1,721,148 research outputs found
Electrochemical treatment as a pre-oxidative step for algae removal using Chlorella vulgaris as a model organism and BDD anodes
No full textAn experimental work is presented in this paper on the inactivation of algae through electrochemical treatment. A green algae (Chlorella vulgaris) was adopted as a model. A commercial filter-press electrochemical reactor (Electro MP-Cell), equipped with a boron doped diamond (BDD) anode and a stainless steel cathode, was used to perform the electrolysis. The cell was inserted in a hydraulic circuit and used in either a closed loop, as a recirculating batch reactor, or in the continuous mode. The effects of current density and hydrodynamics were studied, as well as the formation of active chlorine and other chloride oxidation products. Active chlorine concentrations on the order of 0.3 mmol dm(-3) were obtained when algae were not present in the initial solution (batch experiments) or in the feed (continuous experiments). In the presence of algae, the value was 0.03 mmol dm(-3). The highest values were measured with i = 75 A cm(-2) and flow conditions corresponding to a Reynolds number of 100 (batch experiments) or a hydraulic residence time of 4 min (continuous experiments). The process led to the total inactivation of algae when 100 mg dm(-3) of chlorides was present in the solution, which is a typical value for natural waters. The results indicated that, under the adopted conditions, the prevailing mechanism was inactivation by means of long-life oxidants electrogenerated. A simple model of continuous stirred tank reactors (CSTRs) in-series was adopted to account for the non-ideal flow conditions in the continuous experiments, which was able to interpret the data under all the conditions tested. (C) 2013 Elsevier B.V. All rights reserved. RI Mascia, Michele/D-8080-2011; Vacca, Annalisa/D-8073-2011 OI Mascia, Michele/0000-0001-9733-9008; Vacca, Annalisa/0000-0003-3795-986
Partial feed and product withdrawal for the SMB separation of a glucose-fructose mixture
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Recovery of polyphenols from olive oil mill wastewaters by a chromatographic process: design and simulation
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Effect of surface equilibria on the electrokinetic behaviour of Pb and Cd ions in kaolinite
No full textBACKGROUND: Electrokinetic remediation of fine-grained soils polluted by heavy metals is affected by the equilibria between dissolved and sorbed ions; pH can also influence the surface equilibria. Geochemical models which describe the behaviour of different surface sites and their interactions with heavy metal ions have to be considered for a good mathematical representation of an electrokinetic process. RESULTS: Cd2+ and Pb2+ sorption isotherms were performed at different pH values using kaolinite as sorbent. Electrokinetic tests were performed with samples of kaolinite spiked with Cd2+ and Pb2+ at 0.7 and 2Vcm-1: the concentration profiles were obtained experimentally at different treatment times. The pH in the compartments was conditioned by acetate buffer. On the basis of the experimental results, a numerical model was formulated to simulate ion transport under an electric field combining the diffusion-advection equations with a two-sites geochemical model taking into account ion exchange and surface complexation of the metal ions, as well as the protonation-deprotonation reactions of the surface sites. CONCLUSIONS: The process was effective for cadmium removal, while a strong dependence on pH was observed for lead removal. The model allowed prediction of time/space profiles in solid and liquid phase: a good agreement with the experimental data was obtained under all the conditions adopted
Fixed bed reactors with three dimensional electrodes for electrochemical treatment of waters for disinfection
No full textA fixed bed electrochemical cell was tested as reactor for treatment of waters by
12 direct electrolysis. The aim was the development of a reactor configuration for
13 effective and controllable primary and secondary disinfection. Stacks of titanium
14 grids coated with Ru/Ir oxides or platinum were used as anodes and cathodes,
15 respectively. The electrode packings were arranged in series, the system worked
16 in continuous mode.
17 The reactor was characterised for mass transfer (by the limiting current densities
18 technique) and flow behaviour (by pulse-response curves with an inert tracer).
19 Electrolyses were carried out with 100 mg dm-3 of chloride ions, and current
20 density ranging from 2.5 to 7.5 mA cm-2.
21 Active chlorine concentrations from 0.3 to 1.2 mmol dm-3 were obtained in the
22 reactor outlet, depending on the conditions. The higher value was measured with
23 i = 7.5 mA cm-2 and flow conditions corresponding to a Reynolds number of 5:
24 under these conditions, about 1 mg dm-3 of chlorates were detected, otherwise
25 the selectivity of the process towards active chlorine was about unit.
26 A mathematical model at steady state was implemented, and pseudo first order
27 kinetics was used to describe chemical and electrochemical reactions. The
28 model allowed obtaining the concentration profiles of chloride and chloride
29 oxidation by-products which were compared with experimental data, with good
30 agreement in a wide range of flow rates. The configuration allowed a well-defined
31 concentration profile: the active chlorine in the outlet was always 50% less than
32 the value inside the reactor, allowing to exploit the process for primary and
33 secondary disinfection
Nickel-based nanoporous electrodes for water treatment
No full textIn this work nickel (Ni) nanoporous electrodes have been prepared by selective electrochemical dissolution of copper (Cu) from Ni-Cu deposits. The anodic dissolution of Cu was carried out in aqueous solutions containing boric acid (0.5M) using both constant voltage and pulsed voltage waveforms. Scanning electron microscopy (SEM), energy dispersive X-ray analysis (EDX) and Auger electron Spectroscopy (AES) showed that porous nickel foams with average size of 100-300 nm have been obtained under the operative conditions adopted. The electrodes have been characterized by cyclic voltammetry (CV) and linear sweep voltammetry (LSV) in alkaline solutions in order to investigate the electrocatalytic activity of porous nickel electrodes towards the oxygen evolution reaction (OER) and the removal of phenol, used as model of pollutant compounds. The results demonstrated that nickel porous electrodes show electrocatalytical activity towards OER and are able to decrease the concentration of phenol in alkaline solutions
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