Date of Award
Low cost and efficient adsorption of heavy metals from wastewater and thorough removal of adsorbent after water treatment have become the two essential needs for the commercial use of any adsorbent. Biochar (BC), the solid byproduct of pyrolysis with microporous carbonaceous structure, has been increasingly recognized as an efficient adsorbent for a vast number of pollutants. Magnetization, though eases the separation and reuse of BC, significantly reduces its adsorption capacity to a comparatively much higher extent. In this study, a hybrid post-pyrolysis magnetization was developed which sustained and even significantly increased the adsorption capacity of biochar. The process included i) structural modification of biochar under ultrasound waves, ii) magnetization with magnetite (Fe3O4) nanoparticles and iii) functionalization with 3-aminopropyl triethoxysilane. Ultrasound irradiation exfoliates and breaks apart the irregular graphite layers of biochar, and creates new/opens the blocked microspores, thus enhancing the BC’s porosity. On the other hand, 3-aminopropyl triethoxysilane stabilizes the magnetic nanoparticles on the biochar surface, while it participates in water treatment through the strong chelation ability of its amino groups toward metal ions. Scanning electron microscope image demonstrated the stable and uniform distribution of Fe3O4 nanoparticles on the surface of microporous biochar and Fourier-transform infrared spectroscopy suggested effective surface functionalization. In addition, although magnetization usually reduces the porosity of carbonaceous adsorbents, acoustic activation prior to magnetization increased the microporosity of biochar (from 123 for Raw-BC to 155 m2/g for acoustic-based magnetic biochar). Preliminary results of Ultraviolet–visible spectroscopy showed that acoustic-based magnetic biochar exhibited a much greater ability to remove Ni and Pb, with 139% and 38% higher adsorption compared to raw biochar. Almost complete removal of Pb (91%) was observed by magnetic-BC.
Shrestha, Ronish, "Ultrasound-Assisted Post-Pyrolysis Magnetization of Microporous Biochar for Effective Removal of Heavy Metals" (2020). Honors Theses. 1446.
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