Mechanistic evaluation of cationic dyes adsorption onto low-cost calcinated aerated autoclaved concrete wastes

Application of construction and demolition (C&D) wastes were considered as sustainable development goals (SDGs) for maintaining raw materials. Also, lightweight concretes such as aerated autoclaved concrete (AAC) were used for partitioning spaces in the building industry. Moreover, the waste products of the mentioned materials were increased due to the rise of old construction demolitions. This study contributes a calcinated aerated autoclaved concrete (CAAC) which is efficient, powerful, highly rapid, non-expensive and novel adsorbent for the removal of cationic dyes including malachite green (MG), methyl violet (MV) and methylene blue (MB) form water samples. The impacts of different variables for the proposed system including initial pH value, stirring rate, dye concentration and contact time are explored to optimize the selected analyses. Most notably, this study analyzes the experimental isotherm data by using two-parameter isotherms such as Dubinin-Radushkevich, Temkin, Langmuir and Freundlich equations and three-parameter isotherms including Koble-Corrigan, Toth, Redlich-Peterson and Sips models. The maximum adsorption capacities for MG, MB and MV are 370.4, 256.4 and 277.8 mg g(-1), respectively. In addition, five kinetic models, Elovich, intraparticle diffusion, main equations of pseudo-first- and second-order, and Boyd mathematical models are employed to follow the kinetic parameters and adsorption process of each dye. The Boyd equations indicate that with regard to all three dyes and at all concentrations, the film diffusion is dominant over intraparticle diffusions. Almost none of the geometric plots of adsorption and desorption curves intersected, indicating the adsorption process is optimally performed.