Sorption Behavior Of Co(Ⅱ) On Carbon

Owing to their unique structure, multi-walled carbon nanotubes(MWCNTs) have attracted numerous researchers’ attentions for wastewater treatment. Because of high cost and difficult separation from solutions, the application of MWCNTs is limited in the field of adsorption. This paper makes the point of incorporating hydrophilic group(–SO3H) and Fe3O4 onto the surface of MWCNTs to improve its dispersion performance and to facilitate recycling, reducing processing costs. The sulfonated magnetic multi-walled carbon nanotubes(SMMWCNTs) were prepared and characterized by scanning electron microscope(SEM), Fourier transform infrared(FTIR), X-ray diffractometer(XRD) and N2 adsorption(BET) test. A lot of influencing factors to the sorption process were investigated, such as contact time, p H, ionic strength, cations, anions, humic acid(HA), fulvic acid(FA) and temperature, and the results indicated that the sorption equilibrium can be achieved in 5min, and the pseudo-second-order model could fit the data well. The Co(II) sorption was strongly controlled by the p H and ionic strength. Moreover, foreign anions, such as F-, Cl- and Br-, exhibited obvious effect on the sorption process wich depended on the electronegativity of the anions. On the other hand, cations restrained sorption strongly, such as Mg2+ and Ca2+. The existence of HA/FA enhanced sorption process at p H < 7 while weakened at p H > 7. Sorption isotherms could fit the the Langmuir adsorption model well, and the thermodynamic analysis suggested that the sorption was a spontaneous and endothermic process.To overcome the high cost of carbon nanotubes,papermaking black liquor lignin activated carbon(BLLAC) was prepared for Co(II) adsorption in this paper, not only can further reduce the cost of adsorbent, but also mitigating pollution to the environment, achieving the purpose of dealing with waste by waste. The BLLAC were prepared and characterized by N2 adsorption(BET), scanning electron microscope(SEM) and X-ray diffractometer(XRD). A lot of influencing factors to the sorption process were investigated, such as contact time, p H, ionic strength, cations, anions, humic acid(HA), fulvic acid(FA) and temperature, and the results indicated that the specific surface area of BLLAC can reach 1400m2/g. The sorption equilibrium can be achieved in 6min, and the pseudo-second-order model could fit the data well. The Co(II) sorption was strongly controlled by the p H and ionic strength. Moreover, the order of removal percentage was Na+ > K+ > Mg2+ when foreign cations existed. The existence of HA/FA enhanced sorption process at p H < 7 while weakened at p H > 7. Sorption isotherms could fit the the Freundlich adsorption model well, and the thermodynamic analysis suggested that the sorption was a spontaneous and endothermic process.In conclusion, two different carbon material adsorbents were used to investigate the effects of Co(II) removal. From the aspect of the adsorbent, the cost of BLLAC is lower than that of SMMWCNTs. And furthermore, the adsorption capacity of BLLAC who has large specific surface area and developed pore structure is much greater than that of adsorption of SMMWCNTs. Therefore, we prefer to choose inexpensive waste to prepare activated carbon with high specific surface area and used to heavy metal removal.