▎ 摘　　要

The adsorption performance of graphene oxide (GO) towards metallic hard (N-a+, Mg2+.), soft (Cd2+ and Pb2+) and borderline ions (Ni2+, Cu2+, Zn2+, Co2+) was studied experimentally giving the sequence of maximum Langmuir adsorption capacities Q(m), mmol/g, as Na+ < Mg2+ < Co2+ < Cd2+ < Zn2+ < Ni2+ < Cu2+ < Pb2+. The results showed that the adsorption capacities Q(m) of hard ions were substantially lower than that of soft and borderline ones. The relationship between the Q(m) values of metal ions and their characteristics was studied using relative correlation analysis. The ion characteristics include atomic number AN, ionic radius r, change in ionization potential Delta IP, electronegativity X-m, atomic weight AW, covalent index X(m)(2)r, absolute difference between electrochemical potential of the ion and that of its first stable reduced state Delta E-0, absolute value of the first hydrolysis constant decimal logarithm vertical bar IgK(OH)vertical bar, atomic radius AR, atomic radius to atomic weight ratio AR/AW, polarization force or ionic index Z(2)/r and softness index sigma(p). The Q(m) value exhibited positive correlation with r, Delta IP, Xmv Z(2)/r, AN/Delta IP, AW, X-m(2)/r and AN, while negative correlation was observed with Delta E-0, vertical bar IgK(OH)vertical bar, sigma(p), AR and AR/AW. The results allow the Q(m) values being predicted by the equation, the correlation coefficient R-2 of which exceeds 0.885: Q(m) = 0.338 Delta IP 0.110 broken vertical bar lgK(OH)vertical bar + 0.114(Z)2/r + 26.934 sigma(p) - 1.479AR - 1.162X(m)(2)r + 0.115AN - 3.059 Density functional theory (DFT) was adopted to study the adsorption mechanism of metal ions at GO, taking Na+, Cu2+ and Pb2+ ions as examples. The results showed the adsorption energy E-ad of GO-Na+ bond being negative indicating Na+ adsorption less likely resulting possibly in relatively low adsorption capacity of GO towards hard ions. The E-ad values of GO bonds with Cu2+ and Pb-2+ comprised the rows GO(O)-Cu2+ > GO (COOH)-Cu2+ > GO(OH)-Cu2+, and GO(COOH)-Pb2+ > GO(OH)-Pb2+ > GO(O)-Pb2+, respectively. The results provide guidelines in predicting the adsorption ability of GO adsorbent towards metal ions.