Removal of methylene blue dye from aqueous solution with hydrocoals obtained from walnut and pistachio outer green shells

In this study, the removal of methylene blue dye from aqueous solution with hydrochars obtained from the outer green shells of walnuts and pistachios was studied. For this, peanut and walnut hydrochars were characterized by FTIR, SEM, EDX and TG-DTA. The characterization process was studied at 298K, 308K and 318K temperatures, respectively, at 50, 100, 150, 200 and 300 concentrations. The adsorption parameters of Langmuir, Freundlich, Temkin and Dubinin-Radushkevich isotherms were calculated. Langmuir correlation coefficients (R2) for Methylene Blue dyestuff on walnut hydrochar adsorbent were calculated as 0.9963, 0.9974 and 0.9950, respectively. Langmuir correlation coefficients (R2) for Methylene Blue dyestuff on peanut hydrochar adsorbent were calculated as 0.9759, 0.9939 and 0.9981, respectively. The RL values for Walnut hydrochar and Peanut hydrochar adsorbents Methylene Blue dyestuffs were calculated as 0.1650 ≥ RL ≥ 0.103, 0.1108 ≥ RL ≥ 0.0177, respectively. It was observed that both adsorbents fit the Langmuir model. It has been observed that the Freundlich constant (KF) values of the walnut hydrochar adsorbent vary between 48.9589 mg/g and 67.1858 mg/g and increase with temperature, so the interaction is endothermic. It has been observed that the Freundlich constant (KF) values of the peanut hydrocoal adsorbent vary between 51.3942 mg/g and 58.5305 mg/g and increase with temperature, so the interaction is endothermic. According to the Freundlich isotherm model, physical adsorption has been observed since the n values of walnut and peanut hydrochars are greater than ˃ 1. According to the Temkin isotherm model, it was observed that the B1 values of the walnut and peanut hydrocoal adsorbents increased with temperature, so it was seen that the adsorption was endothermic. According to the Dubinin-Radushkevich isotherm model, it was observed that the adsorption process was physical since the E values of walnut and peanut hydrochars were less than ˂ 8 kJmol-1. Thermodynamic parameters (ΔHo and ΔGo) were calculated. The ΔHo values of the walnut and peanut hydrocarbon adsorbents were found to be 37.0940 and 22.2493, respectively. Positive ΔHo values indicated that the adsorption was endothermic. The ΔGo values of both adsorbents were observed to be negative, indicating that the adsorption took place spontaneously. As a result of these data obtained, it has been shown that activated carbons produced from the outer green shell of walnut and pistachio by hydrochar method can be used as adsorbent.