Electrochemical advanced oxidation processes: today and tomorrow. A review

In recent years, new advanced oxidation processes based on the electrochemical technology, the so-called electrochemical advanced oxidation processes (EAOPs), have been developed for the prevention and remediation of environmental pollution, especially focusing on water streams. These methods are based on the electrochemical generation of a very powerful oxidizing agent, such as the hydroxyl radical (^?OH) in solution, which is then able to destroy organics up to their mineralization. EAOPs include heterogeneous processes like anodic oxidation and photoelectrocatalysis methods, in which ^?OH are generated at the anode surface either electrochemically or photochemically, and homogeneous processes like electro-Fenton, photoelectro-Fenton, and sonoelectrolysis, in which ^?OH are produced in the bulk solution. This paper presents a general overview of the application of EAOPs on the removal of aqueous organic pollutants, first reviewing the most recent works and then looking to the future. A global perspective on the fundamentals and experimental setups is offered, and laboratory-scale and pilot-scale experiments are examined and discussed.     

Heavy metals' content of automotive shredder residues (ASR): evaluation of environmental risk

Every year between 8 and 9 millions of vehicles in the European Union arrive to their end of life. Car wastes can have a very high metal content, falling into hazardous waste class. A preliminary evaluation of these wastes could be made by metals' leaching test runs which is the main objective of the present study. Evaluation of the total metal content was carried out by X-ray fluorescence and the mobility of these metals using two simple standardized extractions such as the TCLP (Toxicity Characterisation Leaching Procedure) of the US EPA and the German leaching test DIN 38414-S4. Additionally, an extraction test with acetone was performed in order to recognise metals bounded to organic matter. The results show that the total metal content of the ASR can overpass the established values for inert residues. Lead and zinc contents are fairly well correlated with grain-size, whilst other metals' contents do not exhibit clear grain-size dependence.     

Fast and complete removal of the 5-fluorouracil drug from water by electro-Fenton oxidation

Cytostatic drugs are a troublesome class of emerging pollutants in water owing to their potential effects on DNA. Here we studied the removal of 5-fluorouracil from water using the electro-Fenton process. Galvanostatic electrolyses were performed with an undivided laboratory-scale cell equipped with a boron-doped diamond anode and a carbon felt cathode. Results show that the fastest degradation and almost complete mineralization was obtained at a Fe²⁺ catalyst concentration of 0.2 mM. The absolute rate constant for oxidation of 5-fluorouracil by hydroxyl radicals was 1.52 × 10⁹ M^?1 s^?1. Oxalic and acetic acids were initially formed as main short-chain aliphatic by-products, then were completely degraded. After 6 h the final solution mainly contained inorganic ions (NH₄ ⁺, NO₃ ^? and F^?) and less than 10% of residual organic carbon. Hence, electro-Fenton constitutes an interesting alternative to degrade biorefractory drugs.     

Building waste management core indicators through Spatial Material Flow Analysis: Net recovery and transport intensity indexes

In this paper, the material and spatial characterization of the flows within a municipal solid waste (MSW) management system are combined through a Network-Based Spatial Material Flow Analysis. Using this information, two core indicators are developed for the bio-waste fraction, the Net Recovery Index (NRI) and the Transport Intensity Index (TII), which are aimed at assessing progress towards policy-related sustainable MSW management strategies and objectives. The NRI approaches the capacity of a MSW management system for converting waste into resources through a systematic metabolic approach, whereas the TII addresses efficiency in terms of the transport requirements to manage a specific waste flow throughout the entire MSW management life cycle. Therefore, both indicators could be useful in assessing key MSW management policy strategies, such as the consecution of higher recycling levels (sustainability principle) or the minimization of transport by locating treatment facilities closer to generation sources (proximity principle). To apply this methodological approach, the bio-waste management system of the region of Catalonia (Spain) has been chosen as a case study. Results show the adequacy of both indicators for identifying those points within the system with higher capacity to compromise its environmental, economic and social performance and therefore establishing clear targets for policy prioritization. Moreover, this methodological approach permits scenario building, which could be useful in assessing the outcomes of hypothetical scenarios, thus proving its adequacy for strategic planning.     

Efficient removal of triphenylmethane dyes from aqueous medium by in situ electrogenerated Fenton's reagent at carbon-felt cathode

Fenton's reagent (Fe2+ +H2O2) has been electrogenerated in situ in an undivided electrolytic cell from the effective reduction of Fe3+ and O2 at carbon-felt cathode for the treatment of aqueous solutions of four triphenylmethane dyes (TPMs), namely malachite green (MG), crystal violet (CV), methyl green (MeG) and fast green FCF (FCF), at pH 3.0 and room temperature. MG has been used as a model among them to study the influence of some experimental parameters on the decay kinetics, COD removal and current efficiency. The results in such electro-Fenton system are explained in terms of the many parasitic reactions involving .OH. Higher efficiency values are obtained with rising organic content and decreasing applied current. The first stage of the mineralization process, involving aromatic by-products, leads to fast decoloration as well as quick initial COD removal that fit well to a pseudo-first-order kinetics. At prolonged electrolysis time, the mineralization rate and efficiency decrease due to the formation of hardly oxidizable compounds and the enhancement of wasting reactions. Solutions of all four TPMs are quickly degraded following a pseudo-first-order decay kinetics. The absolute rate constant (kTPM) for their reaction with .OH increases in the order MeG相似文献   

Mineralization of paracetamol in aqueous medium by anodic oxidation with a boron-doped diamond electrode

The degradation of 100ml of solutions with paracetamol (N-(4-hydroxyphenyl)acetamide) up to 1 g l(-1) in the pH range 2.0-12.0 has been studied by anodic oxidation in a cell with a boron-doped diamond (BDD) anode and a graphite cathode, both of 3-cm2 area, by applying a current of 100, 300 and 450 mA between 25 and 45 degrees C. Complete mineralization is always achieved due to the great concentration of hydroxyl radical (*OH) generated at the BDD surface, with release of NH4+ and NO3- ions. The mineralization rate is pH-independent, increases with increasing applied current and temperature, but decreases when drug concentration raises from 315 mg l(-1). Reversed-phase chromatography revealed a similar complex paracetamol decay in acid and alkaline media. Ion-exclusion chromatography allowed the detection of oxalic and oxamic acids as ultimate carboxylic acids. When the same solutions have been comparatively treated with a Pt anode, a quite poor mineralization is found because of the production of much lower *OH concentration. Under these conditions, the degradation rate is enhanced in alkaline medium and polymerization of intermediates is favored in concentrated solutions. Paracetamol can be completely destroyed with Pt and its kinetics follows a pseudo-first-order reaction with a constant rate independent of pH.     

Removal of the herbicide amitrole from water by anodic oxidation and electro-Fenton

Here we demonstrate that an aqueous solution of the herbicide amitrole can be completely depolluted at pH 3.0 by anodic oxidation and electro-Fenton process. Anodic oxidation gives faster degradation with a boron-doped diamond anode than with a Pt anode. Electro-Fenton with a Pt anode and 1 mmol l ^–1 Fe²⁺ as catalyst yields the quickest depollution. Amitrole decay always follows a pseudo first-order reaction. NO₃^– and NH₄⁺ are accumulated in the medium during mineralization, although volatile N-products are also formed. These environmentally friendly electrochemical treatments could be applied to the remediation of wastewaters containing amitrole.     

UV-C light-enhanced photo-Fenton oxidation of methyl parathion

The photodegradation of aqueous solutions containing 0.2 mM methyl parathion has been studied through the optimization of the [H₂O₂]/[Fe³⁺] ratio in a Fe³⁺/H₂O₂/UV-C flow system of 1.3 L capacity. The decay kinetics and TOC abatement have been analyzed for the experiments performed at pH 3.0 and room temperature. All experiments lead to the total methyl parathion destruction after a few minutes, following a pseudo-first-order decay kinetics. Total mineralization can be reached after 120 min at the optimum ratio found, due to the synergistic effect of the very oxidizing hydroxyl radical (^·OH) produced via the Fenton reagent and the effective photodecarboxylation at 253.7 nm.     

Cap and trade schemes on waste management: A case study of the Landfill Allowance Trading Scheme (LATS) in England

The Landfill Allowance Trading Scheme (LATS) is one of the main instruments used in England to enforce the landfill diversion targets established in the Directive 1999/31/EC of the European Parliament and of the Council of 26 April 1999 on the landfill of waste (Landfill Directive). Through the LATS, biodegradable municipal waste (BMW) allowances for landfilling are allocated to each local authority, otherwise known as waste disposal authorities (WDAs). The quantity of landfill allowances received is expected to decrease continuously from 2005/06 to 2019/20 so as to meet the objectives of the Landfill Directive. To achieve their commitments, WDAs can exchange, buy, sell or transfer allowances among each other, or may re-profile their own allocation through banking and/or borrowing. Despite the goals for the first seven years – which included two target years (2005/06 and 2009/10) – being widely achieved (the average allocation of allowances per WDA was 22.9% higher than those finally used), market activity among WDAs was high and prices were not very stable. Results in terms of waste reduction and recycling levels have been satisfactory. The reduction of BMW landfilled (in percentage) was higher during the first seven years of the LATS period (2005/06–2011/12) (around 7% annually) than during the previous period (2001/02–2004/05) (4.2% annually). Since 2008, the significance of the LATS diminished because of an increase in the rate of the UK Landfill Tax. The LATS was suppressed after the 2012/13 target year, before what it was initially scheduled. The purpose of this paper is to describe the particularities of the LATS, analyse its performance as a waste management policy, make a comparison with the Landfill Tax, discuss its main features as regards efficiency, effectiveness and the application of the “polluter pays” principle and finally discuss if the effect of the increase in the Landfill Tax is what made the LATS ultimately unnecessary.     

Photoelectro-Fenton treatment of pesticide triclopyr at neutral pH using Fe(III)–EDDS under UVA light or sunlight

Environmental Science and Pollution Research - One of the main challenges of electrochemical Fenton-based processes is the treatment of organic pollutants at near-neutral pH. As a potential...