@phdthesis{Mehrjouei2012, author = {Mehrjouei, Mohammad}, title = {Advanced oxidation processes for water treatment : reactor design and case studies}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-opus-26619}, school = {BTU Cottbus - Senftenberg}, year = {2012}, abstract = {The aim of this work was to study in detail the physical-chemical aspects of water and wastewater treatment using different so-called "advanced oxidation systems". Our target was to construct an annular multiphase falling film reactor with a fixed photocatalyst (TiO2) and to compare its performance with that of a planar reactor in different chemical oxidation regimes. The annular design of the falling film reactor was prepared for heterogeneous photocatalytic oxidation systems by combining three different phases (solid fixed photocatalyst, falling liquid wastewater and an ozone/oxygen gaseous mixture). UVA light sources were employed for irradiation of the photocatalyst surface. In the first step, the design, construction and characterisation of the reactor was performed. The next step was the assessment of the performance of the falling film reactor in the decomposition of selected organic chemicals as model compounds. Six different oxidation methods were evaluated for the degradation of model compounds. Photo-oxidation (UVA/O2), photo-ozonation (UVA/O3), ozonation (O3), catalytic ozonation (TiO2/O3), photocatalytic oxidation (TiO2/UVA/O2) and photocatalytic ozonation (TiO2/UVA/O3) processes were investigated in this study. It was shown that due to the synergetic effects between ozone molecules and the irradiated surface of TiO2, photocatalytic ozonation was the most effective oxidation process for the decomposition of model compounds. Oxalic acid, dichloroacetic acid, citric acid, terephthalic acid, p-chlorobenzoic acid, methyl tert-butyl ether, ethyl tert-butyl ether, tert-amyl ethyl ether and tert-butanol were chosen as model compounds. Two different immobilisation techniques were employed and evaluated for fixing TiO2 nanoparticles onto the reactor walls. The immobilisation of photocatalysts was performed on borosilicate glass and polymethylmethacrylate. It was observed that the photoactivity of fixed TiO2 particles on borosilicate glass was higher than that on polymethylmethacrylate. The stability of immobilised photocatalysts on both substrates was good. The influences of different experimental parameters, such as the initial concentration of model compounds, ozone concentration, solution pH, temperature and solution recycling rate on the degradation rate and efficiency of the oxidation systems were studied and discussed. In terms of the characterisation of the falling film reactor, different aspects were studied. The thickness and distribution pattern of falling films, the gas washing effects of falling films, the absorption of ozone in the falling films, the adsorption of organic pollutants on the photocatalyst surface, the effect of UVA irradiation on ozone decomposition, etc. were studied in detail. The concentration of model compounds was determined by ion chromatography (IC), high performance liquid chromatography (HPLC) and headspace techniques. Chemical oxygen demand (COD) was applied to quantify the quality of wastewaters and total organic carbon (TOC) measurements were employed for the determination of model compound mineralisation. At the end of this study, treatment of real wastewater was performed by means of the falling film reactor as a case study. The real wastewater was produced in a pyrolysis process. More than 30 organic and inorganic compounds were included in the composition of this wastewater. The application of ozone-based advanced oxidation processes showed good results in terms of colour and odour removal of pyrolysis wastewater as well as in terms of decreasing its COD.}, subject = {Wasseraufbereitung; Photokatalyse; Ozonisierung; Moderne Oxidationprozesse; Fallfilmreaktor; Wasseraufbereitung; Photokatalyse; Photokatalytische Ozonisierung; Advanced oxidation processes; Falling film reactor; Water treatment; Photocatalysis; Photocatalytic ozonation}, language = {en} } @phdthesis{TianKunze2001, author = {Tian-Kunze, Xiangshan}, title = {Experimental and theoretical study of S(IV)/S(VI) ratio in rain and cloud events}, url = {http://nbn-resolving.de/urn:nbn:de:kobv:co1-000000093}, school = {BTU Cottbus - Senftenberg}, year = {2001}, abstract = {Production of atmospheric sulfate from SO2 emitted into the troposphere is the key question we have to answer for assessing main problems like acid rain, forest decline and negative climate forcing which is believed to counteract the green house effect. About one decade ago many researchers agreed that sulfate formation occurs dominantly (80-90 \%) via the aqueous phase chemical transformation, where the SO2 dissociation is the first step. However, there is still a high uncertainty on the amount of sulfite (dissolved SO2) being oxidized and on that removed by wet deposition in the reduced form S(IV) (sulfite). This important question, whose answer gives climate modellers an essential input on the percentage of emitted SO2 converted into sulfate, was the aim of this work. This work presents experimental and theoretical results from studies of the ratio sulfite/sulfate in rainwater and cloudwater to assess the contribution of S(IV) to the total sulfur amount in the aqueous phase. The wet deposition of S(IV) in rainwater was studied by collecting rainwater samples from two different levels using a 324 m high tower. The increase of S(IV) wet deposition flux from the 324 m level to the ground level via sub-cloud scavenging of SO2 is significant. 13-51 \% (36 \% in average) of sulfur in rainwater on the ground level was found to be in the form of S(IV). The result that S(IV) is an important form of sulfur in rainwater was further confirmed by our theoretical study using a one-dimensional time-dependant physical-chemical cloud model. Model calculations show that most of sub-cloud scavenged SO2 will remain as free S(IV) in rainwater. In highly polluted areas the ratio can be as high as 0.9. This ratio in cloudwater is much less than that in rainwater according to our field experiment carried out at Mt. Brocken. Neverthless, under some special conditions, this ratio can be as high as 0.2, which means that the role of S(IV) in cloudwater is not ignorable. Thus, this study has confirmed the very few S(IV) measurements found in literature, suggesting the importance of S(IV) wet deposition. Our findings suggest that considerable part of emitted SO2 will not be transformed to sulfate especially in the sub-cloud layer. Therefore, the production of climate affecting sulfate aerosol via aqueous phase transformation of dissolved SO2 is more limited than believed by climate modellers.}, subject = {Berlin-Frohnau; Regen; Sulfite; Sulfate; Brocken; Wolke; Wasser; S(IV); S(IV)/S(VI) ratio; sub-cloud scavenging; cloud chemistry; cloud modelling}, language = {en} }