Sorption of the organic cation metoprolol on silica gel from its aqueous solution considering the competition of inorganic cations

Systematic batch experiments with the organic monovalent cation metoprolol as sorbate and the synthetic material silica gel as sorbent were conducted with the aim of characterizing the sorption of organic cations onto charged surfaces. Sorption isotherms for metoprolol (>99% protonated in the tested pH of around 6) in competition with mono- and divalent inorganic cations (Na+, NH4+, Ca2+, and Mg2+) were determined in order to assess their influence on cation exchange processes and to identify the role of further sorptive interactions. The obtained sorption isotherms could be described well by an exponential function (Freundlich isotherm model) with consistent exponents (about 0.8). In general, a decreasing sorption of metoprolol with increasing concentrations in inorganic cations was observed. Competing ions of the same valence showed similar effects. A significant sorption affinity of metoprolol with ion type dependent Freundlich coefficients K-F,K-0.77 between 234.42 and 426.58 (L/kg)(0.77) could still be observed even at very high concentrations of competing inorganic cations. Additional column experiments confirm this behavior, which suggests the existence of further relevant interactions beside cation exchange. In subsequent batch experiments, the influence of mixtures with more than one competing ion and the effect of a reduced negative surface charge at a pH below the point of zero charge (pH(PZC) approximate to 2.5) were also investigated. Finally, the study demonstrates that cation exchange is the most relevant but not the sole mechanism for the sorption of metoprolol on silica gel. (C) 2014 Elsevier Ltd. All rights reserved

Sindrome extrapiramidale e dermatite da ipocorticosurrenalismo. Case report

Due to rapid economic development and population growth, China is facing severe water problems that include sea-level rise and increasing salinization, floods, water pollution, water shortage, soil erosion and ecosystem deterioration, as well as biodiversity loss. In recent decades, China is progressively more concerned with its water issues that are now at the center of social and political attention. Having to overcome similar challenges, Germany has taken a leading role in the field of water sciences and technology. In particular, China can benefit from the lessons learnt in Germany concerning the rehabilitation of water resources in areas heavily affected by chemical industry and mining after the reunification in 1989. German-Chinese cooperation in water sciences started over 25 years ago and dealt with increasing challenges in the 21st century. Following the open space workshop during the Water Research Horizon Conference in Berlin 2014, this article provides a view of some of the challenges and potential opportunities of German-Chinese cooperation in water science and technology

Evaluation of riverbank filtration in the removal of pesticides: an approximation using column experiments and contaminant transport modeling

Abstract: The potential of riverbank filtration in the removal of five pesticides commonly used in Colombia (atrazine, ametryn, carbofuran, diuron and propanil) was evaluated through a series of column experiments and solute transport modeling. The experiments consisted of two soil columns run under saturated regime, with sediments and water collected from the rivers Loessnitztal and Elbe (East Germany), respectively. Six experiments were performed at 10 and 20 °C, and the final concentrations of the pesticides were used to solve the one-dimensional advection–dispersion equation using an inverse approach. Variables such as retardation factor, first-order degradation coefficient, and dispersion coefficient were assessed for all the pesticides except propanil, which rapidly degraded in solution. The parameters obtained for one of the experiments were introduced into a groundwater flow model from the Loessnitztal site, and the code MT3DMS was used to simulate a contaminant pulse coming from the river. Four different scenarios were considered to determine the effect of adsorption and degradation on the fate of the pesticides. The results showed that, although the persistence of pesticides depends on the properties of each compound, a maximum of 30% removal was achieved during the column experiments, and a log removal of 9 through the numerical modeling. Because of the sensitivity of the fate of contaminants to sorption and degradation, field and laboratory work should be carried on to determine the removal coefficient of the dissolved and adsorbed phases of the compounds, the type of degradation to be expected, and the real values of longitudinal and transverse dispersivity. Graphical Abstract: [Figure not available: see fulltext.]. © 2018, Springer-Verlag GmbH Germany, part of Springer Nature