Paola Avetta

Oxidative degradation of Remazol Turquoise Blue G 133 by soybean peroxidase

Reactive dyes are widely employed in textile industries and their removal from wastewaters is a relevant environmental problem. In addition to chemical and physical methods, several bioremediation approaches, involving intact micro-organisms or isolated enzymes, have been proposed to decolorize dye solutions. In this paper, we report the complete and fast decolourization of a Cu(II)-phthalocyanine based reactive dye (Remazol Turquoise Blue G 133) by means of the soybean peroxidase/H(2)O(2) system. The oxidative degradation of the dye in aqueous solution at 25°C was studied as function of pH, revealing a quantitative decolourization yield at acidic pH values with a maximum of activity at pH 3.3. The reaction products were identified and characterized by HPLC-diode array detector (DAD)-mass spectrometry (MS), ionic chromatography and EPR techniques. This analysis showed that the enzyme catalyses the breaking of the phthalocyanine ring producing sulfophthalimide as the main degradation product, and the release of stoichiometric amount of ammonium and Cu(II) ions.

Hernia-repair prosthetic devices functionalised with chitosan and ciprofloxacin coating: Controlled release and antibacterial activity

Polypropylene nets are widely used as hernioplasty prostheses. The reproduction of bacteria within the net fibers intersections can occur after the application of the prosthesis causing infections. For this reason, bacteria have to be removed in the very early stage of surgical implantation. Activation of the prosthesis surface was done by an innovative oxidizing plasma treatment (APP-DBD) working under atmospheric conditions in order to favor the deposition of an antibacterial coating of chitosan (biocompatible carbohydrate) and ciprofloxacin (broad spectrum antibiotic). Two different coating mixtures were realised and the antibacterial properties of such functionalised nets were investigated, together with their effectiveness. Physico-chemical characterisations of meshes were carried out before and after functionalisation by SEM-EDS and infrared spectroscopy. The release of both chitosan and ciprofloxacin, under controlled experimental conditions, was followed respectively by colorimetric determination (using UV-Visible spectroscopy) and chromatographic analysis (using HPLC). In vitro tests allow verifying antimicrobial activity (inoculation of specimens in a Staphylococcus aureus suspension).

Waste-derived bioorganic substances for light-induced generation of reactive oxygenated species.

Urban waste-derived bioorganic substances (UW-BOS) have shown promise as chemical auxiliaries for a number of technological applications in the chemical industry and in environmental remediation. In this study, the application of these substances in the photodegradation of organic pollutants is addressed. The experimental work is specifically focused on the photolysis mechanism promoted by AC8, a UW-BOS isolated from a 2:1 w/w mixture of food and green residues, composted for 110 days, using 4-chlorophenol (4-CP) as probe molecule. The production of (⋅)OH and the ¹O₂ is monitored by EPR spectroscopy. The correlation between radical species evolution and photodegradation of 4-CP is investigated. The effect of ¹O₂ and (⋅)OH scavengers on the 4-CP degradation process is also checked. The results suggest that the role of these species in the photodegradation of 4-CP depends on AC8 concentration. AC8 is thereby proven to be a photosensitizer for applications in environmental remediation. The results on AC8 further support the use of urban bio-waste as a versatile source of chemical auxiliaries of biological origin for use in diversified applications.

A new, sustainable LaFeO3 material prepared from biowaste-sourced soluble substances

For the first time, sustainable LaFeO3 powders were prepared from soluble bio-based substances (SBO) extracted from urban wastes. For the preparation of the perovskite-type powders, a modified solution combustion synthesis route was used, where SBO have the triple role of fuel, complexant and microstructural templates. A careful examination of the LaFeO3 powders, using complementary characterization techniques, evidenced their peculiar microstructural, morphological, textural and photocatalytic properties. Preliminary photodegradation tests of a phenol-based wastewater pollutant and photobleaching of a model dye were performed on the waste-derived and reference LaFeO3 powders; the obtained results encourage further studies on the application of these materials as heterogeneous catalysts for wastewater treatment. Moreover, a meaningful amount of entrapped matter was evidenced in the powders, which is responsible for most of their peculiar properties.

Assessing the phototransformation of diclofenac, clofibric acid and naproxen in surface waters: Model predictions and comparison with field data

Phototransformation is important for the fate in surface waters of the pharmaceuticals diclofenac (DIC) and naproxen (NAP) and for clofibric acid (CLO), a metabolite of the drug clofibrate. The goal of this paper is to provide an overview of the prevailing photochemical processes, which these compounds undergo in the different conditions found in freshwater environments. The modelled photochemical half-life times of NAP and DIC range from a few days to some months, depending on water conditions (chemistry and depth) and on the season. The model indicates that direct photolysis is the dominant degradation pathway of DIC and NAP in sunlit surface waters, and potentially toxic cyclic amides were detected as intermediates of DIC direct phototransformation. With modelled half-life times in the month-year range, CLO is predicted to be more photostable than DIC or NAP and to be degraded mainly by reaction with the •OH radical and with the triplet states of chromophoric dissolved organic matter (3CDOM*). The CLO intermediates arising from these processes and detected in this study (hydroquinone and 4-chlorophenol) are, respectively, a chronic toxicant to aquatic organisms and a possible carcinogen for humans. Hydroquinone is formed with only ∼5% yield upon CLO triplet-sensitised transformation, but it is highly toxic for algae and crustaceans. In contrast, the formation yield of 4-chlorophenol reaches ∼50% upon triplet sensitisation and ∼10% by ·OH reaction. The comparison of model predictions with field data from a previous study yielded a very good agreement in the case of DIC and, when using 4-carboxybenzophenone as proxy for triplet sensitisation by CDOM, a good agreement was found for CLO as well. In the case of NAP, the comparison with field data suggests that its direct photolysis quantum yield approaches or even falls below the lower range of literature values.

Synthesis, characterization and environmental application of silica grafted photoactive substances isolated from urban biowaste

A waste-derived photoactive substance sourced from the green fraction of urban refuses (CVT230) was immobilized on different types of silica support, one amorphous and the other two with controlled porosity (HMS and SBA). In this fashion, three hybrid systems were obtained, which contained CVT230 as an insoluble photoactive component. They were tested in the photodegradation of 4-methylphenol in aqueous solution irradiated by simulated solar light and results showed that they are able to promote the total photodegradation of the pollutant. The materials, both before and after irradiation, were characterized by high-resolution transmission electron microscopy (TEM), small angle X-ray scattering (SAXS), N2 gas-volumetric adsorption, infrared spectroscopy (FTIR) and thermogravimetric analysis (TGA). The SBA silica hybrid system showed the best performance in terms of stability and reusability, after multiple irradiation cycles. This behaviour can be correlated to the silica morphology and texture, being capable to better allocate and stabilize the CVT230 molecules.

CHAPTER 4:Food Wastes Conversion to Products for Use in Chemical and Environmental Technology, Material Science and Agriculture

Food wastes are shown as a cost-effective source of added-value products for a wide number of uses. For soluble substances isolated from municipal biowastes, the present chapter reviews work performed in the last 7 years investigating the chemical nature, the physical-chemical properties, and the performance in chemical and environmental technologies, in material chemistry and in agriculture. Very recent unpublished data are also reported to show that ongoing research is a worthwhile effort to realise the full potential of the above refuse-derived biobased products. The available data allow a viable situation to be envisioned where urban waste-treatment plant are turned into biorefinery for the production of energy, chemicals and consumer products with friendly environmental impact. The perspectives for this scenario to become real are discussed.

Selective porous gates made from colloidal silica nanoparticles

Summary Highly selective porous films were prepared by spin-coating deposition of colloidal silica nanoparticles on an appropriate macroporous substrate. Silica nanoparticles very homogenous in size were obtained by sol–gel reaction of a metal oxide silica precursor, tetraethyl orthosilicate (TEOS), and using polystyrene-block-poly(ethylene oxide) (PS-b-PEO) copolymers as soft-templating agents. Nanoparticles synthesis was carried out in a mixed solvent system. After spin-coating onto a macroporous silicon nitride support, silica nanoparticles were calcined under controlled conditions. An organized nanoporous layer was obtained characterized by a depth filter-like structure with internal porosity due to interparticle voids. Permeability and size-selectivity were studied by monitoring the diffusion of probe molecules under standard conditions and under the application of an external stimulus (i.e., electric field). Promising results were obtained, suggesting possible applications of these nanoporous films as selective gates for controlled transport of chemical species in solution.

Soluble Bio-based Substances Obtained from Urban Wastes: Isolation and Characterization

The organic fraction of urban wastes can be considered a cost effective source of added value products for a wide number of uses. The present chapter describes different possible strategies for the treatment of organic wastes, used at the present time in many waste treatment plants. Subsequently the chapter deals with the isolation process of soluble bio-based substances (SBO) from urban biowastes at both laboratory and pilot plant scale. A detailed description of SBO composition and physical-chemical characterization is given.

Ecofriendly in-line process monitoring: a case study. Anthracene photodegradation in the presence of refuse-derived soluble bio-organics.

Photodegradation of anthracene has been studied in aqueous solutions containing soluble bio-organic substances isolated from urban refuse. To perform a preliminary rapid feasibility study of this process while reducing the amount of analytical effort and reagents, an experimental set-up was developed comprising a Teflon coil surrounding a UV-lamp and coupled with an in-line spectrofluorimeter. In this fashion only few millilitres of solution are needed to study the degradation process. Furthermore, the in-line spectroscopic approach enables monitoring of the process without consumption of reagents. Additional studies by liquid chromatography and use of toxicity tests clearly indicated that the apparent inhibition effect of bio-organic compounds on anthracene degradation is not relevant. The results imply that urban refuse may be used as an auxiliary in the recovery of polycyclic aromatic hydrocarbons from contaminated soil by washing, without deleterious effects on the photodegradation of anthracene and other aromatic pollutants.