| Bentonite is a new family of functional materials, and can be used widely in the field of environmental protection and agriculture and industrial catalysis. In the paper, we used bentonite as adsorbent of different molecular weight of200to2000polyethylene glycol from synthetic wastewater. It lays stress on researching the promotion of absorption capabilities by adding metal ion. The influences of absorption conditions such as the best species of metal ion, the amount of adsorbent, the addition amount of metal ion, adsorption time, reaction temperature and pH were studied. The morphological structure, surface functional groups and crystalline structure of bentonite before and after adsorption was expressed and characterized by Transmission Electron Microscope(TEM), fourier transform infrared spectrum (FT-IR), X-ray diffraction(XRD), etc. The effect of adsorption performance and mechanism of action on bentonite with metal ions was preliminarily discussed.This paper main research contents were as follows:(1)It could be enhanced the absorption efficiency by adding all kinds of metallic cation into absorption solution, specifically Ba2+, the best removal rate could be obtained. when molar ratio of PEG:Ba2+was1:2, reaction temperature was30℃, reaction time was30min,38.80%of PEG200and86.30%of PEG400could be eliminated by adding4.000g of bentonite into synthetic wastewater, respectively. Besides,98.58%of PEG1000or99.25%of PEG2000could be removed from synthetic wastewater with2.000g bentonite. In addition, it was no effect on solution pH between4to10, but PEG2000removal rate has been raised when pH below3, while PEG200removal rate reduced slightly. Absorption efficiency has been reduced when solution pH over11, and removement rate was affected slightly by the increase of molecular weight.(2)The absorption isotherms of Ba2+on bentonite with different molecular weight of PEG were abided by Langmuir equation. The adsorption saturation capacity increased with the increase of molecular weight. Besides, PEG200qmax=43.69mg/g, PEG400qmax=61.62mg/g, PEG1000qmax=96.54mg/g, PEG2000qmax=115.64mg/g. (3)TEM and FT-IR and XRD analysis showed that PEG were surrounded in montmorillonite, and the construction layers of clumpy aggregation become loose. Besides, the layer spacing of bentonite was expended with the insertion of PEG, basal spacing become more extended with the existence of Ba2+.(4) Complex reactions between PEG and Ba2+caused lower conductivity before absorption, and a certain amount of Ba2+could be taken away after absorption. The main complexation capacities of metal ions as follows:Ba2+>Fe3+>Ca2+>K+. in a word, adding Ba2+into solution could promoting adsorption abilities of bentonite on PEG, and could not cause secondary pollution. |
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