@article{OfomajaUnuabonah2013,
  author    = {Ofomaja, Augustine Enakpodia and Unuabonah, Emmanuel Iyayi},
  title     = {Kinetics and time-dependent Langmuir modeling of 4-nitrophenol adsorption onto Mansonia sawdust},
  series = {Journal of the Taiwan Institute of Chemical Engineers},
  volume    = {44},
  journal   = {Journal of the Taiwan Institute of Chemical Engineers},
  number    = {4},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1876-1070},
  doi       = {10.1016/j.jtice.2012.12.021},
  pages     = {566 -- 576},
  year      = {2013},
  abstract  = {Often time's adsorption of large molecules onto untreated lignocellulosic materials is viewed as a two stage process and has frequently been characterized only by kinetic models while the rate limiting step of adsorption is determined only at various stages of the adsorption process. In this study the kinetics and the contribution of diffusion processes to 4-nitrophenol adsorption onto untreated sawdust was examined and the overall rate limiting step evaluated. The adsorption profile showed an initial rapid uptake of 4-nitrophenol which decreased and became almost constant after 5 min of contact. Analysis of the adsorption profile with the intraparticle diffusion equation and fractional 4-nitrophenol uptake with time showed that the profile can be divided into three different stages. The rate determining step of 4-nitrophenol adsorption was then evaluated based on the activation energies of each processes along with their activation parameters (Delta G*, Delta H* and Delta S*). The results revealed that external mass transfer was the overall rate limiting step with activation parameters E-a = 21.11, Delta H* = 23.75 and Delta S* = 144.97. Time dependent Langmuir modeling was carried out to optimize process parameters. (c) 2013 Taiwan Institute of Chemical Engineers. Published by Elsevier B.V. All rights reserved.},
  language  = {en}
}
@article{OmorogieBabalolaUnuabonahetal.2016,
  author    = {Omorogie, Martins O. and Babalola, Jonathan Oyebamiji and Unuabonah, Emmanuel Iyayi and Song, Weiguo and Gong, Jian Ru},
  title     = {Efficient chromium abstraction from aqueous solution using a low-cost biosorbent: Nauclea diderrichii seed biomass waste},
  series = {Journal of Saudi Chemical Society},
  volume    = {20},
  journal   = {Journal of Saudi Chemical Society},
  publisher = {Elsevier},
  address   = {Amsterdam},
  issn      = {1319-6103},
  doi       = {10.1016/j.jscs.2012.09.017},
  pages     = {49 -- 57},
  year      = {2016},
  abstract  = {Toxic Cr(III) which poses environmental hazard to flora and fauna was efficiently abstracted by low-cost Nauclea diderrichii seed biomass (NDS) with good sequestral capacity for this metal was investigated in this study. The NDS surface analyses showed that it has a specific surface area of 5.36 m(2)/g and pHpzc of 4.90. Thermogravimetric analysis of NDS showed three consecutive weight losses from 50-200 degrees C (ca. 5\%), 200-400 C (ca. 35\%), >400 degrees C (ca. 10\%), corresponding to external water molecules, structural water molecules and heat induced condensation reactions respectively. Differential thermogram of NDS presented a large endothermic peak between 20-510 degrees C suggesting bond breakage and dissociation with the ultimate release of small molecules. The experimental data showed kinetically fast biosorption with increased initial Cr(III) concentrations, indicating the role of external mass transfer mechanism as the rate controlling mechanism in this adsorption process. The Langmuir biosorption capacity of NDS was 483.81 mg/g. The use of the corrected Akaike Information Criterion tool for ranking equilibrium models suggested that the Freundlich model best described the experimental data, which is an indication of the heterogeneous nature of the active sites on the surface of NDS. N. diderrichii seed biomass is an easily sourced, cheap and environmental friendly biosorbent which will serve as a good and cost effective alternative to activated carbon for the treatment of polluted water and industrial effluents. (C) 2012 King Saud University. Production and hosting by Elsevier B.V. All rights reserved.},
  language  = {en}
}