Pre-deposition layers for alleviating ultrafiltration membrane fouling by organic matter: Role of hexagonally and cubically ordered mesoporous carbons

Abstract

In this study, ordered mesoporous carbons (OMCs), i.e., CMK-3 and CMK-8 were pre-deposited on ultrafiltration membrane surface to alleviate membrane fouling by organic matter in the water. CMK-3 shows a typical 2D hexagonal symmetrical structure with long straight parallel channels, while CMK-8 exhibits a 3D porous structure with cubic channels. The pre-deposited CMK-3/CMK-8 layers exhibited significantly superior performance for both flux enhancement and fouling mitigation, whereas powdered activated carbon (PAC) showed limited influence. The fouling mechanism was apparently altered by the OMCs pre-deposition layers, and pore blocking always dominated throughout the filtration process without the formation of cake filtration. In comparison with PAC, CMK-3 and CMK-8 were more effective for the rejection of tryptophan-like protein substances, which were the major foulants causing membrane fouling. The effects of pollutant fraction and deposited amount (i.e., 6, 12, 25 and 50 g/m2) were systematically explored, and the results indicated that this technology was more efficient for alleviating the fouling induced by humic acid and bovine serum albumin, whereas ineffective for sodium alginate fouling, and the optimal deposited amount varied with the pollutant fraction. CMK-3 exhibited significantly superior performance than CMK-8, likely due to its long straight parallel channels with lower internal resistance for pollutants adsorption. Both adsorption and size exclusion of the pre-deposited layers contributed to fouling mitigation. These results demonstrate that pre-depositing with OMCs as alternatives to conventional PAC shows promising potential for mitigating membrane fouling in water treatment.