Heavy metals can be adsorbed into biochar structure through different mechanisms including ion exchange, co-precipitation, electrostatic surface complexation, inner-sphere complexation and physical adsorption. Among which electrostatic surface complexation between ions of heavy metals and oxygen-containing functional groups (particularly -COOH and –OH) is the most promising mechanism. Electrostatic surface complexation can be further boosted by addition of extra potential sites for adsorption of heavy metals. Amine groups efficiently interact with heavy metals and make strong complexes with them due to the high stability constants of the metal complexes. This study aims at investigating the capability of biochar in adsorbing Ni(II) as a hazardous contaminant and enhancing its adsorption capacity by addition of extra amine sites using a novel ultrasono-chemical modification mechanism. To reach this objective, biochar physically modified by ultrasound (USB) was chemically activated by phosphoric acid (H3PO4) and then functionalized by urea (CO(NH2)2) which attaches amino (-NH2) functional groups to the surface of USB producing USBU (with urea). In this process, cavitation induced by low frequency ultrasound exfoliates and breaks apart of irregular shape of graphite oxide layers of biochar; cleans and smooths surfaces and increases the porosity and permeability of biochar’s carbonaceous structure. These phenomena synergistically contributed with urea functionalization in attaching the amine groups onto the biochar surface remarkably increased the absorption of Ni(II). The modified biochar could remove &gt;99% of 100 mg Ni(II)/L within only 6 hrs. Applying ultrasound and functionalizing biochar is an economical and efficient way of adsorbing nickel and other heavy metal ions found in water and can be applied easily to protect human health from the corrosion of degrading piping in cities with aging infrastructure.

Urea functionalization of biochar activated by ultrasound: An efficient strategy for heavy metal adsorption

255th National Meeting (2018)

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