Intrinsic orthorhombic nanocrystals in mango seed starch: Isolation, structural characterization, and application as sustainable flocculants

This study examines the isolation and characterization of starch nanoparticles (SNP) and intrinsic nanocrystals from mango seed starch, focusing on their application as environmentally friendly flocculants in wastewater treatment. Starch nanoparticles were synthesized by nanoprecipitation and analyzed using high-resolution scanning electron microscopy in STEM mode. The SNP have an average diameter of 70 nm. Nanocrystals naturally embedded in starch granules were isolated by acid hydrolysis. TEM showed that these nanocrystals are elongated particles with a length of 15 ± 2 nm and a thickness of 6 ± 1 nm. X-ray diffraction (XRD) analysis supporting their orthorhombic crystal structure, confirming their natural origin. In flocculation tests, the SNP performed better than native starch, reducing water turbidity to 2.59 NTU compared to 3.71 NTU for native starch, indicating improved aggregation of impurities, likely due to their larger surface area. The enhanced flocculation performance was also influenced by the mango starch's amylose/amylopectin ratio and higher lipid content, which affect the interaction mechanisms with suspended particles.