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  • 1. Bayat, N.
    et al.
    Lopes, V. R.
    Sanchez-Dominguez, M.
    Lakshmanan, Ramnath
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Rajarao, Gunaratna Kuttuva
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Cristobal, S.
    Assessment of functionalized iron oxide nanoparticles in vitro: introduction to integrated nanoimpact index2015In: Environmental Science: Nano, ISSN 2051-8153, Vol. 2, no 4, p. 380-394Article in journal (Refereed)
    Abstract [en]

    Functionalization of super paramagnetic iron oxide NPs (SPIONs) with different coatings renders them with unique physicochemical properties that allow them to be used in a broad range of applications such as drug targeting and water purification. However, it is required to fill the gap between the promises of any new functionalized SPIONs and the effects of these coatings on the NPs safety. Nanotoxicology is offering diverse strategies to assess the effect of exposure to SPIONs in a case-by-case manner but an integrated nanoimpact scale has not been developed yet. We have implemented the classical integrated biological response (IBR) into an integrated nanoimpact index (INI) as an early warning scale of nano-impact based on a combination of toxicological end points such as cell proliferation, oxidative stress, apoptosis and genotoxicity. Here, the effect of SPIONs functionalized with tri-sodium citrate (TSC), polyethylenimine (PEI), aminopropyl-triethoxysilane (APTES) and Chitosan (chitosan) were assessed on human keratinocytes and endothelial cells. Our results show that endothelial cells were more sensitive to exposure than keratinocytes and the initial cell culture density modulated the toxicity. PEI-SPIONs had the strongest effects in both cell types while TSC-SPIONS were the most biocompatible. This study emphasizes not only the importance of surface coatings but also the cell type and the initial cell density on the selection of toxicity assays. The INI developed here could offer an initial rationale to choose either modifying SPIONs properties to reduce its nanoimpact or performing a complete risk assessment to define the risk boundaries.

  • 2.
    Lakshmanan, Ramnath
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Application of magnetic nanoparticles and reactive filter materials for wastewater treatment2013Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Lately sewage wastewater treatment processes (WWTP) are facing challenges due to strict regulations in quality of effluent standards and waste production. The reuse of wastewater treatment effluents is rapidly gaining attention as a means of achieving sustainable water supply. Therefore, new methods are required to achieve an efficient WWTP. The foremost emphasis of the present study is to investigate filter materials, synthesis, characterization, and application of magnetic nanoparticles (NPs) for WWTP. Primarily commercially available reactive filter materials such as Polonite and Sorbulite were tested for the effective reduction of contaminants in recirculation batch mode system. Secondly, the magnetic nanoparticles were synthesized using different techniques such as water-in-oil (w/o) microemulsion and co- precipitation methods and testing for their ability to remove contaminants from wastewater. Thirdly, toxicity test of magnetic NPs were performed using human keratinocytes (HaCaT) and endothelial (HMEC-1) cells (Papers I-VII).

    The magnetic iron oxide nanoparticles (MION) synthesized using the co-precipitation method were further functionalized with tri-sodium citrate (TSC), 3-aminopropyl triethoxysilane (APTES), polyethylenimine (PEI) and chitosan. The functionalized MION were further characterized prior to use in removal of contaminants from wastewater. The sewage wastewater samples were collected from Hammarby Sjöstadsverk, Sweden and analyses were performed for the reduction of turbidity, color, total nitrogen, total organic carbon, phosphate and microbial content on the retrieval day.

    The experimental results imply that Polonite and Sorbulite require high pH for the efficient reduction of phosphate and the reduction of microbes. Microemulsion prepared magnetic nanoparticles (ME-MION) showed ≈100% removal of phosphate in 20 minutes. Results from TEM implied that the size of magnetic Nps were around 8 nm for core (uncoated MION), TSC (11.5 nm), APTES (20 nm), PEI (11.8 nm) and chitosan (15 nm). Optimization studies using central composite face centered (CCF) design showed the potential of magnetic nanoparticles for the removal of turbidity (≈83%) and total nitrogen (≈33%) in 60 minutes. The sludge water content was reduced significantly by ≈87% when magnetic NPs were used whilst compared to the chemical precipitant used in WWTP. PEI coated MION showed ≈50% removal of total organic carbon from wastewater in 60 minutes. Effluents from wastewater treated with magnetic NPs were comparable with effluent from the present WWTP. There was no significant change observed in mineral ion concentration before and after treatment with MION. In addition, toxicity results from HMEC-1 and HaCaT cells revealed no formation of reactive oxygen species in the presence of magnetic NPs. Furthermore, laboratory experiments revealed the effectiveness and reusability of magnetic NPs. Thus magnetic NPs are a potential wastewater treatment agent and can be used for effective removal of contaminants, thereby reducing the process time, sludge water content and complex process steps involved in conventional WWTP.

  • 3.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Bayat, Narges
    Stockholm University, Department of Biochemistry and Biophysics.
    R-Lopes, Viviana
    Linköping University, Department of Clinical and Experimental Medicine.
    Cristobal, Susana
    Linköping University, Department of Clinical and Experimental Medicine.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Synthesis, characterization and toxicity assessment of magnetic nanoparticles on skin and endothelial cells in vitro: water treatment applicationManuscript (preprint) (Other academic)
  • 4.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Effective water content reduction in sewage wastewater sludge using magnetic nanoparticlesManuscript (preprint) (Other academic)
  • 5.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Effective water content reduction in sewage wastewater sludge using magnetic nanoparticles2014In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 153, p. 333-339Article in journal (Refereed)
    Abstract [en]

    The present work compares the use of three flocculants for sedimentation of sludge and sludge water content from sewage wastewater i.e. magnetic iron oxide nanoparticles (MION), ferrous sulfate (chemical) and Moringa crude extract (protein). Sludge water content, wet/dry weight, turbidity and color were performed for, time kinetics and large-scale experiment. A 30% reduction of the sludge water content was observed when the wastewater was treated with either protein or chemical coagulant. The separation of sludge from wastewater treated with MION was achieved in less than 5. min using an external magnet, resulted in 95% reduction of sludge water content. Furthermore, MION formed denser flocs and more than 80% reduction of microbial content was observed in large volume experiments. The results revealed that MION is efficient in rapid separation of sludge with very low water content, and thus could be a suitable alternative for sludge sedimentation and dewatering in wastewater treatment processes.

  • 6.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Bioprocess Technology (closed 20130101).
    Okoli, Chuka
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology. KTH, School of Biotechnology (BIO), Bioprocess Technology (closed 20130101).
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Bioprocess Technology (closed 20130101).
    Effect of Magnetic Iron Oxide Nanoparticles for Surface Water Treatment: Trace Minerals and MicrobesManuscript (preprint) (Other academic)
  • 7.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Okoli, Chuka
    KTH, School of Biotechnology (BIO), Industrial Biotechnology. KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Effect of magnetic iron oxide nanoparticles in surface water treatment: Trace minerals and microbes2013In: Bioresource Technology, ISSN 0960-8524, E-ISSN 1873-2976, Vol. 129, p. 612-615Article in journal (Refereed)
    Abstract [en]

    The existing water treatment process often uses chemicals, which is of high health and environmental concern. The present study focused on the efficiency of microemulsion prepared magnetic iron oxide nanoparticles (ME-MIONs) and protein-functionalized nanoparticles (MOCP. +. ME-MIONs) in water treatment. Their influence on mineral ions and microorganisms present in the surface water from lake Brunnsviken and örlången, Sweden were investigated. Ion analysis of water samples before and after treatment with nanoparticles was performed. Microbial content was analyzed by colony forming units (CFU/ml). The results impart that ME-MIONs could reduce the water turbidity even in low turbid water samples. Reduction of microbial content (98%) was observed at 37 °C and more than 90% reduction was seen at RT and 30 °C when compared to untreated samples from lake örlången. The investigated surface water treatment method with ME-MIONs was not significantly affecting the mineral ion composition, which implies their potential complement in the existing treatment process.

  • 8.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Okoli, Chuka
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Microemulsion prepared magnetic nanoparticles for phosphate removal: Time efficient studies2014In: Journal of Environmental Chemical Engineering, ISSN 2213-3437, Vol. 2, no 1, p. 185-189Article in journal (Refereed)
    Abstract [en]

    The present study investigates the effective removal of phosphate in sewage wastewater using magnetic iron oxide nanoparticles (MION). The microemulsion-prepared magnetic iron oxide nanoparticles (ME-MION) of around 7-10 nm was synthesized using water-in-oil microemulsion method. The interaction of ME-MION and phosphate was studied using In situ FT-IR technique. Batch experiments were carried out with wastewater to determine the conc. and time efficiency using ME-MION for removal of phosphate. The vibration peak at 1004 cm-1 and the presence of hydroxyl group (OH-) at 3673 cm-1 confirms the binding of phosphate to ME-MION. ME-MION with 0.44 g L-1 exhibited more than 95% phosphate reduction in 5 min and close to 100% in 20 min. Conversely the experimental data obtained has been fitted with Langmuir isotherm model and also exhibited high correlation coefficients. The ME-MION was regenerated and can be reused for minimum 5 consecutive times. Efficient and fast reduction of phosphate was attained while the recovery of nanoparticles was achieved by an external magnetic field. To the author's knowledge, this is the first report that underscores around 100% phosphate removal from wastewater using ME-MION in 20 min. The approach utilized in this study offers a potential technique in the reduction of phosphate in wastewater whilst, reducing the time and reuse of nanoparticles.

  • 9.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Rajaraman, P.
    Okoli, Chuka
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Boutonnet, Magali
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Järås, Sven
    KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Application of magnetic nanoparticles for wastewater treatment using response surface methodology2013In: Technical Proceedings of the 2013 NSTI Nanotechnology Conference and Expo, NSTI-Nanotech 2013: Volume 3, 2013, 2013, p. 690-693Conference paper (Refereed)
    Abstract [en]

    Nanotechnology is considered as one of the key techniques that provide unique materials with high reactivity due to large surface to volume ratio and which could address the fundamental issues in water sector and environment. The present study investigates the efficiency of magnetic iron oxide nanoparticles in wastewater treatment based on Central Composite Face centered (CCF) matrix of response surface methodology for the reduction of turbidity and total nitrogen. The multiple linear regression fit (MLR) obtained for turbidity (r2 0.97) and total nitrogen reduction (r 0.94) supports the future predictions obtaining a significant model. The maximum reduction of turbidity and total nitrogen achieved was 93% and 41% respectively. Other contaminants such as color, total organic carbon, nitrate and microbial content could be reduced. The present study reveals that magnetic property, time and reduction of pollutants by magnetic nanoparticles could impart an efficient treatment process.

  • 10.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Rajaraman, Premanand
    Sri Sairam Engineering College, Department of Physics.
    Okoli, Chuka
    KTH, School of Biotechnology (BIO), Industrial Biotechnology. KTH, School of Chemical Science and Engineering (CHE), Chemical Engineering and Technology, Chemical Technology.
    Boutonnet, Magali
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Järås, Sven
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Application of Magnetic Nanoparticles for the removal of turbidity and total nitrogen from sewage wastewater: Modelling studiesManuscript (preprint) (Other academic)
  • 11.
    Lakshmanan, Ramnath
    et al.
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Sanchez-Dominguez, Margarita
    Centro de Investigacion en Materials Avanzados (CIMAV) S.C., Mexico.
    Matutes-Aquino, Jose
    Centro de Investigacion en Materials Avanzados (CIMAV) S.C., Mexico.
    Wennmalm, Stefan
    KTH, School of Engineering Sciences (SCI), Applied Physics, Experimental Biomolecular Physics. KTH, Centres, Science for Life Laboratory, SciLifeLab.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Removal of total organic carbon from sewage wastewater using poly(ethylenimine)-functionalized magnetic nanoparticles2014In: Langmuir, ISSN 0743-7463, E-ISSN 1520-5827, Vol. 30, no 4, p. 1036-1044Article in journal (Refereed)
    Abstract [en]

    The increased levels of organic carbon in sewage wastewater during recent years impose a great challenge to the existing wastewater treatment process (WWTP). Technological innovations are therefore sought that can reduce the release of organic carbon into lakes and seas. In the present study, magnetic nanoparticles (NPs) were synthesized, functionalized with poly(ethylenimine) (PEI), and characterized using TEM (transmission electron microscopy), X-ray diffraction (XRD), FTIR (Fourier transform infrared spectroscopy), CCS (confocal correlation spectroscopy), SICS (scattering interference correlation spectroscopy), magnetism studies, and thermogravimetric analysis (TGA). The removal of total organic carbon (TOC) and other contaminants using PEI-coated magnetic nanoparticles (PEI-NPs) was tested in wastewater obtained from the Hammarby Sjöstadsverk sewage plant, Sweden. The synthesized NPs were about 12 nm in diameter and showed a homogeneous particle size distribution in dispersion by TEM and CCS analyses, respectively. The magnetization curve reveals superparamagnetic behavior, and the NPs do not reach saturation because of surface anisotropy effects. A 50% reduction in TOC was obtained in 60 min when using 20 mg/L PEI-NPs in 0.5 L of wastewater. Along with TOC, other contaminants such as turbidity (89%), color (86%), total nitrogen (24%), and microbial content (90%) were also removed without significant changes in the mineral ion composition of wastewater. We conclude that the application of PEI-NPs has the potential to reduce the processing time, complexity, sludge production, and use of additional chemicals in the WWTP.

  • 12.
    Nilsson, Charlotte
    et al.
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Lakshmanan, Ramnath
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Renman, Gunno
    KTH, School of Architecture and the Built Environment (ABE), Sustainable development, Environmental science and Engineering, Land and Water Resources Engineering.
    Kuttuva Rajarao, Gunaratna
    KTH, School of Biotechnology (BIO), Industrial Biotechnology.
    Efficacy of reactive mineral-based sorbents for phosphate, bacteria, nitrogen and TOC removal - Column experiment in recirculation batch mode2013In: Water Research, ISSN 0043-1354, E-ISSN 1879-2448, Vol. 47, no 14, p. 5165-5175Article in journal (Refereed)
    Abstract [en]

    Two mineral-based materials (Polonite and Sorbulite) intended for filter wells in on-site wastewater treatment were compared in terms of removal of phosphate (PO4-P), total inorganic nitrogen (TIN), total organic carbon (TOC) and faecal indicator bacteria (Escherichia coli and Enterococci). Using an innovative, recirculating system, septic tank effluent was pumped at a hydraulic loading rate of 3000 L m(2) d(-1) into triplicate bench-scale columns of each material over a 90-day period. The results showed that Polonite performed better with respect to removal of PO4-P, retaining on average 80% compared with 75% in Sorbulite. This difference was attributed to higher CaO content in Polonite and its faster dissolution. Polonite also performed better in terms of removal of bacteria because of its higher pH value. The total average reduction in E. coli was 60% in Polonite and 45% in Sorbulite, while for Enterococci the corresponding value was 56% in Polonite and 34% in Sorbulite. Sorbulite removed TIN more effectively, with a removal rate of 23%, while Polonite removed 11% of TIN, as well as TOC. Organic matter (measured as TOC) was accumulated in the filter materials but was also released periodically. The results showed that Sorbulite could meet the demand in removing phosphate and nitrogen with reduced microbial release from the wastewater treatment process.

  • 13.
    Singh, Lakhvinder
    et al.
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Pavankumar, Asalapuram Ramachandran
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Lakshmanan, Ramnath
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Rajarao, Gunaratna Kuttuva
    KTH, School of Biotechnology (BIO), Environmental Microbiology.
    Effective removal of Cu2+ ions from aqueous medium using alginate as biosorbent2012In: Ecological Engineering: The Journal of Ecotechnology, ISSN 0925-8574, E-ISSN 1872-6992, Vol. 38, no 1, p. 119-124Article in journal (Refereed)
    Abstract [en]

    Removal of heavy metals present in the environment is always of high importance in order to balance ecology with healthy life forms. Biosorption of Cu2+ ions from simulated aqueous medium were studied using calcium alginate beads. Experiments were designed and performed according to Box-Behnken matrix of response surface methodology. The effects of four vital operating variables on the metal-ion sorption characteristics of calcium alginate beads were studied: alginate dosage, initial copper concentrations, pH and agitation time. A high regression coefficient between the variables and response (R-2 = 0.9974) supported excellent evaluation of experimental data by second order polynomial regression model. Maximum removal of Cu2+ ions from aqueous medium was observed at pH 5.5, alginate dosage 2.5% and initial copper concentration of 275 mg l(-1) with an agitation time of 50 min. Thus, the experimental data obtained has been fitted well with Langmuir and Freundlich isotherm models and also exhibited very high correlation coefficients which confirmed suitability of the model and biosorption process. The study revealed that the alginate beads could be used as an ideal material for the removal of Cu2+ ions about 85.3% from aqueous medium and it would be applicable in the process development to treat industrial effluents.

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