title: Equilibrium, kinetic and thermodynamic studies on the adsorption of 2-nitroaniline onto activated carbon prepared from cotton stalk fibre.
abstract: Activated carbon prepared from cotton stalk fibre has been utilized as an adsorbent for the removal of 2-nitroaniline from aqueous solutions. The influence of adsorbent mass, contact time and temperature on the adsorption was investigated by conducting a series of batch adsorption experiments. The equilibrium data at different temperatures were fitted with the Langmuir, Freundlich, Tempkin, Redlich-Peterson and Langmuir-Freundlich models. The Langmuir-Freundlich isotherm was found to best describe the experimental data. The adsorption amount increased with increasing temperature. The maximum adsorption capacity of 2-nitroaniline was found to be 383 mg/g for initial 2-nitroaniline concentration of 200mg/L at 45 degrees C. The kinetic rates were modeled by using the Lagergren-first-order, pseudo-second-order and Elovich models. The pseudo-second-order model was found to explain the adsorption kinetics most effectively. It was also found that the pore diffusion played an important role in the adsorption, and intraparticle diffusion was the rate-limiting step at the first 30 min for the temperatures of 25, 35 and 45 degrees C. FTIR and (13)C NMR study revealed that the amino and isocyanate groups present on the surface of the adsorbent were involved in chemical interaction with 2-nitroaniline. The negative change in free energy (Delta G degrees) and positive change in enthalpy (Delta H degrees) indicated that the adsorption was a spontaneous and endothermic process.
authors.affiliation: State Key Laboratory of Pollution Control and Resource Reuse, School of the Environment, Nanjing University, Nanjing 210093, China.
authors.forename: Kunquan
authors.initials: K
authors.lastname: Li
authors.forename: Zheng
authors.initials: Z
authors.lastname: Zheng
authors.forename: Xingfa
authors.initials: X
authors.lastname: Huang
authors.forename: Guohua
authors.initials: G
authors.lastname: Zhao
authors.forename: Jingwei
authors.initials: J
authors.lastname: Feng
authors.forename: Jibiao
authors.initials: J
authors.lastname: Zhang
mesh_terms: D000327:Adsorption; D000814:Aniline Compounds / Q000302:isolation & purification*; D002606:Charcoal / Q000138:chemical synthesis* / Q000737:chemistry; D032561:Cotton Fiber; D004058:Diffusion; D007700:Kinetics; D016062:Porosity; D012996:Solutions; D013696:Temperature; D013816:Thermodynamics; D014873:Water Pollutants / Q000302:isolation & purification*; D018508:Water Purification / Q000379:methods
chemical_list: D000814:Aniline Compounds; D012996:Solutions; D014873:Water Pollutants; D002606:Charcoal; C008625:nitroaniline