Adsotption Of Cu(Ⅱ)、Eu(Ⅲ)、Th(Ⅳ)、and U(Ⅵ)on Carbon Nanotubes In The Presence-of Soluble Fullerenes

Batch experiments were conducted under ambient conditions to study the adsorption of Cu(Ⅱ), Eu(Ⅲ), Th(Ⅳ) and U(Ⅵ) onto oxidized multi-walled carbon nanotubes (oMWCNTs) which was choosed as a adsorbent. The effect of contact time, pH, ionic strength of background electrolyte, the concentration of adsorbent and temperature on the adsorption of Cu(Ⅱ), Eu(Ⅲ), Th(Ⅳ) and U(Ⅵ) onto oMWCNTs and the influence of hydroxylated fullerene (C60(OH)n) and carboxylated fullerene (C60(C(COOH)2)n) on the adsorption of Cu(Ⅱ), Eu(Ⅲ), Th(Ⅳ) and U(Ⅵ) was also investigated.The results showed that the adsorption of Cu(Ⅱ), Eu(Ⅲ), Th(Ⅳ) and U(Ⅵ) are rapidly reached equilibrium on the surface of oMWCNTs and the kinetic process was well described by a pseudo-second-order rate model. It was found that the adsorption of Cu(Ⅱ), Th(Ⅳ), U(Ⅵ) and Eu(Ⅲ) onto oMWCNTs are strongly depended on pH. Cu(Ⅱ), Th(Ⅳ) and U(Ⅵ) adsorption are independent of ion strength, but the adsorption of Eu(Ⅲ) decrease with increasing ion strength. The adsorption of Cu(Ⅱ), Th(Ⅳ), and U(Ⅵ) onto oMWCNTs increase with the increase of temperature. The adsorption isotherms can be described better by the Langmuir model than by the Freundlich model. The thermodynamic data calculated from temperature-dependent adsorption isotherms suggested that the adsorption was spontaneous and enhanced at higher temperature. Desorption studies indicated that Th(Ⅳ) adsorption was ireversible. The drastic effect of C60(OH)n on Cu(Ⅱ), Th(Ⅳ) and U(Ⅵ) adsorption of oMWCNTs was not significant at low concentration of C60(OH)n, whereas a negative effect was observed at higher concentration. The adsorption of Cu(Ⅱ) onto oMWCNTs was enhanced with increasing pH values at pH<5, but decreased after pH reached5. The inhibition effect of C60(OH)n on the adsorption of Th(IV) appeared at pH>4. U(Ⅵ) adsorption onto oMWCNTs in the presence of C60(OH)n as a function of pH can be divided into three different parts. In the first region, the drastic effect of C60(OH)n on U(Ⅵ) adsorption of oMWCNTs was not significant. Within the second region (3≤pH≤6), the adsorption of U(Ⅵ) increases with increasing pH in the presence of C60(OH)n. However, the adsorption hindrance of U(Ⅵ) in the presence of high concentration of C60(OH)n (i.e.125and250mg/L). The third region lies when pH exceeds6, where the adsorption of Th(IV) is markedly decreased with increasing pH in ternary system. The inhibitation effect of C60(OH)n on Eu(Ⅲ) adsorption explored even at its low concentration. The adsorption of Eu(Ⅲ) on oMWCNTs in the presence of C6o(OH)n is similer to that free of C60(OH)n. The competetion of C60(OH)n with Cu(II), Eu(Ⅲ), Th(Ⅳ) and U(Ⅵ) for the adsorption site of oMWCNTs may be attributed to the inhibitation effect of C60(OH)n. The double sorption site model was applied to simulate the adsorption isotherms of Cu(Ⅱ), Eu(Ⅲ), Th(Ⅳ) and U(Ⅵ) in the presence of C60(OH)n and fitted the experimental data well. The presence of C60(C(COOH)2)n inhibited the adsorption of Cu(Ⅱ) onto oMWCNTs between pH4to pH6. The promotion effect of C60(C(COOH)2)n on Th(IV) adsorption showed at pH<3. The inhibitation effect of C60(C(COOH)2)n on U(Ⅵ) adsorption is similer to that of C60(OH)n. However, the inhibitation effect of C6o(OH)n is stronger than that of C60(C(COOH)2)n. The drastic effect of C60(C(COOH)2)n on Eu(Ⅲ) adsorption of oMWCNTs was not significant. The influence of C6o(OH)n and C60(C(COOH)2)n on the adsorption of metal ions different from each other due to their properties. The different effect of C6o(OH)n and C60(C(COOH)2)n varied with different typicale of cations and different pH values.