Elisabetta Petrucci

Treatment of industrial landfill leachate by means of evaporation and reverse osmosis.

In this paper a process for the treatment of landfill leachate involving evaporation and reverse osmosis was proposed. Experimental tests were performed on an industrial landfill leachate. The leachate was subjected to evaporation so as to obtain a distillate containing a small amount of organic material and a substantial amount of inorganic substances (consisting primarily of metals and ammonium salts). The distillate of the evaporation treatment was then subjected to reverse osmosis. The reverie osmosis tests were performed using two different membranes: the AD membrane (thin two-ply film of polyamide) and the SC membrane (thin three-ply film of polyamide). Tests carried out at different values of pH showed a reduction of organic content of about 88% when AD membranes were used and about 80% with SC membranes independently of pH. As regards ammonium, comparable reductions of over 97% were registered for both types of membrane in the optimal conditions of pH = 6.4 (97.1% for AD membranes and 97.7% for SC).

Hexavalent chromium reduction in contaminated soil: A comparison between ferrous sulphate and nanoscale zero-valent iron.

Iron sulphate (FeSO4) and colloidal nano zero-valent iron (nZVI) as reducing agents were compared, with the aim of assessing their effectiveness in hexavalent chromium [Cr(VI)] removal from a contaminated industrial soil. Experiments were performed on soil samples collected from an industrial site where a nickel contamination, caused by a long-term productive activity, was also verified. The influence of reducing agents amount with respect to chromium content and the effectiveness of deoxygenation of the slurry were discussed. The soil was fully characterized before and after each test, and sequential extractions were performed to assess chemico-physical modifications and evaluate metals mobility induced by washing. Results show that both the reducing agents successfully lowered the amount of Cr(VI) in the soil below the threshold allowed by Italian Environmental Regulation for industrial reuse. Cr(VI) reduction by colloidal nZVI proved to be faster and more effective: the civil reuse of soil [Cr(VI)<2mg/kg] was only achieved using colloidal nZVI within 60min adopting a nZVI/Cr(VI) molar ratio of 30. The reducing treatment resulted in an increase in the amount of chromium in the oxide-hydroxide fraction, thus confirming a mechanism of chromium-iron hydroxides precipitation. In addition, a decrease of nickel (Ni) and lead (Pb) content in soil was also observed when acidic conditions were established.

Influence of Soil Organic Matter on Copper Extraction from Contaminated Soil

Column experiments of copper extraction from four contaminated soils characterized by a content of Soil Organic Matter (SOM) ranging from 1% to 25% are presented and discussed. The extraction was performed by flushing the soil with an aqueous solution of a sodium salt of ethylene diamminotetraacetic acid (EDTA). Preliminary tests were performed on a soil containing 25% of organic matter, to investigate the influence of pH, concentration and volumes of EDTA on its chelant action and on the dissolution of SOM. Having selected the optimal conditions for the extraction process, a further series of tests was conducted on the four soils to evaluate the influence of organic content on copper extraction yields. EDTA solutions at 0.01 M, 0.05 M, 0.1 and 0.2 M were injected at 0.33 ml/s; copper and organic matter extraction yield were determined. At a pH of 5, 15 pore volume (PV) of a solution containing 0.05M EDTA, extracted about 99% of copper contained by the soil with the higher organic matter content. Under the same conditions, and for soil with > 6% SOM, extraction yields over 80% were achieved, while at lower organic content, copper extraction was dramatically reduced. This was attributed to the formation of highly stable copper-humate complexes and to their increasingly dissolution that occurred in the soils with higher organic matter level. Experimental tests performed at different contamination levels (1200 mg/kg, 2400 mg/kg) showed that EDTA extraction effectiveness also depended upon initial soil Cu concentration.

Production and characterization of adsorbent materials from sewage sludge by pyrolysis

The conventional sludge disposal options include landfill, application to farmland and forestry and incineration. However, since in the last decade sewage sludge and industrial sludge are being generated in increasing amounts due to the rapid urbanization and industrialization, a growing interest has been devoted in developing cost effective and renewable disposal alternatives. Among them, the manufacture of adsorbents to remove metals from water and wastewater appears to be promising, also considering the high cost of commercial carbons. In this paper copper, zinc and cadmium removal from wastewater using adsorbents produced from pyrolysis of sewage sludge is investigated in comparison with commercial adsorbents. The kinetic of the pyrolytic process was studied, and the adsorbents produced under different pyrolysis conditions were characterized. The adsorption capacity of the pyrolyzed material were estimated in batch tests performed in an activated sludge reactor. Results show that the adsorbent materials obtained by sewage sludge pyrolysis increased organic matter removal in activated sludge systems, and limited the inhibition effects of heavy metals. In addition, a chemical activation of the sludge before the pyrolysis resulted in an increase of the adsorption capacity of the obtained adsorbent.

A steady-state model for the evaluation of disk rotational speed influence on RBC kinetic: model presentation.

The physical and biological mechanisms of attached-biomass growth were analyzed and a steady-state model was proposed to determine the soluble carbonaceous removal in an RBC unit for different organic loading rates in the reactor. The objective of the model was the prediction of the organic loading rate corresponding to the maximum removal capacity in the system. A system of equations was solved where the influent soluble carbonaceous substrate concentration was the main variable. Monods rate law was used for the growth of microorganism: the soluble carbonaceous substrate was the limiting substrate. Endogenous decay was neglected. The influence of disk rotational speed on the RBC removal capacity was investigated, the disk rotational speed being a parameter acting on oxygen transfer in the biofilm. The criteria for the evaluation of the kinetic parameter in the model were proposed.

Experimental study of the remediation of atrazine contaminated soils through soil extraction and subsequent peroxidation

This paper presents a feasibility study in the field of the remediation of soils contaminated with atrazine. Experimental tests were performed on an artificially contaminated synthetic soil. Atrazine was removed from the soil by flushing with an aqueous solution at 5 vol.% of ethanol. Experimental tests of evaporation and Fentons oxidation on the extracted solution were then performed in order to transform atrazine into its oxidation products. Tests were performed in the presence of a peroxide excess the ratio between Fe(2+) and H(2)O(2) was 1:10. Peroxide was first added in order to reduce the consumption of hydroxyl radicals by their reaction with the excess of Fe(2+). The degradation mechanism of atrazine during oxidation with Fentons reagent in the presence of ethanol was investigated. Results showed that due to the non selective nature of Fentons reagent a high consumption of reagent was needed to achieve a significant atrazine oxidation from solutions at 4.5 vol.% of ethanol. While at a Fe(2+) concentration of 3mM atrazine practically disappeared from pure aqueous solutions within 2h, a degradation yield of only 28.1% was observed in the presence of ethanol even when Fe(2+) concentration was 15 mM.

Influence of surface roughening of Titanium substrate in the electrochemical activity of Manganese oxide thin film electrode in anodic oxidation of dye-containing solutions

Previous work has verified the possibility to obtain mechanically, chemically and electrically stable electrodes based on manganese oxide (MnOx) thin films for anodic oxidation of solutions containing the Reactive Violet 5 (RV5) azo dye. To improve the morphological and electrochemical properties of these materials, in this study, a surface modification of the titanium support has been presented. Chemically modified surfaces were obtained by etching titanium substrates in hydrocloridric acid at high temperature. Untreated and modified electrodes were coated sequentially with a RuOx film, as interlayer and a MnOx film obtained by adopting three different techniques including anodic electrodeposition, cathodic electrodeposition and thermal decomposition. Surface morphology, topography and composition of all the electrodes were investigated by profilometric and TOF–SIMS analysis. The electrochemical activity of anodes were first determined by cyclic voltammetry, and then in the treatment of solutions containing the RV5 azo dye, as model pollutant, in undivided cell under galvanostatic conditions. The results show that the surface microstructure modifies substantially the electrochemical response of selected electrodes.

Production and characterization of manganese oxide-based electrodes for anodic oxidation of organic compounds

Production and Characterization of Manganese OxideBased Electrodes for Anodic Oxidation of Organic Compounds Giovanni Sotgiu, Matteo Foderà, Francesco Marra, Elisabetta Petrucci a Dipartimento di Ingegneria, Università di Roma Tre, Via Vito Volterra, 62 00146, Roma b Dipartimento di Ingegneria Chimica Materiali Ambiente, Università degli Studi di Roma “La Sapienza”,Via Eudossiana, 18 00184, Roma *elisabetta.petrucci@uniroma1.it

Biocides electrogeneration for a zero-reagent on board disinfection of ballast water

The feasibility of a quick electrochemical process for on board zero-reagent treatment of ballast water by anodic and cathodic production of oxidants was proposed. The process has been tested in the inactivation of the marine dinoflagellates Alexandrium minutum and A. taylori, both responsible for algal blooms and toxin-producing, and against the marine bacterium Pseudomonas aeruginosa, a Gram-negative pathogenic micro-organism. A complete inactivation of both dinoflagellates was quickly achieved with electro-generated active chlorine, while higher resistance to oxidising agents was verified for P. aeruginosa. A combined sequential treatment involving anodic oxidation followed by extended exposure time in the absence of current, and a final cathodic treatment was proposed. The cathodically electro-generated hydrogen peroxide contributed to the reduction of treatment time and the removal of residual species.

Sequential extraction analysis provides decision-making tools for the use of contaminated sediments

To construct a new tourist harbour in Marina di Ragusa (Sicily), the dredging of 300,000 m3 of marine sediment is required. To evaluate potential disposal options, a detailed physico-chemical characterisation of this material is needed. A very cost-effective solution is represented by the re-use of the dredged material for beach nourishment. To this aim, compliance with environmental standards and a strong homogeneity between the receiving beach and the source sediments must be proved. Analytical determinations for the main parameters show an arsenic content exceeding the Italian quality standard (12 mg·kg−1). In order to evaluate arsenic mobility and availability, and therefore the actual release into the environment, a three-step sequential extraction procedure was applied to a limited number of samples. The results obtained seem to exclude the risk, showing that arsenic is almost totally bound to the resistant fraction and thus does not represent an impediment to the beneficial re-use of sediment.