Chemical, sorptive and morphological properties of montmorillonite treated with ammonium bifluoride (NH₄HF₂) solutions

Abstract

A B S T R A C T:The fluorination of montmorillonite by aqueous ammonium bifluoride solution (NH4HF2) has been investigated by chemical, sorptive, porosimetric and electron microscopic methods. Changes in the chemical composition of the montmorillonite during the fluorination were compared both in the crystal surface and in the bulk sample. The accumulation of fluorine was distinctly zonal, being present mainly in the surface layers. The electron microscope studies showed that the 300--400 nm thick macrodomains in the initial montmorillonite were cracked into small microdomains 20-30 nm in thickness, this resulting from disruption in the continuity of the octahedral sheets. These distinct changes in morphology of the montmoriUonite aggregates particularly influenced the porosity and sorptive properties.

Structural Fluorine in Sepiolite

“…The composition of the solid residue was also determined. An attempt to introduce fluorine into the sepiolite structure was made by treating the sample with NH4HF 2 in methanol (Fijal et al, 1985). The solvent was eliminated in a rotary evaporator, and the treated samples were heated at 100~ for 8 hr in a Teflon pressure reactor.…”

“…The mF-NMR signal of sepiolite treated with 1 N HCI at 20~ for 8 hr (extraction of about 25% Mg 2+ and 22% F-) showed ( Figure 4D) the same width as the signal of natural sepiolite, indicating that the m/e environments of the remaining F-was not altered by the acid treatment. A procedure based in the method used by Fijal et al (1985) to fluorinate montmorillonite was followed in an attempt to incorporate more fluorine into the sepiolite structure. As a result of this drastic treatment with NH4HF2, the products contained 2 to 5 wt.…”

Characterization, properties and microstructure of spent drilling mud from the point of view of environmental protection

“…4). Combining knowledge on the surface properties and reactivity of the functional groups on clay minerals [2,3,6,7] as well on the chemistry, structure and active centers confi guration on the surfaces of selected groups of organic polymers and macromolecules [9,13], it will be possible to predict most probable interactions between the two types of substances [1,4,5,8,12]. The results of the mentioned works could be applicated into the explanation of the mutual interactions between the components in the organo-mineral spent drilling mud colloid systems (see Tab.…”

Time changeability model of the bog ore sorption ability

“…The content of iron oxides and organic substance in the ores is of the highest importance for its sorption properties. By fixing to surface of ore mineral components (mainly iron oxide-hydroxides and hydroxides), humus substances block the sorbent pores [36]. There are no bibliography references with simple relationships between composition of bog ores and their sorption properties.…”

“…Activation of the ore consists in calcining at 673 K [36], fluffing (eg by adding sawdust) and alkalizing with calcium hydroxide, sodium hydroxide or sodium carbonate (hydroxides bond with CO 2 to carbonates which are also reacting with H 2 S). The aforementioned methods of chemical and physical activation allow to enlarge the specific surface and porosity, to improve alkaline-acid properties, hydrophilicity or hydrophobicity and also catalyst properties [36].…”