By Chloride guards:

[i] Activated alumina; the adorption being physical; the reaction is reversible

[ ii] Promoted alumina = alumina containing Na2O as a promoter; undergoes chemical reaction to form NaCl and thus the process Is irreversible.

Thank you Manohar

Hope you find Mini-Donut  the latest chloride trapper[ Pls. find attached a file.

The researchers “clicked” four small rings together to form a large ring. This process also generates four more rings, made of three nitrogen atoms and two carbon atoms (triazole rings). These are not only by-products of the click chemistry, they are essential for binding the chloride ion, which can comfortably nestle into the empty center of the large donut-shaped ring. The triazoles hold on to the chloride ion by means of bridging hydrogen bonds, which is amazing because it was previously assumed that hydrogen bonds were not strong enough to form a sufficiently stable bond between a halogen ion and a chelate complex. It is probably vital that the binding sites in the structurally stable macrocycle are preorganized into the correct configuration so that the chelator does not have to rearrange itself around the ion before binding can occur, as is the case for open-chain chelators.

The four other nonbinding rings of the macrocycle can be varied almost as desired, so the researchers hope to generate a whole family of new chelators that are able to bind a spectrum of other anions with high specificity.

Citation: Amar H. Flood, Pure C-H Hydrogen Bonding to Chloride Ions: A Preorganized and Rigid Macrocyclic Receptor, Angewandte Chemie International Edition 2008, 47, No. 14, 2649–2652.