The UV spectroscopic properties of the principal inorganic ionic species in natural waters were investigated at 25 °C in the wavelength range 195 to 280 nm. All absorbing species were identified and the corresponding molar absorptivities were determined experimentally. No cations were found to influence the UV spectrum. Relatively high molar absorptivities were observed for iodide, bromide and nitrate. The UV spectra of natural waters were calculated using the molar absorptivities and compared with observed signals from synthetic samples. This enabled the dominant components to be determined. Both bromide and nitrate have significant influence on the UV spectrum of natural waters. The study results can be used to predict the UV spectra of ionic solutions and thus evaluate the suitability of UV spectroscopy for given measurement projects.
Auf der ACHEMA 2018 stellten sich 24 Firmen mit Bezug zum Themenfeld Adsorption vor. Das weit gefächerte Ausstellerfeld reichte von Adsorbentienherstellern über Messgeräteentwickler bis hin zu Anlagenbauern. Aufgrund der zeitlichen Nähe zur Fachmesse IFAT/Entsorga waren in diesem Jahr etwas weniger Aussteller vertreten als in den vorausgehenden Jahren. Der Bericht umreißt die wichtigsten Trends und Neuerungen aus der Adsorptionstechnik, die auf den Ständen präsentiert und in Gesprächen von den Ausstellern thematisiert wurden.
In conventional reverse osmosis processes for seawater desalination, a disinfection of the process stream with chlorine compounds is carried out for antifouling. After disinfection the reduction agent Na2S2O5 is used for the removal of residual chlorine in a strongly overstoichiometric way in order to protect the membranes from oxidational damages. To save chemicals a controlled dosing of Na2S2O5 based on a reliable concentration measurement is desirable. Therefore, a measuring method for the determination of the sulfur(IV) components bisulfite and sulfite in seawater is developed based on the combination of UV spectroscopy and a PLS regression method. Experimental results as well as the development of the regression model for sulfur species in ultrapure and seawater is described.
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