Biochar characterization for its environmental and agricultural utilization. Occurrence, distribution and fate of labile organic carbon and polycyclic aromatic hydrocarbons

In this thesis the potential risks associated to the application of biochar in soil as well the stability of biochar were investigated. The study was focused on the potential risks arising from the occurrence of polycyclic aromatic hydrocarbons (PAHs) in biochar. An analytical method was developed for the determination of the 16 USEPA-PAHs in the original biochar and soil containing biochar. The method was successfully validated with a certified reference material for the soil matrix and compared with methods in use in other laboratories during a laboratory exercise within the EU-COST TD1107. The concentration of 16 USEPA-PAHs along with the 15 EU-PAHs, priority hazardous substances in food, was determined in a suite of currently available biochars for agricultural field applications derived from a variety of parent materials and pyrolysis conditions. Biochars analyzed contained the USEPA and some of the EU-PAHs at detectable levels ranging from 1.2 to 19 µg g-1. This method allowed investigating changes in PAH content and distribution in a four years study following biochar addition in soils in a vineyard (CNR-IBIMET). The results showed that biochar addition determined an increase of the amount of PAHs. However, the levels of PAHs in the soil remained within the maximum acceptable concentration for European countries. The vineyard soil performed by CNR-IBIMET was exploited to study the environmental stability of biochar and its impact on soil organic carbon. The stability of biochar was investigated by analytical pyrolysis (Py-GC-MS) and pyrolysis in the presence of hydrogen (HyPy). The findings showed that biochar amendment significantly influence soil stable carbon fraction concentration during the incubation period. Moreover, HyPy and Py-GC-MS were applied to biochars deriving from three different feedstock at two different pyrolysis temperatures. The results evidenced the influence of feedstock type and pyrolysis conditions on the degree of carbonisation.

Methylmercury and polycyclic aromatic hydrocarbons in Mediterranean seafood: a molecular anthropological perspective

Seafood carries several contaminants, among which mercury and polycyclic aromatic hydrocarbons are those that cause major concern. Evidence exists that human populations are exposed to these environmental chemicals since ancient times, which may have driven the positive selection of specific genetic polymorphisms related to chemicals toxicokinetic. Both mercury and polycyclic aromatic hydrocarbons are able to cause DNA methylation changes in humans. Some Mediterranean populations may be particularly exposed to these contaminants, being the Mediterranean Sea at a high-risk for contamination by toxic compounds, and because of their traditionally high consumption of locally caught seafood. Starting from these premises the present thesis aims to contribute to the understanding of the molecular impact of seafood consumption on the biology of the Mediterranean population. To this end the work has been divided into four main parts: (1) the development and meta-analysis of a georeferenced database on polycyclic aromatic hydrocarbons in Mediterranean seafood aimed at identifying geographical patterns of contamination and trends that could be related to the biology of the marine organisms, to the physico-chemical properties of each hydrocarbon and to the oceanographic characteristic of the Mediterranean; (2) the development and validation of a food frequency questionnaire to estimate the intake of mercury through seafood consumption among a population living in a geographic area that is usually considered a contamination hotspot; (3) the creation of a biobank made of biological samples from members of several Italian communities together with information on their dietary habits, lifestyle and general health; (4) a review of the literature on the genetic component of individual susceptibility to methylmercury and polycyclic aromatic hydrocarbons exposure in humans, to the effects that these pollutants have on human DNA methylation, and to the evidence that Mediterranean coastal communities represent an informative case study to investigate the potential molecular impact of these chemicals.

Electrochemistry of polycyclic aromatic molecules for advanced carbon nanostructures: luminescence and transistor applications

Polycyclic aromatic hydrocarbons (PAHs) are a large class of π-conjugated organic molecules with fused aromatic rings, which can be considered as fragments of 2D-graphene and have been extensively studied for their unique optical and electronic properties. The aim of this study is to understand the complex electrochemical behaviour of planar, curved, and heteroatom doped polycyclic aromatic molecules, particularly focusing on the oxidative coupling of their radical cations and the electrochemically induced cyclodehydrogenation reactions. In the first part of this thesis, the class of PAHs and aromatic nanostructures are introduced, and the reactivity of electrogenerated species is discussed, focusing on the electrochemical approach for the synthesis of extended π-conjugated structures. Subsequently, the electrochemical properties and reactivity of electrogenerated radical ions of planar and curved polyaromatics are correlated to their structures. In the third chapter, electrochemical cyclodehydrogenation of hexaphenylbenzene is used to prepare self-assembled hexabenzocoronene, directly deposited on an interdigitated electrode, which was characterised as organic electrochemical transistor. In the fourth chapter, the electrochemical behaviour of a family of azapyrene derivatives has been carefully investigated together with the electrogenerated chemiluminescence (ECL), both by ion-annihilation and co-reactant methods. Two structural azapyrene isomers with different nitrogen positions are thoroughly discussed in terms of redox and ECL properties. Interestingly, the ECL of only one of them showed a double emission with excimer formation. A detailed mechanism is discussed for the ECL by co-reactant benzoyl peroxide, to rationalise the different ECL behaviours of the two isomers on the basis of their topologically modulated electronic properties. In conclusion, the different electrochemical behaviours of PAHs were shown, focussing on the chemical reactivity of the electrogenerated species and taking advantage of it for important processes spanning from unconventional synthesis methods for carbon nanostructures to the exploitation of self-assembled nanostructured systems in organic electronics, to novel organic emitters in ECL.

Nuovi catalizzatori per l'idrogenazione, l'idrogenolisi/ring-opening di composti aromatici policiclici

The removal of aromatic hydrocarbons from diesel has received considerable attention after environmental regulations that require petroleum refiners to raise cetane number and to limit aromatics in diesel fuel in order to improve combustion efficiency and reduce particulate and NOx emissions. An alternative is blending with Fischer–Tropsch (FT) gas-to-liquid diesel fuel; however, this option may not be economically viable solution in case of extensive blend. Another alternative is to incorporate in the diesel pool a greater fraction of the so-called light cycle oil (LCO). Due to its high aromatics content and its low cetane number (typically between 20 and 30), the incorporation of LCO may have a negative impact on the quality of diesel. Current technologies for LCO improvement are based on hydrogenation to adjust both sulphur and cetane number but while an important fraction of the aromatics present in LCO can be saturated in a deep hydrogenation process, the cetane number may still be lower than the target values specified in diesel legislations, so further upgrading is needed. An interesting technology for improving the cetane number of diesels and maintaining meanwhile high diesel yields is achieved by combining a complete hydrogenation process with a selective ring opening (SRO) reaction of the naphthenic rings. The SRO can be defined as naphthene ring-opening to form compounds with high cetane number, but without any carbon losses. Controlling the interconversion of six- and five- membered rings via an acid-catalyzed ring-contraction step is also of great importance, since selective conversion of six-membered to five-membered naphthene rings greatly influences ring-opening rates and selectivity. High intrinsic activity may be enhanced by deposition of noble metals on acidic, high surface area supports, because it is possible to arrange close proximity of the metal and acid sites. Moreover, in large-pore supports, the diffusion resistance of liquid reactants into the pores is minimized. In addition to metal centres, the acid sites of support also plays role in aromatics hydrogenation. However, the functions of different kinds of acid sites (Brønsted vs. Lewis acidity), and their optimal concentrations and strengths, remain unclear. In the present study we investigated the upgrading of an aromatic-rich feedstock over different type of metal supported on mesoporous silica-alumina. The selective hydrogenolysis and ring opening of tetrahydronaphthalene (THN or tetralin) was carried out as representative of LCO fractions after deep hydrogenation process. In this regards the aim of this study is to evaluate both the effect of metals and that of the supports characterized by different acid distribution and strength, on conversion and selectivity. For this purpose a series of catalysts were prepared by impregnation. The catalysts were characterized and conversion tests of THN were performed in a lab-scale plant operating in the pressure range from 7.0-5.0 MPa and in the temperature range from 300 to 360°C.

Sviluppo di tecniche di analisi ifenate per la quantificazione di biomarcatori di esposizione a tossici ambientali: gli acidi mercapturici

Human biomonitoring (HBM) is an ideal tool for evaluating toxicant exposure in health risk assessment. Chemical substances or their metabolites related to environmental pollutants can be detected as biomarkers of exposure using a wide variety of biological fluids. Individual exposure to aromatic hydrocarbon compounds (benzene, toluene, and o-xylene –“BTX”) were analysed with a liquid chromatography coupled to electrospray ionisation-mass spectrometry (μHPLC-ESI-MS/MS) method for the simultaneous quantitative detection of the BTX exposure biomarker SPMA, SBMA and o-MBMA in human urine. Urinary S-phenylmercapturic acid (SPMA) is a biomarker proposed by the American Conference of Governmental Industrial Hygienists (ACGIH) for assessing occupational exposure to benzene (Biological Exposure Index of 25 microg/g creatinine). Urinary S-benzylmercapturic (SBMA) and o-methyl S-benzyl mercapturic acid (o-MBMA) are specific toluene and o-xylene metabolites of glutathione detoxicant pathways, proposed as reliable biomarkers of exposure. To this aim a pre-treatment of the urine with solid phase extraction (SPE) and an evaporation step were necessary to concentrate the mercapturic acids before instrumental analysis. A liquid chromatography separation was carried out with a reversed phase capillary column (Synergi 4u Max-RP) using a binary gradient composed of an acquous solution of formic acid 0.07% v/v and methanol. The mercapturic acids were determinated by negative-ion-mass spectrometry and the data were corrected using isotope-labelled analogs as internal standards. The analytical method follows U.S. Food and Drug Administration guidance and was applied to assess exposure to BTX in a group of 396 traffic wardens. The association between biomarker results and individual factors, such as age, sex and tobacco smoke were also investigated. The present work also included improvements in the methods used by modifying various chromatographic parameters and experimental procedures. A partial validation was conducted to evaluate LOD, precision, accuracy, recovery as well as matrix effects. Higher sensitivity will be possible in future biological monitoring programmes, allowing evaluation of very low level of BTX human exposure. Keywords: Human biomonitoring, aromatic hydrocarbons, biomarker of exposure, HPLC-MS/MS.

Chemical analysis and reactivity of biomass pyrolysis products. Application to the development of carbon-neutral biofuels and chemicals

In this dissertation the pyrolytic conversion of biomass into chemicals and fuels was investigated from the analytical point of view. The study was focused on the liquid (bio-oil) and solid (char) fractions obtainable from biomass pyrolysis. The drawbacks of Py-GC-MS described so far were partially solved by coupling different analytical configurations (Py-GC-MS, Py-GC-MIP-AED and off-line Py-SPE and Py-SPME-GC-MS with derivatization procedures). The application of different techniques allowed a satisfactory comparative analysis of pyrolysis products of different biomass and a high throughput screening on effect of 33 catalysts on biomass pyrolysis. As the results of the screening showed, the most interesting catalysts were those containing copper (able to reduce the high molecular weight fraction of bio-oil without large yield decrease) and H-ZSM-5 (able to entirely convert the bio-oil into “gasoline like” aromatic products). In order to establish the noxious compounds content of the liquid product, a clean-up step was included in the Py-SPE procedure. This allowed to investigate pollutants (PAHs) generation from pyrolysis and catalytic pyrolysis of biomass. In fact, bio-oil from non-catalytic pyrolysis of biomass showed a moderate PAHs content, while the use of H-ZSM-5 catalyst for bio-oil up-grading determined an astonishing high production of PAHs (if compared to what observed in alkanes cracking), indicating an important concern in the substitution fossil fuel with bio-oil derived from biomass. Moreover, the analytical procedures developed in this thesis were directly applied for the detailed study of the most useful process scheme and up-grading route to chemical intermediates (anhydrosugars), transportation fuels or commodity chemicals (aromatic hydrocarbons). In the applied study, poplar and microalgae biomass were investigated and overall GHGs balance of pyrolysis of agricultural residues in Ravenna province was performed. A special attention was put on the comparison of the effect of bio-char different use (fuel or as soil conditioner) on the soil health and GHGs emissions.

Food Safety and Mineral Oil Contaminated Paperboard Packaging: an Analytical Challenge and a Migration Study

Food packaging protects food, but it can sometimes become a source of undesired contaminants. Paper based materials, despite being perceived as “natural” and safe, can contain volatile contaminants (especially if made from recycled paper) able to migrate to food, as mineral oil, phthalates and photoinitiators. Mineral oil is a petroleum product used as printing ink solvent for newspapers, magazines and packaging. From paperboard printing and from recycled fibers (if present), mineral oil migrates into food, even if dry, through the gas phase. Its toxicity is not fully evaluated, but a temporary Acceptable Daily Intake (ADI) of 0.6 mg kg-1 has been established for saturated mineral oil hydrocarbons (MOSH), while aromatic hydrocarbons (MOAH) are more toxic. Extraction and analysis of MOSH and MOAH is difficult due to the thousands of molecules present. Extraction methods for packaging and food have been optimized, then applied for a “shopping trolley survey” on over 100 Italian and Swiss market products. Instrumental analyses were performed with online LC-GC/FID. Average concentration of MOSH in paperboards was 626 mg kg-1. Many had the potential of contaminating foods exceeding temporary ADI tens of times. A long term migration study was then designed to better understand migration kinetics. Egg pasta and müesli were chosen as representative (high surface/weight ratio). They were stored at different temperatures (4, 20, 30, 40 and 60°C) and conditions (free, shelved or boxed packs) for 1 year. MOSH and MOAH kinetic curves show that migration is a fast process, mostly influenced by temperature: in egg pasta (food in direct contact with paperboard), half of MOSH is transferred to food in a week at 40°C and in 8 months at 20°C. The internal plastic bag present in müesli slowed down the startup of migration, creating a “lag time” in the curves.

Crystal engineering of co-crystals and host-guest systems for environmentally friendly applications: sunscreens stabilization, pollutant sequestering and herbicide reformulation.

Solid state engineered materials have proven to be useful and suitable tools in the quest of new materials. In this thesis different crystalline compounds were synthesized to provide more sustainable products for different applications, as in cosmetics or in agrochemistry, to propose pollutants removal strategy or to obtain materials for electrocatalysis. Therefore, the research projects presented here can be divided into three main topics: (i) sustainable preparation of solid materials of widely used active ingredients aimed at the reduction of their occurrence in the natural environment. The systems studied in this section are cyclodextrins host-guest compounds, obtained via mechanochemical and slurry synthesis. The first chemicals studied are sunscreens inclusion complexes, that proved to have enhanced photostability and desired photoprotection. The same synthetic methods were applied to obtain inclusion complexes of bentazon, a herbicide often found to leach in groundwaters. The resulting products showed to have desired water solubility properties. The same herbicide was also adsorbed on amorphous calcium phosphate nanoparticles, to obtain a biocompatible formulation of this agrochemical. This herbicide could benefit by the adsorption on nanoparticles for what concerns its kinetic release in different media as well as its photostability. (ii) Sustainable synthesis of co-crystals based on polycyclic aromatic hydrocarbons, for the proposal of a sequestering method with a resulting material with enhanced properties. The co-crystallization via mechanochemical means proved that these pollutants can be sequestered via simple solvent-free synthesis and the obtained materials present better photochemical properties when compared to the starting co-formers. (iii) Crystallization from mild solvents of nanosized materials useful for the application in electrocatalysis. The study of compounds based on nickel and cobalt metal ions resulted in the obtainment of 2D and 1D coordination polymers. Moreover, solid solutions were obtained. These crystals showed layered structures and, according to preliminary results, they can be exfoliated.

Liquid biofuels for aviation: valorisation of the by-product biochar

Biochar is a carbonaceous material produced through pyrolysis of biomass. One promising application of biochar is phosphorus recovery from wastewater. Phosphorus is a vital nutrient for plant growth, but its use in fertilizers often leads to runoff or leaching. Wastewater treatment plants discharge large amounts of phosphorus-rich wastewater, contributing to eutrophication and ecological harm. Biochar can sorb phosphorus, retaining it in solid form. In this thesis, two composites made of biomass and dolomite or shells exhibited superior phosphate sorption compared to biochar alone, reaching up to 100% sorption. Biochar also finds use in soil remediation, specifically in cleaning up contaminated soil. Polycyclic aromatic hydrocarbons (PAHs), which can be carcinogenic and toxic, can be present in soil. Biochar adsorb PAHs, preventing their leakage or bioaccumulation. Hetero-PAHs, a subclass of PAHs with nitrogen, sulfur, or oxygen atoms in their ring structures, are particularly challenging to degrade. Little is known about their behavior or sorption onto biochar. In this thesis, biochar and activated carbon were effective in immobilizing PAHs and hetero-PAHs in real soils, with rates of immobilization reaching 100%. Biochar performed equally or better than activated carbon, offering a cost-effective alternative due to its lower price. Biochar reduce of metal(loid)s mobility in soil. Metal(loid)s like lead, zinc, and arsenic can contaminate soil through industrial sources, agricultural runoff, and other pollution, and are toxic to plants and animals, rendering the soil unsuitable for agriculture. When biochar is added to contaminated soil, it binds to metal(loid)s, preventing leaching into the environment. A biomass-dolomite composite was compared to activated carbon for immobilizing metal(loid)s in contaminated soils. The composite generally outperformed activated carbon and exhibited the ability to immobilize arsenic. In summary, biochar shows promise for phosphorus recovery, soil remediation, and reducing the mobility of heavy metals, offering cost-effective and sustainable solutions to these environmental challenges.

Halogenated aliphatic and aromatic aerobic biodegradation via direct metabolism and cometabolism: batch and continuous tests

In this thesis the application of biotechnological processes based on microbial metabolic degradation of halogenated compound has been investigated. Several studies showed that most of these pollutants can be biodegraded by single bacterial strains or mixed microbial population via aerobic direct metabolism or cometabolism using as a growth substrates aromatic or aliphatic hydrocarbons. The enhancement of two specific processes has been here object of study in relation with its own respective scenario described as follow: 1st) the bioremediation via aerobic cometabolism of soil contaminated by a high chlorinated compound using a mixed microbial population and the selection and isolation of consortium specific for the compound. 2nd) the implementation of a treatment technology based on direct metabolism of two pure strains at the exact point source of emission, preventing dilution and contamination of large volumes of waste fluids polluted by several halogenated compound minimizing the environmental impact. In order to verify the effect of these two new biotechnological application to remove halogenated compound and purpose them as a more efficient alternative continuous and batch tests have been set up in the experimental part of this thesis. Results obtained from the continuous tests in the second scenario have been supported by microbial analysis via Fluorescence in situ Hybridisation (FISH) and by a mathematical model of the system. The results showed that both process in its own respective scenario offer an effective solutions for the biological treatment of chlorinate compound pollution.

Conformation and Stereodynamic of Hindered Aromatic System

The preparation of conformationally hindered molecules and their study by DNMR and computational methods are my thesis’s core. In the first chapter, the conformations and the stereodynamics of symmetrically ortho-disubstituted aryl carbinols and aryl ethers are described. In the second chapter, the structures of axially chiral atropisomers of hindered biphenyl carbinols are studied. In the third chapter, the steric barriers and the -barrier of 1,8-di-aylbiphenylenes are determined. Interesting atropisomers are found in the cases of arylanthrones, arylanthraquinones and arylanthracenes and are reported in the fourth chapter. By the combined use of dynamic NMR, ECD spectroscopy and DFT computations, the conformations and the absolute configurations of 2-Naphthylalkylsulfoxides are studied in the fifth chapter. In the last chapter, a new synthetic route to ,’-arylated secondary or tertiary alcohols by lithiated O-benzyl-carbamates carrying an N-aryl substituent and DFT calculations to determinate the cyclic intermediate are reported. This work was done in the research group of Prof. Jonathan Clayden, at the University of Manchester.

Stereoselective Catalytic Processes for the Synthesis of Polycyclic Aromatic Compounds

In this PhD-thesis, two methodologies for enantioselective intramolecular ring closing reaction on indole cores are presented. The first methodology represents a highly stereoselective alkylation of the indole N1-nitrogen, leading to 3,4-dihydro-pyrazinoindol-1-ones – a structural class which is known for its activity on the CNS and therefore of high pharmacological interest concerning related diseases. In this approach, N-benzyl cinchona-alkaloids were used for the efficient catalysis of intramolecular aza-Michael reactions. Furthermore, computational studies in collaboration with the research group Prof. Andrea Bottoni (Department of Chemistry “G. Ciamician”, Bologna) were accomplished in order to get insight into the key interactions between catalyst and substrate, leading to enantiomeric excesses up to 91%. The results of the calculations on a model system are in accordance with the experimental results and demonstrate the high sensibility of the system towards structural modifications. The second project deals with a metal catalyzed, intramolecular Friedel-Crafts (FC)-reaction on indolyl substrates, carrying a side chain which on its behalf is furnished with an allylic alcohol unit. Allylic alcohols are part of the structural class of “π-activated alcohols” – alcohols, which are more easily activated due to the proximity to a π-unit (allyl-, propargyl-, benzyl-). The enantioselective intramolecular cyclization event is catalyzed efficiently by employment of a chiral Au(I)-catalyst, leading to 1-vinyl- or 4-vinyl-tetrahydrocarbazoles (THCs) under the formation of water as byproduct. This striking and novel process concerning the direct activation of alcohols in catalytic FC-reactions was subsequently extended to similar precursors, leading to functionalized tetrahydro-β-carbolines. These two methodologies represent highly efficient approaches towards the synthesis of scaffolds, which are of enormous pharmaceutical interest and amplify the spectra of enantioselective catalytic functionalisations of indoles.