Dual-function multinuclear microcapsules with long-term scale inhibition and antibacterial properties

Scale and biofouling are two critical problems in industrial circulating cooling water systems, urging the development of innovative solutions to address both issues simultaneously. The direct usage of liquid scale inhibitors and biocides often fails to provide long-term effective control and results in significant wastage of agents. In this work, the melamine formaldehyde resin/clove oil/1‑hydroxy ethylidene-1,1-diphosphonic acid (MCH) microcapsules were successfully synthesized by double emulsion water-in-oil-in-water (W/O/W) in-situ polymerization method. The 1‑hydroxy ethylidene-1, 1-diphosphonic acid (HEDP) acted as a scale inhibitor and clove oil as a natural biocide, which offered a comprehensive solution to both scaling and biofouling issues. The as-prepared MCH microcapsule exhibited a smooth multinuclear spherical structure, a uniform size. UV–vis results confirmed the successful encapsulation of HEDP and clove oil within the MF shell, with encapsulation amounts of approximately 7.47 % and 23.67 %, respectively. Remarkably, the release of the HEDP and clove oil could extend up to 60 h and 160 h, respectively, which was consistent with the First-order model, displaying an excellent sustained-release performance. Static scale inhibition experiments indicated that the microcapsules possess sustained scale inhibition ability. The scale inhibition efficiency of the dynamic release solution of MCH microcapsules remained above 90 % for the initial 14 h, with the highest scale inhibition rate exceeding 98 %. Furthermore, these microcapsules displayed remarkable antibacterial activity against Escherichia coli and Bacillus subtilis, with both antibacterial rates exceeding 99.9 %. Overall, the sustained release of the scale inhibitors and biocides ensures long-term control and reduction in agent wastage, which presents a promising application in addressing the scaling and biofouling issues in industrial circulating water systems.