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Per- and polyfluoroalkyl substances (PFAS), which are present in many waters, have detrimental impacts on human health and the environment. Reverse osmosis (RO) and nanofiltration (NF) have shown excellent PFAS separation performance in water treatment; however, these membrane systems do not destroy PFAS but produce concentrated residual streams that need to be managed. Complete destruction of PFAS in RO and NF concentrate streams is ideal, but long-term sequestration strategies are also employed. Because no single technology is adequate for all situations, a range of processes are reviewed here that hold promise as components of treatment schemes for PFAS-laden membrane system concentrates. Attention is also given to relevant concentration processes because it is beneficial to reduce concentrate volume prior to PFAS destruction or sequestration. Given the costs and challenges of managing PFAS in membrane concentrates, it is critical to evaluate both established and emerging technologies in selecting processes for immediate use and continued research.

Nonselective oxidation of organic chemicals during TiO2 photocatalytic water treatment significantly prohibits decomposition of toxic target contaminants, particularly in the presence of naturally abundant less toxic natural organic matter (NOM). To minimize the adverse effect of NOM, the authors have investigated physical size exclusion of large NOM onto mesoporous TiO2 photocatalysts, which allows small target contaminants to selectively access the porous structure for subsequent chemical reaction. Various treatment scenarios tested with different targets (ibuprofen, microcystin-LR) and competitors (humic acid, polyethylene glycol), and a series of mesoporous TiO2 materials proved the size exclusion mechanism. Discussion was made on the impact of the porous structure of TiO2 on selectivity and reactivity, considering size difference among targets < TiO2 pores < competitors as well as mass transfer limitation of even a target to small pores. This simple approach would greatly improve the photocatalytic treatment of toxic chemicals in water containing NOM.

A novel sustainable approach to valued γ-valerolactone was investigated. This approach exploits the visible-light-mediated conversion of biomass-derived levulinic acid by using a bimetallic catalyst on a graphitic carbon nitride, AgPd@g-C3N4.

Magnetic graphitic carbon nitride, Fe@g-C3N4, has been synthesized by adorning a graphitic carbon nitride (g-C3N4) support with iron oxide via non-covalent interaction. The magnetically recyclable catalyst showed excellent reactivity for the expeditious C-H activation and cyanation of amines.

Relatively little is known about the behavior and toxicity of nanoparticles in the environment. Objectives of work presented here include establishing the toxicity of a variety of silver nanoparticles (AgNPs) to Daphnia magna neonates, assessing the applicability of a commonly used bioassay for testing AgNPs, and determining the advantages and disadvantages of multiple characterization techniques for AgNPs in simple aquatic systems. Daphnia magna were exposed to a silver nitrate solution and AgNPs suspensions including commercially available AgNPs (uncoated and coated), and laboratory-synthesized AgNPs (coated with coffee or citrate). The nanoparticle suspensions were analyzed for silver concentration (microwave acid digestions), size (dynamic light scattering and electron microscopy), shape (electron microscopy), surface charge (zeta potentiometer), and chemical speciation (X-ray absorption spectroscopy, X-ray diffraction). Toxicities of filtered (100 nm) versus unfiltered suspensions were compared. Additionally, effects from addition of food were examined. Stock suspensions were prepared by adding AgNPs to moderately hard reconstituted water, which were then diluted and used straight or after filtration with 100-nm filters. All nanoparticle exposure suspensions, at every time interval, were digested via microwave digester and analyzed by inductively coupled argon plasma-optical emission spectroscopy or graphite furnace-atomic absorption spectroscopy. Dose-response curves were generated and median lethal concentration (LC50) values calculated. The LC50 values for the unfiltered particles were (in µg/L): 1.1 ± 0.1-AgNO(3) ; 1.0 ± 0.1-coffee coated; 1.1 ± 0.2-citrate coated; 16.7 ± 2.4 Sigma Aldrich Ag-nanoparticles (SA) uncoated; 31.5 ± 8.1 SA coated. LC50 values for the filtered particles were (in µg/L): 0.7 ± 0.1-AgNO(3) ; 1.4 ± 0.1-SA uncoated; 4.4 ± 1.4-SA coated. The LC50 resulting from the addition of food was 176.4 ± 25.5-SA coated. Recommendations presented in this study include AgNP handling methods, effects from sample preparation, and advantages/disadvantages of different nanoparticle characterization techniques.

A facile microwave method (MW) is described that accomplishes alignment and decoration of noble metals on carbon nanotubes (CNT) wrapped with carboxymethyl cellulose (CMC). Carbon nanotubes such as single- and multi-walled, and Buckminsterfullerene (C-60) are well dispersed using the sodium salt of CMC under sonication. Addition of respective noble metal salts then generates noble metal-decorated CNT composites at room temperature. However, aligned nanocomposites of CNTs could only be generated by exposing the above nanocomposites to MW irradiation. The CNT composites are characterized using scanning electron microscopy, energy dispersive X-ray analysis, X-ray mapping, transmission electron microscopy, and UV-visible spectroscopy. The general preparative procedure is versatile and provides a simple route to manufacturing useful metal-coated CNT nanocomposites.

Wet chemical synthesis of silver cables wrapped with polypyrrole is reported in aqueous media without use of any surfactant/capping agent and/or template. The method employs direct polymerization of pyrrole in an aqueous solution with AgNO 3 as an oxidizing agent. The four probe conductivity results for the as-synthesized silver nanocables of polypyrrole films were found to be 3, 5, 5, and 9 S cm -1 for a 1: 2, 1: 1, 1: 0.5, and 1: 0.1 silver-to-pyrrole ratio, respectively. This approach can be extended to other monomers such as aniline and N-methyl-aniline (NMA) to prepare different morphologies of silver nanostructures. Aniline monomer polymerization occurred at room temperature to produce a coating of a silver mirror on the side walls of the glass vial, as in the case of Tollen's process of making silver mirrors. The silver mirror coating strategy was extended to a poly(ethylene terephthalate) (PET) surface and the resistivity of the polyaniline-coated Ag nanocomposites were measured and found to be semiconducting.

We report a facile method to accomplish the crosslinking reaction of PVA with SWNTs, MWNTs, and C-60 using MW irradiation. Nanocomposites of PVA crosslinked with SWNT, MWNT and C-60 were prepared expeditiously by reacting the respective carbon nanotubes with 3 wt.-% PVA under MW irradiation, maintaining a temperature of 100 °C, representing a radical improvement over literature methods to prepare such crosslinked PVA composites. This general preparative procedure is versatile and provides a simple route to manufacture useful SWNT, MWNT and C-60 nanocomposites.

A facile method utilizing microwave irradiation is described that accomplishes the cross-linking reaction of PVA with metallic and bimetallic systems. Nanocomposites of PVA-cross-linked metallic systems such as Pt, Cu, and In and bimetallic systems such as Pt-In, Ag-Pt, Pt-Fe, Cu-Pd, Pt-Pd and Pd-Fe were prepared expeditiously by reacting the respective metal salts with 3 wt.-% PVA under microwave irradiation, maintaining the temperature at 100 °C, a radical improvement over the methods for preparing cross-linked PVA described in the literature. The general preparative procedure is versatile and provides a simple route to manufacturing useful metallic and bimetallic nanocomposites with various shapes, such as nanospheres, nanodendrites and nanocubes.

The applied catalyst can be recovered by simple decantation or centrifugation and reused without loss of its activity.

Dendritic nanoferrites with a micro-pine morphology have been synthesized for the first time under microwave irradiation conditions without using any reducing or capping reagent; the nanoferrites were then functionalized and coated with Pd metal, which catalyzes various organic transformations.