Table 1.

Comparison of inorganic and organic flocculants for microalgal biomass harvesting [25]

Parameters	Inorganic flocculants	Organic flocculants
Nature of flocculants	Multivalent salts	Polyelectrolytes/polymers
Key characteristics of an effective flocculant	Increasing molecular weight can increase the binding capabilities	Flocculants that have a high charge density are therefore more effective
Sensitivity to pH	Coagulation using inorganic coagulants is highly sensitive to pH level	Coagulation using organic coagulants is less sensitive to pH
Sensitivity to biomass concentration	Highly sensitive to concentration	Highly sensitive to concentration
Dosage of flocculants required	A large concentration of inorganic flocculant is needed in order to maintain flocculation efficiency, and may contaminate the end product (e.g., addition of aluminum and iron salts)	Lower dosages of organic flocculants are required, and less or no contamination occurs
Applicability	Although some coagulants may work for some microalgal species, they do not work for others	Wide range of applications for larger number of microalgal species