Morten Enggrob Simonsen

Comparison of methods for evaluation of activity of photocatalytic films

ObjectiveThis work aims to investigate the correlation between the photocatalytic activity determined by methylene blue bleaching (DIN 52980), stearic acid degradation, and degradation of acetone in gas phase. MethodThe photocatalytic TiO2 coatings included in this investigation ranged from thin commercially available coatings (ActivTM and BioCleanTM) and ready to use suspensions (Nano-X PK1245) to lab-produced PVD and sol–gel coatings. XRD analysis of the photocatalytic coatings showed that all the coatings consisted of nanocrystalline anatase, although the thickness and porosity varied considerably.ResultsThe study showed that the reproducibility of the activity measurements was good. However, more importantly, the investigation showed that there is a good correlation between the activities determined by the different methods even though the characteristics of the photocatalytic coatings and the organic probe molecules varied considerably.ConclusionThe overall findings of this work suggest that there is a good correlation between the investigated methods. These results are promising for the future work concerning standardization of methods for determination of the activity of photocatalytic films.

Chapter 4 – Heterogeneous Photocatalysis

Heterogeneous photocatalysis is one of the advanced oxidation processes that couples light activation with semiconductors acting as photocatalysts. In the field of photocatalysis most applications are concerned with water and air purification or self-cleaning coatings/materials for outdoor and indoor uses. This chapter provides a discussion of the fundamentals of heterogeneous photocatalysis and some examples of application.

Investigation of degradation products produced by recycling the solvent during chemical degradation of fiber-reinforced composites:

Recycling of fiber-reinforced thermoset composites using chemical solvolysis has been investigated thoroughly in recent years, where solvents such as water, alcohols and ketones have been used. However, high costs are related to the use of organic solvents, decreasing the sustainability of the process. In this study, acetone has been used as the organic solvent. To increase the sustainability of the process, the solvent was recycled in eight consecutive batches using new glass fiber-reinforced composites in each recycling. No additional amount of acetone was added, resulting in a reduction of solvent consumption by 88%. It was found that the recycled solvent became increasingly more concentrated with degradation products from the epoxy resin and compounds produced by acetone aldol reactions. These degradation products promoted and enhanced the degradation of the composite. Among the compounds produced by acetone aldol reaction, the industrially important bulk chemical mesityl oxide accounted for 68–79% of the total chromatographic peak area. Simultaneously, with the optimization of a process for converting composite waste into its constituent (fibers and resin), valuable bulk chemicals can be produced to increase the overall commercial interest.

Comparison of Different UV-activated AOP methods

Abstract In this study the photonic efficiency of different UV activated AOP methods are compared in regard to the oxidation of the dye p-nitrosodimethylaniline (RNO). The UV activated methods include heterogeneous photocatalysis (TiO2/UV), UV activated persulfate (UV/S2O82-) and hydrogen peroxide (UV/H2O2), vacuum UV irradiation (VUV) and combination of these. The photonic efficiencies were determined both by measuring the bleaching of RNO by UV/VIS and by measuring the decomposition by TOC. The results of this investigation showed that the highest photonic efficiency was observed for the system consisting of VUV/H2O2 (3.06%). Similar photonic efficiencies were observed for the UV/H2O2, UV /TiO2 (suspension), and UV/S2O82- process. These numbers suggest that only around 3% of the emitted photons are used in the bleaching of RNO. The photonic efficiency for the mineralization of RNO for the UV/H2O2 process was determined to around 20%. No synergistic effect was observed when combining photocatalysis with H2O2, S2O82- or VUV irradiation. In all the latter cases it was found that the bleaching rates for these techniques alone were higher than those observed combined with photocatalysis. The only process showing synergistic effects was the system consisting of VUV/H2O2.

Identification of Ti clusters during nucleation and growth of sol-gel derived TiO2 nanoparticles

In the present work, electrospray ionization mass spectrometry (ESI-MS) was used to investigate the titanium clusters present during nucleation and growth of sol–gel derived TiO2 nanoparticles. Depending on the alkoxide precursor used, Ti clusters of different sizes were identified [titanium isopropoxide (TTIP) ∼ 11–12 Ti atoms, titanium butoxide (TTB) ∼ 10–11 Ti atoms and titanium tetraethoxide (TTE) ∼ 5–7 Ti atoms]. The Ti–O–Ti backbone/core of the titanium clusters were found to be quite stable after formation and do not easily break up into smaller clusters. The results of this investigation suggest that these clusters are used as building blocks in the growth during the induction period. The h-ratio (n H2O/n alcoxide) and the pH were not found to influence the identity of the Ti clusters present during nucleation of the growth of sol–gel derived TiO2 nano-particles, although the induction period was greatly influenced. The reactivity of the alkoxy group are OEt > OPri > OBu. The difference in reactivity of the alkoxides is generally believed to be due to the increasing size of the alkoxy group which causes sterical hindrance during the nucleophilic substitution reaction.

Photocatalytic Degradation of Chloroform Using a New Type of Photo-Reactor

In the present study a new type of continuous photo-reactor is developed in which the TiO2 catalyst is immobilized on the surface of quartz tubes surrounding the UV lamps. The paper presents the results of an initial investigation of the performance of a laboratory scale photo-reactor using chloroform as a model compound. The study showed that an initial chloroform concentration of 7 mg/1 was degraded to under the detection limit in a period of 350 h. The half time t1/2 for the photo-reactor was found to be 8 h.