Sintesis dan Karakterisasi Material Mangan Ferit (MnFe2O4 dan MnFe2O4/NGP) untuk Aplikasi Fotokatalis dan Sonokatalis dalam Mendegradasi Methylene Blue = Synthesis and Characterization of Manganese Ferrite (MnFe2O4 and MnFe2O4 / NGP) Materials for Photocatalyst and Sonocatalyst Applications in Degradation of Methylene Blue