Sintesis dan karakterisasi Carboxymethyl Cellulose (CMC) dari selulosa eceng gondok (Eichhornia crassipes) dengan menggunakan campuran media reaksi isobutil-isopropil alkohol = Synthesis and characterization of Carboxymethyl Cellulose (CMC) from water hyacinth (Eichhornia crassipes) cellulose using isobutyl-isopropyl mixture as reaction medium