Abstract
Effects of ionic strength, pH, temperature, humic acid (HA) and adsorbate concentration on Np(V) sorption to Na-bentonite were investigated in detail. The sorption of Np(V) to Na-bentonite was significantly dependent on pH and independent of temperature. In the presence of HA, Np(V) sorption was enhanced significantly at low pH; while an obvious negative effect was observed in higher pH range. Np(V) sorption followed the Freundlich isotherm indicating a heterogeneous sorption of Np(V) on the surface of Na-bentonite. The surface complexation model (SCM) suggests that sorption of Np(V) on Na-bentonite was mainly dominated by ion exchange at low pH values, and two dominant monodentate inner-sphere complexes of ≡SiONpO20 (logK=−4.55) and≡AlO(NpO2OH)− (logK=−13.80) contributed to Np(V) sorption on Na-bentonite over high pH range.
Published Version
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