Then the primary secondary amine functionalized magnetic silica microspheres (PSA-Fe 3 O 4 ) were prepared via a sol–gel polymerization approach. 1.0 g of magnetic Fe 3 O 4 microspheres were dispersed in a mixture of ethanol (120 mL) and ultrapure water (30 mL) under ultrasonication for 5 min. 3.0 mL of ammonia solution (25–28%, w/w) was added into the microspheres solution, and then was TEOS (0.5 mL). The reaction was allowed to proceed under mechanical stirring for 12 h. 10 mL of N-(2-aminoethyl)-3-aminopropyltrimethoxysilanne was added and the mixture was stirred for another 12 h. The harvested particles were collected by a magnet, washed several times with ethanol and ultrapure water and dried under vacuum at 60 °C for 6 h.