Treatment of wastewater containing nickel by complexation- ultrafiltration using sodium polyacrylate and the stability of PAA-Ni complex in the shear field

Abstract

Efficient and green process for industrial treatment of heavy metal wastewater is much needed. Herein, complexation-ultrafiltration using sodium polyacrylate (PAAS) as complexation agent was used to recover nickel from wastewater containing nickel by a rotating disk membrane module. The Ni2+ rejection could reach 98.26% at n < 848 rpm, pH = 7.0 and P/Ni = 13 (mass ratio). When n > 848 rpm, the high shear rate produced by the rotating disk causes the PAA-Ni complex to dissociate, and the recycling of Ni2+ and the reuse of PAAS can be achieved, which has huge economic and environmental benefits. The established membrane partition model reveals the shear instability mechanism of PAA-Ni and the distribution of the critical shear radius of the membrane at the corresponding disk rotating speed. The critical shear rate of PAA-Ni is 2.1 × 10−4 s−1 at pH = 7. These findings suggest that complexation-ultrafiltration is a viable industrial treatment approach for heavy metal wastewater. This work provides an alternative way to selectively separate and recover heavy metal from the wastewater.