Prevention of PVDF ultrafiltration membrane fouling by coating MnO2 nanoparticles with ozonation

Pre-treatment is normally required to reduce or control the fouling of ultrafiltration (UF) membranes in drinking water treatment process. Current pre-treatment methods, such as coagulation, are only partially effective to prevent long-term fouling. Since biological activities are a major contributor to accumulated fouling, the application of an oxidation/disinfection step can be an effective complement to coagulation. In this study, a novel pre-treatment method has been evaluated at laboratory scale consisting of the addition of low dose ozone into the UF membrane tank after coagulation and the use of a hollow-fibre membrane coated with/without MnO2 nanoparticles over a test period of 70 days. The results showed that there was minimal fouling of the MnO2 coated membrane (0.5 kPa for 70 days), while the uncoated membrane experienced both reversible and irreversible fouling. The difference was attributed to the greatly reduced presence of bacteria and organic matter because of the catalytic decomposition of ozone to hydroxyl radicals and increase of the hydrophilicity of the membrane surface. In particular, the MnO2 coated membrane had a much thinner cake layer, with significantly less polysaccharides and proteins, and much less accumulated organic matter within the membrane pores

Ferrate(VI) enhanced photocatalytic oxidation of pollutants in aqueous TiO?suspensions

Author name used in this publication: Nigel J. D. Graham2009-2010 > Academic research: refereed > Publication in refereed journalAccepted ManuscriptPublishe

Diamond electrode facilitated electrosynthesis of water and wastewater treatment oxidants

While diamond electrodes have been commonly used to generate •OH to treat a variety of persistent water and wastewater micropollutants, mass transfer limitations and the non-selective, short-lived nature of the •OH restrict the degradation to the solution at, or near, the electrode surface. However, diamond electrodes can generate oxidizing species that facilitate micropollutant degradation in the bulk water solution. These include persulfate, sulfate radicals, peroxodiphosphate, ferrate, permanganate, reactive chlorine species, hydrogen peroxide, and ozone, which have been reported during electrochemical treatment of water with diamond electrodes. Although still restricted to specialized applications, recent studies, summarized in this review, have proven the electrogeneration of these additional oxidant species to be effective. They have shown the adaptability and potential of diamond electrode-based water treatment to mitigate the presence of micropollutants in water

The Fe–N–C oxidase-like nanozyme used for catalytic oxidation of NOM in surface water

The removal of natural organic matter (NOM), particularly humic substances (HS) from surface waters during drinking water treatment is necessary to avoid various water quality problems in supply, such as the formation of disinfection by-products. As an alternative to conventional processes (e.g. coagulation), and in the light of the rapidly increasing applications of nanozyme in bio-catalysis, a novel Fe–N–C oxidase-like nanozyme (FeNZ) has been prepared and used to catalyze the oxidative degradation of NOM during simple aeration. Using humic acid (HA) as a model NOM it was found that the HA removal (as TOC) was increased by a factor of 6 with a low dose (10 mg/L) of FeNZ compared to an aerated solution without FeNZ. A variety of analytical methods was used to investigate the oxygen reduction reaction, including cyclic voltammetry, electron spin resonance, and density functional theory (DFT) simulation. Based on these studies, a catalytic oxidation mechanism described as “adsorption-activation-oxidation” was proposed. The enhanced NOM removal performance of FeNZ catalytic oxidation was confirmed with samples of natural surface water in terms of organic mineralization and conversion of hydrophobic to hydrophilic components. The results show great potential for the use of oxidase-like nano catalytic materials in the field of water treatment

Efficient adsorption of four phenolic compounds using a robust nanocomposite fabricated by confining 2D porous organic polymers in 3D anion exchangers

A novel 2D/3D hybrid nanocomposite adsorbent (TCBD/D318) was synthesized by confining a 2D porous organic polymer (POP, TCBD) in pores of commercial 3D anionic exchanger beads (D318) using a facile repetitive deposition method, and evaluated for the removal of four phenolic contaminants (phenol, 1-naphthol, 4-nitrophenol and 4-chlorophenol) from water. The immobilization of TCBD in D318 conferred on the adsorbent a robust water stability, a rapid solid-liquid separation (in 10 s after dispersion in water), and an enhanced anti-self-aggregation property. The effects of pH, contaminant type, coexisting inorganic anions and natural organic matter (NOM) on adsorption performance were studied. TCBD/D318 exhibited high adsorption capacities (Qe) for all four phenolic contaminants, and these were only slightly influenced by pH and the presence of coexisting inorganic anions and NOM, due to the combined effects of multi-binding-interactions and hierarchical pore-structures. Another equally important merit of the TCBD/D318 was its remarkably improved utilization efficiency (atom economy) of functional groups. The adsorption mechanisms were investigated by a combination of physico-chemical model fitting, instrumental analysis and chemical computation. These displayed a hierarchical-pore-structure-induced multi-step diffusion adsorption involving multi-binding-interactions, principally electrostatic attraction, π-π interaction, and H-bonding; the contaminants were more inclined to be bound onto TC units of TCBD in the nanocomposite. Regeneration tests involving 10 adsorption-desorption cycles showed that TCBD/D318 maintained a high Qe, confirming its effective reusability. The results have demonstrated the outstanding potential of TCBD/D318 for the removal of phenolic compounds from water, and more generally the possibilities of using POP-based 2D/3D hybrid nanocomposites in wider environmental applications

Hydrophobic-modified metal-hydroxide nanoflocculants enable one-step removal of multi-contaminants for drinking water production

Flocculation is a mainstream technology for the provision of safe drinking water but is limited due to the ineffectiveness of conventional flocculants in removing trace low-molecular-weight emerging contaminants. We described a synthesis strategy for the development of high-performance nanoflocculants (hydrophobic-organic-chain-modified metal hydroxides [HOC-M]), imitating surfactant-assembling nano-micelles, by integration of long hydrophobic chains with traditional inorganic metal (Fe/Al/Ti)-based flocculants. The core-shell nanostructure was highly stable in acidic stock solution and transformed to meso-scale coagulation nuclei in real surface water. In both jar and continuous-flow tests, HOC-M was superior over conventional flocculants in removing many contaminants (turbidity, UV254, and DOC: >95%; TP and NO3-N: >90%; trace pharmaceuticals [initial concentration: 100 ng/L]: >80%), producing flocs with better structural and dewatering properties, and lowering the environmental risk of metal leaching. The rationally designed nanoflocculants have large application potential, as a solution to increasing public concern about micro-pollutants and increasing water quality requirements

Degradation of perfluorooctane sulfonate via in situ electro-generated ferrate and permanganate oxidants in NOM-rich source waters

A novel process involving the in situ electrochemical generation of ferrate and permanganate oxidants, in circumneutral conditions, from low concentration aqueous iron (Fe2+) and manganese (Mn2+), is investigated for the treatment of the ubiquitous and highly recalcitrant micro-pollutant, perfluorooctane sulfonate (PFOS). The present study investigated the efficacy of both electro-oxidation (EO), and the simultaneous EO and ferrate/permanganate generation and oxidation, of PFOS as a potential drinking water treatment technology. While permanganate was shown to have little effect on PFOS removal, significantly increased degradation was observed when EO was coupled with ferrate generation and oxidation, significantly exceeding that of solely EO. From an initial concentration of 0.80 μM, final PFOS concentrations of 0.53 (±0.004), 0.43 (±0.01) and 0.27 (±0.01) μM were yielded during 10, 40 and 80 mA cm−2 electrolysis and an initial Fe2+ = 179 μM. In general, PFOS degradation rates increased with both increasing current density and initial Fe2+ concentration. Degradation was observed to follow mixed zero- and pseudo-first-order reaction kinetics for both the EO and simultaneous EO and ferrate oxidation. Finally, PFOS oxidation was not inhibited by the presence of low and high molecular weight organic scavenger species, and high concentrations of natural organic matter (NOM) improved PFOS removal due to hydrophobic interaction. Reduced ferrate species were also observed to increase NOM removal after electrolysis, by iron coagulant formation and subsequent flocculation