The effect of surface charge on threshold flux and fouling behavior of silicon carbide membrane with O/W emulsion and sodium alginate solution as typical pollutants

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Abstract

Colloidal fouling has attracted increasing interest in the membrane field. Oil and water (O/W) emulsion droplet and Extracellular polymeric substance (EPS) are significant colloids in produced water and surface water, respectively. Oily wastewater is produced in many industrial processes such as oil and gas extraction processes, and can take a product, a by-product or a waste stream. In this study, silicon carbide (SiC) membranes were employed to separate oil droplets from O/W emulsion. The effect of ionic strength, pH, surfactant concentration on threshold flux of commercially SiC MF using O/W emulsion stabilized by the sodium dodecyl sulfonate (SDS) were investigated. The results indicated that the threshold fluxes, determined by both the TMPavg method and fouling rate method, increased with an increase of SDS concentration, but decreased with the salinity when using commercial SiC MF membrane filtering 400 mg/L O/W emulsions. Besides, a higher threshold flux was observed for emulsions with a higher pH. Moreover, the high absolute value of zeta potential of O/W emulsion could alleviate fouling. In the end, we produced SiC UF membrane by depositing SiC layer on the alumina supports by low pressure vapor deposition (LPCVD) due to its low fabrication cost. We investigated the anti-fouling abilities of pristine Al2O3 UF membrane and SiC-UF membrane by using sodium alginate as foulant (SA) solution in multi-stage experiments. When fouling experiments operated with pure SA solution or SA solution with a low calcium ion concentration, SiC UF membrane has a better anti-fouling ability compared with pristine Al2O3 UF membrane due to a lower reversible and irreversible fouling resistance and a slower increase of TMP.