Absorption of NH3 into water-in-oil (W/O) microemulsion in a rotor-stator reactor (RSR) was investigated in this work. The microemulsion comprised triton X-100, 1-pentanol, cyclohexane and water while the gas phase was a mixture of NH3 and N-2. Experiments were performed to study the mass transfer process between the gas and the microemulsion. The effects of water content on the physical properties of the microemulsion as well as the influences of operating conditions including water content of the microemulsion, rotation speed, liquid volumetric flow rate and gas volumetric flow rate on the mass transfer coefficient (K(y)a) were investigated. The results showed that the density and viscosity of the microemulsion increased with an increasing water content whereas the Henry's constant of the NH3-microemulsion system decreased. K(y)a increased with an increase in water content of the microemulsion, rotation speed, liquid volumetric flow rate and gas volumetric flow rate. A comparison of the K(y)a of NH3 in the RSR and in a packed tower showed that the K(y)a of NH3 in the RSR was 65% higher than that in the packed tower under the same operating conditions, thus, revealing that the RSR has higher mass transfer efficiency than the packed tower. (C) 2014 Elsevier B.V. All rights reserved.