Ammonia pretreatment for enhancement of Pb ions adsorption on smithsonite surface and its flotation performance

Abstract

The surface modification of smithsonite with Pb ions is an effective method to improve the sulfidization-xanthate flotation process. In the present study, NH3·H2O was employed to enhance Pb ion adsorption on the smithsonite surface, thus improving its flotation performance. The time-of-flight secondary ion mass spectrometry (TOF-SIMS) and X-ray photoelectron spectroscopy analyses showed that the main species of Pb adsorbed were Pb(OH)2 and Pb3(CO3)2(OH)2 precipitates. Adsorption of the main Pb species increased by 35.29% (TOF-SIMS) on the smithsonite surface at an appropriate NH3·H2O concentration. Analysis of the chemical reactions in the aqueous solution indicated that the aqueous NH3 interacted with the smithsonite surface, and more uncoordinated carbonate ions and hydroxyl ions were produced. The uncoordinated sites further combined with free Pb3(OH)42+ and PbOH+ in solution, forming more Pb precipitates on the smithsonite surface during Pb ion adsorption. As a result, the recovery of NH3·H2O-pretreated smithsonite was increased by approximately 10% in a Pb ion-modified sulfidization–xanthate flotation system.