Valorisation of Prochilodus magdalenae by-products for the development of natural coagulants: Hydroxyapatite/collagen-based solutions for water treatment in rural communities

• Fish by-products ( P. magdalenae scales/skeletons) were valorized into natural bio-coagulants (HAP/COL and COL). • High yields were achieved (HAP/COL over 50%), and the composite structure (hydroxyapatite and collagen) was confirmed by FTIR and XRD. • Both bio-coagulants demonstrated high turbidity removal efficiency (HAP/COL: 90–94%; COL: 95–99%). • A major drawback is that the final pH was too acidic (ranging from 4.1 to 5.1), falling below the minimum regulatory standard of 6.5. This study aimed to prepare a bio-coagulant using the scales and skeletons of Prochilodus magdalenae for application in turbidity removal from water. Hydroxyapatite/collagen (HAP/COL) and collagen in solution (COL) were extracted using the precipitation method and the ASH method, respectively. The obtained HAP/COL was dried and ground to a particle size of less than 1 mm. The resulting samples were characterised using FTIR, SEM-EDS, and XRD analyses. Yields of over 50% were achieved for HAP/COL and between 24% and 29% for COL. Following the confirmation of efficient production, the materials were applied as bio-coagulants and evaluated using the jar test method. Turbidity removal efficiency, pH, and conductivity were assessed according to the standards established in Resolution 2115 of 2007. The results demonstrated turbidity removal efficiencies ranging from 90% to 94% for HAP/COL and from 95% to 99% for COL. These removal rates were achieved within pH ranges of 4.1 to 5.1 for HAP/COL and 4.3 to 4.7 for COL, with conductivities ranging from 32 to 95 μS and 112 to 198 μS, respectively.