Low-cost supports used to immobilize fungi and reliable technique for removal hexavalent chromium in wastewater

The main goal of this study was to exploit low-cost and efficient sorbents for the removal and recovery of Cr(VI) in wastewater. Three supports of sawdust, polyurethane and alginate were applied to immobilize living and dead R. cohnii cells, respectively. There was a distinct increase in the Cr(VI) removal efficiency before and after the HCl-pretreatment. Langmuir adsorption isotherm model was well used to describe the distribution of Cr(VI) between the liquid and solid phases in batch studies. The values of q0 predicted by Thomas model were near to experimental ones in the experiments of packed column. The breakthrough curves calculated with this model were consistent well with experimental ones at a largely extent. Desorption, regeneration and reuse of the packed column were studied. After 5 cycles, adsorption capacity was still kept at higher level, reaching to 91.4, 87.9, 91.4 and 93.3 mg/l contrasted with the first cycle (94.1, 90.4, 94.8 and 98.5 mg/l) and the desorption efficiency were 85.0%, 96.2%, 93.4% and 91.4% compared with the first cycle (87.6%, 95.4%, 96.7% and 94.3%), corresponding to living cells immobilized with sawdust, polyurethane, and dead cells immobilized with polyurethane and alginate, respectively. The results indicated that the packed columns with the immobilized living and dead R. cohnii cells were the better option to adsorb, desorb and recover Cr(VI) from wastewater.