Influence of synthesis temperature of eggshell-derived hydroxyapatite on biofilm formation and microbial fuel cell performance

Abstract

Microbial fuel cells (MFCs) enable simultaneous wastewater treatment and bioelectricity generation, but their performance is often constrained by poor bacterial adhesion and slow anode electron transfer. Hydroxyapatite (HA) can address these limitations; however, most studies rely on commercial HA and rarely examine biowaste-derived sources or synthesis-route effects. In this study, eggshell-derived HA was synthesized via room-temperature precipitation (CHP) and hydrothermal treatment at 250 °C for 3 h (CHH), then blended with carbon to fabricate composite anodes. Dual-chamber MFCs inoculated with Shewanella putrefaciens were evaluated using electrochemical analyses (CV, EIS, polarization) and biofilm characterization (CFU counts, crystal violet staining, SEM). CHH achieved a peak power density of 0.164 W m⁻², approximately 167% higher than bare carbon and 23–33% higher than carbon and CHP. CHP exhibited slightly lower peak power but superior sustained output over a wider current-density range, attributed to its low-crystallinity structure and rapid early colonization. The results demonstrate that HA nanostructure, governed by synthesis route, directly influences biofilm formation and electron transfer. Overall, eggshell-derived HA anodes significantly enhance MFC performance, establishing a clear synthesis–nanostructure–biofilm–performance relationship.