In microalgae-based biorefinement, one of the highest practical priorities is to reduce the costs of downstream processes. As one potential solution, microalgae harvesting by organoclays has received particularly keen research interest. In the present study, cationic charged aluminum- and magnesium-backboned organoclays were synthesized and solubilized in aqueous solution due to their high-density of amino sites. Each, within 30 min of its injection into 1.7 g/L-concentration microalgal feedstocks, effected harvesting efficiencies of almost 100% at concentrations above 0.6 g/L while maintaining a neutral pH. Conclusively, organoclays, if recycled efficiently, can be uniquely effective microalgae harvesting agents. (C) 2013 Elsevier Ltd. All rights reserved.