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An amendment to this paper has been published and can be accessed via the original article.

Tamara Grummt passed away on January 26, 2020 in Oelsnitz/Vogtland, Germany. Tamara was one of the scientific pioneers in the field of environmental toxicology, namely genotoxicity and hygiene of drinking and bathing waters. Her passing is not only a great loss to environmental research and to the global environmental toxicology community—we have lost an outstanding personality with the heart in the right place, who has become, for many of us, a wonderful friend.

The present study explained the inhibitory effect of natural organic matter (NOM) on the photocatalytic degradation of clofibric acid (CA), and attempted to eliminate this inhibition by changing reaction conditions. The NOM degradation was followed by size-exclusion chromatography for dissolved organic carbon and ultraviolet absorption (SEC-DOC and SEC-UV254).The results demonstrated that the deactivation of NOM on catalyst was more dependent on the molecular weight of NOM than on its concentration. Higher molecular weight fractions were prone to adsorb onto the catalysts’ surface and acted as electron-hole scavengers and light filters to reduce the photocatalytic degradation rate of CA. pH adjustment changed the adsorption property of NOM, while, decreasing of its inhibition was not observed. However, the oxygen addition can significantly eliminate this inhibitory effect by increasing the degradation rate of high molecular size fractions of NOM.

The influence of ionic strengthen and dissolved organic matter (DOM) on the aggregation of TiO 2 nanoparticles (NPs) in municipal effluent was investigated. The results demonstrated that DOM promoted the mobility of NPs in aquatic system by synergism between static repulsion and steric effect, while electrolytes were opposite by charge-neutralization. The physical-chemical characteristics of DOM played the major role on the mobility of NPs. Bovine serum albumin (BSA) showed the strongest enhancement on the mobility of TiO 2 NPs. High adsorption of BSA introduced vast negative charges on the TiO 2 NPs’ surface, leading to static repulsion and neutralizing positive charges of electrolytes in surrounding as well. By contrast, another protein α-amylase retarded the aggregation rate of TiO 2 NPs through steric repulsion of the long-chain construction. Humic substances (Fulvic acid and alginate) also reflected the combination of static repulsion and steric effect. However, in the high electrolytes concentration (especially Ca 2+ ), the long-chain aliphatic compounds were prone to form calcium bridge which increased the hydrodynamic diameter of TiO 2 aggregates consequently. Sodium dodecylbenzene sulfonate (SDBS) showed low adsorption capacity, while the unabsorbed SDBS retarded the aggregates caused by the changes of pH and electrolytes. These data indicated that decreasing of DOC concentration in aqueous system was important to reduce the mobility and potential risk of NPs in aqueous system.

The W0-factor is a common metric to express the aggressivity of water against unalloyed iron. It accounts for multiple parameters, called rating numbers, which represent the concentration of chloride, sulfate and calcium ions, the pH-value and the acid capacity of the immersion medium. The use of ranges in the physical quantities metric rating number, however, allows for unaccounted variations in the immersion medium composition, i.e., slightly different immersion media may produce the same W0-factor. To verify the results, the experiments were also carried out with natural waters as immersion media and their W0-factors were determined. In addition, the DOC content, which is not included in the W0-factor, has an impact on the corrosive character of the immersion medium. In order to account for the influence of the DOC content in the measurements, multiple solutions with different DOC concentrations were investigated. The results show that a higher DOC content (based on humic substances) in the observed solutions causes a reduction in the corrosion rate. This result agrees with observations of nature.

Generally, corrosion rates for sheet pile walls observed in nature and those obtained in the laboratory are different. In order to compare natural and laboratory corrosion rates, corrosion tests were carried out with an electrochemical corrosion cell. Various mild steel samples which were taken out from different sheet pile structures were examined with synthetic brackish water and synthetic seawater as immersion media. It was ensured that the electrical conductivity and the pH-values were identical to those of the natural waters from which the sheet pile samples came from. The experimental results indicate that underwater corrosion rates in nature are only about one tenth to one eighth of the laboratory values. The corrosion rates in nature depend on the media and the corrosion zone. Furthermore, in laboratory test procedures, the initial corrosion is always tested whereas in nature a “protecting” layer of rust is formed, that lowers corrosion. Therefore, comparison of the values of the experiments with those from nature should be defined in accordance to age and zone of hydraulic steel structures. As a consequence, a corrosion coefficient with consideration of the age of structures was formed. The introduction of the coefficients's dependence on the lifetime of the construction allows improved corrosion rate predictions when the chemical composition of the immersion media is detected.

In this work, the photocatalytic generation of free OH radicals ( OH free ) in aqueous TiO 2 suspensions was studied using an 18 O isotope labeling and a “remote” photocatalysis approach. A probe compound, 1,3,5-trichlorobenzene (TCB), was adsorbed in pores of silica gel (SG) microparticles and, by this, was shielded from the direct hole oxidation. Penetration of the TiO 2 particles (25 nm in size) to the TCB, adsorbed in the SG pores, was blocked due to a small size of the SG pores (4 nm). Therefore, the “remote” degradation of the TCB was solely driven by OH free , and this allowed us to selectively determine the quantum yield of the OH free generation. The isotope labeling with 18 O has demonstrated that the major pathway of the OH free formation is the direct hole oxidation of H 2 O, whereas the reduction of dissolved O 2 by photogenerated electrons contributes in less than 5% of the total amount of OH free . Nevertheless, the latter pathway becomes more important if holes are scavenged. This work sheds light on the intrinsic roles of photogenerated holes and electrons in the mechanism of the OH free formation in aqueous TiO 2 photocatalysis.

Natural organic matter (NOM) is ubiquitous in aquatic environment, which plays a predominant role in the sorption of pharmaceuticals onto the TiO 2 nanoparticles. It is a matter of concern whether NOM could act as a surface sensitizer of TiO 2 or not. In this context, the role of NOM is investigated for the photocatalytic degradation of carbamazepine (CBZ) using TiO 2 . Four different ratios of NOM:TiO 2 were used varying from 400 μg g −1 to 400 mg g −1 . The findings reveal that small amounts of NOM could enhance the TiO 2 efficiency up to 8%. Electron paramagnetic spectroscopy (EPR), along with size exclusion chromatography with dissolved organic carbon detection (SEC-OCD) and nuclear magnetic resonance spectroscopy (NMR) reveal the occurring mechanism. TiO 2 binds small molecular size fractions of NOM and breaks aromatic bonds of adsorbed NOM transforming it to stranded alkyl groups. This modified TiO 2 bears a significant amount of electrons (e − ) and lesser holes (h + ) than the purified TiO 2 and when irradiated, produces hydroxyl radicals which degrade CBZ.

The influence of ionic strengthen and dissolved organic matter (DOM) on the aggregation of TiO

The article contains sections titled: 1. Properties of Pure Water 1.1. Molecular Properties 1.1.1. Isotopic Composition 1.1.2. The Water Molecule 1.1.3. Hydrogen Bonding and Water Structure 1.2. The Phase Behavior of Water 1.2.1. Invariant Points 1.2.2. Liquid-Vapor Equilibria 1.2.3. Solid-Liquid and Solid-Solid Equilibria 1.2.4. Supercooled Water and Amorphous Ice 1.3. Properties of Liquid and Supercritical Water 1.3.1. Water over Wide Ranges in Temperature and Pressure 1.3.2. Equation of State and Volumetric Properties 1.3.3. Thermodynamic Properties 1.3.4. Transport Properties 1.3.5. Surface Tension 1.3.6. Auto-protolysis 1.3.7. Dielectric Properties 2.2.2. Transport Properties 2. Water as a Solvent 2.1. Solvent Properties of Water 2.2. Solutions of Nonpolar Gases and Hydrophobic Species 2.3. Hydrophilic Solutes 2.4. Electrolyte Solutions 2.5. Supercritical Water as a Solvent 3. Water Analysis 3.1. Sampling and Sample Preservation 3.2. Physicochemical and Sum Parameters 3.3. Inorganic Analysis 3.3.1. Determination of Cations 3.3.2. Anion Analysis 3.3.3. Determination of Dissolved Gases 3.3.4. Rapid Tests 3.4. Organic Analysis 3.4.1. Spectrometric Methods 3.4.2. Gas and Liquid Chromatography 3.5. Bioanalytical Methods 4. Hydrological Cycle and Water Use 4.1. World Water Balance 4.2. Hydrological Cycle 4.3. Demand for Water 4.4. Source of Water Used 4.5. Water Treatment