Synthesis of Cross-linked Carboxyl Modified Polyvinyl Alcohol and its Application in Selective Adsorption Separation of Cu(II) from Cd(II) and Ni(II)

A cross-linked copolymer (XL-P(AA-co-VAc)) of vinyl acetate and acrylic acid was prepared using azobisisobutyronitrile as initiator andN,N'-methylenebisacrylamide as crosslinker. Then, XL-P(AA-co-VAc) was reacted with ethanol to prepare a crosslinked carboxyl modified polyvinyl alcohol (XL-P(AA-co-VA)). The as-prepared XL-P(AA-CO-VA) hydrogel was characterized by FTIR, XRD, SEM and BET, and investigated as an selective heavy metal ion adsorbent. The adsorption characteristics of the XL-P(AA-CO-VA) hydrogel were studied with a aqueous solution containing ternary metal ions Cu(II), Cd(II) and Ni(II). It was found that XL-P(AA-CO-VA) can selectively adsorb Cu(II) in competition with Cd(II) and Ni(II), and the selectivity coefficients of 48 (beta(Cu(II)/Cd(II))) and 80 (beta(Cu(II)/Ni(II))) were obtained. The kinetics were demonstrated to match well with the pseudo-second order kinetics model with the rate constants (K-2, g/(mg center dot min)) of 3.71 & x2715;10(- 4), 0.0011 and 0.0015 for Cu(II), Cd(II) and Ni(II), respectively. The equilibrium adsorption of Cu(II) to the XL-P(AA-CO-VA) hydrogel follows the Langmuir adsorption model withq(max)of 41.27 mg/g andK(L)of 0.94 L/mg. The thermodynamic studies indicate that Delta G(0)was negative and increased with temperature, and the adsorption process of XL-P(AA-CO-VA) for Cu(II) ion was spontaneous and exothermic. Delta Hand Delta Swere - 56.57 kJ/mol and - 171.18 J center dot(mol center dot K)(-1), respectively. The XL-P(AA-CO-VA) hydrogel is of interest for the selective separation of Cu(II) from industrial wastewater containing Cd(II) and Ni(II).

Automated summary

A cross-linked copolymer of vinyl acetate and acrylic acid was synthesized and reacted with ethanol to prepare a crosslinked carboxyl modified polyvinyl alcohol. The hydrogel showed selective adsorption of Cu(II) in competition with Cd(II) and Ni(II), with promising kinetics and equilibrium adsorption characteristics for Cu(II) ion. Thermodynamic studies indicated the adsorption process for Cu(II) ion was spontaneous and exothermic.