Adsorptive Removal of Toxic Metal Chromium (VI) from Aqueous Solutions by Using Sawdust

Sawdust is obtained from naturally and easily available which is biodegradable. The bio sorption capacity of the sawdust for hexavalent chromium was studied at different solution pH values (1.5-6), initial metal concentration (50-450 mg/L), adsorbent dose (1-7 g/L). The maximum adsorption of Cr (VI) is obtained at pH 1.5, initial concentration 50 ppm and adsorbent dose 5 g/l. The adsorption of chromium attained equilibrium at about 4 h, with maximum removal percent of 99.99% at initial metal concentration of 50 mg/L at optimum pH. The equilibrium data for the adsorption of Cr (VI) on sawdust is studied with various adsorption isotherm models such as Langmuir, Freundlich, and, Temkin. The equilibrium adsorption data is better fitted to Langmuir isotherm (R²=0.9938). Kinetic modeling is also studies for the adsorption of Cr (VI) on sawdust in which process follows the second-order kinetics and the corresponding rate constants are obtained.