Faculty Publications
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Publications by NITK Faculty
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Item Contact Angle Measurements(Elsevier Inc., 2017) Hebbar, R.S.; Isloor, A.M.; A.F., A.F.Contact angle has been an important parameter to determine the wetting ability of the polymer membrane surface. Contact angle has gained interest in surface science in regards to its fundamental aspects and application point of view. This chapter will give an insight into fundamentals of contact angle including the theoretical backgrounds, brief history, and importance of contact angle. The various factors that affect the contact angle measurement will also be discussed. The chapter will also present contact angle hysteresis phenomena, comprising of advancing and receding contact angles along with the manifestations of contact angle hysteresis. The chapter will highlight the various methods and techniques available for the measurement of contact angle along with the comprehensive description of the methods. The chapter also covers the application contact angle on surface characterization, permeation, and antifouling nature of the membrane. © 2017 Elsevier B.V. All rights reserved.Item Carbon nanotube- and graphene-based advanced membrane materials for desalination(Springer Verlag, 2017) Hebbar, R.S.; Isloor, A.M.; Siddique, I.; Asiri, A.M.The development of membrane-based desalination and water purification technologies offers new alternatives to meet the global freshwater demand. Rapid advancement in carbon nanotube-based and graphene-based nanomaterials has drawn the attention of scientific investigators on various desalination technologies. These nanomaterials indeed offer advantageous structure, size, shape, porosity and mass transport behavior for membrane separation process. This article reviews theoretical and experimental investigations of carbon nanotube- and graphene-based composite materials for desalination. Special attention is given to the simulation of molecular transport through these materials. Further, recent advances in the application of functionalization of carbon nanotube- and graphene-based materials for salt rejection and hydraulic permeation properties are discussed. © 2017, Springer International Publishing AG.Item Preparation and evaluation of heavy metal rejection properties of polyetherimide/porous activated bentonite clay nanocomposite membrane(Royal Society of Chemistry, 2014) Hebbar, R.S.; Isloor, A.M.; A.F., A.F.The acid activated bentonite clay ranging from 1.0 to 4.0 wt% was incorporated into polyetherimide membranes and was extensively studied for its morphology, porosity, membrane hydraulic resistance and hydrophilic properties. The nanocomposite membrane has shown an increment in porosity, hydrophilicity and a reduction in hydraulic resistance. Elemental mapping studies confirmed the intercalation of activated bentonite clay within the polymer matrix. Studies have been conducted to analyse the permeate flux and rejection of Cu(ii), Ni(ii) and Cd(ii) ions by varying the pH and initial feed concentration. The results revealed that membranes with higher clay dosage showed enhanced flux and rejection, whereas lower rejection was observed in the case of lower pH and higher initial feed concentrations. It has also been demonstrated that the affinity of metal ions to form the hydration sphere and the adsorption capacity towards bentonite clay plays a vital role in the effective removal of metal ions. The membrane showed good rejection of heavy metal ions without any external chelating agent. The membranes showed maximum rejection of 69.3%, 76.2% and 82.5% for 250 ppm of Cd(ii), Ni(ii) and Cu(ii) ion solutions, respectively. The low level of heavy metal concentration in the permeate indicates that good quality water could be reclaimed for further reuse. This journal is © the Partner Organisations 2014.Item Preparation of antifouling polyetherimide/hydrolysed PIAM blend nanofiltration membranes for salt rejection applications(Royal Society of Chemistry, 2014) Hebbar, R.S.; Isloor, A.M.; A.F., A.F.Nanofiltration (NF) membranes are continually sought for their unique physical and chemical properties, which allow filtration of electrolytes, dyes and other substances. In continuation of our efforts to prepare NF membranes, flat sheet polyetherimide/hydrolysed poly(isobutylene-alt-maleic anhydride) (PIAM) blend membranes have been prepared. The main aim was to explore the effect of addition of PIAM on morphological features and permeation properties of the membranes. The presence of dicarboxlic acid functionality leads to an enhancement in the hydrophilicity and antifouling properties. The results revealed that increasing the content of hydrolysed PIAMdecreases the pore size of the membranes and subsequently increases the electrolyte rejection. The PEI/hydrolysed PIAM composition (80 : 20) showed reasonably good salt rejection (sodium sulphate of 1000 ppm) of up to 76% with a pure water flux of 11.8 L m-2 h-1 at 0.4 MPa transmembrane pressure. This study provides a simple and effective approach to produce a negatively charged NF membranes for water desalination applications with low energy consumption. © The Royal Society of Chemistry 2014.Item Probing the morphology and anti-organic fouling behaviour of a polyetherimide membrane modified with hydrophilic organic acids as additives(Royal Society of Chemistry, 2015) Hebbar, R.S.; Isloor, A.M.; A.F., A.F.; Shilton, S.J.; AlObaid, A.; Fun, H.-K.A facile approach for the preparation of an organic antifouling polymer membrane has been developed using low molecular weight organic acids as additives. The presence of these additives in the membrane was analysed by FTIR spectroscopy. The properties of the modified membranes were investigated in terms of contact angle, water uptake capacity, SEM and AFM analysis. These additives exerted a strong impact on the rheological properties of the casting solution, thereby altering the membrane morphology, surface roughness, water flux and the hydrophilicity of the membranes, as compared to those of the pristine polyetherimide (PEI) membrane. The organic antifouling properties of the modified membrane were analysed by filtering both bovine serum albumin (BSA) and humic acid solutions. The results showed that the additives exhibited a remarkable improvement in the antifouling properties (FRR of 72%) and a humic acid rejection of up to 86%. These outcomes offer new insights into the use of cheaper and readily available organic acids as additives, compared to the traditional, synthetic polymer materials as additives in membrane preparation. ©2015 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Item Fabrication of polydopamine functionalized halloysite nanotube/polyetherimide membranes for heavy metal removal(Royal Society of Chemistry, 2016) Hebbar, R.S.; Isloor, A.M.; Kulal, K.; A.F., A.F.Polydopamine modified halloysite nanotubes (HNTs) were synthesised through a one step facile procedure and employed as a well dispersed hydrophilic additive to enhance the filtration properties of polyetherimide (PEI) membranes. The nanocomposite membranes were prepared by an immersion precipitation method with different amounts of modified HNTs (MHNTs) in the casting solution. The good dispersion of MHNTs throughout the membrane matrix was confirmed by elemental mapping analysis. The prepared nanocomposite membranes were extensively studied in terms of their porosity, morphology, membrane hydraulic resistance and hydrophilicity. The permeation experiments showed that the modified membranes exhibited higher water flux than a pristine PEI membrane. The antifouling and anti-biofouling behaviour of the modified membranes was investigated in detail. The results revealed that a membrane with a 3 wt% MHNT dosage showed a higher Fouling Resistance Ratio (FRR) of 74.5% with reversible membrane fouling of 64.3%. Moreover, the membrane showed excellent resistance to microbial growth on the membrane surface. The well performing membrane was subjected to heavy metal ion rejection. Results indicated that membranes had the capacity to adsorb Pb2+ and Cd2+. Overall, PEI-MHNTs nanocomposite membranes could have great potential to improve antifouling, anti-biofouling and filtration properties. © The Royal Society of Chemistry 2016.Item Fabrication of a novel hollow fiber membrane decorated with functionalized Fe2O3 nanoparticles: Towards sustainable water treatment and biofouling control(Royal Society of Chemistry, 2017) Hebbar, R.S.; Isloor, A.M.; Kulal, K.; Abdullah, M.S.; A.F., A.F.The development of sustainable, surface-functionalized hollow fiber membranes with advanced nanomaterials has enabled the tailoring and targeted control of their physicochemical properties. This provides the material with improved features of hydrophilicity and permeability, excellent selectivity, and superior antifouling and antimicrobial activity. We explored a new strategy using well dispersed functionalized Fe2O3 nanoparticles to fabricate a polyetherimide nanocomposite hollow fiber membrane with enhanced surface and anti-biofouling properties. To confirm the membrane modification, a series of characterizations such as contact angle, surface energy, water uptake capacity, porosity, zeta potential, and morphological analysis were performed. The permeation experiment indicated superior hydrodynamic permeability and antifouling properties with more than 95% rejection of BSA protein molecules after inclusion of a 1.5 wt% additive dosage. Moreover, the nanocomposite membrane exhibited a relatively higher normalized flux and rejection up to 94% during the filtration of hazardous natural organic matter (NOM) with differing parameters such as the feed solution pH and ionic strength. The presence of modified Fe2O3 nanoparticles in the membrane significantly inhibits the growth of bacteria and other microorganisms on the membrane surface, resulting in an enhanced anti-biofouling property. In particular, the demonstrated method illustrates a fast, facile strategy for the functionalization of Fe2O3 nanoparticles to improve the membrane properties and anti-biofouling activity, giving them great potential for effective and sustainable water treatment applications. © 2017 The Royal Society of Chemistry and the Centre National de la Recherche Scientifique.Item Improvement in performance of polysulfone membranes through the incorporation of chitosan-(3-phenyl-1h-pyrazole-4-carbaldehyde)(Cogent OA info@CogentOA.com, 2017) Balakrishna Prabhu, K.; Saidutta, M.B.; Isloor, A.M.; Hebbar, R.S.Pure polysulfone membranes are known to exhibit poor permeability, and high fouling. This study was conducted to explore the possibility of improving the permeation characteristics of polysulfone membranes by using a chitosan derivative as an additive. Polysulfone membranes blended with chitosan derivative 3-phenyl-1H-pyrazole-4-carbaldehyde (ChD) were prepared by the method of wet coagulation. The hydroxyl, amine and the imine functional groups present in the ChD evidently increased the hydrophilicity of the surface of the blended membranes which was confirmed by contact angle measurements. The contact angle of the blended membrane having 2 wt.% ChD was 62 ± 1 as compared to 70 ± 1 of neat polysulfone membrane. The SEM analysis of the blended membranes revealed a highly porous structure with a very thin surface skin layer, finger like projections in the sub-layer with a macro void structure at the base. The blended membranes also showed significant improvement in pure water flux of 351 L m?2 h?1 at 0.8 MPa trans membrane pressure (TMP) as compared to 24 L m?2 h?1 of neat polysulfone membrane at the same TMP. The anti-fouling test using bovine serum albumin exhibited improved anti-fouling characteristic of blended membranes with a maximum flux recovery ratio (FRR) of 57%. The heavy metal rejection study revealed that membrane P-1 showed maximum 36 and 29% rejection for Pb and Cu respectively. © 2017 The Author(s). This open access article is distributed under a Creative Commons Attribution (CC-BY) 4.0 license.Item Efficient treatment of hazardous reactive dye effluents through antifouling polyetherimide hollow fiber membrane embedded with functionalized halloysite nanotubes(Taiwan Institute of Chemical Engineers, 2017) Hebbar, R.S.; Isloor, A.M.; Zulhairun, A.K.; Sohaimi Abdullah, M.; A.F., A.F.A simple, efficient and scalable approach was developed for the fabrication of highly fouling resistance nanocomposite hollow fiber membranes with the aim of effective removal of environmentally detrimental reactive dyes. The naturally occurring halloysite nanotubes were functionalized via facile self-polymerization of m-aminophenol in mild acidic condition and employed as a hydrophilic additive. The chemical modification was confirmed by FTIR, TEM and energy dispersed X-ray (EDX) analysis. The hybrid nanocomposite membrane was prepared by dry–wet spin technique with different additive dosage. The resultant membrane was characterized in terms of contact angle, surface energy, porosity, zeta potential, elemental mapping and morphology. The permeation experiments illustrated superior water flux of 104.9 Lm?1 h?1 and 9.6% of irreversible fouling with more than 90.3% of flux recovery by the simple hydraulic cleaning. Most importantly, prepared membrane was subjected for hazardous reactive dye removal application with different experimental parameters. The hybrid membrane with 2 wt. % of additive concentration showed more than 97% and 94% for the Reactive Red 102 and Reactive Black 5 dyes respectively. This approach may also be very useful in developing high flux, fouling resistant ultrafiltration hollow fiber membranes for the other similar type applications such as hemodialysis membranes. © 2017 Taiwan Institute of Chemical EngineersItem Removal of metal ions and humic acids through polyetherimide membrane with grafted bentonite clay(Nature Publishing Group Houndmills Basingstoke, Hampshire RG21 6XS, 2018) Hebbar, R.S.; Isloor, A.M.; Balakrishna Prabhu, B.; Siddique, I.; Asiri, A.M.; A.F., A.F.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. © 2018 The Author(s).