title: Selective Removal of Technetium from Water Using Graphene Oxide Membranes.
abstract: The effective removal of radioactive technetium ((99)Tc) from contaminated water is of enormous importance from an environmental and public health perspective, yet many current methodologies are highly ineffective. In this work, however, we demonstrate that graphene oxide membranes may remove (99)Tc, present in the form of pertechnetate (TcO4(-)), from water with a high degree of selectivity, suggesting they provide a cost-effective and efficient means of achieving (99)Tc decontamination. The results were obtained by quantifying and comparing the free energy changes associated with the entry of the ions into the membrane capillaries (ΔFperm), using molecular dynamics simulations. Initially, three capillary widths were investigated (0.35, 0.68, and 1.02 nm). In each case, the entry of TcO4(-) from aqueous solution into the capillary is associated with a decrease in free energy, unlike the other anions (SO4(2-), I(-), and Cl(-)) investigated. For example, in the model with a capillary width of 0.68 nm, ΔFperm(TcO4(-)) = -6.3 kJ mol(-1), compared to ΔFperm(SO4(2-)) = +22.4 kJ mol(-1). We suggest an optimum capillary width (0.48 nm) and show that a capillary with this width results in a difference between ΔFperm(TcO4(-)) and ΔFperm(SO4(2-)) of 89 kJ mol(-1). The observed preference for TcO4(-) is due to its weakly hydrating nature, reflected in its low experimental hydration free energy.
authors.affiliation: School of Chemical Engineering and Analytical Science, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Christopher D
authors.initials: CD
authors.lastname: Williams
authors.affiliation: School of Chemical Engineering and Analytical Science, The University of Manchester , Oxford Road, Manchester M13 9PL, United Kingdom.
authors.forename: Paola
authors.initials: P
authors.lastname: Carbone
mesh_terms: D002712:Chlorides / Q000737:chemistry; D003666:Decontamination / Q000295:instrumentation / Q000379:methods; D006108:Graphite; D008567:Membranes, Artificial; D056004:Molecular Dynamics Simulation; D010087:Oxides; D013670:Sodium Pertechnetate Tc 99m / Q000302:isolation & purification; D013431:Sulfates / Q000737:chemistry; D013667:Technetium / Q000302:isolation & purification*; D014874:Water Pollutants, Chemical / Q000302:isolation & purification*; D014875:Water Pollutants, Radioactive / Q000302:isolation & purification*; D018508:Water Purification / Q000295:instrumentation / Q000379:methods*
chemical_list: D002712:Chlorides; D008567:Membranes, Artificial; D010087:Oxides; D013431:Sulfates; D014874:Water Pollutants, Chemical; D014875:Water Pollutants, Radioactive; D013667:Technetium; D006108:Graphite; D013670:Sodium Pertechnetate Tc 99m