PNNL

Abstract

Mineral dissolution is a common phenomenon in both nature and industry. However, its atomistic details are rarely known due to the complex mineral/fluid interfacial environment. Here, ab initio molecular dynamics simulations with enhanced sampling have been used to explore the detailed process of the detachment of an aluminate monomer to the solution from two types of step edges at the surface of the gibbsite, a primary mineral within the industrial processing of aluminum. The results indicate two potential pathways for detachment that are differentiated based upon the extent of water hydration. The energy profiles of the elementary bond-breaking events indicate the scission of the first or the second hydroxo bridge is the rate-limiting step for the monomer dissociation. The heights of the energy barriers depend on either the number of bridges (quasi-)simultaneously broken (1 or 2) at the zigzag edge or the Al-O coordination of the neighboring aluminum atoms (5 or 6) at the armchair edge.