Marco Stoller

Photocatalytic Degradation of Organic Dyes under Visible Light onN-Doped Photocatalysts

This study was focused on the application of white and blue light emitting diodes (LEDs) as sources for the photocatalytic degradation of organic dyes in liquid phase with visible light. The photocatalytic activity of N-doped titanium dioxide, synthesized by direct hydrolysis of titanium tetraisopropoxide with ammonia, was evaluated by means of a batch photoreactor. The bandgap energy of titanium dioxide was moved in the visible range from 3.3 eV to 2.5 eV. The visible light responsive photocatalysts showed remarkably effective activity in decolorization process and in the removal of total organic carbon. Methylene blue was also used as a model dye to study the influence of several parameters such as catalyst weight and initial concentration. The effect of dye on the photocatalytic performance was verified with methyl orange (MO). The results demonstrated that the right selection of operating conditions allows to effectively degrade different dyes with the N-doped TiO2 photocatalysts irradiated with visible light emitted by LEDs.

Influence of the photoreactor configuration and of different light sources in the photocatalytic treatment of highly polluted wastewater

Abstract In this study, a highly polluted wastewater from tannery industry is treated by photocatalysis using home-made N-doped TiO2 as catalyst. The doping by nitrogen of titania particles leads to a reduction in the absorption threshold from 3.2 to 2.5 eV, permitting the absorption of radiation characterized by a wavelength in the visible spectrum.Experiments were carried out by using different light sources, in particular white LEDs, blue LEDs, and UV lamps, with the aim to evaluate the process efficiency at different operating conditions. The obtained performances were compared with those using an undoped commercial TiO2 catalyst (Degussa P25).Moreover, a simplified mathematical model capable to correlate the power input of the used light sources, the geometrical properties of the reactor, and emitting sources spectra with the performances of the photocatalytic reaction was developed.

Microalgal biomass production by using ultra- and nanofiltration membrane fractions of olive mill wastewater

Olive milling produces huge amounts of wastewater (OMWW) characterized by an extremely high organic load. Its polyphenols content is a hindrance to conventional biological treatment and to using it as growing medium for common microbial biomasses. The practice to dump it on soil is in conflict with the latest EU directives about waste management. OMWW can be effectively and efficiently treated by means of membrane technology to a fraction of the initial volume, but membrane processing concentrates still require treatment. Reversing the overall cost balance of membrane processing and subsequent treatment requires valorizing the concentrates through their reuse, as well as ensuring long-term service of the membrane system through effective wastewater pretreatment and sustainable, fouling-controlling, membrane operation conduite. Aim of this work is to reuse and valorize the ultra- and nanofiltration membrane concentrates as media for biomass production of microalgae and cyanobacteria. Scenedesmus dimorphus and Arthrospira platensis, usable as a food, feed, nutraceutical component or feedstock for biofuels, were selected for this investigation. Microalgal growth was experimentally determined and related to the composition of the concentrate-based media and to the irradiance distribution within the photobioreactor volume to decouple light limitation and medium chemical composition effects.

Successful Integration of Membrane Technologies in a Conventional Purification Process of Tannery Wastewater Streams

The aim of this work is to design and integrate an optimized batch membrane process in a conventional purification process used for the treatment of tannery wastewater. The integration was performed by using two spiral wound membrane modules in series, that is, nanofiltration and reverse osmosis, as substitutes to the biological reactor. The membrane process was designed in terms of sensible fouling issues reduction, which may be observed on the nanofiltration membrane if no optimization is performed. The entity of the fouling phenomena was estimated by pressure cycling measurements, determining both the critical and the threshold flux on the nanofiltration membrane. The obtained results were used to estimate the need of the overdesign of the membrane plant, as well as to define optimized operating conditions in order to handle fouling issues correctly for a long period of time. Finally, the developed membrane process was compared, from a technical and economic point of view, with the conventional biological process, widely offered as an external service near tannery production sites, and, here, proposed to be substituted by membrane technologies.

About Merging Threshold and Critical Flux Concepts into a Single One: The Boundary Flux

In the last decades much effort was put in understanding fouling phenomena on membranes. One successful approach to describe fouling issues on membranes is the critical flux theory. The possibility to measure a maximum value of the permeate flux for a given system without incurring in fouling issues was a breakthrough in membrane process design. However, in many cases critical fluxes were found to be very low, lower than the economic feasibility of the process. The knowledge of the critical flux value must be therefore considered as a good starting point for process design. In the last years, a new concept was introduced, the threshold flux, which defines the maximum permeate flow rate characterized by a low constant fouling rate regime. This concept, more than the critical flux, is a new practical tool for membrane process designers. In this paper a brief review on critical and threshold flux will be reported and analyzed. And since the concepts share many common aspects, merged into a new concept, called the boundary flux, the validation will occur by the analysis of previously collected data by the authors, during the treatment of olive vegetation wastewater by ultrafiltration and nanofiltration membranes.

Photocatalytic Treatment of Olive Mill Wastewater by Magnetic Core Titanium Dioxide Nanoparticles

The photocatalytic degradation of organic compounds of olive mill wastewater (OMWW) was investigated by using core-shell-shell Fe3O4/SiO2/TiO2 nanoparticles as catalyst. The preparation of nanoparticles was performed by coating onto magnetic nanoparticles a SiO2 layer, using Stober method and TiO2 layer, using sol-gel method. The photo catalyst was characterized by dynamic light scattering (DLS), zeta-potential measurement, UV-visible spectroscopy, energy-dispersive X-ray diffraction (EDX), scanning electron microscopy (SEM). Batch photo reactor, irradiated by an UV lamp of 45 W, was used to check the photocatalytic activity of the produced nanoparticles. The organic content of OMWW was evaluated by COD measurements. The photo degradation process was optimized by using 1.5 g/L core-shell-shell nanoparticles. The obtained results showed a high activity of synthesized nanoparticles for photocatalytic degradation of the OMWW organic compounds. Moreover, the recovery of the magnetic core photo catalyst by using a magnetic trap was proven.

Phenolic Content of Hypodaphnis Zenkeri and Its Antioxidant Effects against Fenton Reactions’ Mediated Oxidative Injuries on Liver Homogenate

Under oxidative stress conditions, endogenous antioxidant defenses are unable to completely inactivate the free radicals generated by an excessive production of reactive oxygen species (ROS). This state causes serious cell damage leading to a variety of human diseases. Natural antioxidants can protect cells against oxidative stress. Hypaodaphnis zenkeri (H. zenkiri) is a plant consumed as a spice in the Cameroonian diet, and its bark has been used in traditional medicine for the treatment of several diseases. The present study aims at investigating the antioxidant activity, which includes free radical scavenging and protective properties of an extract from H. Zenkiri against oxidative damage on a liver homogenate. The free radical assays determined the scavenging activities of 2,2-diphenyl-1-picrylhydrazyl (DPPH), hydroxyl (OH), nitrite oxide (NO) and 2,2-azinobis(3-ethylbenzthiazoline)-6-sulfonic acid (ABTS) radicals and the enzymes, whose protection was to be considered in the liver homogenate, including superoxide dismutase, catalase, and peroxidase. The antioxidative activities were studied using the ferric reducing antioxidant power (FRAP), reductive activity, and phosphomolybdenum antioxidant power (PAP) methods. In addition, the phenolic contents of the extracts were examined. The results showed that these extracts demonstrated significant scavenging properties and antioxidant activities, with the hydro-ethanolic extract of the bark of H. zenkeri (EEH) being the most potent. This extract had the highest total polyphenol (21.77 ± 0.05 mg caffeic acid (CAE)/g dried extract (DE)) and flavonoids (3.34 ± 0.13 mg quercetin (QE)/g dried extract) content. The same extract had significantly greater protective effects on enzyme activities compared to other extracts. The high performance liquied chromatography (HPLC) profile showed higher levels of caffeic acid, OH-tyrosol acid, and rutin in the leaves compared to the bark of H. zenkeri. In conclusion, the ethanolic and hydro-ethanolic extracts of the bark and leaves from H. zenkeri showed an antioxidant and protective potential against oxidative damage.

Comparison of critical and threshold fluxes on ultrafiltration and nanofiltration by treating 2-phase or 3-phase olive mill wastewater

Comparison of Critical and Threshold Fluxes on Ultrafiltration and Nanofiltration by Treating 2-Phase or 3Phase Olive Mill Wastewater Marco Stoller*, Javier Miguel Ochando Pulido , Angelo Chianese a a University of Rome “La Sapienza”, Department of Chemical Engineering, Via Eudossiana 18, 00184 Rome, Italy b University of Granada, Department of Chemical Engineering, Granada, Spain * marco.stoller@unitoma1.it

Production of nanoparticles of hydroxy apatite by using a rotating disk reactor

This paper deals with the feasibility to produce, in a continuous mode, nanoparticles of hydroxyapatite (HAP) by means of a rotating disk reactor. This device is capable to establish the required conditions of micromixing in correspondence of the reagents feeding point. The experimental work consists mainly of investigating the effect of the feed location of the reagents over the rotating disk surface. It was observed a great influence of the feed location on the particle size distribution of the produced HAP, only the best feed location allow the production of particles smaller than 100 nanometers. The obtained experimental results were interpreted on the light of a simplified simulation model. The model provided the map of the specific dispersed energy, thus allowing identifying the zones of the disk where micromixing may occur.

Photocatalytic removal of phenol by ferromagnetic N-TiO2/SiO2/Fe3O4 nanoparticles in presence of visible light irradiation

Photocatalytic Removal of Phenol by Ferromagnetic NTiO2/SiO2/Fe3O4 Nanoparticles in presence of Visible Light Irradiation Vincenzo Vaiano, Olga Sacco, Diana Sannino, Marco Stoller, Paolo Ciambelli, Angelo Chianese Department of Industrial Engineering, University of Salerno, Via Giovanni Paolo II 132, 84084 Fisciano (SA), Italy Department of Chemical Material Environmental Engineering, University of Rome “La Sapienza”, Via Eudossiana 18, 00184 Rome, Italy. vvaiano@unisa.it