A cyanobacterium, Oscillatoria sp., isolated from the Mazandaran Rivers, Iran, was studied for its ability to eliminate Co(II) ions from aqueous solutions. Optimum conditions for biosorption of Co(II) ions by Oscillatoria sp. were investigated in terms of critical parameters such as pH, temperature, contact time, biomass concentration, initial metal concentration and influence of co-ions. Dried biomass of Oscillatoria sp. exhibited higher biosorption capacity than wet biomass. The maximal Co(II) ion biosorption capacities of the dried and wet biomass were recorded at pH 7 and 5, respectively. The range of initial Co(II) ion concentration tested was 5—200 mg/L and the experimental biosorption data was found to fit the Langmuir model better than the Freundlich model. Maximum biosorption capacity calculated for dried biomass of Oscillatoria sp. was 30.12 ± 0.10 mg/g based on the Langmuir model and optimum conditions were pH 7, 25°C, 0.08 mg/mL of biomass, 50 mg/L initial Co(II) and 6 h of contact time. Biosorption of Co(II) was reduced in the presence of equimolar amounts of co-ions. Lastly, the capacity of the dried biomass was tested for removal of Co(II) from river water samples supplemented with ∼14 mg/L Co(II), under the optimized experimental conditions.
Ultrasonic atomization, a process of generating fine droplets through irradiation of high-frequency ultrasound to a gas-liquid interface from the liquid underneath, is applied to separating ethanol from its aqueous solution. Towards its practical use, the process of collecting in two cooling stages the ethanol-enriched mist-generated via an ultrasonic atomizer (ultrasonic transducer operated at 2.4 MHz) with continuous feed of ethanol-water solution-using two cooling units in a series has been developed. The effects of operating conditions, especially cooling temperatures and gas flowrate, on ethanolenrichment and condensation characteristics are examined. It is found that the highly-enriched ethanol recovery could be attained in the 2nd stage by optimizing the 1st- and 2nd-stage cooling temperatures (as moderate as 5°C and up to-10°C, respectively). Regarding the carrier-gas flowrate, ethanol-rich mist consisting of small-size droplets tends to be carried selectively in favor of lower gas flowrate. Nevertheless, the desired recovery of enriched ethanol-i.e., a highest possible value of the recovered quantity of ethanol as well as the recovery concentration itself-is expected to be obtained in the 2nd stage by raising the carrier-gas flowrate under the present operating conditions. While the proposed two-stage cooling process tends to collect rather an appreciable quantity of less-enriched ethanol solution in the 1st stage, it is the 2nd stage that assures the desired quality of enriched-ethanol recovery.