Bioavailability in soils

The consumption of locally-produced vegetables by humans may be an important exposure pathway for soil contaminants in many urban settings and for agricultural land use. Hence, prediction of metal and metalloid uptake by vegetables from contaminated soils is an important part of the Human Health Risk Assessment procedure. The behaviour of metals (cadmium, chromium, cobalt, copper, mercury, molybdenum, nickel, lead and zinc) and metalloids (arsenic, boron and selenium) in contaminated soils depends to a large extent on the intrinsic charge, valence and speciation of the contaminant ion, and soil properties such as pH, redox status and contents of clay and/or organic matter. However, chemistry and behaviour of the contaminant in soil alone cannot predict soil-to-plant transfer. Root uptake, root selectivity, ion interactions, rhizosphere processes, leaf uptake from the atmosphere, and plant partitioning are important processes that ultimately govern the accumulation ofmetals and metalloids in edible vegetable tissues. Mechanistic models to accurately describe all these processes have not yet been developed, let alone validated under field conditions. Hence, to estimate risks by vegetable consumption, empirical models have been used to correlate concentrations of metals and metalloids in contaminated soils, soil physico-chemical characteristics, and concentrations of elements in vegetable tissues. These models should only be used within the bounds of their calibration, and often need to be re-calibrated or validated using local soil and environmental conditions on a regional or site-specific basis.Mike J. McLaughlin, Erik Smolders, Fien Degryse, and Rene Rietr

A Review on Progress in QSPR Studies for Surfactants

This paper presents a review on recent progress in quantitative structure-property relationship (QSPR) studies of surfactants and applications of various molecular descriptors. QSPR studies on critical micelle concentration (cmc) and surface tension (γ) of surfactants are introduced. Studies on charge distribution in ionic surfactants by quantum chemical calculations and its effects on the structures and properties of the colloids of surfactants are also reviewed. The trends of QSPR studies on cloud point (for nonionic surfactants), biodegradation potential and some other properties of surfactants are evaluated

QSPR Studies on Aqueous Solubilities of Drug-Like Compounds

A rapidly growing area of modern pharmaceutical research is the prediction of aqueous solubility of drug-sized compounds from their molecular structures. There exist many different reasons for considering this physico-chemical property as a key parameter: the design of novel entities with adequate aqueous solubility brings many advantages to preclinical and clinical research and development, allowing improvement of the Absorption, Distribution, Metabolization, and Elimination/Toxicity profile and “screenability” of drug candidates in High Throughput Screening techniques. This work compiles recent QSPR linear models established by our research group devoted to the quantification of aqueous solubilities and their comparison to previous research on the topic

Environmentally Benign Production of Ionic Liquids in CO2-Expanded Systems

The need to reduce air pollution in chemical manufacturing processes continues to drive the search for alternative solvents. Ionic Liquids (ILs) have emerged in recent years as a promising solution. In contrast to traditional organic solvents, ILs have negligible volatility, which eliminates air emissions and harmful worker exposure concerns. Various combinations of cations and anions afford distinct properties to an IL, such as melting point, solvation properties, and phase behavior; thus making it possible to molecularly design or engineer ILs for specific tasks across many chemical sectors. Unfortunately, many ILs are synthesized and processed using the very organic solvents which they are purportedly replacing. Despite the exponential growth in this field, very little work focuses on developing alternative synthesis and production methods for ILs. The objective of this dissertation is to investigate novel economically viable and environmentally benign methodologies for ionic liquid production. Three solvent platforms: 1) conventional organic solvents; 2) compressed and supercritical CO2; 3) CO2-Expanded DMSO are considered for the synthesis of IL synthesis. A full understanding of the kinetics and effects of solvent in the synthesis of ILs is of great importance for optimally selecting a benign and economically viable solvent for IL production. Empirical LSER expression, correlating kinetic rate constant with solvent polarity was obtained, which will facilitate rapid data generation needed for engineering production processes of different ILs in varied solvent systems. While some general trends for these Mentshukin-type reactions are widely known, quantitative second (2nd) order rate constants are reported here. The use of CO2 in the synthesis of ILs has many advantages over conventional solvents. CO2 induces IL-solvent mixtures to split into IL-rich and organic solvent-rich phases that can be decanted or extracted for easy separations, simply by controlling pressure, temperature and CO2 loading. This work demonstrates that CO2 is a flexible and tunable solvent for the synthesis of the model IL 1-hexyl-3-methylimidazolium bromide ([HMIm][Br]). Previously, our group has found that among ten organic solvents, DMSO has the highest kinetic rate for the synthesis of [HMIm][Br]). Although DMSO is a relatively environmentally benign solvent, it is beset with a high boiling point (189oC), rendering it both economically and environmentally non-feasible as a solvent option. The synthesis and processing of ILs in gas-expanded DMSO alleviates these issues. Furthermore, gas expanded liquids reduce the amount of organic solvent needed for the reaction. This work, for the first time, leverages the kinetic benefits of DMSO and the thermodynamic advantages of benign CO2 for the production of ILs. Specifically, this study explored another promising solvent media; CO2 expanded liquid DMSO (CXLs).Non-complex separation schemes are proposed from mixture phase behavior. Kamlet-Taft polarity parameters for CO2 expanded DMSO are also reported. Experimental high-pressure phase equilibria data were measured and modeled for CO2 binary, ternary and pseudo-binary systems encountered in the synthesis of [HMIm][Br]. Unique chemical and thermodynamic behaviors are observed in the IL-synthesis mixtures. Using estimated critical properties to correlate the vapor-liquid equilibrium, the Peng-Robinson equations of state, with van der waals 2-parameter mixing rules, were found to sufficiently correlate data. The phase equilibrium data allow better understanding and kinetic characterization of the synthesis of ILs with CO2. Results have important ramifications on the kinetics and process constraints of an actual IL synthesis in high pressure systems. Design considerations for optimizing solvents ratio, kinetic properties and separations are discussed. Here, the systematic risk assessment methodology was extended to ILs systems. Environmental assessments of different IL synthesis routes studied here are performed and presented. Potential issues (unit operations that have the most impact on the environment and profitability) in the life cycle of the processes are identified. Green sustainable methodology was extended to applications of ILs viz cellulose valorization and processing, separations and the fabrication of cellulosic materials

Rehabilitation of a complex industrial wastewater containing heavy metals and organic solvents using low cost permeable bio-barriers from lab-scale to pilot-scale

This work addresses the treatment of a complex industrial effluent containing high concentrations of metals and spiked with two organic solvents (diethylketone DEK, and methyl ethyl ketone - MEK) using an eco-friendly approach. The treatment system herein proposed consists of a bio-barrier that combines the adsorption capacity of sepiolite with the properties of a Streptococcus equisimilis biofilm with proven ability in the degradation and bioremoval of a wide range of pollutants. Results from the open-systems experiments conducted with raw sepiolite exposed to a binary mixture of DEK and MEK revealed the preference of the sorbent towards DEK. The results from the biodegradation experiments also revealed the preference of S. equisimilis to degrade/bioremove DEK over MEK independently of their initial concentration (100 mg/L to 3200 mg/L). Bioremoval percentages higher than 95 % were reached for all the concentrations of DEK tested. The lab-scale experiments conducted in open-system with sepiolite and sepiolite covered with biofilm, and the pilot-scale experiment conducted in closed-loop, revealed similar performances on the rehabilitation of an industrial effluent containing heavy metals and additionally spiked with DEK and MEK. Regarding the selectivity towards the different pollutants, Cu was preferentially removed over Cr and Ni, and DEK over MEK. The presence of the biofilm allowed an improvement on the removal of heavy metals, particularly Cr, besides preventing the leaching of Al, Fe, and Mg from the sepiolite structure, an extremely important advantage in comparison to the system without biofilm. EDS analyses performed in sepiolite samples revealed the presence of several metals (Cr, Cu and Ni), proving thus the occurrence of sorption processes by sepiolite and by sepiolite covered by biofilm. The breakthrough data obtained in the open-systems were properly described by the Dose Response and the Yoon and Nelson mathematical models. More research work needs to be performed with complex industrial effluents aiming the optimization of the treatment systems to be applied in real context scenarios.This study was supported by the Portuguese Foundation for Science and Technology (FCT) under the scope of the research project PTDC/ AAG-TEC/5269/2014, the strategic funding of UID/BIO/04469/2020 unit and BioTecNorte operation (NORTE-01-0145-FEDER-000004) funded by the European Regional Development Fund under the scope of Norte2020 - Programa Operacional Regional do Norte, Portugal. A. Lago and V. Rocha, thank FCT for the concession of their PhD grants (SFRH/ BD/132271/2017 and SFRH/BD/141073/2018).info:eu-repo/semantics/publishedVersio

Review of risk from potential emerging contaminants in UK groundwater

This paper provides a review of the types of emerging organic groundwater contaminants (EGCs) which are beginning to be found in the UK. EGCs are compounds being found in groundwater that were previously not detectable or known to be significant and can come from agricultural, urban and rural point sources. EGCs include nanomaterials, pesticides, pharmaceuticals, industrial compounds, personal care products, fragrances, water treatment by-products, flame retardants and surfactants, as well as caffeine and nicotine. Many are relatively small polar molecules which may not be effectively removed by drinking water treatment. Data from the UK Environment Agency’s groundwater screening programme for organic pollutants found within the 30 most frequently detected compounds a number of EGCs such as pesticide metabolites, caffeine and DEET. Specific determinands frequently detected include pesticides metabolites, pharmaceuticals including carbamazepine and triclosan, nicotine, food additives and alkyl phosphates. This paper discusses the routes by which these compounds enter groundwater, their toxicity and potential risks to drinking water and the environment. It identifies challenges that need to be met to minimise risk to drinking water and ecosystems

Facilitated Transport of Triclosan in the Receiving Environment of an Onsite Wastewater Treatment System: Agent of Aquatic Concern

Triclosan (TCS) is an antibacterial found in a host of consumer products ranging from toothpaste to textiles. While initially confined to health care settings, the increased popularity of antimicrobial products has resulted in a surge of products containing this compound and can currently be found in over 700 consumer products. The fate of TCS in wastewater treatment plants (WWTPs) and loss mechanisms once exposed to the environment is a topic that has gained much attention over recent years. However, similar research in onsite systems, where its presence and subsequent persistence can have similar adverse environmental effects, is lacking. It is the objective of this study to examine the interaction of TCS to a sorbing medium in the presence of treated effluent from an onsite wastewater treatment system (OWTS). Experiments conducted to examine factors that govern this behavior were centered around three main points of interest: 1) the interaction of TCS to the sorbing medium in the presence and absence of DOM, 2) the mobility of TCS in the presence and absence of DOM, and 3) the effect DOM with a high and low organic carbon concentrations on sorption and mobility. Laboratory scale batch sorption equilibrium and column transport studies were used to observe the solution interaction of TCS in the presence of a sorptive material, 100% quartz sand. Treatments consisted of three solutions: 1) low organic content (LOC) wastewater filtrate (\u3c0.45µm), 2) high organic content (HOC) wastewater filtrate (\u3c0.45µm), and 3) 5 mM CaCl2 serving as the organic free control (NOC). Human derived wastewater from OWTSs was collected for wastewater treatment solutions. Sorption data fit to the Freundlich isotherm model indicates the greatest amount of TCS sorption to sand in the presence of CaCl2 as compared to LOC and HOC treatments. The Freundlich sorption coefficient (KF) revealed the least amount of sorption in the LOC treatment. Statistical analysis showed significant differences (P\u3c0.001) between all three treatment means. Based on isotherm results, TCS has the potential to be preferentially transported by DOM. Column transport experiments also indicate the potential for facilitated transport by DOM in both LOC and HOC treatments. Breakthrough curves demonstrate earlier breakthrough in DOM treatments as compared to NOC. Although DOM treatments (LOC and HOC) were not found to be significantly different from each other, both were significantly different from the NOC treatment (P\u3c0.001). Batch and transport results indicate potential for the facilitated transport of TCS by DOM. However, predicted (batch sorption) and calculated (CXTFIT v2.0) retardation factors did not correlate well with each other. Equilibrium effects were expected to be the dominant factor behind this discrepancy