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Adsorption of Ag+ ions on hydrolyzed lignocellulosic materials based on willow, paulownia, wheat straw and maize stalks
Vassileva, P. S.; Radoykova, T. Hr.; Detcheva, A. K.; Avramova, I. A.; Aleksieva, K. I.; Nenkova, S. K.; Valchev, I. V. & Mehandjiev, D. R.
Abstract
In the present work, the adsorption of Ag+ ions
on hydrolyzed plant biomass (willow, paulownia, wheat
straw and maize stalks) was investigated. Chemical analyses
were performed to establish the composition of the
obtained materials. Adsorption mechanism, adsorption
sites and specific surface areas of these materials were
examined by BET analysis, IR spectroscopy, XPS and
EPR. The effects of contact time, acidity of initial solutions
and Ag+ ion concentrations were followed. Pseudo-firstorder,
pseudo-second-order and intra-particle diffusion
models were used to analyze kinetic data. In all cases, the
adsorption was significantly affected by the pH value.
Different types of adsorption isotherms of Ag+ ions (either
Langmuir or Freundlich) were registered depending on the
adsorbing material. The adsorption mechanism is complex,
and the process passes through different stages as clustering
of Ag+ ions and formation of elemental Ag. The
maximal adsorption capacities varied from 2.05 to
6.07 mg g-1. The obtained results revealed that the
examined waste lignocellulosic materials are promising
adsorbents for Ag+ ions.
Keywords
Ag+ ions; Hydrolyzed lignocellulosic materials; Adsorption equilibrium; Adsorption mechanism
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