Investigation on washing effects for nano-bubble/surfactant mixtures in an alternating flow

Abstract

Laundry wastewater is known to contribute to water pollution, and the need to reduce the amount of detergents used is recognized. Extensive research has focused on the washing effects of micro-bubbles and nano-bubbles, and mechanical work has been found to account for 50% of the washing effect. In the present research a water/nano-bubble mixture and several types of surfactants were investigated in an alternating flow system. The nano-bubble water achieved a washing rate of about 5% greater than that of ion exchanged water. In addition, nano-bubbles mixed with an aqueous solution of surfactant exhibited a washing rate that depended on the ionization of the surfactant: the mixture of nano-bubbles and anionic surfactant exhibited a washing rate that was 10% higher than that of aqueous anionic surfactant solution without nano-bubbles. As measured by the du Noiiy method, the surface tension of nano-bubble water and anionic surfactant/nano-bubble mixtures were lower than that of water and aqueous anionic surfactant solution, respectively. These results provide evidence of an enhanced washing effect for nano-bubble mixtures. © 2011 The Japan Society of Mechanical Engineers.