Investigation of organic matter adsorption from TNT red water by modified bamboo charcoal

Abstract: Bamboo charcoal impregnated with ZnCl₂ (ZnCl₂-BC) was used as an adsorbent to remove organic matters from TNT red water. The adsorption parameters, such as the adsorbent dosage, pH, contact time, dilution ratios of TNT red water, and temperature were studied. The equilibrium adsorption data were analyzed using Langmuir, Freundlich, and Temkin isotherms models. The Langmuir isotherm fitted the experimental results well. Kinetic analyses results showed that the adsorption kinetics was more accurately represented by the pseudo-second-order model. The studies of external diffusion and intraparticle diffusion models showed that external as well as intraparticle diffusions influenced on the actual adsorption process at different times and the removing velocity of organic matters from solution to the surface of adsorbent was very rapid. Thermodynamic studies showed that the adsorption of organic matters from TNT red water on ZnCl₂-BC was a spontaneous, endothermic, and random process at the solid/solution interface. The Dubinin–Radushkevich (D–R) models, thermodynamics, and the activation energy analysis indicated the adsorption was a physical mechanism. The adsorption was enforced by van der Waals force, hydrogen bonding formation electron, donor–acceptor interaction, and base and acid interaction based on HSAB theory.