Efficiency of gas discharge methods for odor control in municipal wastewater transportation and treatment systems

В процессе транспортировки и очистки сточных вод в воздух выделяются дурнопахнущие вещества, среди которых одним из наиболее трудноудаляемых является сероводород. Для очистки воздуха от дурнопахнущих веществ используются различные методы, в том числе газоразрядные (плазменные, ионизационные), которые хорошо зарекомендовали себя в других областях промышленности. Вентиляционные выбросы, образующиеся при обработке и очистке сточных вод, имеют ряд особенностей: высокая влажность, высокая концентрация сероводорода, потенциальная взрывоопасность. Эти свойства ограничивают возможность использования газоразрядных методов для очистки данного типа вентиляционных выбросов. Описывается специфика применения газоразрядных методов при очистке воздуха на очистных сооружениях канализации и канализационных насосных станциях. Приведены возникающие при этом технические сложности. In the process of wastewater transportation and treatment malodorous substances are released into the air; among them hydrogen sulfide being one of the most difficult to remove. Various methods are used to remove malodorous substances from the air, including gas-discharge (plasma, ionization) methods that have proven remarkably effective in other industries. Vent emissions generated during wastewater treatment are specified by high humidity, high concentration of hydrogen sulfide, potential explosion hazard. These properties limit the possible use of gas discharge methods for the purification of this type of vent emissions. The specificity of applying gas discharge methods for air purification at the wastewater treatment facilities and wastewater pumping stations is described. The arising technical difficulties are presented.

Studying the Complexity of Biomass Derived Biofuels

Biofuel produced from biomass pyrolysis is a good example of a highly complex mixture. Detailed understanding of its composition is a prerequisite for optimizing transformation processes and further upgrading conditions. The major challenge in understanding the composition of biofuel derived from biomass is the wide range of compounds with high diversity in polarity and abundance that can be present. In this work, a comprehensive analysis using mass spectrometry is reported. Different operation conditions are studied by utilizing multiple ionization methods (positive mode atmospheric pressure photo ionization (APPI), atmospheric pressure chemical ionization (APCI) and electrospray ionization (ESI) and negative mode ESI) and applying different resolving power set-ups (120 k, 240 k, 480 k and 960 k) and scan techniques (full scan and spectral stitching method) to study the complexity of a pyrolysis biofuel. Using a mass resolution of 960 k and the spectral stitching scan technique gives a total of 21,703 assigned compositions for one ionization technique alone. The number of total compositions is significantly expanded by the combination of different ionization methods.

Low Density Interior in Supercooled Aqueous Nanodroplets Expels Ions to the Subsurface

The location of a single and multiple ions in aqueous droplets plays a key role in chemical reactivity of atmospheric and man-made aerosols. We report direct computational evidence that in supercooled aqueous nanodroplets a lower density core of tetrahedrally coordinated water molecules expels the sodium ions to a higher density and more disordered subsurface. In contrast, at ambient temperature the single Na+ density is higher in the core region and has a broad maximum at the droplet's center of mass. We analyse the expulsion of a single ion in terms of a general reference electrostatic model that we have developed. The energy of the system in the analytical model is expressed as the sum of electrostatic and surface energy of a fluctuating droplet. The model predicts that the energy associated with the distance of the ion from the droplet's center of mass is quadratic in this distance. We name thiseffect "electrostatic confinement". The predictions of the model are consistent with the simulations fndings for a single Na+ ion at ambient conditions. Our results assist in understanding the mechanisms of charging of macromolecules in spray-based ionization methods used in native mass spectrometry and the physical chemistry of atmospheric aerosols.<br>

Low Density Interior in Supercooled Aqueous Nanodroplets Expels Ions to the Subsurface

The location of a single and multiple ions in aqueous droplets plays a key role in chemical reactivity of atmospheric and man-made aerosols. We report direct computational evidence that in supercooled aqueous nanodroplets a lower density core of tetrahedrally coordinated water molecules expels the sodium ions to a higher density and more disordered subsurface. In contrast, at ambient temperature the single Na+ density is higher in the core region and has a broad maximum at the droplet's center of mass. We analyse the expulsion of a single ion in terms of a general reference electrostatic model that we have developed. The energy of the system in the analytical model is expressed as the sum of electrostatic and surface energy of a fluctuating droplet. The model predicts that the energy associated with the distance of the ion from the droplet's center of mass is quadratic in this distance. We name thiseffect "electrostatic confinement". The predictions of the model are consistent with the simulations fndings for a single Na+ ion at ambient conditions. Our results assist in understanding the mechanisms of charging of macromolecules in spray-based ionization methods used in native mass spectrometry and the physical chemistry of atmospheric aerosols.<br>

Using matrix-assisted ionization method for mass spectral identification of fullerene-dye conjugates

Traditional soft ionization methods are not always suitable for mass spectral analysis of complex compounds. Factors such as laser radiation and heating resulting in fragmentations of sample molecules in the case of matrix-assisted laser desorption/ionization and difficulties in preparing suitable sample solutions in the case of electrospray ionization make it impossible to use these methods in some cases. Matrix-assisted ionization was used to analyze products of chemical synthesis involving pyropheophorbide and fullerene. Mass spectra were acquired using a simple effective modification of the Exactive Orbitrap mass spectrometer electrospray interface. Reliable identification of pyropheophorbide-fullerene dyad ions and its derivatives was carried out. An experimental comparison of a matrix-assisted ionization and an electrospray ionization technique demonstrated the significant advantage in sensitivity to the ions under study (approximately 20 times higher) of the matrix-assisted ionization method in this particular study.