HAp and Zr-doped HAp nanoparticles were synthesized from bovine bone and local zircon material by using the hydrothermal method. XRD analysis showed that the HAp and Zr-doped HAp nanoparticles had hexagonal structure with a crystallite size of 20-36 nm and the lattice constants a = 9.8-9.9? and c = 6.5-6.8 ?. XRD data also showed that up to 20 at.% of Zr can be accommodated in HAp crystal structure. The lattice constant and cell volume decreased with increasing Zr concentration. FTIR data confirmed that the majority of functional groups that exist on the surface of the HAp and Zr-doped HAp nanoparticles were the hydroxyl and phosphate groups. Suspensions with the HAp and Zr-doped HAp nanoparticles prepared using citric acid as dispersant were stable with zeta potential between ?31 and ?35mV at pH = 7. Reactive oxygen species are generated on the produced HAp and Zr-doped Hap nanoparticles and confirm their potential for application in photodynamic therapy.

Nanoparticles of Al 2 O 3 have been synthesized from local bauxite mineral, and ethylene glycol (EG)-Al 2 O 3 nanofluids have been prepared. Powder Al(OOH) was extracted from local bauxite using bayer process, and heated at 600 o C for 3 hours to get Al 2 O 3 nanoparticles. XRD analyses showed that the Al 2 O 3 nanoparticles crystallizes in -Al 2 O 3 with crystallite size of 4.12 nm. The specific surface area of the Al 2 O 3 nanoparticles was 296.72 m 2 /gr. Viscosity of the EG-Al 2 O 3 nanofluids was temperature dependent, and decreased with increasing temperature. The viscosity of the nanofluids increased with the concentration of the Al 2 O 3 nanoparticles. Meanwhile, Critical Heat Flux (CHF) enhancement of the nanofluids increased with the concentration of the Al 2 O 3 nanoparticles. The largest CHF enhancement was 54% at Al 2 O 3 concentration of 0.095 vol %.

Nanofluids have big potential to replace conventional coolant such as water. Nanoparticles of Al₂O₃ for nanofluids has been successfully synthesized using self combustion method using sugar as fuel. Al(OH)₃ was used as precursor. It was extracted from local bauxite. The combustion was performed at 450°C. The combusted material was calcined at 1200°C for 1 hour to get Al₂O₃ nanoparticles. The Al₂O₃ nanoparticles were dispersed into an amount of water as base fluid to form nanofluids. XRD analysis revealed that the Al₂O₃ nanoparticles crystallized in theta phase with crystallite size of 15.5 nm. According to TEM analyses, the particle size was 30 nm. The nanofluid with concentration of 0.025 vol % and pH 10 possessed zeta potential of -45 mV indicating a stable suspension. Compared to water as base fluid, the nanofluid prepared in this study had a CHF enhancement of 70% making the nanofluids are potential for cooling fluids of metal machining, quenching, Reactor Vessel Cooling System (RVCS), and Emergency Core Cooling System (ECCS).

Metilen biru merupakan salah satu zat pewarna dalam limbah cair tekstil yang dapat merusak ekosistem perairan dan mempunyai nilai ambang batas 5 mg/L. Salah satu cara untuk mengolah MB dalam larutan yaitu dengan fotokatalisis mengingat sederhana, cepat, dan mudah diregenerasi. Namun, cara ini memiliki kekurangan yakni waktu pemisahan yang lama. Penambahan sifat magnetik ke dalam material fotokatalis yang kemudian disebut fotokatalis magnetik dapat mengatasi kelemahan dari fotokatalis konvensional. Dalam penelitian ini, fotokatalis magnetik berbasis komposit ZrO2-ZnFe2O4 telah berhasil disintesis menggunakan metode kopresipitasi sederhana dengan memanfaatkan mineral lokal pasir Zircon. Komposit yang dihasilkan dikarakterisasi menggunakan X-Ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS), Surface Area Analyzer (SAA). Evaluasi terhadap kinerja fotokatalis diamati menggunakan metode spektrofotometri UV-Vis. ZrO2-ZnFe2O4 yang dihasilkan mengandung kristal ZnFe2O4 berstruktur kubik. Partikel komposit memiliki bentuk irregular dan teraglomerasi. Komposit mengandung 6,52 Zr; 9,31 Zn; 23,58 Fe; dan 58,73 O dalam %atom, sesuai dengan stoikiometrinya. Luas permukaan spesifik ZrO2-ZnFe2O4 sebesar 112,375 m2/g. Sifat magnet dikonfirmasi menggunakan medan magnet ekstenal yang menunjukkan bahwa komposit ZrO2-ZnFe2O4 memiliki sifat magnet lemah. Kondisi optimum untuk fotodegradasi MB oleh komposit ZrO2-ZnFe2O4 dihasilkan pada pH 10 selama 120 menit dengan %degradasi MB sekitar 94,00%. Synthesis of ZrO2-ZnFe2O4 Composite Ceramics as Magnetic Photocatalyst for Methylene Blue Degradation. Methylene blue (MB) is one of the dye compounds in textile wastewater that can damage aquatic ecosystems and has a threshold value of only 5 mg/L. The alternative way to treat MB in aqueous solutions is photocatalysis which has simple, fast, and easy regenerate properties but has a drawback such as a long separation time. Immersing magnetic properties to photocatalyst material called magnetic photocatalyst can solve the weakness of conventional photocatalyst. In this work, the magnetic photocatalyst of ZrO2-ZnFe2O4 was synthesized by simply co-precipitation method from local natural sources Zircon sand. The composites were then characterized using X-Ray Diffraction (XRD), Scanning Electron Microscopy with Energy Dispersive Spectroscopy (SEM/EDS), Surface Area Analyzer (SAA). The evaluation of photocatalytic performance was observed by using a spectrophotometer UV-Vis. The obtained ZrO2-ZnFe2O4 reveals a cubic structure of ZnFe2O4. The composites particles have an irregular and agglomerated shape. The obtained ZrO2-ZnFe2O4 contained 6.52 of Zr, 9.31 of Zn, 23.58 of Fe, and 58.73 of O in atomic percentage, corresponding to its stoichiometry. The specific surface area of ZrO2-ZnFe2O4 was 112.376 m2/g. The magnetic properties were confirmed by an external magnetic field showing that the composite has weak magnetic properties. The optimum condition for photodegradation of methylene blue by ZrO2-ZnFe2O4 was obtained at pH 10 for 120 minutes with methylene blue degradation percentage (%D) approximately 94.00%.