Adsorption of Thallium(I) Ions on Titania Particle Surfaces in Aqueous Media

A description is given of the modification of the adsorption of Tl(I) on a titania (Degussa P-25) surface by the presence of organic or inorganic co-additives in aqueous suspensions. The addition of oxalate, formate, acetate and phosphate anions (the latter at low levels below ~0.03 M) increased Tl(I) adsorption while the phosphate anion (at levels > ~0.03 M) inhibited Tl(I) adsorption. A surface complexation model comprising the titania surface sites, the anchor co-additives and bound Tl(I) species was invoked to explain the adsorption enhancement observed. The data presented build upon and complement those acquired earlier showing how metal ion adsorption on a TiO 2 surface is strongly influenced by co-additives in the aqueous medium

Techno-economic comparative assessment of novel lignin depolymerization routes to bio-based aromatics

This paper presents a techno-economic assessment of three novel routes for the production of bio-based aromatics from lignin. It aims to provide insights into their feasibility and hotspots at an early stage of development to guide further research and development and to facilitate commercialization. The lignin conversion routes are: (non-catalytic) lignin pyrolysis, direct hydrodeoxygenation (HDO), and hydrothermal upgrading (HyThUp). The products generated are mixed oxygenated aromatic monomers (MOAMON), light organics, heavy organics, and char. For the technical assessment, conceptual design followed by process modeling in Aspen Plus was based on experimental yields. The models generated indispensable data on material and energy flows. An economic assessment was then conducted by estimating operating and capital costs. Return on investment (ROI), payback period (PBP), and net present value (NPV) were used as key performance indicators. Downstream processing was especially demanding in the HyThUp process due to the presence of a significant flow rate of water in the system, which significantly increased external utility requirements. Due to complex separations, the HyThUp process showed the highest capital cost (35% more than pyrolysis). Operating costs were the highest for the direct HDO process (34% more than pyrolysis) due to the use of hydrogen. Overall, the direct HDO process showed the highest ROI (12%) and the shortest PBP (5 years) due to high yields of valuable heavy organics (32%) and MOAMON (24%). Direct HDO was found to be feasible with a positive NPV based on prices used in the assessment. Among the three processes investigated, the direct HDO process therefore appeared to be the most promising, and consideration should be given to further development and commercialization of this process.Energy & Industr

Heterogeneous photocatalytic treatment of organic dyes in air and aqueous media

This review focuses on the heterogeneous photocatalytic treatment of organic dyes in air and water. Representative studies spanning approximately three decades are included in this review. These studies have mostly used titanium dioxide (TiO2) as the inorganic semiconductor photocatalyst of choice for decolorizing and decomposing the organic dye to mineralized products. Other semiconductors such as ZnO, CdS, WO3, and Fe2O3 have also been used, albeit to a much smaller extent. The topics covered include historical aspects, dark adsorption of the dye on the semiconductor surface and its role in the subsequent photoreaction, semiconductor preparation details, photoreactor configurations, photooxidation kinetics/mechanisms and comparison with other Advanced Oxidation Processes (e.g., UV/H2O2, ozonation, UV/O3, Fenton and photo-Fenton reactions), visible light-induced dye decomposition by sensitization mechanism, reaction intermediates and toxicity issues, and real-world process scenarios. © 2008 Elsevier B.V. All rights reserved