ABSTRACT
Cadmium has been classified as a kind of human carcinogens, and has a strong mobility in the water environment and this can result in serious harm to human health and environmental safety. Here, a new selective and efficient extraction-recovery strategy for Cd purification is provided by using C6MimT/[C6Mim]PF6 as the green extractant. Due to the high compatibility between C6MimT and [C6Mim]PF6, C6MimT-Cd was efficiently separated from the aqueous phase. When the concentration of Cd(II) was 1000 mg/L, the extraction rate could reached 99.9 %. By comparing [C6MIm]BF4 with [C6MIm]PF6, the hydrophobicity restrained the ion exchange between cation and Cd and significantly reduced the loss of extractant. The extracted Cd(II) was separated in the form of precipitation after stripping. The extraction system of C6MimT/[C6Mim]PF6 was stable after several extraction-stripping cycles. The extraction of Cd(II) by C6MimT/[C6Mim]PF6 system mainly realized by forming a neutral and extractable cadmium complexes between Cd(II) and thione. Based on the natural complexation mechanism between metal and C6MImT, Cd exists as obvious competitive advantage in coordination with C6MimT compare to Pb, Zn, Mg, Cr, Fe. This work overcomes the problems of extractant loss and organic pollution caused by volatile or ion exchange, which can only reduce environmental hazards, but also promote the recovery of cadmium and other valuable resources.
Subject(s)
Cadmium , Metals , HumansABSTRACT
Volatile organic compounds (VOCs) are perceived as serious pollutants due to their great threat to both environment and human health. Recovery and removal of VOCs is of great significance. Herein, novel MOF-199 derived porous carbon materials (MC-T-n) were prepared by using MOF-199 as precursor, glucose as additional carbon source and KOH as activator, and then characterized. Adsorption performance of MC-T-n materials for benzene vapor was investigated. Isotherms of MC-T-n samples towards benzene and water vapor were measured. The adsorption selectivities of benzene/water were estimated by DIH (difference of the isosteric heats) equation. Results indicated that BET surface area and pore volume of MC-T-n materials reached separately 2320 m2/g and 1.05 m3/g. Benzene adsorption capacity of MC-T-n materials reached as high as 12.8 mmol/g at 25 °C, outperforming MOF-199 and some conventional adsorbents. Moreover, MC-T-n materials presented type-V isotherms of water vapor, suggesting their excellent water resistance. The isosteric heats of benzene adsorption on MC-500-6 were much greater than that of water adsorption, leading to a preferential adsorption for C6H6 over H2O. The adsorption selectivity of C6H6/H2O on MC-500-6 reached up to 16.3 superior to some previously reported MOFs. Therefore, MC-500-6 was a promising candidate for VOC adsorption and seperation. This study provides a strong foundation for MOF derived porous carbons as adsorbents for VOC removal.