Membrane fouling reduction through electrochemically regulating flocs aggregation in an electro-coagulation membrane reactor

Coupling coagulation and applied electric field is an efficient method to regulate cake layer porosity and hydrophilicity for alleviating ultrafiltration membrane(UF) fouling. However,the Al/Fe flocs aggregation behavior are induced from electric field and determine the cake layer structure, which has not been studied comparatively yet. Herein, the anti-fouling performance in an efficient electro-coagulation membrane reactor(ECMR, in which UF membrane modules are placed between electrodes) was investigated with Al/Fe anode and various electrochemical parameters from the viewpoint of regulating flocs aggregation.Both the cake layers formed from Al and Fe flocs under an electric field were more porous and hydrophilic in comparison with that formed without electric fields, resulting in an enhanced water flux under higher electric field strength. Comparing with Fe flocs, Al flocs had a faster growth rate and larger size, facilitating membrane pore block resistant, which was more pronounced in a higher current density. Furthermore, the cake layer formed from Al flocs was more porous than that formed from Fe flocs. Therefore, the anti-fouling performance of ECMR with Al anode was superior to that of ECMR with Fe anode. When the electric field strength increased from 0 to 10 V/cm, the normalized specific flux was improved from 71.2% to 89.4% for ECMR(Al) and from 48.1% to 70.1% for ECMR(Fe) at 30 min.

Demulsification performance and mechanism of oil droplets by electrocoagulation: Role of surfactant

Surfactants are widely used to improve the solubility of oil in water in petrochemical,making it more difficult to remove oil–water emulsions during the water treatment process.Electrocoagulation(EC) is an appropriate method for treating oily wastewater and destabilizing emulsions. However, the demulsification mechanism of oil–water droplets emulsified by surfactants with different charges have not been investigated systematically. The demulsification performance of electrocoagulation on emulsions wastewater containing cationic,non-ionic, and anionic surfactants was studied. The results showed that the removal rate of total organic carbon(TOC) in oily wastewater with anionic surfactant by EC reached92.98% ± 0.40% at a current density of 1 mA/cm^(2), while that of the non-ionic surfactant was 84.88% ± 0.63%. The characterization of flocs showed that EC has the highest coagulation and demulsification of oil droplets with a negative charge on the surface(-70.50 ± 10.25mV), which indicated that the charge neutralization of oil droplets was beneficial for the destabilization of the formed oily flocs. However, when the zeta potential of the oil droplets reached 75.50 ± 1.25 mV, the TOC removal efficiency was only 11.80% ± 1.43%. The TOC removal could achieve 33.23% ± 3.21% when the current density improved from 1 mA/cm^(2)to 10 mA/cm^(2). The enhanced removal was due to the sweep coagulation rather than charge neutralization. This study provides a fundamental basis for the electrochemical treatment of oily wastewater.