Abstract
Adsorption technology is one of the most promising technologies to remove heavy metals from water. This paper aims to remove arsenite As(III) from contaminated water using a less costly, easier to handle and efficient absorbent. Purified natural clay was characterized and tested as an adsorbent. Mineralogical and textural analysis showed that this adsorbent is a nonswelling clay mineral (illite + kaolinite) and a mesoporous material with specific surface area S-BET = 128 m(2) . g(-1). A series of batch tests were performed as a function of contact time (10-180 min), temperature (25-55 degrees C), initial As(III) concentration (20-100 mg . L-1) and solid/ liquid ratio (5-25 g . L-1). The adsorption equilibrium studies revealed that Freundlich isotherm was followed with a better correlation than the Langmuir isotherm, moreover, it was intra particle diffusion controlled. The adsorption of As(III) onto the mixture illite-kaolinite was significant in the pH range 9-10.8 with a maximum adsorption capacity q(max) = 233.1 mg . g(-1). At 298 K, the thermodynamic investigation indicates that the adsorption processes is spontaneous (Delta G degrees(ads) = -9.3 kJ . mol(-1)) and exothermic (Delta H degrees(ads) = -4.58 kJ u mol-1). The Delta S degrees(ads) parameter was found to be + 15.8 J u mol-1 . K-1 meaning an increase in the randomness of the processes at the surface of clay particles.