Calcined alluvium of agricultural streams as a recyclable and cleaning tool for cationic dye removal from aqueous media

Abstract

Abstract The purpose of the current study was to examine the potential of raw and calcined alluvium, prepared from water streams in agricultural land, as a novel adsorbent for removing methylene blue (MB) and methyl violet (MV) from the aqueous media. Central composite design (CCD) was used to optimize the adsorption process as well as the interaction between parameters (adsorbent dose, initial pH, ultrasonic time and initial dye concentration). The physicochemical properties and surface changes of raw and calcined alluvium were investigated using scanning and transmission electron microscopy (SEM and TEM), X-ray diffraction (XRD), Brunauer–Emmett–Teller (BET), and Fourier transform infrared spectroscopy (FTIR). The BET surface and pore diameter of the calcined alluvium was obtained 68.13 m2/g and 16.58 nm, respectively. Langmuir, Freundlich, and Tamkin equations were used to model the adsorption equilibrium. The results showed that the adsorption of the dyes is physical and desirable, and the interaction between the surfaces of the alluvium adsorbents with the pollutants is weak. The Langmuir adsorption capacity of the studied dyes using raw alluvium (MB: 49.36 mg/g and MV: 57.84 mg/g) and calcined alluvium (MB: 71.96 mg/g and MV: 78.13 mg/g) was calculated. Adsorption data were more consistent with the pseudo-second-order kinetic model. Also, the adsorption/desorption process was investigated for up to 10 cycles. The difference in the amount of dye adsorption efficiency for the fresh adsorbent and its 10th recycled one was only 5%, indicating that the adsorbent was stable and reusable.