Adsorption characteristics and mechanism of Pb(II) by agricultural waste-derived biochars produced from a pilot-scale pyrolysis system
2019
Liu, Lingqin | Huang, Yaji | Zhang, Shuping | Gong, Yan | Su, Yinhai | Cao, Jianhua | Hu, Huajun
The objective of this study was to investigate the feasibility of removing Pb²⁺ by pilot-scale fluidized bed biochar, and then to put forward an industrial-scale fluidized bed pyrolysis progress of cogeneration of biochar and high-temperature gas. Corn stalk biochars (CSBs) were prepared at 400–600 °C, in which the maximum Pb²⁺adsorption capacity (Qₘ) of CSB450 is 49.70 mg⋅g⁻¹ at the optimal condition. Adsorption isotherms, kinetics, and thermodynamics were determined, and Pb²⁺-loaded biochar was analyzed by fourier transform infrared spectroscopy (FTIR), x-ray photoelectron spectroscopy (XPS), x-ray diffraction (XRD) and scanning electron microscope with energy dispersive spectrometer (SEM-EDS). Ion exchange, complexation and mineral precipitation together contributed to Pb²⁺ adsorption on CSBs. For high-temperature CSBs with fewer oxygen functional groups (OFGs) and stronger aromatization, Pb²⁺ adsorption by ion exchange and functional group complexation was reduced. The mineral precipitationwas formed during the adsorption process. Using the pilot-scale fluidized bed in this study, the carbon yield per year would achieve 31.79 t, and about 1.58 t of Pb²⁺ would be adsorbed according to the adsorption capacity at the pyrolytic temperature of 450 °C.The results are beneficial to screen for effective biochar as a cost-effective industrial adsorbent to remove Pb²⁺ in contaminated water.
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