title: A novel sequential process for remediating rare-earth wastewater.
abstract: A novel and economic sequential process consisting of precipitation, adsorption, and oxidation was developed to remediate actual rare-earth (RE) wastewater containing various toxic pollutants, including radioactive species. In the precipitation step, porous air stones (PAS) containing waste oyster shell (WOS), PASWOS, was prepared and used to precipitate most heavy metals with >97% removal efficiencies. The SEM-EDS analysis revealed that PAS plays a key role in preventing the surface coating of precipitants on the surface of WOS and in releasing the dissolved species of WOS successively. For the adsorption step, a polyurethane (PU) impregnated by coal mine drainage sludge (CMDS), PUCMDS, was synthesized and applied to deplete fluoride (F), arsenic (As), uranium (U), and thorium (Th) that remained after precipitation. The continuous-mode sequential process using PAS(WOS), PU(CMDS), and ozone (O3) had 99.9-100% removal efficiencies of heavy metals, 99.3-99.9% of F and As, 95.8-99.4% of U and Th, and 92.4% of COD(Cr) for 100 days. The sequential process can treat RE wastewater economically and effectively without stirred-tank reactors, pH controller, continuous injection of chemicals, and significant sludge generation, as well as the quality of the outlet met the EPA recommended limits.
authors.affiliation: School of Civil, Environmental, and Architectural Engineering, Korea University, 5 Anam-dong, Seoul 136-701, Republic of Korea.
authors.forename: Mingcan
authors.initials: M
authors.lastname: Cui
authors.affiliation: Department of Civil Engineering, Faculty of Engineering, University of Malaya, Kuala Lumpur 50603, Malaysia; Nanotechnology and Catalysis Research Centre (NANOCAT), University of Malaya, 50603 Kuala Lumpur, Malaysia. Electronic address: minjang@um.edu.my.
authors.forename: Min
authors.initials: M
authors.lastname: Jang
authors.affiliation: School of Civil, Environmental, and Architectural Engineering, Korea University, 5 Anam-dong, Seoul 136-701, Republic of Korea.
authors.forename: Kyounglim
authors.initials: K
authors.lastname: Kang
authors.affiliation: Korea Mine Reclamation Corporation, Cheonan-si, 331-803, Republic of Korea.
authors.forename: Dukmin
authors.initials: D
authors.lastname: Kim
authors.affiliation: Chemical and Environmental Engineering, University of Arizona, Tucson, AZ, USA.
authors.forename: Shane A
authors.initials: SA
authors.lastname: Snyder
authors.affiliation: School of Civil, Environmental, and Architectural Engineering, Korea University, 5 Anam-dong, Seoul 136-701, Republic of Korea. Electronic address: hyeong@korea.ac.kr.
authors.forename: Jeehyeong
authors.initials: J
authors.lastname: Khim
mesh_terms: D000327:Adsorption; D011232:Chemical Precipitation; D008674:Metals, Rare Earth / Q000737:chemistry*; D008962:Models, Theoretical; D010084:Oxidation-Reduction; D013816:Thermodynamics; D014865:Waste Disposal, Fluid / Q000379:methods*; D062065:Wastewater / Q000032:analysis*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D008674:Metals, Rare Earth; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Adsorption; Oxidation; Precipitation; Rare-earth; Wastewater