| The massive amounts of untreated oily wastewater produced by industrialization are directly discharged into the environment,causing a severe ecological issue.To address these issues,choosing the appropriate separation material is a highly effective method of separating water from oily wastewater.Polymeric based membraneseparation technologies can be employed as an ideal separation membrane,giving a reliable,efficient,and sustainable solution for oily wastewater separation.Among them,biaxialoriented polypropylene membrane(PP)can replace widely used other conventional membranes due to their high mechanical strength in both machine and transitional directions.Such mechanical stability provides long service life with outstanding reusability.Unfortunately,the PP membrane’s intrinsic hydrophobicity makes it easily clogged by oil droplets during separation,reducing permeability,efficiency,and reusability.To get rid of oil fouling and lessen the toxicity of oily wastewater,several effective surface modification techniques have been studied.Irradiation-induced graft polymerization approaches have been found to be the most successful and effective.This dissertation work aimed to construct a high-performance biaxial PP membrane separation technology using the influence of different monomers on the irradiation-induced graft polymerization method.The first work modified the hydrophobic biaxial PP membrane using electron beam irradiation and subsequent chemical grafting utilizing acrylic acid and polyvinyl alcohol monomers.This simple surface modification approach considerably enhanced wettability and thermal and mechanical properties.Special attention has been given to increasing the anti-fouling phenomena,which can enhance the membrane’s service life during oily wastewater separation areas.The deposition of acrylic acid and polyvinyl alcohol as grafting monomers constructs a micro-nano rough structure to enhance the wettability with an amount of carboxyl and hydroxyl functional groups.The second work developed a robust modified biaxial PP membrane that can withstand high operating pressure.A facile and scalable two-step surface modification method was developed by employing electron beam irradiation and grafting reaction using acrylic acid and sodium hydrogen carbonate monomers.This modification method aims to develop excellent underwater superoleophobicity,which can separate any kind of surfactant-stabilized emulsion with high separation efficiency.During the NaHCO3 reaction process,a unique formation of super hydrophilic-COONa functional groups are covalently attached and evenly distributed on a smooth biaxial PP surface thus creating a multi-scale stable rough surface through the grafting process.Such achieved rough surface assured oil droplets’ aggregation upon contact and permitted straightforward water separation from oil/water emulsion.The robustness of the engineered super-wetting rough surfaces was studied under different harsh environments.The third work focused on developing a super hydrophilic biaxial PP membrane modified via corona discharge treatment,followed by a grafting reaction with hydrophilic acrylamide monomer.Different acrylamide parameters(such as concentration,reaction temperature,and grafting duration)were studied comprehensively to find acceptable conditions for acrylamide monomer grafting reaction to produce surface nanostructures with permanent super hydrophilicity and underwater super oleophobicity.Significant separation performances were achieved for layered mixtures,surfactant-free,and surfactant-stabilized emulsions by the highly energy-saving gravity-driven separation method.The fourth work developed an advanced PP membrane through a highly efficient layer-by-layer modification technique using corona treatment,polyethylene imine and levo3,4 dihydroxyphenylalanine crosslinked multi-layer assembling process.Through this synergistic development of the modification method,advanced antibacterial properties were generated.Modified PP membrane is antibacterial against S.aureus and E.coli bacteria.Notably,this highly efficient modified membrane was designed to remove multi pollutants(oil particles and bacteria)from oily wastewater in a more energy-efficient way.The improved properties of all modified biaxial PP membrane surfaces can anticipate being a substantial and prospective mass-scale industrial application for long-term oily wastewater separation. |
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