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Enhancement of Cu(II) removal by carbon disulfide modified black wattle tannin gel

Xubing Sun,Jiayong Zhang,Yaohui You

Xanthated black wattle tannin gel (XBTG) was prepared by modifying black wattle tannin gel (BTG) with carbon disulfide to improve the performance of Cu(II) removal. Structure characterization demonstrated that xanthate groups were successfully introduced onto BTG and surface morphology of BTG was maintained after CS 2 -modification. Zeta potential measurement showed that XBTG was negative charged at a pH range from 1 to 5. Compared to the BTG, the thermal stability and the surface area of XBTG decreased, but the Cu(II) adsorption rate and adsorption capacity increased. The adsorption kinetics of BTG and XBTG followed pseudo-second-order model. The adsorption isotherms fitted well with Langmuir model, and the calculated maximum adsorption capacity for the XBTG increased to 149.25 mg/g at 298 K, which was 228.95 % higher than BTG. Moreover, the Cu(II) loaded XBTG could be regenerated using 0.1 M ethylenediaminetetraacetic acid disodium salt solution. The adsorption capacity of the regenerated XBTG after five cycles decreased to 58 % compared with the fresh adsorbent, which was equivalent to that of BTG. The adsorption mechanism was attributed to the surface complexation of Cu(II) by adjacent phenolic hydroxyl groups and xanthate groups or to the ion exchange between Na(I) and Cu(II).