Magnesia-Based Cements: A Journey of 150 Years, and Cements for the Future?

This review examines the detailed chemical insights that have been generated through 150 years of work worldwide on magnesium-based inorganic cements, with a focus on both scientific and patent literature. Magnesium carbonate, phosphate, silicate-hydrate, and oxysalt (both chloride and sulfate) cements are all assessed. Many such cements are ideally suited to specialist applications in precast construction, road repair, and other fields including nuclear waste immobilization. The majority of MgO-based cements are more costly to produce than Portland cement because of the relatively high cost of reactive sources of MgO and do not have a sufficiently high internal pH to passivate mild steel reinforcing bars. This precludes MgO-based cements from providing a large-scale replacement for Portland cement in the production of steel-reinforced concretes for civil engineering applications, despite the potential for CO2 emissions reductions offered by some such systems. Nonetheless, in uses that do not require steel reinforcement, and in locations where the MgO can be sourced at a competitive price, a detailed understanding of these systems enables their specification, design, and selection as advanced engineering materials with a strongly defined chemical basis

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

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)

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

Investigating the effect of polarity of stationary and mobile phases on retention of cannabinoids in normal phase liquid chromatography

This work reports about a screening of four adsorbents with different polarity employed for the separation of the main phytocannabinoids contained in Cannabis sativa L., under normal phase liquid chromatography (NPLC). The effect of polarity and type of interaction mechanisms of the adsorbents (namely Si-, CN-, Diol-, and NH2-based SPs) on retention has been investigated under a variety of conditions either by using different combinations of apolar solvents (heptane or hexane) and alcohols (ethanol or isopropanol). The columns have also been employed for the separation of a real cannabis sample. [Figure not available: see fulltext.

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

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 an industrial commercial lignin was developed by a three step procedure set-up either in aqueous or in an environmentally friendly organic solvent in order to obtain sustainable and scalable processes.1,2 The first step consisted in a microfiltration or a Soxhlet extraction, depending on the type of solvent used. Then a cascade membrane-mediated ultrafiltration allowed to obtain at the end three refined lignin fractions. The parent lignin and the different lignin fractions were fully characterized. The two-step process reported here allows accessing lignin fractions with well-defined physico-chemical properties (including mass distribution, glass transition temperature, aliphatic and phenolic hydroxyl groups concentration, syringyl/guaiacyl unit ratio) and represents a valuable approach towards the development of bio-based polymers and the preparation of key platform chemicals, thereby paving the way for an effective exploitation and valorization of this remarkable resource. [1] Allegretti, C.; 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; DOI: 10.1021/acssuschemeng.8b01410. [2] Allegretti, C.; Fontanay, S.; Rischka, K.; Strini, A.; Troquet, J.; Turri, S.; Griffini, G.; D’Arrigo P. ACS Omega 2019, in press; DOI: 10.1021/acsomega.8b02851

Green cannabigerol purification through simulated moving bed chromatography

Cannabigerol (CBG) is a minor cannabinoid present in Cannabis sativa L. This molecule is gaining increasing popularity thanks to its antibacterial, antimicrobial, antidepressant and antitumoral properties. In parallel, there is growing attention towards the search of efficient, cost-effective, rapid, high-throughput, and green purification techniques. In this work, CBG has been purified from a real cannabis extract by means of simulated moving bed chro­matography. The proposed application is very promising, allowing to achieve a CBG extract free of tetrahy­ drocannabinol (a psychoactive cannabinoid) with 100% recovery and 97% final purity by using a faster and greener method if compared to traditionally used ones

Chemo-enzymatic depolymerization of lignin

Lignin is a highly complex phenolic matrix that acts as a binder in plants conferring them structural integrity and strength, and is one of the three major subcomponents of lignocellulosic biomass. Although burning lignin is still considered a valuable contribution in saving fossil sources, the exploitation of this extremely abundant natural polymer in terms of higher value-added applications is very appealing as it represents the only viable source to produce aromatic compounds as fossil fuels alternative. Due to the very broad composition in terms of molecular weight of the raw material, a pretreatment strategy becomes necessary for an efficient lignin valorization as macromolecular building block for polymeric materials or as precursor for aromatic small molecules. This procedure is an essential tool for a thorough exploitation of the main three different fractions recovered, namely a high, an intermediate and a low molecular weight fraction. The first one is characterized by the presence of high molecular weight polymers and is used without further chemical modification for developing bio-based polymeric materials;[1] the last one can be separated by chromatography into small aromatic molecules for preparative organic chemistry; whereas the middle fraction, characterized by an intermediate molecular weight, is the ideal starting material for oxidative depolymerization assays.[2,3] On this fraction, a new cascade process has been investigated involving at first a chemical step aiming at a partial conversion of macromolecules to lower molecular weight intermediates followed by a biocatalytic step performed by different classes of O2-dependent laccases (EC 1.10.3.2) in the presence of TEMPO as a mediator. Promising results have been obtained and extensive research is now in progress

Differentiation between Candida albicans and Candida dubliniensis using hypertonic Sabouraud broth and tobacco agar

INTRODUCTION: Opportunistic fungal infections in immunocompromised hosts are caused by Candida species, and the majority of such infections are due to Candida albicans. However, the emerging pathogen Candida dubliniensis demonstrates several phenotypic characteristics in common with C. albicans, such as production of germ tubes and chlamydospores, calling attention to the development of stable resistance to fluconazole in vitro. The aim of this study was to evaluate the performance of biochemistry identification in the differentiating between C. albicans and C. dubliniensis, by phenotyping of yeast identified as C. albicans. METHODS: Seventy-nine isolates identified as C. albicans by the API system ID 32C were grown on Sabouraud dextrose agar at 30°C for 24-48h and then inoculated on hypertonic Sabouraud broth and tobacco agar. RESULTS: Our results showed that 17 (21.5%) isolates were growth-inhibited on hypertonic Sabouraud broth, a phenotypic trait inconsistent with C. albicans in this medium. However, the results observed on tobacco agar showed that only 9 (11.4%) of the growth-inhibited isolates produced characteristic colonies of C. dubliniensis (rough colonies, yellowish-brown with abundant fragments of hyphae and chlamydospores). CONCLUSIONS: The results suggest that this method is a simple tool for screening C. albicans and non-albicans yeast and for verification of automated identification