Removal of azo dye from aqueous solution by a low-cost activated carbon prepared from coal: adsorption kinetics, isotherms study, and DFT simulation

• Published in: Environmental science and pollution research international Vol. 28; no. 8; pp. 10234 - 10247
• Main Authors: Jan, Saeed Ullah, Ahmad, Aziz, Khan, Adnan Ali, Melhi, Saad, Ahmad, Iftikhar, Sun, Guohua, Chen, Cheng-Meng, Ahmad, Rashid
• Format: Journal Article
• Language: English
• Published: Berlin/Heidelberg Springer Berlin Heidelberg 01.02.2021; Springer Nature B.V
• Subjects: Activated carbon; Adsorption; Aquatic Pollution; Aqueous solutions; Atmospheric Protection/Air Quality Control/Air Pollution; Azo Compounds; Azo dyes; Charcoal; Charge transfer; Coal; Configurations; Dyes; Earth and Environmental Science; Ecotoxicology; endothermy; energy; Enthalpy; Environment; Environmental Chemistry; Environmental Health; Environmental science; Hydrogen-Ion Concentration; Kinetics; Pollutants; Research Article; Sorbents; Spectroscopy, Fourier Transform Infrared; surface area; Surface charge; Surface chemistry; Thermodynamics; Waste Water Technology; Water Management; Water Pollutants, Chemical - analysis; Water Pollution Control; Zeta potential; Thermodynamics; Anionic dyes; DFT; Kinetics; Adsorption; Activated carbon
• ISSN: 0944-1344; 1614-7499; 1614-7499
• DOI: 10.1007/s11356-020-11344-4

The high-risk organic pollutants produced by industries are of growing concern. The highly porous coal-based activated carbon (AC) having a specific surface area of 3452.8 m 2 /g is used for the adsorption of azo dye from synthetic solution. The sorbent is characterized through BET, SEM, TEM, XRD, FT-IR, TGA, and zeta potential. The sorbent exhibits − 18.7 mV surface charge, which is high enough for making suspension. The maximum dye uptake of 333 mg/g is observed in sorbent under acidic medium. The thermodynamics parameters like ∆G , ∆H , and ΔS were found to be − 12.40 kJ mol −1 , 39.66 kJ mol −1 , and 174.55 J mol −1  K −1 at 293 K, respectively, revealing that the adsorption mechanism is spontaneous, endothermic, and feasible. The experimental data follows the Langmuir and D–R models. The adsorption follows pseudo 2nd-order kinetics. DFT investigation shows that the dye sorption onto AC in configuration No. 4 (CFG-4) is more effective, as this configuration has high ∆H (enthalpy change) and adsorption energy (E ads ). This is confirmed by Mullikan atomic charge transfer phenomenon.