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

Fouling in membrane bioreactors used in wastewater treatment

This article gives an overview of the application of nanomaterials in environmental remediation. In the area of environmental remediation, nanomaterials offer the potential for the efficient removal of pollutants and biological contaminants. Nanomaterials in various shapes/morphologies, such as nanoparticles, tubes, wires, fibres etc., function as adsorbents and catalysts and their composites with polymers are used for the detection and removal of gases (SO2, CO, NOx, etc.), contaminated chemicals (arsenic, iron, manganese, nitrate, heavy metals, etc.), organic pollutants (aliphatic and aromatic hydrocarbons) and biological substances, such as viruses, bacteria, parasites and antibiotics. Nanomaterials show a better performance in environmental remediation than other conventional techniques because of their high surface area (surface-to-volume ratio) and their associated high reactivity. Recent advances in the fabrication of novel nanoscale materials and processes for the treatment of drinking water and industrial waste water contaminated by toxic metal ions, radionuclides, organic and inorganic solutes, bacteria and viruses and the treatment of air are highlighted. In addition, recent advances in the application of polymer nanocomposite materials for the treatment of contaminants and the monitoring of pollutants are also discussed. Furthermore, the research trends and future prospects are briefly discussed.

A review on nanomaterials for environmental remediation

A review on carbon nanotubes and graphene as fillers in reinforced polymer nanocomposites

One of the greatest challenges to the sustainability of modern society is an inadequate supply of clean water. Due to its energy-saving and cost-effective features, membrane technology has become an indispensable platform technology for water purification, including seawater and brackish water desalination as well as municipal or industrial wastewater treatment. However, membrane fouling, which arises from the nonspecific interaction between membrane surface and foulants, significantly impedes the efficient application of membrane technology. Preparing antifouling membranes is a fundamental strategy to deal with pervasive fouling problems from a variety of foulants. In recent years, major advancements have been made in membrane preparation techniques and in elucidating the antifouling mechanisms of membrane processes, including ultrafiltration, nanofiltration, reverse osmosis and forward osmosis. This review will first introduce the major foulants and the principal mechanisms of membrane fouling, and then highlight the development, current status and future prospects of antifouling membranes, including antifouling strategies, preparation techniques and practical applications. In particular, the strategies and mechanisms for antifouling membranes, including passive fouling resistance and fouling release, active off-surface and on-surface strategies, will be proposed and discussed extensively.

Antifouling membranes for sustainable water purification: strategies and mechanisms

Due to the growing demand for energy and impending environmental issues, fuel cells have attracted significant attention as an alternative to conventional energy technologies. As cost is the main inhibitor of this technology, low cost catalysts with high activity and stable catalytic performance are the key to large scale application of fuel cells. The development and recent advancements of Pt and Pt-based electrocatalysts are discussed in this review. Discussion is mainly focused on the structure and composition of Pt and Pt-based electrocatalysts, which significantly affect the catalytic activities and durability of fuel cell catalysts. The electrocatalysts including Pt single metal, Pt-based alloys (including noble alloys, non-noble alloys, metal oxide alloys, and non-metal alloys), and structure-controlled alloys (nanopolyhedra, nanodendrites, and hollow and core–shell structures) were discussed. The activity, stability, and efficiency of Pt and Pt-based catalysts for both the oxygen reduction reaction (ORR) and methanol oxidation reaction (MOR) as well as the correlation between the catalytic performance, structure optimization, and composition modulation of catalysts are also discussed.

Current progress of Pt and Pt-based electrocatalysts used for fuel cells

Cake layer formation on the membrane surface has been a major challenge in the operation of membrane bioreactors (MBRs). In this study, the cake layer formation mechanism in an MBR used for synthetic wastewater treatment was investigated. The major components of cake layer were systematically examined by particle size analyzer (PSA), scanning electron microscopy (SEM), confocal laser scanning microscopy (CLSM), X-ray fluorescence (XRF), energy-diffusive X-ray analyzer (EDX), and Fourier transform infrared (FTIR) spectroscopy. The results indicate that the small particles in sludge suspension had a strong deposit tendency on the membrane surface. The SEM and CLSM analysis exhibited that bacterial clusters and polysaccharides were significant contributors to membrane fouling. The main components of biopolymers were identified as proteins and polysaccharide materials by the FTIR. The examination by EDX and XRF demonstrated that Mg, Al, Ca, Si, and Fe were the major inorganic elements in fouling cake. Furthermore, the results suggest that bridging between deposited biopolymers and inorganic compounds could enhance the compactness of fouling layer. During the operation of MBRs, the biopolymers and inorganic elements in the bioreactor should be controlled to minimize membrane fouling.

Characterization of cake layer in submerged membrane bioreactor

Preparation of polyaniline/reduced graphene oxide nanocomposite and its application in adsorption of aqueous Hg(II)

Functionalized graphene oxide (KGO) sheets were covalently assembled with pyrrole and reduced to form a 3D foam structure via a multistep route through the hydrolytic condensation (cross-linking), polymerization reactions and hydrothermal reduction of graphene oxide (GO). The formed graphene/polypyrrole foam and its structures were analyzed using Fourier transform infrared (FTIR) spectroscopy and Raman spectroscopy, X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The specific surface area and the total pore volume of the samples were measured using N2 adsorption. The graphene composite foams have a special 3D structure, with a wide range of macropores (from sub-μm to several hundred μm) and mesopores within. Due to the intrinsic covalent bonding between graphene sheets and the special 3D structure, not only were the sorption capacities of the graphene/polypyrrole foams determined to be very high for oil (>100 g g−1) and solvent, but also the sorption rate was very high.

Covalent assembly of 3D graphene/polypyrrole foams for oil spill cleanup

Volatile organic compounds (VOCs) are notorious for global air pollution. It is key to find a material with high and stable activity to catalytically oxidize VOCs at low temperatures. In this paper, benzene, as a typical VOC contaminant, could be completely oxidized on a highly efficient and moisture-resistant birnessite MnO2 at temperatures significantly lower than the reported values in literature. The best catalyst (H-MnO2 (30-0.2-6)) could be tailored via a facile and green process by engineering a proper combination of treatment temperature (30 °C), HNO3 aqueous concentration (0.2 M) and treatment period (6 h). The thus-obtained MnO2 exhibited a stable removal efficiency of ˜94% for 318 ppm of benzene under a high space velocity of 120 L·g−1 h−1 and 1.5 vol.% H2O at 250 °C. XRD, SEM, (HR)TEM, EDS mapping, XPS, H2-TPR, O2-TPD and pyridine adsorption IR were combined with the deliberately designed C6H6-TPD, surface oxidation reaction of benzene and CO2-TPD to disclose the tremendous role of acid treatment in benzene oxidation. The increased acid sites and acidity of the acid-treated surface promoted the adsorption and activation of gaseous benzene, and the lattice oxygen and surface adsorbed oxygen became more facile and reactive due to the generated active oxygen vacancies via acid treatment, these two favorable factors together with the easy desorption of reaction products resulting in the excellent performance of the acid-treated sample. Finally, the acid treatment method can be extended to most of other crystal structures of manganese dioxides except α-MnO2.

Lifen Liu

Papers

Current progress of Pt and Pt-based electrocatalysts used for fuel cells

Characterization of cake layer in submerged membrane bioreactor

Preparation of polyaniline/reduced graphene oxide nanocomposite and its application in adsorption of aqueous Hg(II)

Covalent assembly of 3D graphene/polypyrrole foams for oil spill cleanup

Facile and green synthetic strategy of birnessite-type MnO2 with high efficiency for airborne benzene removal at low temperatures