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A series of hyperbranched polyethyleneimine (h-PEI) functioned with terminal amine groups is synthesized to remove oil from O/W emulsion. The demulsifier dehydration rate of h-PEI is systematically evaluated with the subsidiary facilities of DLS analysis, digital tensiometer and UV–vis spectrophotometer. The results indicate that h-PEI demulsifier displays satisfactory demulsification (the oil removal rate＞90%) with small dosage (＜80 mg L−1) and short settling time (＜30 min). The relatively short equilibrium time and great demulsification are ascribed to the amine groups and the molecular weight. On one hand, the hyperbranched macromolecules with amine groups can rapidly diffuse and adsorb to the oil-water interface, on the other hand, the molecules with adequate molecular weight are apt to flocculate, coalesce oil droplets, and then obtain high-efficient demulsification. The exceptional demulsification performance of h-PEI exhibits a potential role application in industrial water treatment or the petroleum demulsification industry. • A convenient synthetic process for h-PEI is developed. • Hyperbranched polymer h-PEI is an effective demulsifier for O/W emulsions of microdroplets with 90% of oil removal rate. • The combination of DLS observation and UV–vis analysis provides a new evidence to explore the demulsification mechanism. [ABSTRACT FROM AUTHOR]

The use of an electrocatalytic surface coating is important in environmental remediation using electrochemistry. In this work, a novel Ti/calcined graphene (CG)/PbO 2 sandwich electrode was successfully fabricated by a simple electrodeposition strategy for the efficient electrocatalytic oxidation of dye wastewater. The Ti/CG/PbO 2 electrode coating was uniform and the structure was compact. As the electrocatalyst was rich in graphene, the novel electrode possessed higher oxygen evolution potential, lower charge transfer resistance, stronger stability, longer service life and higher instantaneous current efficiency (ICE) compared with traditional Ti/PbO 2 electrode, thus exhibited better electrocatalytic oxidation activity and mineralization capacity. At a current density of 50 mA/cm2, up to 30 mg/L of methylene blue (MB) was almost completely oxidized in 1 h, while the MB removal efficiency at the Ti/PbO 2 electrode only reached 78.2 ± 0.01%. Various influencing factors were designed to simulate the changes of the wastewater system, importantly and interestingly, the electrode still owned the advantages of high-efficiency electrocatalytic oxidation in the complex changes of a wastewater system like pH range of 3–11 and various electrolyte concentrations. The as-prepared electrode could still maintain good degradation efficiency after 30 cycles. It was worth mentioning that the COD value was reduced to about 0 when using this electrode to deal with the actual printing and dyeing wastewater. The results showed that the Ti/CG/PbO 2 electrode was promising in the degradation of pollutants. Unlabelled Image • A novel sandwich electrode with a 0.231 mm coating and graphene intermediate layer • Successfully fabricated by electrochemical deposition • Maintained excellent electrocatalytic oxidation efficiency • Coped with changes in the water body well • Proposed the degradation mechanism and mechanism analysis of the degradation process [ABSTRACT FROM AUTHOR]