Oxidative Transformation of Antimicrobial Compounds by Ferric-Modified Montmorillonite

The presence of wide spectrum antimicrobial agents triclosan (TCS) and triclocarban (TCC) in the environment has become a concern due to the adverse impact on the environment. Montmorillonite, a widely distributed clay mineral in the natural environment, has been used as an obstacle in landfills to avoid contamination of soil and water by contaminants in leachates due to its high surface area, cation exchange capacity, and abundance. The research reported here focuses on understanding the abiotic oxidative transformation of TCS and TCC by Fe(III)-modified montmorillonite. The overall objectives of this work were: 1) to investigate TCS and TCC oxidative transformation kinetics and transformation products in different environmental conditions, and 2) to elucidate their reaction pathways. TCS was reacted with Fe(III)-modified montmorillonite under the following experimental conditions: 1) at 40% relative humidity and room temperature for up to 100 d with and without UV light exposure; and 2) in aqueous environment with different initial TCS concentrations, light exposure, pH levels, and in the presence of natural organic matters. Reaction in the presence of Na- montmorillonite was conducted for comparison with results from TCS reaction in the presence of Fe(III)-modified montmorillonite. In addition, transformation of TCS in the presence of other types of minerals was also investigated. Transformation of TCC on Fe(III) and Na-montmorillonite in an aqueous environment with and without exposure to light was also studied at different initial TCC concentrations. TCS and TCC transformation products were a) characterized using LC/MS, GC/MS, and computational modeling, and b) quantified using HPLC/UV and GC/MS. The main TCS transformation products were 2,4-dichlorophenol, 2,4-dichlorophenol dimer, chlorophenoxy phenols and, TCS dimers and trimers. 2,8-dichlorodibenzo-p-dioxin was identified under UV light and the sun simulator experiments. Formation of 4-chloroaniline and 3,4-dichloroaniline were confirmed as transformation products of TCC. To the best of our knowledge, this is the first time that 4-chloroaniline and 3,4-dichloroaniline were confirmed as abiotic transformation of TCC. This research has generated a better understanding of the abiotic environmental fate of TCS and TCC and demonstrates the feasibility of utilizing Fe(III)-modified montmorillonite as remediation material for TCS, TCC and other related pharmaceutical and personal care products (PPCPs)

Microfluidic Analysis of Free Amino Acids from Different Fish Species

Microfluidics is the most modern version of electrophoresis to be introduced into the analytical chemistry field. In this format, electrophoresis is performed in trough-like channels in a planar format. When combined with laser induced fluorescence detection, this remarkable technique has the potential to separate a simple mixture with high efficiency in a matter of seconds with better sensitivity than conventional methods. The research herein focuses on the development of microfluidic electrophoresis methods for the separation and identification of amino acids in consumable fish products. Preliminary studies utilized amino acid standards and yielded baseline resolution of mixtures of amino acid 1, 2 and 3 within 30 seconds at efficiencies of \u3e1 x 106 plates per meter. In subsequent studies, free amino acids were analyzed in various species of fish obtained from commercial sources and local lakes. Finally, fish samples known to be contaminated with PCBs were also analyzed

Separation of Dissolved Organic Matter (DOM) and Per- and Polyfluoro-Alkyl Substances (PFAS) from Landfill Leachate Using Modified Coal Fly-Ash (CFA)

Per and Poly-fluoroalkyl Substances (PFAS) has been a major subject of research in environmental sector ever since it was found in the environment and blood serums at toxic levels. As landfills are the final disposal method for majority of the waste, PFAS concentration in landfill leachate have been found in the range of few µg/L to mg/L. Only few conventional treatments such as Activated Carbon, Reverse Osmosis, and Ion-Exchange has been proven effective in removing PFAS. However, these treatment methods are proving to be very expensive and generate secondary contamination that needs to be disposed-off or treated. Since the phase out of C8-PFAS compounds, more short chain PFAS compounds are detected in landfill leachate. Hence, an effective treatment strategy is needed to keep up with the rising concentration levels and variety of PFAS compounds. The purpose of this study was to develop a sustainable and cost-effective process using modified Coal Fly-Ash (CFA) that can treat both short chain and long chain PFAS compounds. Previous studies have shown application of CFA in removal of dye and metals from different types of wastewaters. In previous studies CFA was modified to enhance its surface properties, that can improve the adsorption of organic and anionic contaminants. In this study, thermo-chemical modification was used on CFA to remove organic matter and PFAS compounds. Preliminary results showed that, CFA can remove more than 90% UV absorbance, more than 80% TOC and approximately 40% of total PFAS compounds. The maximum adsorption capacity for total PFAS was found to be 84 ng PFAS per g CFA, out of which 70 ng was for short chain PFAS and 14 ng for long chain PFAS compounds. An effective removal of organic matter and PFAS compounds, show a promising application of CFA in leachate treatment. However, further research is needed to analyze the adsorption dynamics, kinetics, post-treatment disposal method, and any possible contamination when mixing CFA with landfill leachate

A Participatory Science Approach to Evaluating Factors Associated with the Occurrence of Metals and PFAS in Guatemala City Tap Water

Limited information is available regarding chemical water quality at the tap in Guatemala City, preventing individuals, water utilities, and public health authorities from making data-driven decisions related to water quality. To address this need, 113 participants among households served by a range of water providers across the Guatemala City metropolitan area were recruited as participatory scientists to collect first-draw and flushed tap water samples at their residence. Samples were transported to the U.S. and analyzed for 20 metals and 25 per- and polyfluoroalkyl substances (PFAS). At least one metal exceeded the Guatemalan Maximum Permissible Limit (MPL) for drinking water in 63% of households (n = 71). Arsenic and lead exceeded the MPL in 33.6% (n = 38) and 8.9% (n = 10) of samples, respectively. Arsenic was strongly associated with groundwater while lead occurrence was not associated with location, water source, or provider. One or more PFAS were detected in 19% of samples (n = 21, range 2.1–64.2 ppt). PFAS were significantly associated with the use of plastic water storage tanks but not with location, water source, or provider. Overall, the high prevalence of arsenic above the MPL in Guatemala City tap water represents a potential health risk that current water treatment processes are not optimized to remove. Furthermore, potential contaminants from premise plumbing and storage, including lead and PFAS, represent additional risks requiring further investigation and public engagement