Binders Based on Natural Anhydrite and Modified by Finely-Dispersed Galvanic and Petrochemical Waste

Controlling the Selective Formation of Calcium Sulfate Polymorphs at Room Temperature

“…[14] The third crystalline polymorph, anhydrite (anhydrous CaSO 4 ), replaces gypsum as the stable phase at temperatures higher than around 50 8C [8,15] and is common in evaporitic deposits, [16] but also in low-temperature hydrothermal settings; [17] it is frequently used as a binder in cements and adhesives. [18] Interestingly, despite its abundance and actual stability in the phase diagram at elevated temperatures, anhydrite does not form spontaneously during precipitation of calcium sulfate below about 120 8C, mainly because of kinetic inhibition. [8,19] Herein we present a simple, solution-based method that allows for the preparation of phase-pure anhydrite at room temperature.…”

Use of sintering to immobilize toxic metals present in galvanic sludge into a stabile glass-ceramic structure

“…Stabilization of heavy metals from galvanic sludge is carried out by various technological processes, such as the incorporation in bricks [4], borosilicate glass [5], glassceramics (along with aluminum slag) [6], clay ceramics [7], transparent glass-ceramics [8], red ceramics [9] or calcium sulphoaluminate cement [10], reuse in the metallurgical industry [11], vitrification [12], solidification by asphalt emulsion [13], etc. Besides, a lot of research has been conducted in order to develop various applications of waste galvanic sludge like obtaining malayaite ceramic pigments [14], Cu-concentrates [15] or binders (along with a petrochemical waste) [16], immobilizing heavy metals using of sodium silicate and tetraborate [17], recovering toxic metals by sulfate treatments [18], removing nickel, copper and chromium in an electrocoagulation system with Fe-and Al-electrodes [19], extracting chromium [20], performing chromium passivation [21] and others.…”

Selektive Kontrolle der Bildung von Calciumsulfat‐Polymorphen bei Raumtemperatur

“…[8,15] Es kommt in evaporitischen [16] sowie in niedertemperierten hydrothermalen Lagerstätten [17] vor und wird häufig als Binder für Zemente und Klebstoffe eingesetzt. [18] Tr otz des breiten Vorkommens in der Natur und der erwiesenen Stabilität im Phasendiagramm bei hçheren Te mperaturen bildet sich Anhydrit jedoch nicht spontan bei der Fällung von Calciumsulfat unter ca. 120 8 8C.…”