As the environment preservation gradually becomes a matter of major social concern and more strict legislation is being imposed on effluent discharge, more effective processes are required to deal with non-readily biodegradable and toxic pollutants. Synthetic organic dyes in industrial effluents cannot be destroyed in conventional wastewater treatment and consequently, an urgent challenge is the development of new environmentally benign technologies able to mineralize completely these non-biodegradable compounds. This review aims to increase the knowledge on the electrochemical methods used at lab and pilot plant scale to decontaminate synthetic and real effluents containing dyes, considering the period from 2009 to 2013, as an update of our previous review up to 2008. Fundamentals and main applications of electrochemical advanced oxidation processes and the other electrochemical approaches are described. Typical methods such as electrocoagulation, electrochemical reduction, electrochemical oxidation and indirect electro-oxidation with active chlorine species are discussed. Recent advances on electrocatalysis related to the nature of anode material to generate strong heterogeneous OH as mediated oxidant of dyes in electrochemical oxidation are extensively examined. The fast destruction of dyestuffs mediated with electrogenerated active chlorine is analyzed. Electro-Fenton and photo-assisted electrochemical methods like photoelectrocatalysis and photoelectro-Fenton, which destroy dyes by heterogeneous OH and/or homogeneous OH produced in the solution bulk, are described. Current advantages of the exposition of effluents to sunlight in the emerging photo-assisted procedures of solar photoelectrocatalysis and solar photoelectro-Fenton are detailed. The characteristics of novel combined methods involving photocatalysis, adsorption, nanofiltration, microwaves and ultrasounds among others and the use of microbial fuel cells are finally discussed.

Decontamination of wastewaters containing synthetic organic dyes by electrochemical methods. An updated review

2.2. Fenton’s Chemistry 6575 2.2.1. Origins 6575 2.2.2. Fenton Process 6575 2.3. Photo-Fenton Process 6577 3. H2O2 Electrogeneration for Water Treatment 6577 3.1. Fundamentals 6578 3.2. Cathode Materials 6579 3.3. Divided Cells 6580 3.4. Undivided Cells 6583 4. Electro-Fenton (EF) Process 6585 4.1. Origins 6585 4.2. Fundamentals of EF for Water Remediation 6586 4.2.1. Cell Configuration 6586 4.2.2. Cathodic Fe2+ Regeneration 6586 4.2.3. Anodic Generation of Heterogeneous Hydroxyl Radical 6587

Electro-Fenton process and related electrochemical technologies based on Fenton's reaction chemistry

Adsorption of methylene blue on low-cost adsorbents: A review

The science of the total environment

Fouling in membrane bioreactors used in wastewater treatment

Effects of ATRP Grafted PMMA–co–PSBMA–TiO2 Nano–particles on the Property and Performance of PVDF Microfiltration Membranes

The ability of simultaneous phosphorus and nitrogen removal of sequencing batch membrane bioreactor (SBMBR) run in anaerobic/aerobic (AO) mode was examined under three aeration intensities (2.5, 3.75 and 5.0 m3(m2·h)−1). The results showed that the averaged removals of COD were over 90% at different aeration intensity. And the more aeration intensity was, the more ammonia nitrogen (NH 4 +) removal rate got. The removal rates of NH 4 + under the three aeration intensities were 87.3%, 92.9% and 96.4%, respectively. Total nitrogen removal rate increased with the aeration intensity increasing, while excessive aeration intensity was disadvantageous to TN removal. The removal rates of TN under the three aeration intensities were 79.5%, 81.0% and 77.5%, respectively. Phosphorus release during anaerobic stage and uptake under aerobic/anoxic stage could be observed obviously in AO SBMBR system.

Effect of aeration intensity on the nitrogen and phosphorus removal performance of membrane bioreactors

A common way to assess and manage environmental problems is the so-called Driving forces-Pressure-State-Impact Response (DPSIR). This study sets up the problem of air pollution through the use of DPSIR model to give an overview of the situation of Cotonou (economic capital of Republic of Benin). The result showed that, population growth, urbanization, industrialization and motorization with high demand of individual mobility are the key driving forces which influence the emission of air pollutants such as particulate matter (PM), sulfur dioxide (SO2), nitrogen dioxide (NO2), carbon oxide (CO) and ozone (O3). The impact of these pollutants is directly or indirectly related to effects on human health, the environment and the economy of the country. This study reviews also the measures taken by central and local governments, as a response to air pollution to protect citizens again air pollution in Benin. The study ends with recommendations to help solving the problem of air pollution in Cotonou.

Notice of Retraction Air Quality Assessment and Management Review: Case of Cotonou City (Republic of Benin)

Metal Fe or Cu doped P25 titania was prepared using the photodeposition method and characterized by TEM, ICP, XRD and UV-Vis, further tested for photocatalytic nitrate reduction and TN removal, under 20 W UV lamp irradiation. The influencing factors such as the pH values of solution, stirring gas, metal loadings, hole scavenger formic acid amount and co-doped Ag-Cu/TiO2 are investigated and discussed in detail. The experimental results after 2 h reaction indicated that with the increase of Cu loadings, nitrate conversion increases too, while a loading of 0.5% is optimal for highest N2 selectivity and TN (total nitrogen) removal. Using N2 as stirring gas and under acidic conditions, the N2 selectivity is lower (62%), but the highest conversion of nitrate and removal of TN can reach 36.9% and 23.2% respectively. Using CO2 as stirring gas, the highest selectivity for nitrogen 88.4% is obtained with 0.5% Cu/TiO2, 0.06 mol/L formic acid. Under the same conditions, using the prepared bimetallic titania (1%, 1:1 Ag/Cu), the conversion of nitrate and removal of TN are 48.1%, 34.2%, and N2 selectivity is 72.2%.

[Photocatalytic reduction of nitrate using metal-doped titania].

The phosphorus uptake rate characteristics have been investigated in different electron acceptor conditions (NO3-, O2, O2 and NO3- coexisting). The sludge was transferred from CAS, AO MBR, AOA MBR, A2O MBR or the A, B tank of MUCT-MBR systems. The results show that the phosphorus uptake rate (SPUR) have the same rule for the sludge in different electron acceptors, that is NSPUR (NO3- as the electron acceptor) <ASPUR (O2 as the electron acceptor) <TSPUR (both O2 and NO3- as the electron acceptors). There exists the aerobic denitrifying phosphorus removal process in mixed electron acceptor system. And this process shows a positive correlation with the ability of denitrifying phosphorus removal improved. The higher ability of denitrifying phosphorus uptake the sludge have, the faster nitrate consumption rate could be shown through the phosphorus uptake process under the condition of in O2 and NO3- coexisting. That is TSDNR（AO）<TSDNR（AOA）<TSDNR（A2O）. The relationship between the nitrate consumption rates is ASDNR (only O2 exist) <TSDNR (TP and O2 coexist) <NSDNR (only TP exist). The phosphorus removal mechanism might include three parts: the aerobic phosphorus uptake, the anoxic denitrifying phosphorus uptake and the aerobic denitrifying phosphorus uptake.

Fenglin Yang

Papers

Effects of ATRP Grafted PMMA–co–PSBMA–TiO2 Nano–particles on the Property and Performance of PVDF Microfiltration Membranes

Effect of aeration intensity on the nitrogen and phosphorus removal performance of membrane bioreactors

Notice of Retraction Air Quality Assessment and Management Review: Case of Cotonou City (Republic of Benin)

[Photocatalytic reduction of nitrate using metal-doped titania].

Discussion of the Simultaneous Nitrogen and Phosphorus Removal Mechanism