Release performance of cement-based control release beads (CRBs) for mineral scale control in water system

Mineral scaling poses major operational challenges in water-transporting systems across various industries, leading to substantial economic losses globally. Scale inhibitors are specialty chemical agents with functional groups to prevent or interfere with scale formation. Traditionally, scale inhibitors are introduced into water-transporting systems through continuous injection. However, this approach is limited by its short protection duration and reliance on continuous inhibitor injection, which results in high capital and operating costs, as well as increased chemical waste. To address this issue, this study synthesized cement-based controlled release beads (CRBs) loaded with 1-hydroxyethylidene-1,1-diphosphonic acid (HEDP) scale inhibitor for scale control. The release performance of HEDP from the CRBs was systematically evaluated through static batch and dynamic column experiments. Quartz crystal microbalance with dissipation monitoring (QCM-D) and turbidity tests confirmed the effectiveness of the CRBs in inhibiting BaSO 4 scale formation. Batch experiments demonstrated that increasing CRB size and lowering the temperature could reduce the release rate of HEDP while prolonging the release duration, without changing the total amount of HEDP released. Dynamic column experiments revealed that higher temperatures resulted in higher peak concentrations of HEDP and earlier peak occurrences, while increasing flow velocity shifted the release curves slightly backward and shortened the overall release time. The presence of Ca 2+ and HCO 3 − ions had no noticeable effect on the dynamic release behavior. These findings deepen our understanding of the release mechanisms of scale inhibitors from cement-based CRBs and highlight their potential as an innovative and sustainable solution for long-term scaling control in water-transporting systems.