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Metals 2017, 7(9), 371; doi:10.3390/met7090371

An Eco-Friendly Neutralization Process by Carbon Mineralization for Ca-Rich Alkaline Wastewater Generated from Concrete Sludge

Center for Carbon Mineralization, Climate Change Mitigation and Sustainability Division, Korea Institute of Geoscience and Mineral Resources (KIGAM), 124 Gwahak-ro, Yuseong-gu, Daejeon 34132, Korea
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Received: 28 July 2017 / Revised: 11 September 2017 / Accepted: 11 September 2017 / Published: 13 September 2017
(This article belongs to the Special Issue Valuable Metal Recycling)
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Abstract

Waste-concrete recycling processes using wet-based crushing methods inevitably generate a large amount of alkaline concrete sludge, as well as wastewater, which contains abundant Ca ions. The Ca-rich alkaline wastewater must then be neutralized for reuse in the waste-concrete recycling process. In this study, the feasibility of a carbon mineralization process for the neutralization of alkaline wastewater was considered from both environmental and economic perspectives. The optimal reaction time, efficiency of Ca removal and CO2 sequestration as a function of the CO2 gas flow rate were assessed. The carbon mineralization process resulted in sequestering CO2 (85–100% efficiency) and removing Ca from the solution (84–99%) by precipitating pure CaCO3. Increasing the gas flow rate reduced the reaction time (65.0 down to 3.4 min for 2.5 L of solution), but decreased CO2 sequestration (from 463.3 down to 7.3 mg CO2 for 2.5 L of solution). Optimization of the gas flow rate is essential for efficient CO2 sequestration, Ca removal, CaCO3 production and, therefore, successful wastewater neutralization following the wet-based crushing process. The method presented here is an eco-friendly and economically viable substitute for dealing with alkaline wastewater. It may also provide a practical guide for the design of carbon mineralization processes for the neutralization of alkaline solutions containing large amounts of Ca. View Full-Text
Keywords: alkaline concrete sludge; carbon mineralization; carbonation; wastewater neutralization; carbon dioxide alkaline concrete sludge; carbon mineralization; carbonation; wastewater neutralization; carbon dioxide
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This is an open access article distributed under the Creative Commons Attribution License which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited. (CC BY 4.0).

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Yoo, J.; Shin, H.; Ji, S. An Eco-Friendly Neutralization Process by Carbon Mineralization for Ca-Rich Alkaline Wastewater Generated from Concrete Sludge. Metals 2017, 7, 371.

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