Sample preparation and analytical techniques for determination of polyaromatic hydrocarbons in soils

Polyaromatic Hydrocarbons (PAHs) have been determined in soil samples for many years. PAHs can arise in the environment from natural sources, oil and petroleum products and combustion processes. Although oil spills influence PAHS concentrations in local areas, the major sources of PAHS are anthropogenic and derived from land based combustion sources. PAHs are globally distributed and the highest concentrations generally occur close to urban centres. Monitoring is essential during the assessment and remediation. It makes further demands on the analytical methods used, since the transformation products are often present in lower concentrations than the parent PAHs and they may be difficult to identify in the complex mixtures found in these samples. It is therefore essential to use powerful analytical tools to fractionate, separate and identify the analyses in the samples. In this paper we review those aspects relating to the analysis and monitoring of PAHs in soils. The aim is to provide an overview of current knowledge, so as to assess the need for future monitoring of PAHs and the present capability for their analysis. Further monitoring of PAHs is justified because of their ubiquity in the environment, their persistence and bioaccumulative properties and their potential for toxicity both to aquatic organisms and human consumers

Une histoire de Vincennes. Mémoire pour l'an 2000

International audienc

Une histoire de Vincennes. Mémoire pour l'an 2000

International audienc

Multi-step fractionation as a tool for enhanced valorization of technical lignins

The valorisation of lignin obtained as a by-product of the pulping and biofuel industries is one of the most promising topics in the bioresource field. Despite its potential value as the only massively available aromatic biopolymer feedstock, technical lignin is nowadays mostly burnt as low cost energy source because of its chemical recalcitrance. The high heterogeneity of this material, largely dependent on the different vegetal sources and the specific biomass recovery methods, restricts its direct use and hinders also the optimization of depolymerisation approaches. The development of effective technical lignin fractionation strategies is therefore today one of the most challenging topic in the green chemistry field. In this study, the fractionation of two industrial commercial lignins was performed by a three step procedure set-up either in aqueous or in environmentally friendly organic solvents in order to obtain sustainable and scalable processes. The first step consisted in a microfiltration or a Soxhlet extraction in function of the solvent used. Then a cascade membrane ultrafiltration allowed to obtain at the end three refined lignin fractions (see Figure below) which were fully characterized, presenting better defined physico-chemical properties compared to the starting raw material. The availability of technical lignin fractions with tailored and reproducible characteristics allows the set-up of enhanced lignin valorization strategies for the development of bio-based polymers and preparation of key platform chemicals, thereby paving the way for an effective exploitation and valorization of this remarkable resource. Allegretti, A.; Fontanay, S.; Krauke, Y.; Luebbert, M.; Strini, A.; Troquet, J.; Turri, S.; Griffini, G.; D’Arrigo, P. ACS Sustainable Chem. Eng. 2018, 6, 9056-9064. Acknoledgements: ValorPlus Project (grant agreement no FP7-KBBE-2013-7-613802)

Tuning Lignin Characteristics by Fractionation: A Versatile Approach Based on Solvent Extraction and Membrane-Assisted Ultrafiltration

Technical lignins, typically obtained from the biorefining of lignocellulosic raw materials, represent a highly abundant natural aromatic feedstock with high potential in a sustainable economy scenario, especially considering the huge primary production volumes and the inherently renewable nature of this resource. One of the main drawbacks in their full exploitation is their high variability and heterogeneity in terms of chemical composition and molecular weight distribution. Within this context, the availability of effective and robust fractionation processes represents a key requirement for the effective valorization of lignin. In the present work, a multistep fractionation of two different well known technical lignins obtained from two distinct delignification processes (soda vs. kraft pulping) was described. A comprehensive approach combining solvent extraction in organic or aqueous medium with membrane-assisted ultrafiltration was developed in order to maximize the process versatility. The obtained lignin fractions were thoroughly characterized in terms of their chemical, physical, thermal, and structural properties, highlighting the ability of the proposed approach to deliver consistent and reproducible fractions of well-controlled and predictable characteristics, irrespective of their biomass origin. The results of this study demonstrate the versatility and the reliability of this integrated multistep fractionation method, which can be easily adapted to different solvent media using the same ultrafiltration membrane set up, thereby enhancing the potential applicability of this approach in an industrial scale-up perspective for a large variety of starting raw lignins

Fractionation: an essential tool for lignin valorization

Lignin is a hydrophobic three-dimensional polymer that acts as a binder accounting for the plants structural integrity and as a regulator for the water flux inside the cell wall. Lignin utilization as a potential feedstock for chemical products has attracted more and more attention. Being one of the three main constituents in biomass, it represents a very attractive low-cost, renewable and largely available starting material. However, lignin is difficult to decompose due to its structural complexity and its high stability and up to now most of lignin is burned as a source of energy. Nowadays valorization of lignin and its transformation into small high value chemicals represent a real challenge and is fully linked to the complexity and the heterogeneity of the starting material. Such variability originates from the source of the biomass, the growing parameters and the extraction conditions. One of the best ways to degrade lignin is by using oxidative depolymerization processes. The main drawback of these methods is the possibility of a fast recombination of the small molecules which are already part of the raw material performed by oxygen-based radical species [1]. In order to obtain more homogeneous starting material for the following oxidative treatments, we set-up an industrial fractionation method. The starting material which has been used in this work has been the Lignin ProtobindTM1000 which is an agricultural fiber soda pulp. The fractionation step is a necessary tool to obtain different fractions which appear much more consistent in terms of average molecular weight, polydispersity and solubility. In this work ProtobindTM1000 has been dissolved in an aqueous/ethanol solution and submitted firstly to a microfiltration under vacuum in order to eliminate the insoluble residue. Then it undergoes the cross-flow filtration process using two subsequent membranes with a cut-off of 3 kDa and 1 kDa. All the retentate and permeate fractions of the fractionation process have been fully characterized in terms of composition, chemical and physical properties. This strategy has offered an essential tool for a more efficient lignin valorization allowing to identify specific applications for all the different fractions, spanning from the material science [2] to the preparative organic chemistry. Acknowledgements This work has been performed as part of the ValorPlus Project that has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no FP7-KBBE-2013-7-613802

Fractionation: an essential tool for lignin valorization

Lignin is a hydrophobic three-dimensional polymer that acts as a binder accounting for the plants structural integrity and as a regulator for the water flux inside the cell wall. Lignin utilization as a potential feedstock for chemical products has attracted more and more attention. Being one of the three main constituents in biomass, it represents a very attractive low-cost, renewable and largely available starting material. However, lignin is difficult to decompose due to its structural complexity and its high stability and up to now most of lignin is burned as a source of energy. Nowadays valorization of lignin and its transformation into small high value chemicals represent a real challenge and is fully linked to the complexity and the heterogeneity of the starting material. Such variability originates from the source of the biomass, the growing parameters and the extraction conditions. One of the best ways to degrade lignin is by using oxidative depolymerization processes. The main drawback of these methods is the possibility of a fast recombination of the small molecules which are already part of the raw material performed by oxygen-based radical species [1]. In order to obtain more homogeneous starting material for the following oxidative treatments, we set-up an industrial fractionation method. The starting material which has been used in this work has been the Lignin ProtobindTM1000 which is an agricultural fiber soda pulp. The fractionation step is a necessary tool to obtain different fractions which appear much more consistent in terms of average molecular weight, polydispersity and solubility. In this work ProtobindTM1000 has been dissolved in an aqueous/ethanol solution and submitted firstly to a microfiltration under vacuum in order to eliminate the insoluble residue. Then it undergoes the cross-flow filtration process using two subsequent membranes with a cut-off of 3 kDa and 1 kDa. All the retentate and permeate fractions of the fractionation process have been fully characterized in terms of composition, chemical and physical properties. This strategy has offered an essential tool for a more efficient lignin valorization allowing to identify specific applications for all the different fractions, spanning from the material science [2] to the preparative organic chemistry. Acknowledgements This work has been performed as part of the ValorPlus Project that has received funding from the European Union's Seventh Framework Programme for research, technological development and demonstration under grant agreement no FP7-KBBE-2013-7-613802