalyst particles must be immobilized on a transparent support: our work proposes, for this reason, a simple and cost effective method for the deposition of ZnO photocatalyst on glass spheres in order to formulate a structured photocatalyst effective in the treatment of aqueous solutions containing various organic dyes, commonly used in the tannery industries and in the treatment of a real wastewater at high COD content (11 g/L) coming from the refining unit of the tanning process. In particular, ZnO was immobilized on glass spheres (ZnO/GS) with a simple dip coating method, starting from zinc acetate aqueous solution, without using complexing agent and strong basic compounds. The optimization of ZnO amount on glass spheres was evaluated employing Acid Blue 7 dye, as model pollutant. In particular, it was found that best performances in terms of discoloration and mineralization of the target dye were obtained using the photocatalyst with a ZnO loading equal to 0.19 wt% (ZnO_ac1), prepared through only one dip-coating step. Moreover, the ZnO_ac1 photocatalyst can be easily separated from the reaction mixture, maintaining excellent photocatalytic activity and durability even after several reuse cycles. Finally, ZnO_ac1 showed a high photocatalytic activity in the treatment of the real wastewater, obtaining a COD removal equal to 70% after 180 min of UV light irradiation

Synthesis and Application of Innovative and Environmentally Friendly Photocatalysts: A Review

Modern society faces two major challenges: removing pollutants from water and producing energy from renewable sources. To do this, science proposes innovative, low-cost, and environmentally friendly methods. The heterogeneous photocatalysis process fits perfectly in this scenario. In fact, with photocatalysis, it is possible both to mineralize contaminants that are not easily biodegradable and to produce hydrogen from the water splitting reaction or from the conversion of organic substances present in water. However, the main challenge in the field of heterogeneous photocatalysis is to produce low-cost and efficient photocatalysts active under visible light or sunlight. The objective of this review is to compare the new proposals for the synthesis of innovative photocatalysts that reflect the requirements of green chemistry, applied both in the removal of organic contaminants and in hydrogen production. From this comparison, we want to bring out the strengths and weaknesses of the proposals in the literature, but above all, new ideas to improve the efficiency of heterogeneous photocatalysis guaranteeing the principles of environmental and economic sustainability

Enhanced removal of water pollutants by dielectric barrier discharge non-thermal plasma reactor

In this work it was studied the removal efficiency of several water pollutants (methylene blue, phenol, paracetamol, caffeine and ceftriaxone) by dielectric barrier discharge (DBD) non-thermal plasma (NTP) reactor. The results evidenced that using oxygen as process gas in the DBD reactor and 20 kV of applied voltage, the complete degradation and mineralization of methylene blue and ceftriaxone was achieved after only 5 min of treatment time, while 15 min were required for the complete degradation and mineralization, of phenol and paracetamol, and 25 min for the caffeine. In addition, kinetic evaluations evidenced that, for each pollutant, the degradation and mineralization occurred at the same rates, underling that the pollutants are selectively converted to carbon dioxide. For this reason, the results obtained in the present work were significantly better than those reported in the current literature about the use of non-thermal technology in the removal of organic pollutants from aqueous solutions

Enhanced photocatalytic hydrogen production from glucose on Rh-doped LaFeO3

The aim of this work was to evaluate effect of different amount of rhodium used for the doping of LaFeO3prepared through solution combustion synthesis in the photocatalytic hydrogen production from glucose solution. The process efficiency was evaluated in terms of both glucose degradation and hydrogen production during the irradiation time. Characterization results showed the formation of orthorhombic perovskite type structure and the absence of rhodium oxide crystallites up to Rh loading of 1.16 mol %. Photocatalytic results showed that the highest value of H2production (1835 μmol/L) was achieved on 0.70%Rh photocatalyst after 4 h irradiation time. The substitutional doping generated by the replacement of Fe4+with Rh4+promotes the separation of charge carriers efficiently, and consequently enhancing the photocatalytic activity

Photocatalytic removal of tartrazine dye from aqueous samples on LaFeO3/ZnO Photocatalysts

Dyes represent a very important group of water pollutants that appear in the effluents of different industries. These contaminants, by preventing the penetration of light, can have negative effects on the aquatic environment, causing problems to the ecosystem, and possibly being carcinogenic and genotoxic on human health. In particular tartrazine is a commonly not-biodegradable dye used in food industries and it, in high amount, could cause allergic and/or intolerance reactions. In the past decade only few effective photocatalysts for organic dye degradation under visible-light irradiation has been reported. Effective photocatalysts, such as ZnO, however, exhibit photodegradation activity only under ultraviolet irradiation. The coupling of ZnO, having a band gap of 3.2 eV, with low band gap photocatalysts could induce the removal of the dyes under visible light. So, in this work, LaFeO3, which has a band gap of about 2.1 eV, was supported on ZnO surface. The aim of this work was to evaluate the efficiency of LaFeO3/ZnO on the degradation of tartrazine under UV but also under visible light. Furthermore it was evaluated the optimal composition in terms of LaFeO3 amount on ZnO

Visible light active Fe-doped TiO2for the oxidation of arsenite to arsenate in drinking water

The aim of this work was to study photocatalysts based on Titania doped with Fe, active in the presence of visible light and effective in the oxidation of As(III) to As(V). Fe-doped TiO2photocatatysts were prepared using sol-gel method and characterized by different techniques, such as XRD, UV-Vis DRS and Raman spectroscopy. Photocatalytic experiments were carried out using a cylindrical photoreactor irradiated with a strip of visible- LEDs (nominal power: 10W) with emission in the range 400 - 600 nm. Aqueous samples containing 6 mg L-1of As(III) were used in photocatalytic experiments. Chemical-physical characterization results evidenced that the doping of TiO2with Fe induced a decrease of band gap value from 3.2 eV to 2.9 eV, thus making the photocatalyst active under visible light. Consistently with the characterization results, the semiconductor Fedoped TiO2exhibited good photoactivity in the visible light driven tests: the complete oxidation of As(III) to As(V) took place after only 30 min of irradiation in distilled water and after 60 min in drinking water

Non-Thermal Plasma as a Biomass Pretreatment in Biorefining Processes

Climatic changes and the growing population call for innovative solutions that are able to produce biochemicals by adopting environmentally sustainable procedures. The biorefinery concept meets this requirement. However, one of the main drawbacks of biorefineries is represented by the feedstocks’ pretreatment. Lately, scientific research has focused on non-thermal plasma, which is an innovative and sustainable pretreatment that is able to obtain a high sugar concentration. In the present review, literature related to the use of non-thermal plasma for the production of fermentable sugar have been collected. In particular, its sugar extraction, time, and energy consumption have been compared with those of traditional biomass pretreatments. As reported, on one hand, this emerging technology is characterized by low costs and no waste production; on the other hand, the reactor’s configuration must be optimized to reduce time and energy demand