title: Phosphate removal from domestic wastewater using thermally modified steel slag.
abstract: This study was performed to investigate the removal of phosphate from domestic wastewater using a modified steel slag as the adsorbent. The adsorption effects of alkalinity, salt, water, and thermal modification were investigated. The results showed that thermal activation at 800°C for 1 hr was the optimum operation to improve the adsorption capacity. The adsorption process of the thermally modified slag was well described by the Elovich kinetic model and the Langmuir isotherm model. The maximum adsorption capacity calculated from the Langmuir model reached 13.62 mg/g. Scanning electron microscopy indicated that the surface of the modified slag was cracked and that the texture became loose after heating. The surface area and pore volume did not change after thermal modification. In the treatment of domestic wastewater, the modified slag bed (35.5 kg) removed phosphate effectively and operated for 158 days until the effluent P rose above the limit concentration of 0.5 mg/L. The phosphate fractionation method, which is often applied in soil research, was used to analyze the phosphate adsorption behavior in the slag bed. The analysis revealed that the total contents of various Ca-P forms accounted for 81.4%-91.1%, i.e., Ca10-P 50.6%-65.1%, Ca8-P 17.8%-25.0%, and Ca2-P 4.66%-9.20%. The forms of Al-P, Fe-P, and O-P accounted for only 8.9%-18.6%. The formation of Ca10-P precipitates was considered to be the main mechanism of phosphate removal in the thermally modified slag bed.
authors.affiliation: College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China; National Center for Rural Water Supply Technical Guidance, Chinese Center for Disease Control and Prevention, Beijing 102200, China. Electronic address: yujian198881@sina.com.
authors.forename: Jian
authors.initials: J
authors.lastname: Yu
authors.affiliation: College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China. Electronic address: lwy@bjfu.edu.cn.
authors.forename: Wenyan
authors.initials: W
authors.lastname: Liang
authors.affiliation: College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.
authors.forename: Li
authors.initials: L
authors.lastname: Wang
authors.affiliation: College of Environmental Science and Engineering, Beijing Forestry University, Beijing 100083, China.
authors.forename: Feizhen
authors.initials: F
authors.lastname: Li
authors.affiliation: Central Research Institute of Building and Construction Co., Ltd., MCC, Beijing 100088, China.
authors.forename: Yuanlong
authors.initials: Y
authors.lastname: Zou
authors.affiliation: Central Research Institute of Building and Construction Co., Ltd., MCC, Beijing 100088, China.
authors.forename: Haidong
authors.initials: H
authors.lastname: Wang
mesh_terms: D000327:Adsorption; D005591:Chemical Fractionation; D006358:Hot Temperature; D008855:Microscopy, Electron, Scanning; D010710:Phosphates / Q000737:chemistry*; D013232:Steel / Q000737:chemistry*; D062065:Wastewater / Q000737:chemistry*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D010710:Phosphates; D013232:Steel; D062065:Wastewater; D014874:Water Pollutants, Chemical
keywords: Adsorption; Fractionation; Phosphate; Steel slag; Thermal modification