Adsorption of Ammonium from Aqueous Solutions on Environmentally Friendly Barbecue Bamboo Charcoal: Characteristics and Kinetic and Thermodynamic Studies

摘要

Environmentally friendly barbecue bamboo charcoal (EFBBC), an inexpensive biosorbent, was successfully used to remove ammonium (NH_4~+ ) from aqueous solutions. The effects of contact time, pH, initial concentration, average particle size, biosorbent dosage, and temperature on NH_4~+ removal were investigated. Biosorption conditions were as follows: contact time, 80 min; pH, 6.0-10; initial concentration, 60 mg/L; optimum particle size, 0.075-0.180 mm; biosorbent dosage, 4.0 g/L; temperature, 30℃. To investigate adsorption mechanisms, pseudo-first-order, pseudo-second-order, Elovich, and intraparticle diffusion models were fit to experimental results. Results indicated that kinetic data for NH_4~+ adsorption were better described by the pseudo-second-order model. Also, the Langmuir, Freundlich, and Temkin models were employed to analyze equilibrium data. Results indicated that the Freundlich isotherm best represented the data for NH_4~+ adsorption Changes in the standard free energy, enthalpy, and entropy were also evaluated: the reaction was spontaneous and endothermic. The EFBBC surface was analyzed by X-ray diffraction, scanning electron microscopy, X-ray energy dispersive spectrometry, and Fourier transform infrared spectrometry. From the results, it was proposed that the adsorption behavior of NH_4~+ on the EFBBC surface depends on the internal structure and chemical composition, and the results highlight the need to understand specific surface characteristics.