Using nanofiltration in a “zero-rejection” process: the removal of Ni²⁺ and Co²⁺ from salty wastewater

Abstract

The use of nanofiltration as a pretreatment step in a zero rejection process was investigated. Nanoflux, a nanofiltration simulation software, was used to predict the rejection of Co²⁺ and Ni²⁺ from a salty multi-element matrix whose concentration is similar to seawater. Orientation simulations prior to filtration experiments were made with Nanoflux® in order to predict ionic rejections. Previously, the multi-element matrix solution speciation was studied by JChess. It was shown that the effective membrane charge and the effective membrane thickness, adjusted through the filtration of a single salt NaNO₃ solution, could be used to predict the ionic rejections of the multi-element solution for two commercial nanofiltration membranes. The elevated concentration of NaNO₃ in the multi-electrolyte solution did not reduce the high ionic selectivity of divalent ions. Predicted values were in good agreement with experimental results at neutral pH of the multi-electrolyte solution.

Keywords:

• Nanofiltration
• Wastewater
• Zero-rejection
• Heavy metals

Notes

Presented at the International Conference on Desalination for the Environment, Clean Water and Energy, European Desalination Society, 23–26 April 2012, Barcelona, Spain