Roberto Lavecchia

Study of the reducibility of copper in CuOZnO catalysts by temperature-programmed reduction

Temperature-programmed reduction (TPR) has been used in this work to study the reduction of copper in CuOZnO catalysts with different CuZn atomic ratios using H2 as reducing agent. In all catalysts, CuO was completely reduced to metal. The influence exerted by ZnO on the reduction of copper was evaluated for a wide range of composition and a scale of reducibility was established. ZnO affects the hydrogen reduction of copper, CuOZnO samples showing a different behaviour with respect to the pure copper oxide. The reduction is always promoted and, in particular, catalysts with lower copper loading (Cu:Zn < 30:70 as atomic ratio) showed the highest reactivity and are characterised by the presence of two reducible copper species. Results of a kinetic analysis based on the TPR profiles confirmed the role played by ZnO as promoter of the copper oxide reduction. The effect of the preparation method on the catalyst reducibility was also verified and discussed in a specific case. H2CO2H2 redox cycles were carried out on some representative samples which, after the first reduction in H2, were reoxidised with CO2 and then reduced again by H2. These experiments revealed that a small percent of metal copper formed in the CuOZnO catalysts is oxidised by CO2 regardless of the catalyst composition, whereas metal copper formed by reduction of pure CuO is not reoxidised at a detectable level. Furthermore, it was evidenced that the small fraction of copper reoxidised by CO2 was extremely reactive, being reduced at temperatures much lower than those found for the reduction of the as-prepared catalysts. Both the TPR investigation and the H2CO2H2 redox cycles clearly assessed the presence of a synergistic effect arising by the contact of CuO with the ZnO particles.

Recovery of natural antioxidants from spent coffee grounds.

Spent coffee grounds (SCG) were extracted with an environmentally friendly procedure and analyzed to evaluate the recovery of relevant natural antioxidants for use as nutritional supplements, foods, or cosmetic additives. SCG were characterized in terms of their total phenolic content by the Folin-Ciocalteu procedure and antioxidant activity by the DPPH scavenging assay. Flavonoid content was also determined by a colorimetric assay. The total phenolic content was strongly correlated with the DPPH scavenging activity, suggesting that phenolic compounds are mainly responsible for the antioxidant activity of SCG. An UHPLC-PDA-TOF-MS system was used to separate, identify, and quantify phenolic and nonphenolic compounds in the SCG extracts. Important amounts of chlorogenic acids (CGA) and related compounds as well as caffeine (CAF) evidenced the high potential of SCG, a waste material that is widely available in the world, as a source of natural phenolic antioxidants.

Enzyme-assisted extraction of lycopene from tomato processing waste

A central composite design was used to optimize the enzyme-assisted extraction of lycopene from the peel fraction of tomato processing waste. Tomato skins were pretreated by a food-grade enzyme preparation with pectinolytic and cellulolytic activities and then subjected to hexane extraction. The factors investigated included extraction temperature (10-50 °C), pretreatment time (0.5-6.5 h), extraction time (0.5-4.5 h), enzyme solution-to-solid ratio (10-50 dm³/kg) and enzyme load (0-0.2 kg/kg). Overall, an 8- to 18-fold increase in lycopene recovery was observed compared to the untreated plant material. From a response surface analysis of the data, a second-degree polynomial equation was developed which provided the following optimal extraction conditions: T=30 °C, extraction time=3.18 h and enzyme load=0.16 kg/kg. The obtained results strongly support the idea of using cell-wall degrading enzymes as an effective means for recovering lycopene from tomato waste.

Response surface methodology (RSM) analysis of photodegradation of sulfonated diazo dye Reactive Green 19 by UV/H2O2 process.

A central composite design was used to investigate the influence of the main process parameters on the degradation of Reactive Green 19 (RG19) azo dye by the UV/H2O2 treatment. The combined use of UV radiation and H2O2 resulted in the decolorization and dearomatization of the dye. They were monitored by measuring the spectral changes occurring, respectively, in the visible and UV regions of the dye spectrum. RG19 degradation was found to be practically complete over a time of 15-60 min, for decolorization, and 50-200 min, for dearomatization, depending on the applied conditions. Both processes followed apparent first-order kinetics. The associated rate constants were used as the response variables and their dependence on initial dye and H2O2 concentrations, pH and reaction time was investigated by the response surface methodology. Response surface plots for the decolorization and dearomatization processes were very similar in shape. For both processes, the initial dye and H2O2 concentrations were the key factors controlling dye degradation.

Evaluation of UV/H2O2 advanced oxidation process (AOP) for the degradation of diazo dye Reactive Green 19 in aqueous solution

ABSTRACTThe azo dye Reactive Green 19 (RG19) is extensively used for dyeing textiles due to its cost effectiveness and excellent fastness properties. Treatment of wastewaters containing this dye by conventional methods is often inadequate because of its resistance to biological and chemical degradation. In this study, the suitability of an advanced oxidation process based on the use of UV radiation and hydrogen peroxide to degrade RG19 was investigated. Analysis of degradation data showed that the decolorization process followed pseudo-first-order kinetics. The existence of an optimum pH and H2O2 dose was also observed. Under the best conditions, complete decolorization of the dye solution was achieved in about 20 min. Total organic carbon (TOC) measurements showed that mineralization was slower than decolorization, but over 63% of TOC was removed in 90 min. Overall, the results obtained indicate that the UV/H2O2 treatment can be an effective method for the removal of RG19 from textile effluents.

Thermal treatment for recovery of manganese and zinc from zinc-carbon and alkaline spent batteries

The aim of this paper is the recovery of manganese and zinc from a mixture of zinc-carbon and alkaline spent batteries, containing 40.9% of Mn and 30.1% of Zn, after preliminary physical treatment followed by removal of mercury. Separation of the metals has been carried out on the basis of their different boiling points, being 357°C and 906°C the boiling point of mercury and zinc and 1564°C the melting point of Mn(2)O(3). Characterization by chemical analysis, TGA/DTA and X-ray powder diffraction of the mixture has been carried out after comminution sieving and shaking table treatment to remove the anodic collectors and most of chlorides contained in the mixture. The mixture has been roasted at various temperatures and resident times in a flow of air to set the best conditions to remove mercury that were 400°C and 10 min. After that, the flow of air has been turned into a nitrogen one (inert atmosphere) and the temperatures raised, thus permitting the zinc oxide to be reduced to metallic zinc by the carbon present in the original mixture and recovered after volatilization as a high grade concentrate, while manganese was left in the residue. The recovery and the grade of the two metals, at 1000°C and 30 min residence time, were 84% and 100% for zinc and 85% and 63% for manganese, respectively. The recovery of zinc increased to 99% with a grade of 97% at 1200°C and 30 min residence time, while the recovery and grade of manganese were 86% and 87%, respectively, at that temperature. Moreover, the chlorinated compounds that could form by the combustion of the plastics contained in the spent batteries, are destroyed at the temperature required by the process.

Fluoride Removal from Water by Adsorption on a High Alumina Content Bauxite

Drinking water contamination by fluoride is recognized as a major public health problem in many parts of the world. In fact, although fluoride is an essential trace element for animals and humans, excessive fluoride intake may cause adverse health effects. In this study we investigated the potential of a natural, high alumina content, bauxite for the removal of fluoride from contaminated water. Both batch and continuous experiments were performed. In continuous-flow column experiments, the effects of inlet fluoride concentration (5–50 mg L

Removal of Lead from Aqueous Solutions by Spent Tea Leaves

Spent tea leaves from black and green tea were assessed for their potential to remove lead (II) from contaminated waters. Batch adsorption experiments made at temperatures between 5 and 40 °C and lead ion concentrations between 0.01 and 2 g/L showed that removal efficiencies higher than 95% can easily be achieved. The results were only marginally affected by the type of tea waste. At low lead loading the adsorption equilibrium was well described by the Langmuir equation, with a maximum adsorption capacity of 85–100 mg/g. A comparison with other adsorbents provided the following order for lead removal efficiency: black tea, coffee grounds > green tea > Fuller’s earth > activated carbon.

Thermal denaturation of erythrocyte carbonic anhydrase

An experimental study on the thermal behaviour of erythrocyte carbonic anhydrase was carried out with the main aim to estimate the thermodynamic parameters that control the stability of the enzyme. The effects of thermal denaturation on the catalytic properties of the enzyme were also investigated. Below 60°C the enzyme was found to be very stable, whereas between 60 and 65°C a drastic decrease in the biological activity was observed. From the obtained results some considerations were made about the stabilization of the active form of the protein.

Enhanced lipid recovery from Nannochloropsis microalgae by treatment with optimized cell wall degrading enzyme mixtures

A statistical mixture design approach was used to investigate the effects of cell wall degrading enzymes on the recovery of lipids from Nannochloropsis sp. A preliminary screening of potentially suitable enzyme preparations, including lysozyme, cellulase and different types of hemicellulases, was carried out. The most effective preparations were then taken as basic components for the formulation of enzyme mixtures. Optimized ternary mixtures consisting of cellulase and two hemicellulases were obtained which allowed the recovery of up to 37.2g of lipids per 100g of dry biomass. SEM and TEM images of the enzymatically treated microalga revealed extensive cell damage, with degradation of the cell wall and release of intracellular material. Overall, the results obtained demonstrate that the mixture design method can be used to prepare cell wall degrading enzyme cocktails that can significantly improve the recovery of lipids or other valuable components from microalgae.