Adsorption of Cr (VI) Onto Clay Modified by Sodium Chloride and Clay Modified by Aluminum Hydroxide of Karewa (North Cameroon)

In this study, removal of Cr (VI) from aqueous solutions by adsorption onto clay modified by sodium chloride and clay modified by aluminum hydroxide was investigated as a function of pH, contact time, adsorbent dosage, initial metal concentration and temperature. Time-dependent experimental studies showed that the adsorption quantity of Cr (VI) increases with initial concentration and decreasing adsorbent dosage. The equilibrium time of 10 and 40 min was observed clay modified by sodium chloride and clay modified by aluminum hydroxide (CSC and CAH) and maximum adsorption was favored at pH 3. The Cr (VI) removal using 0.1 g of adsorbent was more than 90%. This dosage (0.1 g) was considered as the optimum dosage to remove Cr (VI) aqueous solutions. Experimental data were investigated by two adsorption isotherms models (Langmuir and Freundlich). Applicability of isotherm equation to describe the adsorption process was analysed by the correlation coefficients values, R². Langmuir and Freundlich models show best fit with R² values superior of 0.95. The mechanism of adsorption of Cr (VI) is therefore based on the assumption of the kinetic model of pseudo-second order in two steps. Thermodynamic parameters such as ∆H°, ∆G° and ∆S° demonstrated that adsorption mechanism of Cr (VI) onto clay modified by sodium chloride and clay modified by aluminum hydroxide, physisorption, spontaneous and exothermic in the ranges of temperature of 203-333K.