Title: Experimental investigation of inorganic nanofiltration membranes prepared by atomic layer deposition and sol-gel methods for saltless water softening

Authors: Gordon N. Nangmenyi; Xiu Lin; Ernie Lee; Chris Yuan

Addresses: A.O. Smith Corporation, 12100 W. Park Place, Milwaukee, WI 53224, USA. ' Department of Mechanical Engineering, University of Wisconsin Milwaukee, Milwaukee, WI 53201, USA. ' A.O. Smith Corporation, 12100 W. Park Place, Milwaukee, WI 53224, USA. ' Department of Mechanical Engineering, University of Wisconsin Milwaukee, Milwaukee, WI 53201, USA

Abstract: This study explored saltless water softening with inorganic Nanofiltration (NF) membranes prepared by Atomic Layer Deposition (ALD) and a Tetraorthosilicate (TEOS) sol-gel process applied by the slip cast method. The experimental investigations were performed on different material-based inorganic NF membranes, including titanium dioxide (TiO₂), alumina (Al₂O₃), silver (Ag) and iron oxide (Fe₂O₃). The experimental results demonstrated that saltless water softening can be achieved with high flux through the viable rejection of Ca²⁺ with an initial rate between 7.1% and 34.1% in a single pass flow through filter in a solution of 0.5 g L⁻¹ CaCl₂ at neutral pH. A maximum rejection of 28.7% and 29.5% was achieved for Ca²⁺ at pH 4 and pH 10, respectively. The highest hardness rejection was achieved with a 25% waste water volume. In the recirculating loop tests with the same solution, a rejection rate of 9% was achieved within 15 min at a flow rate of 0.3 L min⁻¹.

Keywords: inorganic nanofiltration; atomic layer deposition; sol-gel; saltless water; water softening; charge-driven separation; Donnan exclusion; nanofiltration membranes; nanotechnology; titanium dioxide; alumina; silver; iron oxide; wastewater.

DOI: 10.1504/IJETM.2013.050684

International Journal of Environmental Technology and Management, 2013 Vol.16 No.1/2, pp.21 - 33

Received: 07 Jul 2011
Accepted: 09 Sep 2011
Published online: 17 Sep 2014 *

Full-text access for editors Full-text access for subscribers Purchase this article Comment on this article