Mineral scale formation reduces heat transfer efficiency and clogs pipes and valves, increasing power consumption. To address the environmental concerns of conventional scale inhibitors, this paper explores biodegradable and eco-friendly alternatives. It examines the effects of organic additives on calcium (Ca) and magnesium (Mg) scaling in water vaporisation. Batch experiments were conducted with potable water and various organic molecules (saponin, caffeine, tannic acid, dextran, citrus pectin, Ficoll 400, and Triton X-100). Saponin showed the highest calcium scale inhibition efficiency (60.9%), followed by caffeine (49.6%) and tannic acid (39.6%), while Ficoll 400, pectin, and Triton X-100 were less effective. For the magnesium scale, caffeine was the most effective (97.4%), followed by saponin (88.6%) and tannic acid (67.1%). Inhibition efficiencies for magnesium-containing scales were generally higher than for calcium scales. Regarding the inhibition mechanisms, saponin, caffeine, dextran, and tannic acid adsorbed onto mineral crystal growth sites according to the Langmuir model, while pectin, Triton X-100, and Ficoll 400 formed complexes with Ca2+ and Mg2+ in solution. Needle-like aragonite was the predominant form of calcium carbonate (CaCO3) with most additives, except tannic acid, which produced rhombohedral calcite, and caffeine, which promoted flower-like vaterite CaCO3 crystallites. Saponin, caffeine, tannic acid, and dextran are effective, biodegradable, and environmentally friendly inhibitors for mineral scaling.
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