title: Application of steel slag coated with sodium hydroxide to enhance precipitation-coagulation for phosphorus removal.
abstract: Phosphorus removal has been studied for decades to reduce the environmental impact of phosphorus in natural waterbodies. Slag has been applied for the phosphorus removal by several mechanisms. In this study, sodium hydroxide coating was applied on the slag surface to enhance the efficiency of precipitation-coagulation process. In the batch test, it was found that the capacity of the slag to maintain high pH decreases with increasing its exposure time to the aqueous solution. In the column test, the coarse-grained coated slag showed higher phosphorus removal efficiency than the fine-grained uncoated slag. The coated slag maintained pH higher than uncoated slag and, accordingly, the removal efficiency of phosphorus was higher. Especially, when pH was less than 8, the removal efficiency decreased significantly. However, coated slag provided an excess amount of aluminum and sodium. Thus, a return process to reuse aluminum and sodium as a coagulant was introduced. The return process yields longer lifespan of slag with higher phosphorus removal and lower concentration of cations in the effluent. With the return process, the phosphorus removal efficiency was kept higher than 60% until 150 bed volumes; meanwhile, the efficiency without return process became lower than 60% at 25 bed volumes.
authors.affiliation: Department of Energy System Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul, 08826, Republic of Korea.
authors.forename: Taejun
authors.initials: T
authors.lastname: Park
authors.affiliation: Department of Energy System Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul, 08826, Republic of Korea.
authors.forename: Vanvimol
authors.initials: V
authors.lastname: Ampunan
authors.affiliation: Department of Civil and Environmental Engineering, Sejong University, Neungdong-ro 209, Gwangjin-gu, Seoul, 05006, Republic of Korea.
authors.forename: Sungkyu
authors.initials: S
authors.lastname: Maeng
authors.affiliation: Department of Energy System Engineering, Seoul National University, Gwanak-ro 1, Gwanak-gu, Seoul, 08826, Republic of Korea. Electronic address: echung@snu.ac.kr.
authors.forename: Eunhyea
authors.initials: E
authors.lastname: Chung
mesh_terms: D011232:Chemical Precipitation; D005427:Flocculation; D007220:Industrial Waste; D010758:Phosphorus / Q000737:chemistry*; D012972:Sodium Hydroxide / Q000737:chemistry*; D013232:Steel / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*; D018508:Water Purification / Q000379:methods
chemical_list: D007220:Industrial Waste; D014874:Water Pollutants, Chemical; D013232:Steel; D010758:Phosphorus; D012972:Sodium Hydroxide
keywords: Coating; Phosphorus removal; Precipitation and coagulation; Slag