The constants of the tested isotherms and the corresponding error functions are presented in Table 2.

Langmuir, Freundlich, Temkin, and Sips isotherms were tested in order to characterize the adsorption equilibrium. The equilibrium times recorded in previous studies that used similar absorbent materials were the following: 20 min for papaya leaves and Humulus japonicas leaves, 60 min for Typha angustifolia leaves and pineapple leaf powder, 70 min for Platanus orientalis leaves, 100 min for Ginkgo biloba leaves and pine tree leaves, 150 min for lotus leaves and phoenix tree’s leaves, 180 min for poplar leaves, and 200 min for Miswak leaves. As the adsorption sites are occupied by the dye molecules, the adsorption rate becomes slower until equilibrium is reached (after about 40 min), and thus the value of the adsorption capacity remains practically constant.

At the beginning of the process, the adsorbent surface has a high number of available adsorption sites therefore, the adsorption rate is fast, and the adsorption capacity increases with the contact time. A desorption study was also performed to determine the possibility of adsorbent regeneration.įigure 6 illustrates the variation of adsorption capacity with the contact time at different adsorbent doses. The contact time was the factor with the highest influence on the process, while the temperature had the lowest influence. The Taguchi method and the ANOVA analysis were used to optimize the adsorption conditions. The maximum adsorption capacity was 244.6 (mg g −1) higher compared to other adsorbents based on plant leaves.

Equilibrium, kinetic, and thermodynamic studies have shown that the adsorption is best described by the Sips isotherm and pseudo-second-order kinetic model and that the process is spontaneous, favorable, and endothermic, involving physisorption as the main mechanism. The effects of pH, ionic strength, contact time, adsorbent dose, initial deconcentration, and temperature on adsorption capacity were investigated. Different techniques (FTIR, SEM, color analysis, and pH PZC determination) were applied for adsorbent characterization.

In this work, raspberry ( Rubus idaeus) leaves were converted to powder and used as a new natural lignocellulosic low-cost adsorbent for methylene blue removal from aqueous solutions.

Methylene blue cyanide