title: Developing energy efficient lignin biomass processing - towards understanding mediator behaviour in ionic liquids.
abstract: Environmental concerns have brought attention to the requirement for more efficient and renewable processes for chemicals production. Lignin is the second most abundant natural polymer, and might serve as a sustainable resource for manufacturing fuels and aromatic derivatives for the chemicals industry after being depolymerised. In this work, the mediator 2,2'-azino-bis(3-ethylbenthiazoline-6-sulfonic acid) diammonium salt (ABTS), commonly used with enzyme degradation systems, has been evaluated by means of cyclic voltammetry (CV) for enhancing the oxidation of the non-phenolic lignin model compound veratryl alcohol and three types of lignin (organosolv, Kraft and lignosulfonate) in the ionic liquid 1-ethyl-3-methylimidazolium ethyl sulfate, ([C2mim][C2SO4]). The presence of either veratryl alcohol or organosolv lignin increased the second oxidation peak of ABTS under select conditions, indicating the ABTS-mediated oxidation of these molecules at high potentials in [C2mim][C2SO4]. Furthermore, CV was applied as a quick and efficient way to explore the impact of water in the ABTS-mediated oxidation of both organosolv and lignosulfonate lignin. Higher catalytic efficiencies of ABTS were observed for lignosulfonate solutions either in sodium acetate buffer or when [C2mim][C2SO4] (15 v/v%) was present in the buffer solution, whilst there was no change found in the catalytic efficiency of ABTS in [C2mim][C2SO4]-lignosulfonate mixtures relative to ABTS alone. In contrast, organosolv showed an initial increase in oxidation, followed by a significant decrease on increasing the water content of a [C2mim][C2SO4] solution.
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. majdkha@yahoo.com george.chen@nottingham.ac.uk anna.croft@nottingham.ac.uk.
authors.forename: Majd
authors.initials: M
authors.lastname: Eshtaya
authors.affiliation: Department of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: Andinet
authors.initials: A
authors.lastname: Ejigu
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. majdkha@yahoo.com george.chen@nottingham.ac.uk anna.croft@nottingham.ac.uk.
authors.forename: Gill
authors.initials: G
authors.lastname: Stephens
authors.affiliation: Department of Chemistry, University of Nottingham, Nottingham NG7 2RD, UK.
authors.forename: Darren A
authors.initials: DA
authors.lastname: Walsh
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. majdkha@yahoo.com george.chen@nottingham.ac.uk anna.croft@nottingham.ac.uk and Department of Chemical and Environmental Engineering, Faculty of Science & Engineering, University of Nottingham Ningbo China, Ningbo 315100, P. R. China.
authors.forename: George Z
authors.initials: GZ
authors.lastname: Chen
authors.affiliation: Department of Chemical and Environmental Engineering, Faculty of Engineering, University of Nottingham, Nottingham NG7 2RD, UK. majdkha@yahoo.com george.chen@nottingham.ac.uk anna.croft@nottingham.ac.uk.
authors.forename: Anna K
authors.initials: AK
authors.lastname: Croft
mesh_terms: D052160:Benzothiazoles / Q000737:chemistry; D001592:Benzyl Alcohols / Q000737:chemistry; D018533:Biomass; D002021:Buffers; D002384:Catalysis; D004526:Efficiency; D004563:Electrochemistry; D004735:Energy Transfer; D007093:Imidazoles; D007202:Indicators and Reagents; D052578:Ionic Liquids / Q000737:chemistry*; D008031:Lignin / Q000737:chemistry*; D010084:Oxidation-Reduction; D013451:Sulfonic Acids / Q000737:chemistry; D014783:Viscosity; D014867:Water / Q000737:chemistry
chemical_list: D052160:Benzothiazoles; D001592:Benzyl Alcohols; D002021:Buffers; D007093:Imidazoles; D007202:Indicators and Reagents; D052578:Ionic Liquids; D013451:Sulfonic Acids; D014867:Water; C002502:2,2'-azino-di-(3-ethylbenzothiazoline)-6-sulfonic acid; D008031:Lignin; C042197:veratryl alcohol; C518739:1-ethyl-3-methylimidazolium