Research has revealed the significant potential of rosemary extract (Salvia rosmarinus) as a natural scale inhibitor for mitigating calcium carbonate (CaCO3) deposits, presenting effective and eco-friendly alternatives to conventional chemical biocides.
Scaling issues—characterized by the accumulation of sparingly soluble inorganic salts—pose considerable threats to water supply systems and industrial processes. The deposition of these minerals can result in corrosion, energy loss, and operational inefficiencies. Traditionally, phosphate-based scale inhibitors have been employed, but their toxicity and limited biodegradability have raised environmental concerns.
Against this backdrop, researchers set out to investigate the scale inhibition capabilities of rosemary extract, leveraging its known antibacterial properties alongside two bio-preservatives, Chitosan and Rhamnolipid, to improve the extract's shelf life against microbial spoilage. The comprehensive study lasted for 24 weeks and involved electrochemical analyses, conductivity tests, and microbiological examinations.
The findings indicate rosemary extract exhibits significant inhibition of CaCO3 scale precipitation, attributed primarily to its carboxylate and hydroxyl functional groups, which effectively interfere with crystal growth. Notably, the study highlighted the effectiveness of combining rosemary extract with Chitosan. Specifically, a 1:2 ratio of Chitosan to the rosemary extract provided not just enhanced scale inhibition but also suppressed the growth of pathogenic bacteria and fungi. The rosemary extract-chitosan mixture demonstrated initial efficiencies of 82% and maintained 80% effectiveness after six months, showcasing its potential for extended shelf life.
Through Fourier-transform infrared (FT-IR) spectroscopy, the researchers characterized key functional groups within the rosemary extract. Further investigations revealed impressive results from electrochemical measurements, where maximal CaCO3 scale inhibition reached about 62% at 100ppm concentration of rosemary extract, and rose to 78.3% when elevated to 200ppm.
While evaluating the biopreservatives, Chitosan proved to be significantly more effective than Rhamnolipid. The addition of Chitosan not only improved the scale inhibition effectiveness of the rosemary extract from 67.8% to 80% after 24 weeks, but it also exhibited superior antimicrobial properties. At the end of the six-month study, the Total Bacterial Count (TBC) was recorded as significantly lower with the Chitosan mixture, compared to the control groups, which showcased higher bacterial counts.
The research undertaken also involved scanning electron microscopy (SEM) to assess the morphology of the CaCO3 crystals. It was observed those treated with the rosemary extract exhibited distorted growth shapes, indicating the effective inhibition mechanism was at play.
Notably, the microbiological assessment revealed the rosemary extract alone exhibited minimal contamination at the outset, but over time both the rosemary-rhamnolipids and rosemary alone showed signs of growth of certain pathogens. The rosemary-chitosan blend maintained its antimicrobial integrity throughout the study period.
This study not only emphasizes the practicality of rosemary extract as an antiscalant, but also points to its broader potential for natural biopreservation. By using biosurfactants and polysaccharides such as Chitosan, these compounds can serve as sustainable alternatives to traditional chemical inhibitors, representing advancements toward greener practices in water treatment. The authors concluded their findings could lead to significant shifts in how industries manage scaling issues, fostering both environmental sustainability and economic efficiency.