Estimation of membrane fouling and its alleviation with novel biocidal silver coordinated metallosurfactant cleaning solution

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Membrane separation using polymeric membranes has evolved as a potent treatment technology for handling ubiquitous emulsified oily waste streams to prevent inadmissible water pollution. Nonetheless, this technology suffers from major bottlenecks i.e. oil fouling and biofouling, which significantly limit its widespread application. Hence, to make this membrane treatment technology sustainable, fouling mitigation is of paramount importance. Henceforth, the scope of the present study is of two-folds. The primary focus is to theoretically investigate the nature of oil fouling with two different polymeric membranes, polyethersulfone (PES) and polysulfone (PSf) during the emulsified feedstock treatment through conventional fouling model. Secondly, for mitigation of fouling, the study elaborates on the formulation and characterization of a novel membrane cleaning agent by coordinating silver into conventional surfactant sodium dodecyl sulfate (SDS). It was observed that the overall fouling propensity of the PSf membrane was 8% higher than that of the PES membrane, which was validated by the model fitting with the cake layer and standard-pore blocking fouling models discussed in the study. However, a higher tendency of the irreversible standard pore-blocking was exhibited by the PES membrane. To alleviate such intrinsic fouling, conventional membrane cleaning agents like sodium hydroxide, sodium hypochlorite, and SDS showed inefficiency by portraying very low permeate flux recovery. However, the prepared silver induced metallocomplex (AgS2) at a very low concentration (0.7 mM) was found with remarkable cleaning potential along with high resistance to biofilm development, showing around 100% and 97% flux recovery for both PES and PSf membrane, respectively. Further, it was also observed that after cleaning with AgS2, cleaned membranes exhibited minimal fouling and bio-fouling propensity for consecutive 9 and 6 cycles of continuous operation, respectively on account of the self-cleaning and anti-biofouling property of metallosurfactant. The profit to cost ratio for AgS2 metallosurfactant (PCAgS2) is found as 3.23, which is almost two times higher than the profit to cost ratio for conventional SDS cleaning (PCSDS = 1.63). Such high fold increase in the profit to cost ratio with AgS2 attributes to an economic operational cost compared to conventional SDS cleaning. Henceforth, it was significantly noted that with the formulated novel metallosurfactant AgS2, one can reduce the washing cycle during membrane operation and subsequently increase the membrane longevity by controlling the irreversible fouling/ biofouling. This will eventually reduce both the process cost of the oily wastewater treatment and membrane replacement cost.