Authors:Yaling Chi, Yuantao Chen, Xia Liu, Zhijun Guo, and Linsen Cai
The sorption of UO22+ from aqueous solution on attapulgite was investigated as a function of contact time, solid content, pH, ionic strength, foreign
ions, humic acid (HA), and fulvic acid (FA) under ambient conditions by using batch technique. The attapulgite sample was
characterized by XRD and FTIR in detail. The results indicated that the sorption of UO22+ was strongly dependent on pH and ionic strength. The sorption of UO22+ on attapulgite increased quickly with rising pH at pH < 6.5, and decreased with increasing pH at pH > 6.5. The presence of
HA or FA enhanced the sorption of UO22+ on attapulgite obviously at low pH because of the strong complexation of surface adsorbed HA/FA with UO22+ on attapulgite surface. Sorption of UO22+ on attapulgite was mainly dominated by ion-exchange or outer-sphere surface complexation at low pH values, but by inner-sphere
surface complexation at high pH values. The results indicate that attapulgite is a very suitable adsorbent for the preconcentration
and solidification of UO22+ from large volumes of aqueous solutions because of its negative surface charge and large surface areas.
Alberts, J. J. & Takács, M.,
2004a. Total Luminescence Spectra of IHSS standard and reference fulvic acids, humicacids and natural organic matter: Comparison of aquatic and terrestrial source terms. Organic
Authors:Baowei Hu, Wen Cheng, Hui Zhang, and Guodong Sheng
In this work, sorption of Ni(II) from aqueous solution to goethite as a function of various water quality parameters and temperature
was investigated. The results indicated that the pseudo-second-order rate equation fitted the kinetic sorption well. The sorption
of Ni(II) to goethite was strongly dependent on pH and ionic strength. A positive effect of HA/FA on Ni(II) sorption was found
at pH < 8.0, whereas a negative effect was observed at pH > 8.0. The Langmuir, Freundlich, and D-R models were applied to
simulate the sorption isotherms at three different temperatures of 293.15 K, 313.15 K and 333.15 K. The thermodynamic parameters
(ΔH0, ΔS0 and ΔG0) were calculated from the temperature dependent sorption, and the results indicated that the sorption was endothermic and
spontaneous. At low pH, the sorption of Ni(II) was dominated by outer-sphere surface complexation or ion exchange with Na+/H+ on goethite surfaces, whereas inner-sphere surface complexation was the main sorption mechanism at high pH.
The effect of humic acid addition on the capacity of inorganic sorbents to sorb radioactive cesium and strontium was studied
on montmorillonites in a calcium and potassium form. The Sips isotherm for humic acid sorption and multisite distribution
model of ion sorption was found to suit well for the description of mobility of ions as a function of equilibrium humic acid
concentration as a single variable at given pH and type of silicate. Complexation of the ions was of minor importance at the
conditions investigated. Influence of humic acid on the specific radiocesium interception potential (SRIP) was also evaluated.