Frank-Dieter Kopinke

Bio: Frank-Dieter Kopinke is an academic researcher from Helmholtz Centre for Environmental Research - UFZ. The author has contributed to research in topics: Adsorption & Catalysis. The author has an hindex of 44, co-authored 185 publications receiving 6381 citations. Previous affiliations of Frank-Dieter Kopinke include University of Potsdam & University of Waterloo.

Interaction of adsorption and catalytic reactions in water decontamination processes: Part I. Oxidation of organic contaminants with hydrogen peroxide catalyzed by activated carbon

Abstract: This series of papers addresses the role of sorption in heterogeneous catalysis aimed at the removal of organic contaminants (OCs) from water. This first part is focused on the oxidative treatment of OCs by H2O2 catalyzed by activated carbon (AC). The relative reaction rates of compounds with different hydrophobicities and therefore different sorption tendencies on AC (methyl tert-butyl ether, trichloroethene, 2,4,5-trichlorophenol) in the AC/H2O2 system differed drastically from those observed in a classical homogeneous Fenton system. Quantitative considerations that take into account the ratio of the reaction rate constants of MTBE and TCE in the AC/H2O2 system and the homogeneous Fenton system as well as the ratio of their freely dissolved fractions lead to the conclusion that the predominant pathway for the degradation reaction in the AC/H2O2 system is the attack of OH radicals on the OC fraction that is freely dissolved in the pore volume of the AC. In contrast, the sorbed fraction is nearly unreactive, i.e. protected against radical attack. Quenching experiments with methanol, a strong competitor for reactions with OH radicals in the solution phase, further confirmed this hypothesis. Consequently, sorption on AC has an adverse effect on the oxidation of OCs via OH radicals, even though the radicals are formed directly on the AC surface, i.e. in close proximity to the sorbed OCs.

Humic acid modified Fenton reagent for enhancement of the working pH range

Abstract: The suitability of the Fenton process for the remediation of soil and groundwater is limited by the necessity to acidify the reaction medium. This study examines the applicability of humic acid (HA) as an iron chelator in a modified Fenton system with the aim of extending the optimum pH range for this process towards neutral conditions. Addition of HA at a concentration of 50–100 mg L−1 greatly enhances the rate of oxidation of organic compounds in a catalytic Fenton system in the range of pH 5–7. Similar rates at pH 5 in the presence of HA can be achieved as at pH 3 for a typical Fenton process in the absence of HA (k′ = 9 × 10−3 min−1 for benzene degradation at c H 2 O 2 = 0.13 M ). A comparison of the relative reactivities of various model compounds supported the hypothesis that OH radicals are the main reactive species in the HA-modified Fenton system. In contrast, however, another type of chelated Fe-catalyst (Fe-TAML) proved to be more selective than expected for OH radicals. A long-term study revealed that the HA itself is oxidized and thereby loses its ability to enhance the degradation of the pollutant molecules. Therefore, the HA-modified Fenton system is effective for degrading pollutants which are at least as reactive towards OH radicals as the HA itself, such as BTEX, phenols or PAHs. The results obtained indicate that the HA-modified Fenton system is also applicable for compounds with a high sorption tendency towards HA.

Combination of non-thermal plasma and heterogeneous catalysis for oxidation of volatile organic compounds: Part 2. Ozone decomposition and deactivation of γ-Al2O3

Abstract: The role of ozone was studied for two different configurations combining non-thermal plasma (NTP) and heterogeneous catalysis, namely the use of a gas phase plasma with subsequent exposure of the effluent to a catalyst in a packed-bed reactor (post-plasma treatment) and the placement of the catalyst directly in the discharge zone (in-plasma catalysis). Non-porous and porous alumina and silica were deployed as model catalysts. The oxidation of immobilised hydrocarbons, toluene as a volatile organic compound and CO as an inorganic pollutant were studied in both operational modes. While conversion and selectivity of hydrocarbon oxidation in the case of catalytic post-plasma treatment can be fully explained by the catalytic decomposition of O3 on γ-Al2O3, the conversion processes for in-plasma catalysis are more complex and significant oxidation was also measured for the other three materials (α-Al2O3, quartz and silica gel). It became obvious that additional synergetic effects can be utilised in the case of in-plasma catalysis due to short-lived species formed in the NTP. The capability of porous alumina for ozone decomposition was found to be correlated with its activity for oxidation of carbon-containing agents. It could be clearly shown that the reaction product CO2 poisons the catalytic sites at the γ-Al2O3 surface. The catalytic activity for O3 decomposition can be partially re-established by NTP treatment. However, for practical purposes the additional reaction pathways provided by in-plasma catalytic processes are essential for satisfactory conversion and selectivity.

Physical and mechanical properties of PLA, and their functions in widespread applications — A comprehensive review

Abstract: Poly(lactic acid) (PLA), so far, is the most extensively researched and utilized biodegradable aliphatic polyester in human history. Due to its merits, PLA is a leading biomaterial for numerous applications in medicine as well as in industry replacing conventional petrochemical-based polymers. The main purpose of this review is to elaborate the mechanical and physical properties that affect its stability, processability, degradation, PLA-other polymers immiscibility, aging and recyclability, and therefore its potential suitability to fulfill specific application requirements. This review also summarizes variations in these properties during PLA processing (i.e. thermal degradation and recyclability), biodegradation, packaging and sterilization, and aging (i.e. weathering and hygrothermal). In addition, we discuss up-to-date strategies for PLA properties improvements including components and plasticizer blending, nucleation agent addition, and PLA modifications and nanoformulations. Incorporating better understanding of the role of these properties with available improvement strategies is the key for successful utilization of PLA and its copolymers/composites/blends to maximize their fit with worldwide application needs.