Peter Fröhlich

Valuable Metals-Recovery Processes, Current Trends, and Recycling Strategies

This Review provides an overview of valuable metals, the supply of which has been classified as critical for Europe. Starting with a description of the current state of the art, novel approaches for their recovery from primary resources are presented as well as recycling processes. The focus lies on developments since 2005. Chemistry strategies which are used in metal recovery are summarized on the basis of the individual types of deposit and mineral. In addition, the economic importance as well as utilization of the metals is outlined.

Phosphatrecycling aus Klärschlammaschen —warum Phosphorsäure der Königsweg ist

Das Element Phosphor (P) ist fur alle Lebewesen und Pflanzen essentiell. In der Natur kommt Phosphor nicht elementar, sondern allein in Form von Phosphaten vor. Im Hydroxylapatit [Ca5(PO4)3OH] beispielsweise bildet anorganisches Phosphat zusammen mit Calcium den Hauptbestandteil von Knochengewebe und Zahnsubstanz. Zugleich sind Phosphate die Grundsubstanz von Nukleinsauren und als Spurenelement am Energiestoffwechsel der Zellen in Form von Adenosin-5‘-triphosphat (ATP) beteiligt.

The Boundary Layer as Reaction Compartment for the Synthesis of Hydroxyalkyl-functionalized Siloxanes

Enzyme catalysis in two-phase systems, particularly in the functionalization of siloxanes, is a new challenge for biocatalysis. On the basis of three different reaction systems, stirred tank reactor, enzyme membrane reactor and micro mixer, the influence of the phase boundary layer along the interface between an aqueous system and an organosiloxane on the synthesis of hydroxyalkylfunctionalized siloxanes is discussed and solutions presented. Micro mixers produce, through a large surface area to volume ratio, boundary layers within which through a formate dehydrogenasecatalyzed reaction the conversion of 1,3-bis-(3-formoxypropyl)tetramethyldisiloxane to 1,3-bis-(3- hydroxypropyl)tetramethyldisiloxane can be achieved. In contrast, in a stirred tank reactor even after 96 h only 45% of the formoxy siloxane has been converted. Graphical Abstract The Boundary Layer as Reaction Compartment for the Synthesis of Hydroxyalkyl-functionalized Siloxanes

Biokatalytische Funktionalisierung von Silikonen

ZusammenfassungDer Einsatz von Hydrolasen eröffnet neue Synthesewege für organofunktionelle Silikone. Insbesondere aminofunktionelle Silikone neigen bei der Polymerisation zu intramolekularen Abbaureaktionen. Eine Lösung bieten Lipasen, sie katalysieren die selektive Einführung wie auch Abspaltung von Schutzgruppen.AbstractThe use of hydrolases opens new synthesis routes for organofunctional silicones. In particular amino silicones tend to intramolecular degradation reactions in the course of the polymerisation process. Lipases catalyse selective protection as well as deprotection of organofunctional silicones.