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Table 1 Comparison of inorganic and organic flocculants for microalgal biomass harvesting [25]

From: Microalgae Chlorella vulgaris biomass harvesting by natural flocculant: effects on biomass sedimentation, spent medium recycling and lipid extraction

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