Microalgal biofuel is garnering many positive and promising reviews as a fuel for the next generation while research effort continues to improve the efficiency of its harvesting for commercial success. In this report, magnetophoretic harvesting of microalgae is conducted through a three-step process, which includes functionalization of magnetic particles by (3-aminopropyl) triethoxysilane (APTES), magnetic separation, and detachment of magnetic particles by increasing pH to higher than the isoelectric point. Detachment process is specifically focused and found that the use of larger magnetic particles is more efficient for detachment of magnetic particles from algae-particle conglomerates. The detaching efficiency improves from 12.5% to 85% when the particle size is increased from 108 nm to 1.17 mu m. Smaller magnetic particles provide larger contact area to microalgae and form strong electrostatic binding to negatively-charged microalgae when pH is lower than the isoelectric point. (C) 2013 Elsevier Ltd. All rights reserved.