Statistical optimization of the ultrasonic assisted removal of methylene blue by bituminous coal-based activated carbon nanosheets using experimental design

Methylene blue (MB) as a thiazine cationic dye is the most commonly used dye for temporary hair colorants, wool, cotton, leather, silk and paper. Although MB not strongly hazardous, it can have numerous harmful effects. MB increases myocardial function in septic shock [1]. Bituminous coal as an inexpensive and abundant natural resource in Iran was used to produce nanoparticle and nanosheets of activated carbon (AC) for removal of methylene blue (as a cationic dye) from effluent. The structural features of these carbon nanoparticles and nanosheets were characterized by means of Fourier transform infrared (FTIR), Barret-Joyner-Halenda (BJH), X-ray diffraction (XRD), scanning electron microscopy (SEM) and transmission electron microscopy (TEM). In this work, rapid/assisted adsorption method followed by ultraviolet–visible spectroscopy (UV/Vis) detection has been used for efficient short time removal of MB. Combination of central composite design (CCD) and response surface methodology (RSM) has been applied to model and optimize the influencing variables on the MB adsorption by produced AC [2]. More specifically, the effects of influencing variables such as adsorbent mass, dye concentration, temperature and sonication time have been investigated. The best adsorption percentage, equal to 100%, was obtained under optimum conditions set as: 0.2008 g of adsorbent, MB concentration of 10.81 mg L-1, temperature equal to 44.2 ̊C, and 7.3 min of sonication time. The results show that the Langmuir model and pseudo-second-order kinetic model fitted well to the adsorption experimental data [3, 4]. Proposed technique in comparison with the recently reported techniques for removal of cationic dye has several advantages such as low cost, abundance of raw materials, ease of production, fast adsorption kinetic and high adsorption capacity.