Cu and Ni functionalized hydroxyapatite biocomposites from common carp scales: green synthesis for antibacterial assessment and wastewater treatment

Industrialization, urbanization and subsequent technological advancements in Pakistan has raised the pollution to threshold level. The current research was conducted with the aim to become the part of the solution not the part of pollution. Keeping in view the same objective, refused fish scales of common carp were used to extract hydroxyapatite (HAp) and then functionalized with metals (Cu and Ni) to synthesize the biocomposites. Samples were characterized using Fourier transform infrared spectroscopy, X-ray diffraction and X-ray fluorescence techniques, which confirmed the synthesis of the HAp, Cu-HAp (3 wt.%) and Ni-HAp (3 wt.%) biocomposites with the particle size of 17, 24 and 25 nm, respectively. The synthesized biocomposites were further employed as adsorbents for the removal of Malachite green (MG) and cadmium ions (Cd2+) from the wastewater. Results showed that Ni-HAp 1:3 (1% metal) and Cu-HAp 1:3 (1% metal) acted as best adsorbents for the removal of MG and Cd2+ with the removal efficiency of 94%, respectively. Furthermore, the antibacterial nature of these biocomposites was also evaluated against the gram-positive bacterial strain (Staphylococcus aureus). Findings showed that selected biocomposites (Cu-HAp 1:1 (1 wt.% metal), Cu-HAp 3:1 (3 wt.% metal), Cu-HAp 1:3 (1 wt.% metal), Ni-HAp 1:1 (1 wt.% metal), Ni-HAp 3:1 (3 wt.% metal), Ni-HAp 1:3 (1 wt.% metal)) can act as the good antibacterial agents but Ni-HAp 3:1 (3 wt.% metal) was proven as best antibacterial agent with inhibition zone equal to 31 mm. Among adsorption isotherms and kinetics, Langmuir isotherm and pseudo-second order shows the best fitting for MG azo dye removal from wastewater whereas Freundlich isotherm and pseudo-first order is best fit for Cd2+ adsorption on both composites. Boyd plot shows the best fit for both the adsorbents.