Enhanced Coagulation-Flocculation Performance of Iron-Based Coagulants: Effects of PO4(3-) and SiO3(2-) Modifiers.
PO4(3-) and SiO3(2-) are often used as modifier to improve stability and aggregating ability of the iron-base coagulants, however, there are few reports about their detailed comparison between the coagulation performance and mechanisms. In this study, three coagulants--polyferric phosphoric sulfate (PFPS), polysilicon ferric sulfate (PFSS), and polyferric sulfate (PFS) were synthesized; their structure and morphology were characterized by Fourier transformed infrared (FT-IR) spectroscopy, X-ray diffraction (XRD) and Scanning electron microscope (SEM). Alkali titration and Ferron species analysis were employed to investigate the hydrolysis performance and species distribution. Jar test was conducted to measure their coagulation behaviors at different dosage, pH, and temperatures in which the flocs properties were measured. The results showed that a number of new compounds were formed due to the presence of PO4(3-) and SiO3(2-). Moreover, PFPS and PFSS had similar level in Fea as well as Feb. Among them, PFPS produced more multi-core iron atoms polymer and content of Feb, and the formed flocs were larger and denser. It exhibited superior coagulation performance in terms of turbidity reduction, UV254 removal and residual ferric concentration. Jar test and floc breakage/regrowth experiments indicated other than charge neutrality, the dominated mechanism involved in PFSS was the adsorption between polysilicic acid and solution particle, while PFPS was sweeping, entrapment/adsorption resulting from larger polymer colloid of Fe-P chemistry bond.
Key laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University, Chongqing, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing, China.
Wei
W
Chen
Key laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University, Chongqing, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing, China.
Huaili
H
Zheng
National Research Center of Industrial Water Treatment Engineering and Technology, Tianjin Chemical Research and Design Institute, Tianjin, China.
Houkai
H
Teng
Research Center for Water Pollution Source Control and Eco-remediation, Beijing Forestry University, Beijing, China.
Yili
Y
Wang
State Key Laboratory of Urban and Regional Ecology, Research Center for Eco-Environmental Sciences, Chinese Academy of Sciences, Beijing, China.
Yuxin
Y
Zhang
Key laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University, Chongqing, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing, China.
Chuanliang
C
Zhao
Key laboratory of the Three Gorges Reservoir Region's Eco-Environment, State Ministry of Education, Chongqing University, Chongqing, China; National Centre for International Research of Low-carbon and Green Buildings, Chongqing University, Chongqing, China.
Yong
Y
Liao
D000327:Adsorption; D003029:Coagulants / Q000737:chemistry*; D005290:Ferric Compounds / Q000737:chemistry*; D005427:Flocculation; D005618:Fresh Water / Q000737:chemistry; D006812:Humic Substances / Q000032:analysis*; D006863:Hydrogen-Ion Concentration; D007616:Kaolin / Q000302:isolation & purification*; D009391:Nephelometry and Turbidimetry / Q000379:methods; D017655:Silicon Compounds / Q000737:chemistry*; D013535:Suspensions; D018508:Water Purification / Q000379:methods
D003029:Coagulants; D005290:Ferric Compounds; D006812:Humic Substances; D017655:Silicon Compounds; D013535:Suspensions; D007616:Kaolin; C024823:ferric sulfate