Abstract
Functional surfaces and polymers with branched structures have a major impact on physicochemical properties and performance of membrane materials. With the aim of greener approach for enhancement of permeation, fouling resistance and detrimental heavy metal ion rejection capacity of polyetherimide membrane, novel grafting of poly (4-styrenesulfonate) brushes on low cost, natural bentonite was carried out via distillation-precipitation polymerisation method and employed as a performance modifier. It has been demonstrated that, modified bentonite clay exhibited significant improvement in the hydrophilicity, porosity, and water uptake capacity with 3 wt. % of additive dosage. SEM and AFM analysis showed the increase in macrovoides and surface roughness with increased additive concentration. Moreover, the inclusion of modified bentonite displayed an increase in permeation rate and high anti-irreversible fouling properties with reversible fouling ratio of 75.6%. The humic acid rejection study revealed that, PEM-3 membrane having rejection efficiency up to 87.6% and foulants can be easily removed by simple hydraulic cleaning. Further, nanocomposite membranes can be significantly employed for the removal of hazardous heavy metal ions with a rejection rate of 80% and its tentative mechanism was discussed. Conspicuously, bentonite clay-bearing poly (4-styrenesulfonate) brushes are having a synergistic effect on physicochemical properties of nanocomposite membrane to enhance the performance in real field applications.
Highlights
Ultrafiltration (UF) has been employed extensively in several membrane filtrations and separation-based technologies, such as the wastewater treatment, chemical and biochemical applications, protein effluent separation, oil-water separation, pollutant rejection etc[1,2]
This study demonstrated that, the addition of bentonite clay can result in the reduction of total membrane fouling[12]
The chemical modification of the bentonite clay was confirmed by taking Fourier transform infrared (FTIR) spectra of both raw bentonite and modified bentonite (Fig. 2)
Summary
Ultrafiltration (UF) has been employed extensively in several membrane filtrations and separation-based technologies, such as the wastewater treatment, chemical and biochemical applications, protein effluent separation, oil-water separation, pollutant rejection etc[1,2]. Without an appropriate treatment process, direct exposure to these carcinogenic by-products can lead to cancers, miscarriages and nervous system complications[6] These examples illustrate that, the presence of heavy metals and humic acid are extremely dangerous, and it is necessary that these substances should be eliminated from water. Naturally available bentonite clays are the new prospective fillers for the polymer composite for water purification applications, which endow with low cost, strong hydrophilicity, net negative charge, facile chemical modification ability and enhances mechanical strength. It is a naturally occurring clay mineral composed of silica tetrahedral sheets and aluminum octahedral sheets. The mechanism of distillation-precipitation polymerization follows the order of radical initiation of monomer or cross-linker and subsequent chain propagation by chain addition, which increases colloidal stability of modified nanoparticles due to high surface charge[17,18]
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