Role of Cationization in Bioflocculant Efficiency: a Review

Organic and synthetic flocculants are conventional flocculants used in wastewater treatment and tap water purification. The challenges of toxic residue and the resultant secondary pollutants generated from organic and synthetic flocculants have attracted research efforts towards microbial extracellular polymers as nontoxic and biodegradable substitutes. However, the bioflocculants themselves have been associated with high production costs and low efficiency. To address these challenges, tremendous efforts have been made to hybridise cations with the bioflocculants. The contradictory reports on the role of cations in bioflocculation have necessitated this review. This paper reviews the relevant and recent literature on EPS-cation structuring, cationization of bioflocculants, the efficiency of the cationization of bioflocculants, the factors affecting cation induced bioflocculation, and the mechanisms of cation induced bioflocculation. Variations in experimental procedures microbial species and growth medium composition yield bioflocculants with positive or negative functional sites and may be responsible for the contradictory effect of the cations. Establishment of a standard fermentation system that could elucidate the mechanism of cation induced bioflocculation and of the standard techniques for evaluation of the cationic content of wastewater treated with cationized bioflocculants is needded for better understanding of the cation stimulated bioflocculation.