Performance assessment of five adsorbents based on fly ash for removal of cadmium ions

Five adsorbents based on fly ash treated with NaOH for the adsorption of cadmium ion from aqueous solutions were investigated. The materials were characterized using scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR) and the Brunauer-Emmett-Teller (BET) surface area methods. The results demonstrated that the specific surface area of fly ash was improved after NaOH treatment, and that the adsorption of cadmiumby the newadsorbents reached equilibriumin less than 120 min. The results also confirmed that the materials treated with NaOH solution by direct activation had a higher adsorption capacity than untreated fly ash. The maximum adsorption capacities obtained were in the range of 9.18-48.5 mg/g. Also, SEM/EDS and FT-IR results of Cd(II) loaded adsorbents were performed. The obtained experimental data were used for kinetics determination using three model equations: a pseudo first-order model, a pseudo second-order model, and the intraparticle diffusion model. Was found that the adsorption of cadmium ions onto the adsorbents studied follows the pseudo second-order model. The adsorption isotherms of the adsorbent synthesized by direct activation for 15 h using 5 M NaOH at 90 degrees C with a ratio of 1:3 fly ash: NaOH (A5) was assessed in terms of the Langmuir (four types of linearization), Freundlich, Temkin, Harkin-Jura, and Halsey models. The effectiveness of the adsorbents was evaluated using the toxicity characteristic leaching (TCLP) procedure. Accordingly, the proposed methods in this study are recommended for advanced capitalization of fly ash, particularly as a potential adsorbent for the removal of cadmium ions from wastewater. (C) 2021 Elsevier B.V. All rights reserved.

Automated summary

The study investigated five adsorbents based on NaOH-treated fly ash for the adsorption of cadmium ions from aqueous solutions. Results showed that the adsorption capacity of the new adsorbents improved significantly after NaOH treatment, with shorter equilibrium time. The adsorption process followed the pseudo second-order model, and the effectiveness of the adsorbents was evaluated using the TCLP procedure, recommending their potential use for wastewater treatment.