Adsorption of radioactive strontium by pristine and magnetic biochars derived from spent coffee grounds
Journal of Environmental Chemical Engineering(2021)
摘要
This study rigorously investigated the adsorption behaviors and mechanisms of strontium ions (Sr2+) by the pristine and magnetic biochars prepared via the pyrolysis of pristine and FeCl3-pretreated spent coffee grounds (SCG). The FeCl3-pretreatment could magnetize successfully the pristine SCG biochars (magnetization value of pristine SCG biochars = 0.19 emu/g; magnetization value of magnetic SCG biochars = 8.99 emu/g) and improved substantially their specific surface area (pristine SCG biochars = 5.3 m2/g; magnetic SCG biochars = 431.7 m2/g) and total pore volume (pristine SCG biochars = 0.002 cm3/g; magnetic SCG biochars = 0.186 cm3/g). However, the removal efficiency of Sr2+ with the pristine SCG biochars (33.4–34.1%) was not significantly different from that with the magnetic SCG biochars (33.1–33.9%). The calculated kinetic parameters indicate that the adsorption of Sr2+ by the pristine and magnetic SCG biochars was governed by the chemisorption (R2 of the pseudo-first-order kinetic equation ≤ 0.602; R2 of the pseudo-second-order kinetic equation = 1.000). The higher R2 values of the Langmuir isotherm (R2 = 0.999) model compared to the Freundlich isotherm model (R2 ≤ 0.950) are evident that the monolayer adsorption mainly determined the adsorptive removal of Sr2+ with the pristine and magnetic SCG biochars. Moreover, the adsorption of Sr2+ using the pristine and magnetic SCG biochars was the spontaneous and endothermic process. These observations indicate that the FeCl3-pretreatment might offer a viable way to effectively recover the residual SCG biochars after the Sr2+ adsorption through the magnetic separation (recovery rate = 90%).
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关键词
Biochars,Magnetization,O-containing functional groups,Spent coffee grounds,Strontium
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