Treatment Of Aluminum Hot-rolled Waste Emulsion By Coagulation-flocculation

Aluminum hot-rolled waste emulsion（AWE）which possessed the properties of high oil content,chemical oxygen demand（COD）and organic pollutants became difficult to treat and demulsify in a traditional way.In this paper,an inorganic flocculant poly-aluminum silicate chloride（PASC）and organic flocculant epichlorohydrin amine cationic polymer（FP-1）made by our laboratory was added.The treatment of aluminum hot-rolled waste emulsion was optimized by dint of employing the response surface method and Box–Behnken design to determine the optimal conditions and achieve complete demulsification.The chemical and physical properties of aluminum hot-rolled waste emulsion were characterized in order to provide the theoretical basis for the conditions and the mechanism of demulsification.The industrial Na₂Si O₃ and Al Cl₃were used as main raw materials to prepare inorganic flocculant PASC by activation and aging.The effects of Al/Si molar ratio,the silicic acid polymerization time and p H of waste emulsion on oil removal efficiency of PASC were determined.The coagulation experiment confirmed that the optimum Al/Si molar ratio was 2:1,the optimum polymerization time of silicic acid was 5 hours,and the optimum p H range of the waste emulsion was 4-7.The organic flocculant FP-1 was prepared by polymerization and acidification using epichlorohydrin,dimethylamineand n-butylamine.The ratios of monomers and crosslinker,polymerization temperature and polymerization time were adjusted to achieve the best demulsification effect.The best reaction conditions:the ratio of epichlorohydrin and dimethylamine was 1.5:1;the amount of n-butylamine was 4%of the total dosage monomers;the polymerization temperature was 70°C;the polymerization time was 5 hours.The response surface method was used to optimize the demulsified conditions of aluminum hot rolled waste emulsion.It is determined that the optimal dosage of PASC and FP-1 was 1.2 g/L-1.8 g/L and 2.0 g/L-2.4 g/L by the concentration experiment of single flocculant.The amounts of PASC and FP-1 including p H were the investigation factors.The oil and COD removal efficiencies were the response values.The three-factor-two-level Box-Behnken test design and the multivariate quadratic regression equation were built to optimize and verify the best demulsification formula.According to the three-dimensional response surface map,the influence of the interaction of the two factors on the oil and COD removal rates can be judged.In addition,the effects of demulsification temperature and time on the flocculation-demulsification were examined and analyzed.The experimental results which were consistent with the polynomial model predictions demonstrated that oil and COD removal efficiencies of 97.1%and 91.5%,could be achieved by dint of utilizing 1.45 g/L PASC,2.22 g/L FP-1 and p H 5.1 at 328 K for 50 min.The optical microscope observation,scanning electron microscopy and zeta potential analysis were used to characterize,compare and analyze the aluminum hot-rolled waste emulsion before and after demulsification.The demulsification mechanism of organic-inorganic flocculant was completely explained and verified.