Submitted to: Chemical Engineering Journal
Publication Type: Peer reviewed journal
Publication Acceptance Date: 6/26/2012
Publication Date: 7/28/2012
Citation: Xue, Y., Gao, B., Yao, Y., Inyang, M., Zhang, M., Zimmerman, A.R., Ro, K.S. 2012. Hydrogen peroxide modification enhances the ability of biochar (hydrochar) produced from hydrothermal carbonization of peanut hull to remove aqueous heavy metals: Batch and column tests. Chemical Engineering Journal. 200-202: 673-680. Interpretive Summary: Hydrochar refers to the solid char product from hydrothermal carbonization (HTC) of carbon-rich biomass in the presence of liquid water, which is also called hydrous pyrolysis or wet pyrolysis. The HTC process usually employs relatively low temperatures (150-350 degrees Celsius) and can be applied directly to wet feedstocks, such as wet animal manures, algae, and biomass with pore moisture. As a result, it is more energetically advantageous than dry pyrolysis processes, which require a greater initial investment of energy and the energy-intensive drying of feedstock. Hydrothermal carbonization was originally designed to simulate natural coalification process, but at accelerated rates using water as the sole reaction medium under pressure and heat to produce artificial coal from biomass. It is environmentally friendly in that the process does not generate any hazardous chemical waste or by-products as dry pyrolysis can. Hydrochars may be used for a variety of environmental applications, such as carbon sequestration, energy storage, soil improvement, and water purification. In this work, the effects of hydrogen peroxide treatment on the removeal of heavy metals by hydrochar made from peanut hull were investigated. It was found that hydrogen peroxide treatment significantly increased the lead removal capacity of the hydrochar comparable to that of commercial activated carbon. This finding suggests that the treated peanut hull hydrochar can be used as a filtering medium for lead removal from water.
Technical Abstract: Experimental and modeling investigations were conducted to examine the effect of hydrogen peroxide treatment on hydrothermally produced biochar (hydrochar) from peanut hull to remove aqueous heavy metals. Characterization measurements showed that hydrogen peroxide modification increased the oxygen-containing functional groups, particularly carboxyl groups, on the hydrochar surfaces. As a result, the modified hydrochar showed enhanced lead sorption ability with a sorption capacity of 22.82 mg/g, which was comparable to that of commercial activated carbon. It was more than 20 times of that of untreated hydrochar (0.88 mg/g). When used as filter media in a packed column, the hydrogen-peroxide treated hydrochar was also much more effective in filtering lead than the untreated hydrochar. The lead removal capacity of the column packed with treated hydrochar was about 20 times of that containing untreated hydrochar. In a multi-metal system, the treated hydrochar column still effectively removed lead, as well as other heavy metals such as copper, nickel, and cadmium.