Removal of molybdate anions from contaminated waters by brown algae biomass in batch and continuous processes

BACKGROUND: In recent years, the discharge of heavy metal ions in natural waters has become a serious problem. Among the various techniques that have been employed for heavy metal removal, adsorption is highly effective and economical because low-cost adsorbents canbe employed. Brownalgae are apotential biosorbent because of their high uptake capacities for various heavy metal ions. Petalonia fascia biomass immobilized in an agar matrix was tested as a new removal agent of Mo-VI from contaminated waters. RESULTS: Sorption studies were performed in batch and continuous systems. Petalonia fascia has a high adsorption capacity (1376 +/- 2mg g(-1)) at 20 degrees C and pH 1.0. Participation of hydroxyl and carboxylate functional groups in the adsorption of molybdate anions was confirmed by FT-IR analysis. SEM images showed that morphological surface changes happen after Mo-VI sorption. Mean free energies of sorption and activation parameters demonstrate that the sorption mechanism was chemical sorption. Mo-VI sorption onto brown seaweed surface was spontaneous and exothermic. Petalonia fascia has an energetically heterogeneous surface. Continuous sorption datawere best fitted by a modified dose-response model. Scale-up of the sorption processes was achieved applying a bed depth service time (BDST) model. The critical bed depth, Z(0) was 1.7 cm. CONCLUSIONS: Petalonia fascia biomass is a good adsorbent material for Mo-VI and it can be used in fixed bed columns for the purification of Mo-VI contaminated effluents. The high value of q(max) and the low cost of this seaweed make this biomass a good sorbent for use in continuous treatment of groundwater and effluents contaminated with molybdate anions. (C) 2016 Society of Chemical Industry