*Article* **Removal of Various Hazardous Materials Using a Multifunctional Biomass-Derived Hydroxyapatite (HAP) Catalyst and Its Antibacterial Effects**

**Sanha Jang <sup>1</sup> , Kyeongmun Park <sup>1</sup> , Sehwan Song <sup>2</sup> , Haksoo Lee <sup>3</sup> , Sungkyun Park <sup>2</sup> , Buhyun Youn 3,\* and Kanghyun Park 1,4,\***


**Abstract:** In the present study, oyster shells, a cause of environmental pollution, were employed effectively to synthesize hydroxyapatite (HAP) by facile oxidation and phosphorylation. The ability of HAP to adsorb various metal cations and inhibit bacterial growth was validated. The biomassderived HAP catalyst exhibited high metal cation adsorption in water at room temperature and under various acidic conditions (M = Cr, Mn, Ni, Cu, Cd, Ba, and Pb). HAP was demonstrated to have a maximum removal efficiency of 92.8% for the heavy metal Pb. Even under different pH conditions, HAP was demonstrated to be effective for the removal of three harmful heavy metals, Cr, Cd, and Pb, with a particularly high removal efficiency demonstrated for Pb under all conditions (average removal efficiency of Cr: 63.0%, Cd: 59.9%, and Pb: 91.6%). In addition, HAP had a significant influence on phosphate ion adsorption in aqueous solution, eliminating 98.1% after 3 min. Furthermore, biomass-derived HAP was demonstrated to have significant antibacterial activity against *E. coli* and *S. aureus* (5 mM: 74% and 78.1%, 10 mM: 89.6% and 96.0%, respectively).

**Keywords:** biomass-derived material; nanomaterial; environmental chemistry; multifunctional catalyst; antibacterial; metal ion adsorption; phosphate ion adsorption
