A Study of Salvaged Cyanobacteria Slurry Treatment Using Liquefied Dimethyl Ether: Dehydration and Organic Matter Extraction

Abstract

Liquefied dimethyl ether (L-DME) was used to dehydrate salvaged cyanobacteria slurry (SCS) and extract its organic matter. The dehydration rate and organic matter extraction efficiency were determined by mixing L-DME with SCS in a sealed reactor for 0–25 min, and the amount of solvent was 6–39 times that of SCS at a stirring rate of 0–800 rpm. Free water in SCS was removed entirely at an L-DME amount of 9 times, and then bound water was gradually removed with an increase in L-DME dosage, with a final SCS lowest moisture content of 16.64% at an L-DME amount of 39 times. Moreover, L-DME extracted 8.72%–21.15% of the organic matter from SCS, with almost complete lipid extraction. The phosphorus and nitrogen were also extracted because they mainly exist in phospholipids and proteins. Subsequently, the solid residue and liquid product were characterized, with fatty acids and plasticizers found in the liquid product. The dehydration rate and organic matter extraction efficiency were also investigated using ethanol as adjuvant of L-DME, with ethanol serving as an adjuvant. The performance of dehydration and organic matter extraction from SCS using L-DME was evaluated to explore the feasibility of applying this process to SCS treatment.