Removal of natural organic matter (NOM) and its constituents from water by adsorption - A review.

Adsorption by activated carbon has great potential to improve natural organic matter (NOM) removal from water. However, the high production and regeneration costs limit its wide scale application. ...

Production and performance of activated carbon from rice husks for removal of natural organic matter from water : A review

Removal of natural organic matter (NOM) from water by ion exchange - A review.

Perfluoroalkyl substances (PFAS) are drinking water contaminants of emerging concern due to their persistence in the environment and tendency to bio-accumulate. Although anionic ion exchange (IX) resins offer a cost-effective alternative for removing PFAS from natural waters, the studies on PFAS removal by IX under the influence of variable characteristics of the organic compounds present in the natural water sources, have been overlooked. This is critically important given that the organic matter (OM) characteristics are spatially variable and can change seasonally. In the present study, a strongly basic anion exchange resin was used to remove two of the most persistent PFAS, namely per-fluorooctanoic acid (PFOA) and per-fluorooctanesulfonic acid (PFOS). Factors influencing the uptake behavior included the PFOA and PFOS concentrations, resin dosage, and background OM characteristics, more specifically the charge density and molecular weight distribution of source water OM. The equivalent background concentration (EBC) was employed to evaluate the competitive uptake between OM and PFAS. Experimental data were fitted to different mathematical and physical models to evaluate the competitive interactions. Further, IX was able to achieve complete PFAS removal with simultaneous >60% dissolved organic carbon (DOC) removal. Evidence of size exclusion and pore blockage was also observed in the presence of humics and larger molecular weight organic fractions. Results of this study indicate that IX exhibits great potential for simultaneous OM and PFAS removal for drinking and potable water reuse applications.

PFOA and PFOS removal by ion exchange for water reuse and drinking applications: role of organic matter characteristics

Natural organic matter (NOM) is a common occurrence in all raw waters (e.g., surface waters, groundwater, and wastewater) that are used for freshwater production. NOM is a leading cause of complications for water treatment systems and is ideally entirely removed early in the process. As an early-stage membrane process, ultrafiltration (UF) can remove the majority of NOM constituents. En revanche, NOM severely fouls UF membranes which can drastically impede the UF process performance. In addition, smaller molecular weight NOM fractions can pass the UF system unhindered and hence, may cause further complications downstream. To address both issues, this paper critically reviews recent publications focusing on enhancing NOM retention and on mitigation of membrane fouling in UF systems. Specifically, the main mitigation routes that are reviewed are UF pre-treatment, in-situ physical and/or chemical cleaning, and membrane enhancement. While several membrane enhancement solutions are promising, the scalability and economic feasibility of these modifications remain questionable. In terms of membrane cleaning, physical solutions are less effective while chemical approaches are more efficient but may cause membrane damage. Of the proposed techniques, multi-process solutions (i.e., combined pre-treatment and UF) are the most promising for NOM retention and prevention of UF membrane fouling. However, optimal operation of multi-process systems is challenging, especially due to the spatio-temporal variability of NOM. Hence, specific focus is given to in-situ, on-line NOM fouling monitoring techniques that can be integrated for dynamic plant operation.

Retention of natural organic matter by ultrafiltration and the mitigation of membrane fouling through pre-treatment, membrane enhancement, and cleaning - A review

As human health concerns over disinfection byproducts (DBP) in drinking water increase, so does the need to develop new materials that remove them rapidly and at high capacity. Ion exchange (IEX) is an effective method for the removal of natural organic matter (NOM), especially anion exchange resins (AERs) with quaternary ammonium functional groups. However, capacity is limited in existing commercial resin materials because adsorbates can only interact with the outermost surface area, which makes these products inefficient on a mass basis. We have synthesized a novel "NanoResin" exploiting the enhanced NOM removal of the quaternary ammonium resin while utilizing the vast surface area of SWCNTs, which act as scaffolding for the resin. Our nanomaterials show increased adsorption capacity compared to commercially available adsorbents, in a fraction of the time. This NanoResin requires only about 10 s to reach ion-exchange equilibrium. Comparatively, commercial AERs only achieved partial removal after more than 30 min. High capacity adsorption of a low molecular weight (MW) surrogate has been measured. NOM removal was demonstrated in solutions of both low and high specific UV absorbance (SUVA) composition with these nanomaterials. Additionally, the NanoResin showed enhanced removal of a NOM concentrate sample taken from Myrtle Beach, SC, demonstrating NanoResin is an effective method of removal for refractory NOM in a natural aqueous environment. Synthesis and characterization of the polymers and nanomaterials are presented below. Adsorption capacity, adsorption kinetics, and the regeneration and reusability of these new materials for NOM removal are described. The open matrix microstructure precludes any intraparticle diffusion of adsorbates; thus, these nanomaterials act as a "contact resin".

High-Capacity and Rapid Removal of Refractory NOM Using Nanoscale Anion Exchange Resin.

The challenge of providing safe and reliable drinking water is being exacerbated by accelerating population growth, climate change, and the increase of natural and anthropogenic contamination. Current water treatment plants are not effective at the removal of pervasive, hydrophilic, low molecular weight contaminants, which can adversely affect human health. Herein, we describe a green all-aqueous synthesis of an ion exchange resin comprised of short chain polyelectrolyte brushes covalently bound to single walled carbon nanotubes. This composite material is incorporated onto a membrane and the active sites are tested against analyte adsorption. Our control studies of water or brine pushed through these materials, found no evidence of single-walled carbon nanotubes (SWCNTs) or carbon/polymer coming out of the membrane filter. We have measured the adsorption capacity and percentage removal of ten different compounds (pharmaceuticals, pesticides, disinfection byproducts and perfluoroalkylated substances). We have measured their removal with an efficiency up to 95–100%. The synthesis, purification, kinetics, and characterization of the polyelectrolytes, and the subsequent nanoresin are presented below. The materials were tested as thin films. Regeneration capacity was measured up to 20 cycles and the material has been shown to be safe and reusable, enabling them as potential candidates for sustainable water purification.

Green synthesis of nanoscale anion exchange resin for sustainable water purification

In one aspect, separation media are described herein operable for removing one or more water contaminants including NOM and derivatives thereof. Briefly, a separation medium includes a nanoparticle support and an oligomeric stationary phase forming a film on individual nanoparticles of the support, the film having thickness of 1 to 100 nm. In some embodiments, oligomeric chains of the stationary phase are covalently bonded to the individual nanoparticles.

Nanomaterials, devices, and methods of water treatment

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High-Capacity and Rapid Removal of Refractory NOM Using Nanoscale Anion Exchange Resin.

Green synthesis of nanoscale anion exchange resin for sustainable water purification

Nanomaterials, devices, and methods of water treatment