Effects from Converter Slag and Electric Arc Furnace Slag on Chlorophyll a Accumulation of Nannochloropsis sp.

The effects of Ca2+ in converter slag and electric arc furnace slag leaching solutions on CO2 content, the effects of CO2 content in solutions on the accumulation of chlorophyll a of Nannochloropsis sp., and the mechanisms were studied. Results showed that addition of 50 mg/L converter slag leaching solution and 400 mg/L electric arc furnace slag leaching solution (lower than 50 vol% concentration) promoted the accumulation of chlorophyll a of Nannochloropsis sp., while an increased concentration of 70 vol% inhibited its accumulation. The highest concentration of chlorophyll a was obtained on the addition of 10 vol%. With 10 vol% leaching solutions added, chlorophyll a concentration for converter slag reached 4.2 mg/L, 1.45 times as much as that of pure F/2 medium, and chlorophyll a concentration for electric arc slag reached 3.2 mg/L, 1.10 times as much as that of pure F/2 medium. Under the same addition proportion, the promoting or inhibiting effect from converter slag on the accumulation of chlorophyll a of Nannochloropsis sp. was more obvious than that for electric arc furnace slag. The reason for the promotion of chlorophyll a accumulation of Nannochloropsis sp. was that an increase of Ca2+ in the solutions led to an increase of CO2, thereby promoting the photosynthetic rate of microalgae. The study provided new ideas for the green application of solid waste and industrial production of microalgae.