Green and sustainable strategies to control scaling in industrial plants: investigation of the efficacy of <i>Rosmarinus officinalis</i> L. Extract against CaCO ₃ scale using experimental and theoretical approaches

In recent years, plant extracts have attracted increased interest as green alternatives to conventional anti-scaling. This is because they contain a wide range of bioactive compounds with high performance against inorganic scale. Additionally, they are biodegradable and pose minimal risks to human health and ecosystems. The present study aimed to assess the protection offered by the <i>Rosmarinus officinalis</i> L. leaf extract for industrial plant surfaces against the CaCO₃ scale. Before assessing the anti-scaling performance of the <i>Rosmarinus</i> extract, phytochemical characterisation was performed by quantitative assays and HPLC-DAD analysis. Subsequently, the inhibition potential of the extract was studied using the conductivity and LCEE tests at 25°C and TH = 40°f. In addition, SEM and XRD analysis were used to assess the effect of the extract on scale morphology and crystalline phases. Finally, DFT calculations and Monte Carlo simulation were carried out to enhance knowledge of the interaction between inhibitor molecules and CaCO₃(104) and (110) surfaces and optimise [extract molecule - Ca]²⁺ complexes. Phytochemical analysis revealed the presence of several phenolic compounds (rosmarinic acid, vanillic acid, cinnamic acid, rutin, kaempferol, trans chalcone and quercetin). Further LCEE studies demonstrated the promising anti-scaling activity of the extract at an effective concentration of 54 mg/L. SEM micrographs and XRD diffractograms revealed a significant change in the morphology and phases of precipitated CaCO₃ scales upon the addition of the inhibitor. In addition, the computational approach strongly supported the experimental results. These results underlined the <i>Rosmarinus</i> extract's potential as a valuable green and sustainable scaling inhibitor source.