Impact of water quality parameters on the sorption of U(VI) onto hematite

In this study, the sorption of U(VI) from aqueous solution on hematite was studied as a function of various water quality parameters such as contact time, pH, ionic strength, soil humic acid (HA) or fulvic acid (FA), solid content and temperature by using a batch technique. The results demonstrated that the sorption of U(VI) was strongly dependent on ionic strength at pH < 6.0, and outer-sphere surface complexation may be the main sorption mechanism. The sorption was independent of ionic strength at pH > 6.0 and the sorption was mainly dominated by inner-sphere surface complexation. The presence of HA/FA increases U(VI) sorption at low pH, whereas decreases U(VI) sorption at high pH. The thermodynamic parameters (ΔH0, ΔS0, and ΔG0) were calculated from the temperature dependent sorption isotherms, and the results suggested that U(VI) sorption was a spontaneous and endothermic process. The results might be important for the application of hematite in U(VI) pollution management.

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► The sorption of U(VI) was strongly dependent on ionic strength at pH < 6.0, but independent of ionic strength at pH > 6.0.
► A positive effect of HA/FA on U(VI) sorption was found at low pH, whereas a negative effect was observed at high pH.
► U(VI) sorption was a spontaneous and endothermic process.
► The results are quite important for the application of hematite in U(VI) pollution management.