Seyed Sajad Seyedayn - Graduate student, Department of Irrigation and Drainage Engineering, University of Zabol, Iran
Shayan Shamohamadi - Associated professor, Department of Irrigation and Drainage Engineering, University of Shahrekord, Iran
Anoosh Sadat Amini Nasab - Department of agriculture and natural resources, Islamic Azad University , Ahwaz, Iran

Nowadays, Activated carbon in water purification columns are being used to remove heavy metal from water in south of Iran. The purpose of this research is to investigate Tamarisk Sawdust as a substituting adsorbent for Cr(VI) removal from aqueous solution. Tamarisk is the only tree which can live in Sistan plain and it’s sawdust is abundantly found in factories. Batch sorption was studied to determine optimal pH, equilibrium time, kinetic models parameters and isotherm models parameters. For removal of Cr(VI) in continuous condition a 30 cm bed depth glass column with diameter of 3 cm was used as a fixed bed with gravitational water flow. Operation of the column was investigated under flow of 5, 6.5 and 8 ml/min, bed depth of 10, 12 and 14 cm and Cr(VI) concentration of 6, 8 and 10 mg/l. The results showed that maximum adsorption efficiency for both of the adsorbents occurred in pH=1 and equilibrium time is 180 and 120 min for natural and modified Tamarisk sawdust respectively. Kinetic studies showed that Ho et al. and Lagergren models are more capable for adsorption description using natural and modified Tamarisk sawdust respectively. Isotherm studies showed that Fruendlich model was better for describing adsorption isotherm for both of the adsorbents. The failure time of the column increases with increase in flow rate, initial concentration and bed depth. The adsorption capacity increases with decrease in bed bed depth and increase in flow rate and initial concentration. Evaluation of column parameters showed that BDST model has a good consistency with experimental data.

Adsorption, Cr(VI), Tamarisk sawdust, Fixed bed column, BDST model