Pengaruh Temperatur dan Waktu Kalsinasi Nanostruktur Titanium Dioksida Hasil Proses Pendidihan dari Residu Mineral Ilmenite terhadap Performa Fotokalitik dalam Mendegradasi Limbah Polutan Organik = The Influence of Temperature and Calcination Time on Titanium Dioxide Nanostructure Derived from Boiled Ilmenite Mineral Residue in Photocatalytic Performance for Degrading Organic Pollutants