Removal of Fluoride Ions from Wastewater Using Green and Blue-green Algae Biomass in a Fluidized Bed System

الملخص

The removal of fluoride ions from aqueous solution onto algal biomass as biosorbent in batch and continuous fluidized bed systems was studied. Batch system was used to study the effects of process parameters such as, pH (2-3.5), influent fluoride ions concentration (10- 50 mg/l), algal biomass dose (0–1.5 g/ 200 ml solution), to determine the best operating conditions. These conditions were pH=2.5, influent fluoride ions concentration= 10 mg/l, and algal biomass dose=3.5 mg/l. While, in continuous fluidized bed system, different operating conditions were used; flow rate (0.667- 0.800 l/min), bed depth (8-15 cm) corresponded to bed weight of (80- 150 g). The results show that the breakthrough time increases with the increase of bed depth but decreases with the increase of flow rate. Thomas and Yoon-Nelson models were used to analyze the experimental data and there was a good matching between the theoretical and the experimental data for both models. Desorption studies indicate that NaOH solutions at different pH values (8-10) were used to recover the fluoride ions sorbed onto the algal biomass. It is noteworthy that the desorption efficiency at pH =10 remains close to 95 % of the initial value of sorption capacity. So the desorption performance remains appreciable.