Structure-Dependent Dissolution and Restructuring of Calcite Surfaces by Organophosphonates

Organophosphonates are well-known to strongly interact with the surfaces of various minerals, such as brucite, gypsum, and barite. In this work, we study the influence of six systematically varied organophosphonate molecules (tetraphosphonates and diphosphonates) on the dissolution process of the (10.4) surface of calcite. In order to pursue a systematic study, we have selected organophosphonates that exhibit similar structural features, but also systematic architectural differences. The effect of this class of additives on the dissolution process of the calcite (10.4) surface is evaluated using in situ dynamic atomic force microscopy. For all of the six organophosphonate derivatives, we observe a pronounced restructuring of the (10.4) cleavage plane of calcite, demonstrated by the formation of characteristically shaped etch pits. To elucidate their specific influence on the dissolution process of calcite (10.4), we vary systematically the number of functional end groups (two for the tetraphosphonates and...