Durch Umsetzung der nach den Bruttogleichungen
stöchiometrisch eingewogenen, sehr fein gepulverten Ausgangssubstanzen wurden bei den angegebenen Temperaturen drei ternäre Cadmiumarsen‐chloride dargestellt. Die gut kristallinen Verbindungen werden von kalten verdünnten Säuren und Laugen nur langsam angegriffen; in der Hitze und durch konzentrierte Säuren und Laugen werden sie schnell zersetzt.
Cd2AsCl2 (hellrot) kristallisiert monoklin mit den Gitterkonstanten a = 8,187, b = 9,187, c = 13,594 Å; β = 91,34° mit 8 Formeleinheiten in der Elementarzelle, wahrscheinlich in der Raumgruppe C 2h5P21/c; es ist offensichtlich isotyp mit Hg2PCl2, Hg2AsCl2, Hg2AsBr2 und Hg2SbBr2.
Cd4As2Cl3 (dunkelrot) kristallisiert wie die analog zusammengesetzten Verbindungen Cd4Sb2J3, Hg4As2Cl3, Hg4As2Br3, Hg4As2J3 und Hg4Sb2J3 kubisch mit a = 12,391 A und ebenfalls 8 Formeleinheiten je Zelle in der Raumgruppe T h6Pa3.
Cd3AsCl3 ist hellgelb und relativ lichtempfindlich. Für die Verbindung wurde eine rhombische Elementarzelle mit a = 13,139, b = 8,097, c = 7,085 Å gefunden, die 4 Formeleinheiten enthält. Als Raumgruppen kommen D 2h16–Pnma oder C 2v9Pna21 in Frage.
Water shortage has risen severely in recent years, confronting mankind with a worldwide challenge, especially as the accessible water resources are further limited by diverse contamination. The most widespread industrial process for water treatment is the activated sludge process, in which, however, excessive sludge production has become an enormous environmental problem worldwide. To overcome this problem, hydrogels possess outstanding potential in view of adsorptive removal of contaminants like heavy metal ions, fertilizers, and dyes. In this paper, we report about the synthesis of biobased alginate hydrogel beads along with polyethyleneimine‐modified composite hydrogels for water treatment. The adsorption of methylene blue as a positively charged and of congo red as a negatively charged model dye is quantitatively investigated, both separately and in combination. In addition, the pH‐dependent adsorption of the dyes is determined. The use of alginate‐based hydrogel systems combines several prospects: they are bio‐based, inexpensive, easily available to a sufficient extent, sustainable, and are applicable in a broad range of wastewater treatment by its charged groups.
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