Polishing treatment of molasses wastewater with iron salts: the role of counter-ions.
The effect of counter-ions on the coagulation of biologically treated molasses wastewater using iron-based coagulants was investigated. Parameters such as removals of chemical oxygen demand (COD) and color, and residual turbidity, were measured to evaluate coagulation performance. Experimental results showed that ferric chloride and ferric nitrate were more effective than ferric sulfate at optimal dosages, achieving 89 to 90% and 98 to 99% of COD and color removals, respectively, with residual turbidity of less than 5 NTU. High-performance size exclusion chromatography (HPSEC) results revealed differences in the removal of the molecular weight fraction of organic compounds using iron salts. Scanning electron microscopy (SEM) showed randomly formed coagulated flocs characterized with irregular, sheet-like shapes. Nitrate and chloride counter-ions had similar effects on coagulation performance compared to sulfate. Both FeCl3 and Fe(NO3)3 yielded better results than Fe(SO4)2 under underdosed and optimum dosage conditions. Coagulation efficiency was less adversely affected in the overdosed regions, however, if sulfate rather than chloride or nitrate was present.
Liang
Zhen
Z
MOE Key Laboratory of Biogeology and Environmental Geology, China University of Geosciences, Wuhan, China.
Wang
Yanxin
Y
Zhou
Yu
Y
Liu
Hui
H
Wu
Zhenbin
Z
D019649:Food Industry; D007220:Industrial Waste; D058085:Iron Compounds / Q000737:chemistry*; D008855:Microscopy, Electron, Scanning; D008965:Molasses / Q000032:analysis*; D014865:Waste Disposal, Fluid / Q000379:methods*; D014867:Water / Q000737:chemistry*; D018508:Water Purification / Q000379:methods*
D007220:Industrial Waste; D058085:Iron Compounds; D014867:Water