Effect of voltage and electrode material on electroflocculation of Scenedesmus acuminatus

Abstract

Background: Microalgae are a promising new source for biomass production. One of the major challenges in regards to cost effectiveness is the biomass harvest. High energy input is required for the separation of the small algal cells from a large volume of surrounding media. Electroflocculation is reported as a promising harvesting technique to improve cost effectiveness within the downstream process. In the present study, six electrode materials were tested for electroflocculation of Scenedesmus acuminatus. Besides the commonly used aluminum and iron electrodes, magnesium, copper, zinc and brass electrodes were tested for biomass harvest and compared. The influence of four different voltages (10, 20, 30 and 40 V) was investigated and evaluated. Results:Electroflocculation was applicable with all tested electrode materials. The highest flocculation efficiency was achieved using magnesium electrodes followed by Al, Zn, Cu, Fe and brass. Using magnesium, 90% of the suspension was clarified at 40, 30, 20, and 10 V after 9.2, 12.5, 18.5, and 43 min, respectively. All electrode materials showed the fastest flocculation at 40 V and the lowest at 10 V. The pH increased from 7.5 to values between 9.3 and 11.9 during the flocculation processes. Reuse of the supernatant showed no adverse effect on algal growth. The highest cell counts after 12 days of incubation were achieved with iron at 1.86 × 10 7 cells ml −1 and the lowest with copper at 1.23 × 10 7 cells ml −1. Conclusion:Besides the commonly used iron and/or aluminum electrodes, other materials like magnesium, copper, zinc and brass can be successfully used for microalgal biomass harvest. For special biomass applications like food or feed additives, metals like magnesium have other advantages besides their high flocculation efficiency such as their low toxicity at high concentrations. Higher voltages increased the maximum flocculation efficiency but also increased the required energy input.

Comparison of Different Anode Materials to Remove Microcystis aeruginosa Cells Using Electro-Coagulation–Flotation Process at Low Current Inputs

“…This may be due to OH − ions generated at the cathode as a result of metal ion oxidation at the anode. A similar result was reported by Bleeke et al [30] for the treatment of Scenedesmus acuminatus using the same anode materials. The Cu anode showed the highest final average pH of 11.46 ± 0.48 (Table 4).…”

Investigation of electrolytic flocculation for microalga Scenedesmus sp. using aluminum and graphite electrodes

“…However, other metals could not form those hydroxides. The results conicted with the research conducted by Bleeke et al, 25 in which the authors stated that magnesium and iron were equally effective as aluminum. The difference of the results may be due to the inuence of current density and electrolysis time.…”

Treatment of paper-recycling wastewater by electrocoagulation using aluminum and iron electrodes

“…Generally, the pH of the medium changes during the EC process and this change depends on the type of electrode material and on the initial pH [49, 58, 59]. According to Fig.…”