ABSTRAK Isolasi nano montmorillonit dari bentonit alam Bener Meriah telah dilakukan dan diaplikasikan pada penyerapan zat warna remazol brilliant blue. Isolasi nano montmorillonit dari bentonit menggunakan cara sedimentasi dan gelombang ultrasonic dengan daya 750 Watt pada suhu kamar. Karakteristik dari bentonit dan nano montmorillonit diuji menggunakan X-Ray Fluorescence (XRF), Fourier Transform Infrared (FT-IR), X-Ray Diffraction (XRD) dan Scanning Electron Microscope (SEM). Hasilnya menunjukkan bahwa bentonit Bener Meriah mirip dengan bentonit standar dan bentonit tersebut merupakan Na-bentonit. Analisis ukuran partikel montmorillonit diuji menggunakan Particle Size Analyzer (PSA) dan hasilnya menunjukkan bahwa partikel montmorillonit hasil isolasi berukuran nano yaitu 67,8 nm. Uji adsorpsi zat warna remazol brilliant blue menggunakan adsorben nano montmorillonit memiliki kondisi optimum pada waktu kontak 60 menit, pH 4 dan massa adsorben 2 gram. Hasil adsorpsi mengikuti model isoterm adsorpsi Freundlich. Berdasarkan persamaan Freundlich diperoleh nilai n sebesar 1,418. Hasil uji regenerasi menunjukkan bahwa adsorben nano montmorillonit dapat digunakan secara berulang-ulang. Kata Kunci : Bentonit, Nano Montmorillonit, Adsorpsi, Remazol brilliant blue. ABSTRACT Isolation of montmorillonite nano-sized from natural bentonite of Bener Meriah has been conducted and applied to the adsorption of remazol brilliant blue dye. Isolation of montmorillonite nano-sized from the bentonite using sedimentation method and ultrasonic waves with 750 Watt at room temperature. Characteristics of bentonite and nano montmorillonite were tested using X-Ray Fluorescence (XRF), Fourier Transform Infrared (FT-IR), X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM). The results show that bentonite of Bener Meriah is similar to standard bentonite and the bentonite is Na-bentonite. Particle size analysis of montmorillonite was tested using Particle Size Analyzer (PSA) and the results showed that nano-sized montmorillonite particles were 67.8 nm. Adsorption test of remazol brilliant blue by adsorbent of nano montmorillonite has an optimum condition at contact time of 60 minutes, pH 4 and 2 gram adsorbent mass. The adsorption results follow Freundlich's adsorption isoterm model. Based on the Freundlich equation obtained the value of n equal to 1,418. The test results showed that the regeneration of adsorbent montmorillonite nano-sized can be used repeatedly. Keywords: Bentonite, Nano montmorillonite, Adsorption, Remazol brilliant blue.