Abstract
Rice husk is a known agricultural residue that commonly available in Zaria and environs. Rice husk activated carbon was produced using combined thermal and chemical method. The rice husk was carbonized at 350oC for the residence time of 1 hour at the heating rate of 10o C/min, after which it was impregnated with 1M of tetraoxophosphate (V) acid at the ratio of 2:1. Furthermore, batch adsorption experiment was carried out at the agitation time of 10 - 120 mins, initial lead concentration of 10 - 60 mg/l, adsorbent dosage of 1.0 - 5.0 g, pH of 2 - 10 and operating temperature of 30-50oC. The result indicated that, at the agitation time of 10 mins and pH of 4, the removal efficiencies of 99.422 and 99.833%, respectively were achieved. In addition, the adsorption data could be described by Freundlich and D-R isotherms with the highest of adsorption capacity of 0.1478 mg/g. Moreover, mean free energy (E) value of: 1.0492 kJ/mol was recorded, which signified that the batch adsorption process was physical and that was further supported by the Temkin heat of sorption value of: 0.2600 kJ/mol. Furthermore, the adsorption kinetics data revealed that the data could be described by Pseudo-second order due to higher R2 of 1.0000. Similarly, the adsorption thermodynamic data indicated that the adsorption process was endothermic with ¢H value of 62.639 kJ/mol. It was concluded that the activated carbon produced from rice husk was effective for lead adsorption from aqueous solution.

Key words: Adsorption, activated carbon, lead and rice husk