Preparation and characterization of pillared montmorillonite: application in adsorption of cadmium

This work concerns the pillaring of Algerian montmorillonite with polyhydroxymetal such as aluminum and chromium and its application in adsorption of inorganic polluant in the water : the cadmium. A systematic study of different parameters was undertaken such as the ratio of Cr/Al (5, 10, 20, 50 and 80 mmoles/g) ; Cr/Al (0, 0.2, 0.6, 1.2 and 5 mol/mole), aging time of metallic hydrolysis (1, 4, 24 and 36 h) and temperature (25, 40, 60 and 95°C). The obtained pillared clays were characterized by X-ray diffraction, physisorption of nitrogene at 77 K and by transmission electronic microscopy. It has been shown that a high temperature and a long time of metallic polymerization (before the intercalation) are in favor to a good pillaring. Indeed, the chromium polymer resulted by the hydrolysis under 95°C for 36 h leads (after intercalation and burn-off at 150°C) to a pillared clays with an interesting and stable textural properties (d001 = 19.13 Å, Asp = 196 m2/g when calcined at 300°C). The effect of ratio Cr/Al shows that its increase is not favorable to the expansion of clay layers. When the ratio Cr/Al goes from 0.2 to 1.2, the basal spacing decreases from 17.8 to 16Å. The samples which have optimal properties were used as adsorbent of heavy metal. In this part of work, a systematic study optimizing the adsorption was also realized. The equilibrium time reaches 20, 40 and 80 min for the clays Mont.Al-Cr (Cr/Al = 0); Mont.Al-Cr (Cr/Al = 0.2) and Mont.Cr respectively. The adsorption yield is about 91%, 27% and 10% for an adsorption at 20 min for the abovementioned clays respectively. These results reveals that the Al pillared clay (Cr/Al = 0) has a better affinity toward the cadmium in our conditions.