High efficiency of methylene blue removal using a novel low-cost acid treated forest wastes, Cupressus semperirens cones: Experimental results and modeling

Abstract

ABSTRACTThe removal of methylene blue (MB) from aqueous solutions using sulfuric acid modified Cupressus semperirens cones (H2SO4-CSC), was investigated. Results showed that a pH value of 12 was favorable for the adsorption of MB and that the moisture and ash yields are suitable for industrial exploitation. A high porosity value was found, 68.1%. In agreement with its low content of basicity compared to its acidity, the H2SO4-CSC absorbent had an acidic behavior. Rate constants of pseudo-first-order, pseudo-second-order, and nth kinetic model were determined to analyze the dynamic of the biosorption process; they showed that adsorption kinetics followed a pseudo-second-order and nth kinetic models. Ionic strength was shown to have a negative impact on the biosorption of MB onto H2SO4-CSC. The Sips isotherm model was found to be the most relevant to describe MB biosorption onto H2SO4-CSC with a correlation factor R2 > 0.999. The biosorption capacity of H2SO4-CSC was found to be 460 mg g−1 at 10°C and 590 mg g−1 at 25°C, confirming biosorbent efficiency for the removal of MB dye from aqueous solutions. Thermodynamic parameters indicated that the biosorption process of MB was endothermic and more effective at high temperatures. The values of ΔG° and ΔH° confirmed that the biosorption of MB onto H2SO4-CSC was spontaneous and endothermic in nature. An irregular increase in randomness at the H2SO4-CSC–solution interface during the biosorption process was suggested by the positive values of ΔS°.