Abstract
Methylene blue was immobilized onto bentonite (BNT). The modified clay (MB–BNT) was used to extract Hg
2+ at pH 6.0 yielding Hg–MB–BNT. BNT, MB–BNT and Hg–MB–BNT were characterized by X-ray diffractometry, infrared spectra, and elemental and thermogravimetric analyses. MB is suggested to be intercalated into the major phase of BNT; montmorillonite mineral (MMT), lying parallel to the aluminosilicate layers, with a capacity of 36
mequiv./100
g. MB–BNT shows good stability in 0.1–1
M hydrochloric or nitric acids, ammonium hydroxide, and concentrated Na
+, K
+ or NH
4
+ chlorides or iodides. It shows good selectivity towards Hg
2+ with an extraction capacity of 37
mequiv./100
g in the presence of I
− giving rise to a ratio of MB/Hg
2+/I
− 1:1:3 in the clay phase. Extracted Hg
2+ could be quantitatively recovered by ammonia buffer at pH 8.5. MB–BNT was successfully applied to recover Hg
2+ from spiked natural water and cinnabar mineral samples using the optimum conditions; pH 6.0, time of stirring 10
min and 10
mL of 0.05
M NH
4Cl/NH
4OH at pH 8.5 as eluent.