Effect of phosphate inhibitors with various chain length on the formation of BaSO₄ crystal

The effects of diethylene triamine penta (methylene phosphonic acid) (DETPMP) and bis(hexamethylene triamine penta (methylene phosphonic acid)) ( BHMTPMP) on formation of BaSO₄ crystal were studied. The surface structure and performance of BaSO₄ crystal were characterized by Zeta potential analysis. The inhibitory mechanism was discussed according to the homogeneous nucleation theory. The morphology of BaSO₄ crystal was characterized by means of SEM. It was found that the effect of the phosphonate inhibitors on the formation of BaSO₄ crystal may be from the increase of surface free energy and activation energy of BaSO₄ crystalline. The inhibition effect of BHMTPMP was better than that of DETPMP. When the inhibitors were added during precipitation of BaSO₄, the absolute Zeta potential value of BaSO₄ crystal increased and reached its maximum value at pH=8 of the solution. The regular shapes of BaSO₄ crystals were changed obviously in the presence of the phosphonate inhibitors. The step growth characteristics presented significantly on the surface of BaSO₄ crystal.