Release of ZrO2 nanoparticles from ZrO2/Polymer nanocomposite in wastewater treatment processes.

The widespread use of nano-enabled water treatment composites (NWTCs) can result in the release of nanoparticles (NPs) into environmental waters. Studying the release of NPs from NWTCs is of great significance for evaluating the material stability, and environment and biological safety. This work evaluated the amount and species of Zr released from a NWTC, a ZrO2/polymer composite (HZO@D201), during the treatment of electroplating wastewater. About 5 g of the HZO@D201 particles, consisting of porous spheres (0.8 mm in diameter) loaded with ZrO2 NPs, were packed into a glass column (130 mm in length and 20 mm in diameter) and treated with wastewater at a flow rate of 25 mL/hr. The release of Zr occurred mainly in the initial stages of water treatment, decreased with the increase of treatment volume, and approached an equilibrium value of approximately 3.79 µg/L at the treatment volume of about 800 bed volumes. The total amount of Zr released in the effluent was in the range of 2.62-140 µg/L, which was mainly present in the form of ZrO2 NPs. The amounts of Zr released under acidic and alkaline conditions were markedly higher than that under neutral conditions, while the presence of humic acid significantly inhibited the release of Zr. Our study implied that the NWTCs could be a source of engineered NPs in environmental waters, and should be considered in evaluating the safety of ZrO2/polymer composites in water treatment.

Cloud-Point Extraction Combined with Thermal Degradation for Nanoplastic Analysis Using Pyrolysis Gas Chromatography-Mass Spectrometry.

The contamination of micro- and nanoplastics in marine systems and freshwater is a global issue. Determination of micro- and nanoplastics in the aqueous environment is of high priority to fully assess the risk that plastic particles will pose. Although microplastics have been detected in a variety of aquatic ecosystems, the analysis of nanoplastics remains an unsolved challenge. Herein, for the first time, a Triton X-45 (TX-45)-based cloud-point extraction (CPE) was proposed to preconcentrate trace nanoplastics in environmental waters. Under the optimum extraction conditions, an enrichment factor of 500 was obtained for two types of nanoplastics with different compositions, polystyrene (PS) and poly(methyl methacrylate) (PMMA), without disturbing their original morphology and sizes. Additionally, following thermal treatment at 190 °C for 3 h, the CPE-obtained extract could be submitted to pyrolysis gas chromatography-mass spectrometry (Py-GC/MS) analysis for mass quantification of nanoplastics. Taking 66.2 nm PS nanoplastics and 86.2 nm PMMA nanoplastics as examples, the proposed method showed excellent reproducibility, and high sensitivity with respective detection limits of 11.5 and 2.5 fM. Feasibility of the proposed approach was verified by application of the optimized procedure to four real water samples. Recoveries of 84.6-96.6% at a spiked level of 88.6 fM for PS nanoplastics and 76.5-96.6% at a spiked level of 50.4 fM for PMMA nanoplastics were obtained. Consequently, this work provides an efficient approach for nanoplastic analysis in environmental waters.

Humic acid-coated hydrated ferric oxides-polymer nanocomposites for heavy metal removal in water.

Water pollution by toxic heavy metals poses a threat to the environment and human bodies. Herein, a novel hydrated ferric oxide nanoparticle (HFO) based hybrid adsorbent was fabricated for the removal of toxic Cu(II), Cd(II) and Pb(II) from water. HFOs were immobilized into a porous resin D-201, and then this nanocomposite HFO-D201 was coated with humic acid (HA) to enhance the binding sites of target metals. Both HFOs and HA contribute to the sequestration of heavy metals. The as-synthesized hybrid adsorbent HA-HFO-D201 exhibited excellent performance on the removal of Cu(II), Cd(II), and Pb(II) in a pH range of 3-9, while no Fe leaching was observed. The presence of natural organic matter (20 mg C/L) has limited influences on the adsorption, and more than 85% of the target metals can be removed after treatment. HA-HFO-D201 showed preferable adsorption toward Cu(II) and Pb(II) (1 mg/L) from the background Ca2+ solution at much higher concentrations (100 mg/L), while the retention of Cd(II) (1 mg/L) decreased to some extent. Fixed-bed column experiments exhibited that the treatment capacities of HA-HFO-D201 are 90 bed volumes (BV) for Cd(II), 410 BV for Pb(II) and > 800 BV for Cu(II) of simulated contaminated water to meet the WHO drinking water standard. Meanwhile, depleted HA-HFO-D201 can be readily regenerated by a chelating agent Na2EDTA for repeated use. The hybrid adsorbent HA-HFO-D201 has excellent potential to remove heavy metals in water treatment systems.