Recovery of polycyclic aromatic hydrocarbons and their oxygenated derivatives in contaminated soils using aminopropyl silica solid phase extraction

Predicting the Occurrence of Substituted and Unsubstituted, Polycyclic Aromatic Compounds in Coking Wastewater Treatment Plant Effluent using Machine Learning Regression

Organic contaminants such as polycyclic aromatic compounds (PACs) occurring in industrial effluents can not only persist in wastewater but transform into more toxic and mobile, substituted heterocyclic products during treatment. Thus, predicting the occurrence of PACs and their heterocyclic derivatives (HPACs) in coking wastewater is of utmost importance to reduce the environmental risks in water bodies that receive industrial effluents. Although HPACs can be monitored through sampling and analysis, the characterisation techniques used in their analyses are costly and time-consuming. In this study, we propose 3 distinct kernel-based machine learning (ML) models for predicting PACs including substituted HPACs and alkylated PACs occurring in coking wastewater. By using routinely measured wastewater quality data as input for our models, we predicted the occurrence of 14 HPACs in the final effluent of a coking wastewater treatment plant. Support Vector Machine based regression model (SVR) used for HPAC prediction showed the highest R2 of 0.83. Performance assessment of SVR model showed a mean absolute logarithmic error (MALE) of 0.46 and root mean square error (RMSE) of 0.073 ng/L. Comparatively, K-Nearest Neighbor and Random Forest models showed lower R2 of 0.75 and 0.76 respectively for HPAC prediction. Feature analysis attributed the superior predictability of SVR model likely to its higher weightage (81%) towards dissolved organic carbon and total ammonia as input variables. Both these variables could capture the underlying secondary PAC transformations likely occurring in the treatment plant. Partial dependence plots predicted that ammonia levels higher than 120 mg/L and DOC levels of 50-60 mg/L were likely linked to higher HPACs occurring in the final effluent. This work highlights the capability of kernel-based ML models in capturing nonlinear wastewater chemistry and offers a tool for monitoring trace organic contaminants released in coking effluents.

Green preparation of magnetic pyrene-based hyper-cross-linked polymer using dual-purpose ferric chloride reagent for extraction of polycyclic aromatic hydrocarbons from natural water bodies

A magnetic hyper-cross-linked polymer Fe3O4/HCPPYR was prepared using pyrene as the monomer and formaldehyde dimethyl acetal (FDA) as the cross-linking agent. The objective of green chemistry was achieved by employing FeCl3 during the synthesis, as it played a dual role of a catalyst for the Friedel-Crafts reaction and an iron source for the synthesis of magnetic Fe3O4, thus maximizing efficiency and minimizing waste. Fe3O4/HCPPYR was applied as a sorbent for magnetic solid-phase extraction (MSPE) to extract fifteen polycyclic aromatic hydrocarbons (PAHs) from water. The effects of different parameters such as the quantity of adsorbent, the extraction time, the desorption conditions, the pH value and the effect of the salt concentration on the extraction efficiency were optimized. A simple and efficient method in combination with gas chromatography-mass spectrometry (GC-MS) (Fe3O4/HCPPYR-MSPE/GC-MS) was developed and successfully applied for the detection of PAHs in environmental water samples The analytical method showed LODs in the range of 0.004-0.06 µg L-1, which proved to be adequate for the detection all 15 PAHs at trace concentration. Spiked recoveries of PAHs in actual water samples ranged from 85.2 % to 118.5 % with relative standard deviations (RSDs) below 10.2%. These results indicate that the method has a good potential for reusability and possesses excellent sensitivity. This study showcased the potential of Fe3O4/HCPPYR composites in effectively removing organic pollutants from the aqueous environments, demonstrating their ability for water treatment applications.

Solid-phase adsorption methodologies of naturally occurring anthraquinones: A review

INTRODUCTION

Solid-phase extraction applied to plant matrices is nowadays a well-validated technique allowing to concentrate and purify different secondary metabolites. Several classes of phytochemicals have been selectively extracted by this methodology. During the last decade attention has been focused on biologically active anthraquinones from numerous sources like edible, healthy, and medicinal plants.

OBJECTIVES

The aim of this review is to provide a detailed literature survey of the solid-phase adsorption methodologies for the extraction of natural anthraquinones reported so far and to discuss and propose future directions in this field of research.

MATERIALS AND METHODS

Substructure search was performed in the SciFinder Scholar, PubMed, Medline, and Scopus databases.

RESULTS

The first report about application of solid-phase adsorption for the purification of anthraquinones appeared in the literature in 2002. From this date, and in particular during recent years, the most notable examples included the use of chitin- and chitosan-based polymers, of molecularly imprinted polymers, of coated magnetic nanoparticles, of miniaturized matrix solid-phase dispersion, of functionalized resins, of differently structured lamellar solids, and finally of vortex-synchronized matrix solid-phase dispersion.

CONCLUSIONS

The herein detailed solid-phase adsorption methodologies are powerful tools to selectively extract natural anthraquinones and/or provide anthraquinone-enriched phytopreparations. Nevertheless, many other important methods have been applied to synthetic anthraquinones (e.g., azo dyes). These could be conveniently employed also for natural anthranoids. Studies in this field are discussed in this review article.

Synthesis of hypercrosslinked polymers for efficient solid-phase microextraction of polycyclic aromatic hydrocarbons and their derivatives followed by gas chromatography-mass spectrometry determination

Three novel hypercrosslinked polymers (HCPs) were synthesized via Friedel-Crafts reaction employing 1,3,5-tris(bromomethyl)-2,4,6-trimethylbenzene as alkylating agent, and triphenylbenzene, tetraphenylethylene and p-quaterphenyl as the aromatic units, respectively. The prepared HCPs were applied as solid-phase microextraction coatings for direct immersion extraction of polycyclic aromatic hydrocarbons (PAHs) and their oxygenated and nitrated derivatives in environmental water samples. The key factors affecting the extraction efficiency including extraction time, extraction temperature, stirring rate, ionic strength and desorption conditions, were carefully studied. Coupled with gas chromatography mass spectrometry analysis, a new method for determining PAHs and their derivatives was developed. Under the optimized conditions, the limits of detection (S/N=3) and limits of quantitation (the lowest concentration for quantification) of the method were in the range of 2.5-25.0 and 7.5-75.0 ng L^-1, respectively. The recoveries of spiked samples were in the range of 73.1-118.3% with relative standard deviations less than 13.0%. The developed method was applied for the simultaneous determination of nine PAHs and their derivatives in environmental water samples, showing good accuracy and reliability.

Evaluation of the effectiveness of VOC-contaminated soil preparation based on AHP-CRITIC-TOPSIS model

Currently, several methods have been adopted for the laboratory preparation of artificial volatile organic compound (VOC) contaminated soils (VCSs). However, it remains unclear whether the prepared contaminated soils are homogenous. In this study, two representative VOCs, toluene and perchloroethylene, were separately mixed with a kaolin-based soil using six preparation methods. Thereafter, the homogeneity and recovery of the contaminated kaolin prepared using these methods were determined and analyzed. The six procedures were quantitatively assessed according to the comprehensive evaluation mathematical model (AHP-CRITIC-TOPSIS), and the final score order of the different procedures was: A > C > E > B > F > D. Additionally, the qualitative evaluation of the procedures was performed based on the phase transformation and mass transfer during the mixing processes. Based on these discussions, method A, which was considered to be optimal, was then adopted for further investigations with various natural soils. The results showed that this optimal method could be applied to natural soils and revealed that the adsorption-related characteristics of natural soils, including total organic carbon, specific surface area, pore volume, pH, plastic limit, particle size, and mineral composition, influenced the homogeneity and recovery through mass transfer. In addition, it was also observed that the chemical properties of VOCs, including molecular structure, vapor pressure, and the octanol/water partition coefficient, could also affect the effectiveness of sample recovery. Through this study, researchers can prepare VCSs with excellent homogeneity and low loss rates to conduct standardized tests for technology development.