In this study, the potential of a new low-cost adsorbent, Syringa vulgaris leaves powder, for methylene blue adsorption from aqueous solution was investigated. The adsorbent surface was examined using SEM and FTIR techniques. The experiments were conducted, in batch system, to find out the effect of pH, contact time, adsorbent dose, initial dye concentration, temperature and ionic strength on dye adsorption. The process is best described by Langmuir isotherm and the pseudo second order kinetic model. Maximum adsorption capacity, 188.2 (mg g⁻¹), is better than other similar adsorbent materials. Thermodynamic parameters revealed a spontaneous and endothermic process, suggesting a physisorption mechanism. A Taguchi orthogonal array (L₂₇) experimental design was used to determine the optimum conditions for the removal of dye. Various desorbing agents were used to investigate the regeneration possibility of used adsorbent. Results suggest that the adsorbent material is very effective for removal of methylene blue from aqueous solutions.

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. Different techniques (FTIR, SEM, color analysis, and pH_PZC determination) were applied for adsorbent characterization. The effects of pH, ionic strength, contact time, adsorbent dose, initial deconcentration, and temperature on adsorption capacity were investigated. 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 maximum adsorption capacity was 244.6 (mg g⁻¹) higher compared to other adsorbents based on plant leaves. The Taguchi method and the ANOVA analysis were used to optimize the adsorption conditions. The contact time was the factor with the highest influence on the process, while the temperature had the lowest influence. A desorption study was also performed to determine the possibility of adsorbent regeneration.

The objective of this paper was to evaluate the potential of a new adsorbent material to recover Au (III) from real wastewater, in a column with a fixed bed in a dynamic regime. The material was obtained through functionalization, by impregnation of the commercial resin, Amberlite XAD 7 type, with L-glutamic acid, which has active groups –NH₂ and –COOH. The goal of the experiments was to follow the correlation of fixed-bed column specific adsorption parameters (the effluent volume, the amounts of adsorbent, heights of the adsorbent layer in column) with the time necessary to cross the column. The experimental data obtained were modeled, using the Bohart–Adams, Yoon–Nelson Thomas and Clark models, to establish the mechanism of the Au (III) recovery process, in a dynamic regime. Also, we established the number of cycles for adsorption–desorption for which the new material can be used. We used 5% HNO₃ (5%) as desorption agent in five adsorption–desorption cycles, until the process was no longer efficient. The degree of desorption varied between 84% and 34% from cycle 1 to cycle 5.

The performance of a new eco-friendly adsorbent, obtained from motherwort (Leonurus cardiaca L.) biomass after minimum processing, in crystal violet dye removal from aqueous solutions was studied. Firstly, the adsorbent material was characterized using several technics, such as FTIR, pH_PZC determination, SEM and color analysis. The next step was to determine the influence of initial dye concentration, contact time, temperature, pH, adsorbent dose and ionic strength on adsorbent adsorption capacity. Equilibrium, kinetic, thermodynamic, optimization and desorption studies were performed in a batch system for studying all aspects related to the adsorption process. The sips isotherm best fit the experimental data with a predicted maximum adsorption capacity of 125.6 (mg g⁻¹). The kinetic data indicate that equilibrium is reached at 50 min and that general order is the best kinetic model to describe the dye retention. The process is endothermic, spontaneous, favorable and supposed to be a physical adsorption. In addition to establishing the optimal adsorption conditions, Taguchi methods and ANOVA analysis showed that the pH is the most influencing parameter of the adsorption process, having a contribution of 61.64%. All the presented data show that the motherwort biomass powder is very suitable to be used as at low-cost, easy available and effective adsorbent for the crystal violet dye removal from aqueous solutions.