Chromium (III) removal from aqueous solutions by adsorption onto pyrophyllite and pyrophyllite-Al

Pyrophyllite was characterized and used for the removal of trivalent chromium, Cr (III), from aqueous solutions by adsorption. The effects of reaction time, pH of test solutions, and amount of adsorbent were investigated. Equilibrium adsorption of Cr (III) by pyrophyllite was reached within 1.5 hours. Adsorption efficiency increased with increasing pH of suspensions and amount of the adsorbent. For an initial Cr (III) concentration of 6.10-4 mol/l at pH 5, 23 % of the Cr (III) initially in solution was adsorbed. The intercalation of natural pyrophyllite by aluminium at pH 5.6 and calcination at 773 K to change the intercalated polycation A17+13 in alumine pillars lead to highest specific surface and best microporosity of the adsorbent. The pyrophyllite thus treated, referred to henceforth as pyrophyllite-Al, showed remarkable increase in chromium sorption capacity (93 % of Cr (III) removed) as compared to untreated pyrophyllite. In addition, equilibrium adsorption was reached within 30 minutes of contact. For both pyrophyllite and pyrophyllite-Al, the experimental data were fitted to the Langmuir adsorption isotherm equation. © by PSP 2005.