CaCO 3 Scale Inhibition by Urtica dioica L. Extract: Fast Controlled Precipitation (FCP) Experiments and DFT Calculations

ABSTRACT This study reports, for the first time, the effectiveness of a green inhibitor extracted from Urtica dioica L. in preventing CaCO 3 scaling in Calco‐Carbonic Pure (CCP) water containing 120 mg·L −1 Ca 2+ at 40°C. Precipitation kinetics were monitored using the Fast Controlled Precipitation (FCP) method through pH, resistivity, and calcium concentration by atomic absorption spectroscopy. The precipitates were characterized by x‐ray diffraction (XRD) with Rietveld refinement, scanning electron microscopy coupled to energy‐dispersive spectroscopy (SEM‐EDS), and Fourier‐transform infrared (FTIR) spectroscopy. Without inhibitor, precipitation occurred at pH p 8.135 after 33 min, yielding mainly vaterite with minor calcite. Addition of the extract increased pH p to 8.521 and prolonged precipitation time to 95 min at 3.125 mL·L −1 , with changes in crystal morphology, polymorph distribution, and composition. FTIR confirms bioactive functional groups, while EDS reveals elements from the extract, suggesting adsorption involving amino acids and phenolic compounds forming complexes with Ca 2+ . Complete inhibition was achieved at 3.75 mL·L −1 (100% efficiency, pH p = 8.576), confirming threshold effect. DFT calculations further supported electronic reactivity and adsorption capacity of the studied molecules, in agreement with experimental results, highlighting Urtica dioica L. extract as an eco‐friendly and efficient antiscalant for sustainable water treatment in industrial scaling control.