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Use of Limestone Sludge in the Preparation of ɩ-Carrageenan/Alginate-Based Films

Summary

Researchers have developed a method to convert limestone waste from stone quarries into a useful material for making biodegradable plastic films. By dissolving limestone in acid to extract calcium ions, they created a crosslinking solution that strengthens films made from seaweed-derived compounds like alginate and carrageenan. These films show promise as environmentally-friendly alternatives to conventional plastic packaging while helping solve industrial waste problems.

Background

Limestone sludge is a waste byproduct from quarrying and stone processing industries, typically containing over 95% calcium carbonate. Calcium ions are valuable for crosslinking polysaccharide films such as sodium alginate and ɩ-carrageenan, which can form water-resistant gels with potential to replace petroleum-based packaging films.

Objective

To develop a method for converting limestone sludge waste into a crosslinking agent suitable for producing chemically and dimensionally stable films based on sodium alginate and/or ɩ-carrageenan with adequate mechanical properties.

Results

Alginate/sorbitol films showed poor dimensional stability with significant shrinkage and cracking. ɩ-Carrageenan/alginate blends demonstrated improved dimensional stability and mechanical properties, particularly at 0.5 wt% sorbitol, showing reduced linear retraction (3.5-8.3%) and smoother surfaces. Higher sorbitol concentrations caused surface cracking and phase segregation phenomena.

Conclusion

ɩ-Carrageenan/alginate/sorbitol films show promise for developing viable bio-based films from algal polysaccharides using limestone sludge as a calcium source. Further optimization of film composition, thickness, and processing conditions is needed to improve mechanical properties and reduce defects while promoting circular economy goals.
  • Published in:Materials (Basel),
  • Study Type:Experimental Research,
  • Source: 10.3390/ma17071668, PMC11012425, PMID: 38612183
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