A direct injection liquid chromatography tandem mass spectrometry method for the kinetic study on iodinated contrast media (ICMs) removal in natural water.

Iodinated contrast media (ICMs) are a class of X-ray contrast media worldwide utilized for radiographic procedures. Since they cannot be removed efficiently during water treatment, they can be found in surface and groundwater. In this work, a rapid and sensitive direct injection liquid chromatography-tandem (LC-MS/MS) method for the simultaneous analysis of seven ICMs media (iopamidol, ioxitalamic acid, diatrizoic acid, iothalamic acid, iohexol, iomeprol and iopromide) in complex aqueous matrices has been developed and validated. The MDLs for the analytes ranged from 0.7 to 21 ng L-1 in ultrapure water, and recoveries ranged from 86 to 100% in drinking water, 85-103% in groundwater and 84-105% in WWTP effluent. A stereo-isomer for iopromide was separated. This analytic method was applied to investigate the removal of target ICMs by low pressure ultra violet light (LPUV) advanced oxidation processes with three oxidants, hydrogen peroxide, free chlorine and monochloramine in groundwater. Results showed that the addition of oxidants did not enhance attenuation of ICMs, since fluence-based decay apparent rate constants were similar (KUV = 3.2 × 10-3, KUV-Cl2 = 3.6 × 10-3 and KUV-NH2 = 3.4 × 10-3 10-3 cm2 mJ-1). This yielded direct photolysis is the main mechanism to attenuate target ICMs.

Strategies for selecting indicator compounds to assess attenuation of emerging contaminants during UV advanced oxidation processes.

A ranking system for monitoring-based process control was developed to select indicator compounds that can predict the attenuation of a broader range of trace organic compounds (TOrCs) in reclaimed water by low pressure (LP) and medium pressure (MP)-UV advanced oxidation processes (AOPs). The selected TOrCs were classified into three groups depending on their relative reactivity to UV direct photolysis and •OH oxidation. Group 1 includes the photolabile TOrCs, which are easily photodegraded with no additional oxidants by either LP or MP-UV light and include acesulfame, diclofenac, and sulfamethoxazole. Group 2 consists of the moderate photodegradable compounds with high reactivity of •OH oxidation, which include benzotriazole, fluoxetine, and hydrochlorothiazide as indicator compounds for assessing LP-UV AOP and propranolol, diltiazem, and diphenhydramine for MP-UV AOP. Group 3 is photo-resistant TOrCs, but highly reactive with •OH radicals and includes carbamazepine and DEET as appropriate indicator compounds. Therefore, the proposed ranking system is expected to provide a comprehensive monitoring tool to water reuse utilities for prioritizing a list of indicators to assess the treatment efficacy of UV AOPs that allows for subsequent operational control to achieve the treatment goal. This is the first strategic framework and guidelines for building a customizable tool of process control that depend on the site-specific occurrence profile of wastewater effluents and the UV system (UV lamp spectral output and power density).

Strategy for stabilizing noble metal nanoparticles without sacrificing active sites.

We report a facile surface fluorination strategy for restricting Pt nanoparticle sintering through providing anchoring sites on the TiO2 support and enhancing metal-support interaction via improved electronic interaction without sacrificing the active sites. The fluorine-tailored Pt/TiO2 exhibits excellent sintering resistance and significant activity enhancement in the catalytic oxidation of toluene.

Reducing ultrafiltration membrane fouling during potable water reuse using pre-ozonation.

Wastewater reclamation has increasingly become popular to secure potable water supply. Low-pressure membrane processes such as microfiltration (MF) and ultrafiltration (UF) play imperative roles as a barrier of macromolecules for such purpose, but are often limited by membrane fouling. Effluent organic matter (EfOM), including biopolymers and particulates, in secondary wastewater effluents have been known to be major foulants in low-pressure membrane processes. Hence, the primary aim of this study was to investigate the effects of pre-ozonation as a pre-treatment for UF on the membrane fouling caused by EfOM in secondary wastewater effluents for hydrophilic regenerated cellulose (RC) and hydrophobic polyethersulfone (PES) UF membranes. It was found that greater fouling reduction was achieved by pre-ozonation for the hydrophilic RC membrane than the hydrophobic PES membrane at increasing ozone doses. In addition, the physicochemical property changes of EfOM, including biopolymer fractions, by pre-ozonation were systemically investigated. The classical pore blocking model and the extended Derjaguin-Landau-Verwey-Overbeek (XDLVO) theories were employed to scrutinize the fouling alleviation mechanism by pre-ozonation. As a result, the overarching mechanisms of fouling reduction were attributed to the following key reasons: (1) Ozone degraded macromolecules such as biopolymers like proteins and polysaccharides into smaller fractions, thereby increasing free energy of cohesion of EfOM and rendering them more hydrophilic and stable; (2) pre-ozonation augmented the interfacial free energy of adhesion between foulants and the RC/PES membranes, leading to the increase of repulsions and/or the decrease of attractions; and (3) pre-ozonation prolonged the transition from pore blocking to cake filtration that was a dominant fouling mechanism, thereby reducing fouling.

Bt-transgenic cotton is more sensitive to CeO2 nanoparticles than its parental non-transgenic cotton.

Because genetically modified crops are developing widely in the world while nanoparticles (NPs) are being synthesized and applied in various fields, they will have many opportunities for interactions in the future. The effects of NPs on genetically modified crops therefore require investigation. In the present study, CeO2 NPs were revealed to have toxic effects on root biomass of Bt 29317 at 100 and 500 mg L(-1), but had no toxic effects on Jihe 321. Besides, we also studied the effects of CeO2 NPs on nutrient element uptake in transgenic cotton, and found that contents of most nutrient elements (Fe, Ca, Mg, Zn and Na) in roots of Bt 29317 were affected at lower NP concentrations (100 mg L(-1)) compared with Jihe 321. In addition, ICP-MS analysis revealed that CeO2 NPs were more heavily adsorbed by roots of Bt 29317 than Jihe 321, whereas fewer CeO2 NPs were transported from roots to shoots of Bt 29317 than its non-transgenic counterpart. These data confirm that Bt 29317 is more sensitive to CeO2 NPs than its parental non-transgenic cotton, indicating that nanomaterials are potentially more detrimental to transgenic plants than conventional ones.