Molecular modeling of several phosphonates onto the stepped calcite (011) surface Original Research Article

The interaction of organic phosphonates with mineral surfaces is of interest owing to their use as scale inhibitors. Molecular dynamic (MD) simulations have been employed to study the adsorption of four phosphonic acids, i.e. amino tris(methylene phosphonic acid) (ATMP), ethylene-diamine tetra(methylenephosphonic acid) (EDTMP), hexamethylene-diamine tetra(methylenephosphonic acid) (HDTMP), and diethylene-triamine penta(methylenephosphonic acid) (DTPMP) onto the stepped calcite (011) surface. It has been found that the phosphonate molecules can energetically interact well with the (011) face on the stepped dihedral nook. Furthermore, the strength of adsorption is DTPMP > HDTMP > EDTMP > ATMP based on the binding energy including vdw and electrostatic interaction, in agreement with the pHCM experiment. The results indicate that the phosphonic group number and the length of the backbone methylene chain play an important role in inhibitor effectiveness.