期刊
JOURNAL OF ENVIRONMENTAL MANAGEMENT
卷 202, 期 -, 页码 38-45出版社
ACADEMIC PRESS LTD- ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jenvman.2017.07.012
关键词
Central composite design; Cr removal; Ca sedimentation; Reduction; Coagulation-precipitation
资金
- National Natural Science Foundation of China [51608148]
- State Key Laboratory of Urban Water Resource and Environment (Harbin Institute of Technology) [2017TS02]
- National Important Items of Science and Technology for the Control and Treatment of Water Pollution [2014ZX07405002]
- Higher Education Institute of Heilongjiang Province of China [16G012]
The removal of Cr(VI) by chemical reduction-precipitation is widely applied in wastewater treatment plants. Nevertheless, the formation of Cr(OH)(3) with gel properties has weak settlement performance, making it necessary to add a coagulant aid to reduce the settling time and improve the settling effect. In this investigation, a high concentration of Cr(VI) was removed using Na2SO3 as a reducing agent and CaO as a coagulant. An improved reduction and precipitation experiment was modeled by applying a three factor central composite experimental design (CCD). To reveal as many mechanisms as possible for CrT removal, other verification experiments were performed. The CrT removal efficiency decreased, which can be explained by the following three reasons: dissolution of Cr(III), competition for adsorption between Ca2+ and Cr(III) at different coagulation times, and formation of a solubility complex with Cr(III) due to the surplus SO3 in solution. The increasing CrT removal efficiency can be explained by the following two reasons: dissolved Ca2+ from CaO can neutralize CrOy that is produced by the dissolution of Cr(OH)3 in alkaline solution and can broaden the optimal final pH range of coagulation. Ca2+ could also strengthen the CrT removal through adsorption bridging and co-precipitation with CaO as the core of flocs. (C) 2017 Elsevier Ltd. All rights reserved.
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