The multifunctional microsized ZnO-PO43- -modified kaolin of average diameter about 500nm with the composition Na2O: ZnO:Na3PO4:SiO2:Al2O3 = 2.5-8.5:0.04-0.65:0.8-4.5:1.5-2.5:1 (molar ratio) were firstly synthesized from ZnO, Na3PO4, NaOH and kaolin and characterized by standard techniques, its application in oilfield produced wastewater purification was also studied. It was found that the physical properties of ZnO-PO43- -modified kaolin such as specific surface area, porous volume and pore diameter increased independently compared to the starting kaolin. It was also found that the prepared kaolin has multifunctional properties to decrease COD and BOD value, remove scaling ion (Fen+, Ca2+ and Mg2+), improve MF, decrease bacteria and inhibit corrosion and can be used effectively in oilfield wastewater purification. (c) 2005 Elsevier B.V. All rights reserved.