Scale inhibition performance of calcium sulfate by 1,6-diaminohexane-contained polyaminoamide dendrimers: Static experiment and MD simulation

The calcium sulfate scale is a common scale in the industrial water system, which is difficult to be removed by common chemical cleaning methods. In this paper, a new phosphorous free of 1,6-Diaminohexane-contained polyaminoamide dendrimers (PAMAM) scale inhibitor with a three-dimensional (3D) branched structure has been developed. The scale inhibition performances of different generations of PAMAM dendrimers (PAMAM-mid, PAMAM-0G, PAMAM-0.5G and PAMAM-1G) are estimated by the static scale inhibition method. Moreover, the effects of the scale inhibitor concentrations and solution temperatures on the CaSO₄ scale inhibition efficiency are thoroughly discussed. Results indicate that the PAMAM-mid and PAMAM-0.5G) exhibit excellent inhibition performance on CaSO₄ precipitation. Especially, the CaSO₄ scale inhibition efficiency of PAMAM-0.5G is above 95% when the dose is 10 mg/L, and the corresponding value is almost 100% when the inhibitor dose is 20 mg/L. In addition, the influence of descaling agents on the crystal and morphology of CaSO₄ scales are studied by XRD and SEM tests. The results show that the scale inhibition ability of the PAMAM molecules mainly inhibits the growth of these crystal planes by adsorption on the surface of the growing crystal. Molecular dynamics simulation results find that the PAMAM-0.5G dendrimer molecule can energetically interact well with three crystal planes of calcium sulfate dihydrate. Finally, the simulation results provide a theoretical guidance to judge the performance of scale inhibitors and synthesize new high-efficiency scale inhibitor.