Adsorptive removal of anionic dye from aqueous solutions using powdered and calcined vegetables wastes as low-cost adsorbent

In this study, we describe a behaviour comparison between powdered and calcined adsorbents prepared from vegetables waste of Persea species to remove Eriochrome Black T as anionic dye from aqueous solutions. Potential capabilities of these two adsorbents have been evaluated by studying some experimental parameters such as solution pH, adsorbent dosage, initial dye concentration, contact time and temperature. Kinetic study has been achieved by the application of pseudo-first and second orders and Elovich model. Results found agreed well with the pseudo-second order model. The experimental data were analysed using Langmuir, Freundlich and Tempkin isotherms models. The equilibrium data fitted well with the Freundlich isotherm and the adsorption capacities were calculated to be 120.50 mg/g and of 96.15 mg/g for calcined and powdered adsorbents, respectively. Thermodynamic study was also undertaken and provided important results indicating a spontaneous reaction and feasibility on the two adsorbents. The two adsorbents have been characterized via spectroscopic data such infrared spectrum, X-ray and by emission scanning electron microscopy

The potential use of activated carbon prepared from Ziziphus species for removing dyes from waste waters

Abstract In this study, the adsorption potential of activated carbon prepared from Ziziphus mauritiana nuts for the removal of methylene blue (MB) from aqueous solution has been investigated using batch mode experiments. The effects of some operating parameters on the removal dye such as, initial pH (2–12), temperature (298–328 K), initial MB concentration (20–100 mg L−1), and contact time (5–70 min) were investigated. Adsorption kinetic showed that the rate adsorption followed the pseudo-second-order kinetic model. Four adsorption isotherms models were applied to experimental equilibrium data (Langmuir, Freundlich, Redlich–Peterson, and Fritz–Schlunder) and the different constants were calculated using non-linear equations models. Fritz–Schlunder model was found the best one to describe the adsorption process which suggests that the adsorption of MB onto activated carbon derived from Ziziphus mauritiana is heterogeneous with a multilayer. Thermodynamic adsorption showed that the process was endothermic and spontaneous in nature

Exploring and studying the adsorption mechanisms of the herbicides 2,4,5-T and 2,4-D on activated carbon from walnut shells, using theoretical DFT analyses and a central composite design

Water depollution via adsorption is an energy-efficient technique that uses activated carbon produced from walnut shells to remove different pollutants. Our research integrates theoretical and experimental approaches to comprehensively understand the subject. By analyzing organic functional groups in the walnut shell-derived activated carbon (AC-Ws), evaluating adsorption performance, employing DFT analysis, and optimizing conditions, we provide valuable insights into the application of AC-Ws for removing pesticide pollutants from wastewater. The properties of this activated carbon (AC-Ws) are identified by techniques such as XRD, FTIR, SEM/EDX, pHzpc, and Boehm titration. A response surface methodology (RSM) has been utilized to develop an adsorption experiment for aqueous solutions of two herbicides, 2,4,5-trichlorophenoxyacetic acid (2.4.5-T), and 2,4-Dichlorophenoxyacetic acid (2,4-D). Abbreviations for technical terms will be explained when first used, and objective language will be used throughout. Grammar and spelling will conform to British standards. The experiment examined the removal of the herbicides based on three independent variables; pH, AC-Ws dosage, and temperature, within specific ranges (pH: 4–10, AC-Ws dosage: 0.1–0.3 g/L, temperature: 20–40 °C). The research conducted 17 experiments using Design-Expert software. Optimal conditions included pH 4 and AC-Ws dosage of 0.3 g/L for 2.4.5-T and pH 5 and AC-Ws dosage of 0.1 g/L for 2,4-D. These conditions demonstrated removal efficiency of 98% and desirability function of 1.000 for 2.4.5-T and 92% and desirability function of 1.000 for 2,4-D. The findings suggest that the adsorption process was thermodynamically favorable and exothermic. The experimental data was described accurately by the pseudo-second order kinetic model, and the Freundlich isotherm model showed good alignment with the equilibrium data. Using the Boehm method, organic functions were identified on the adsorbent's surface, and the density functional theory (DFT) was applied to evaluate the adsorption mechanism on AC-Ws surface sites