The use of magnetic iron oxide based nanoparticles to improve microalgae harvesting in real wastewater

A novel approach for harvesting Scenedesmus sp. microalgae from real wastewater by using adsorbents of magnetite-based nanoparticles (Fe3O4 NPs) was tested in this study for the first time for this microalgae. Using these NPs, the harvesting efficiency was even higher than 95%. The optimal conditions (0.14 gNPs/L, a short magnetic separation time of only 8 min and 27 min of contact time) were found using the response surface methodology. The best fitting of the adsorption equilibrium results was achieved by the Langmuir isotherm model, and the maximum adsorption capacity for Scenedesmus sp. reached 3.49 g dry cell weight (DCW)/g Fe3O4 NPs. Zeta potential measurements and the Dubinin-Radushkevich isotherm model analysis pointed out that the main adsorption mechanism between Scenedesmus sp. cells and Fe3O4 NPs was electrostatic interaction. Finally, Fe3O4 NPs were six times successfully reused by combining an alkaline treatment with an ultrasonication process, which implies microalgae lysis. The results herein obtained highlight the potential for magnetic separation of microalgae from wastewater, which is capable of reaching a high harvesting efficiency in a very short time.Peer ReviewedPostprint (author's final draft

Adsorption process of fluoride from drinking water with magnetic core-shell Ce-Ti@Fe₃O₄ and Ce-Ti oxide nanoparticles

Synthesized magnetic core-shell Ce-Ti@FFe₃O₄ nanoparticles were tested, as an adsorbent, for fluoride removal and the adsorption studies were optimized. Adsorption capacity was compared with the synthesized Ce-Ti oxide nanoparticles. The adsorption equilibrium for the Ce-Ti@Fe₃O₄ adsorbent was found to occur in <15min and it was demonstrated to be stable and efficient in a wide pH range of 5-11 with high fluoride removal efficiency over 80% of all cases. Furthermore, isotherm data were fitted using Langmuir and Freundlich models, and the adsorption capacities resulted in 44.37 and 91.04mg/g, at pH7, for Ce-Ti oxides and Ce-Ti@Fe₃O₄ nanoparticles, respectively. The physical sorption mechanism was estimated using the Dubinin-Radushkevich model. An anionic exchange process between the OH- group on the surface of the Ce-Ti@Fe₃O₄ nanomaterial and the F- was involved in the adsorption. Moreover, thermodynamic parameters proved the spontaneous process for the adsorption of fluoride on Ce-Ti@Fe₃O₄ nanoparticles. The reusability of the material through magnetic recovery was demonstrated for five cycles of adsorption-desorption. Although the nanoparticles suffer slight structure modifications after their reusability, they keep their adsorption capacity. Likewise, the efficiency of the Ce-Ti@Fe₃O₄ was demonstrated when applied to real water to obtain a residual concentration of F- below the maximum contaminated level, 1.5mg/L (WHO, 2006)

Novel magnetic core-shell Ce-Ti@Fe₃O₄ nanoparticles as adsorbent for water contaminants removal

Magnetic core-shell Ce-Ti@Fe₃O₄ nanoparticles were synthesized by coating cerium titanate on magnetite under mild experimental conditions. Combining magnetism, crystallinity, stability and adsorption capacity, it can be a promising nanomaterial as an adsorbent for anionic water contaminants, exhibiting high removal capacity, from 85% to 100%, for nitrates, phosphates and fluoride

Critical review of existing nanomaterial adsorbents to capture carbon dioxide and methane

Ajuts: Dimitrios Komilis is grateful to the TECNIOspring fellowship programme (TECSPR13-1-0006) which was co-financed by the European Union through the Marie Curie Actions and ACCIÓ (Generalitat de Catalunya)Innovative gas capture technologies with the objective to mitigate CO₂ and CH₄ emissions are discussed in this review. Emphasis is given on the use of nanoparticles (NP) as sorbents of CO₂ and CH₄, which are the two most important global warming gases. The existing NP sorption processes must overcome certain challenges before their implementation to the industrial scale. These are: i) the utilization of the concentrated gas stream generated by the capture and gas purification technologies, ii) the reduction of the effects of impurities on the operating system, iii) the scale up of the relevant materials, and iv) the retrofitting of technologies in existing facilities. Thus, an innovative design of adsorbents could possibly address those issues. Biogas purification and CH₄ storage would become a new motivation for the development of new sorbent materials, such as nanomaterials. This review discusses the current state of the art on the use of novel nanomaterials as adsorbents for CO₂ and CH₄. The review shows that materials based on porous supports that are modified with amine or metals are currently providing the most promising results. The Fe₃O₄-graphene and the MOF-117 based NPs show the greatest CO₂ sorption capacities, due to their high thermal stability and high porosity. Conclusively, one of the main challenges would be to decrease the cost of capture and to scale-up the technologies to minimize large-scale power plant CO₂ emissions

Core-shell Au/CeO2 nanoparticles supported in UiO-66 beads exhibiting full CO conversion at 100 °c

Hybrid core-shell Au/CeO nanoparticles (NPs) dispersed in UiO-66 shaped into microspherical beads are created using the spray-drying continuous-flow method. The combined catalytic properties of nanocrystalline CeO and Au in a single particle and the support and protective function of porous UiO-66 beads make the resulting composites show good performances as catalysts for CO oxidation (T = 72 °C; T = 100 °C) and recyclability

Arsenic removal by magnetite-loaded amino modified nano/microcellulose adsorbents: Effect of functionalization and media size

Comparative adsorption study related to benefits of parent media size, i.e. microfibrillated cellulose (MC) versus nanocellulose (NC) support, for the preparation of magnetite (MG) based high performance adsorbent for arsenic removal was conducted. Precipitation of MG on amino terminal branched organic structure, L, either linked by maleic acid residue on NC surface (NC-MA/L) or linked by oxalyl bridge on MC surface (MC-O/L) produced NC-MA/L-MG and MC-O/L-MG adsorbents, respectively. Precipitation of nanosized MG on amino functionalized NC-MA/L and MC-O/L, performed according to optimized procedure, contributed to improved textural properties and adsorptive/kinetic performances of novel adsorbents. Adsorption capacity of arsenate, As(V), was in favor of NC-MA/L-MG (85.3 versus 18.5 mg g(-1)) while MC-O/L-MG exhibited faster kinetics (0.541 versus 0.189 g mg(-1) min(-1)). Lower capacity of arsenite, As(III), removal, 68.3 mg g(-1) for NC-MA/L-MG and 17.8 mg g(-1) for MC-O/L-MG, were obtained. Calculated activation energies, 13.28 and 10.87 kJ mol(-1) for NC-MA/L-MG and MC-O/L-MG with respect to As(V), respectively, suggest, in accordance with results of Weber-Morris fitting, that internal mass transfer controls adsorption process. Model free adsorption kinetics confirmed beneficial uses of MC-O/L-MG due to low activation energy dependence on the extent of adsorption

Environmental applications of engineered nanomaterials: synthesis and characterization

Aquesta tesi es basa en el desenvolupament (síntesi) de diferents nanomaterials per a la seva aplicació com a materials adsorbents per a l'eliminació de contaminants en aigua (anions inorgànics, metalls pesats i pesticides) i per l'adsorció de gas metà. El desenvolupament dels diferents materials s'ha basat en una extensa recerca bibliogràfica de l'estat de l'art dels materials utilitzats actualment per a aquesta aplicació, i s'ha tractat de millorar l'eficiència del procés mitjançant l'ús de nanomaterials. Amb aquest objectiu s’han sintetitzat materials magnètics per diferents mètodes. En alguns casos, aquests han estat funcionalitzats amb grups orgànics per adaptar i/o millorar la seva funció d'adsorció o estabilitzar-los en suports (polímers, zeolites, esponges, etc.) per millorar la seva aplicació a una escala real en un futur. A més, es va desenvolupar un nou mètode per a la formació de nanopartícules core-shell amb un nucli de magnetita. Tots els nanomaterials sintetitzats s'han caracteritzat en profunditat, utilitzant les tècniques més avançades per a la caracterització dels nanomaterials. Tècniques com ara la microscòpia electrònica, difracció de raigs X, entre d'altres, permeten conèixer les característiques i propietats dels materials (mida, dispersió, estructura cristal·lina, etc.) i per tant concloure la seva contribució a l'eficàcia de cada un dels materials adsorbents. Pel que fa als contaminants en aigua, el treball se centra en el fluorur, el fosfat, el nitrat, els metalls cadmi i níquel i pesticides, destacant l'obtenció de resultats excepcionals per a les nanopartícules de Ce-Ti@Fe3O4. En el cas de tractament de gas, per una banda s'ha desenvolupat un nou nanomaterial basat en nanopartícules magnètiques estabilitzades en esponges de poliuretà que ha presentat resultats interessants per a l'adsorció de metà. A més, s'ha col·laborat amb la Institut Català de Nanotecnologia per a l'aplicabilitat dels Metal Organic Frameworks en l'oxidació de CO. Una altra aplicació que s'ha donat a les nanopartícules magnètiques ha estat la seva utilització en la separació de algues procedents de processos de tractament d’aigües, per tal de substituir el procés actual de decantació. Amb tot això, la tesi ofereix una gamma de nanomaterials per a diferents usos en enginyeria ambiental, amb la possibilitat d'investigar i desenvolupar en la seva aplicabilitat a gran escala. Amb aquesta finalitat, es proporcionen diferents solucions per a la millora del medi ambient.This thesis is based on the development (synthesis) of different nanomaterials for their application as adsorbent materials for the removal of pollutants from water (inorganic anions, heavy metals and pesticides) and for the adsorption of methane gas. The development of the different materials has been based on an extensive bibliographical search of the state of the art of the materials currently used for this application, and it has been tried to improve the efficiency of the process by using nanomaterials. Thus, magnetic (magnetite) nanoparticles are synthesized by different methods. These are functionalized with organic groups to adapt and/or improve their adsorption function or stabilize in supports (polymers, zeolites, sponges, etc.) to improve their application on a real scale. In addition, a new method for the formation of core-shell nanoparticles with a magnetite core is developed. All the synthesized nanomaterials have been characterized in depth, using the most advanced techniques for the characterization of nanomaterials. Techniques such as electron microscopy, X-ray diffraction, among others, allow to know the characteristics and properties of the materials (size, dispersion, crystallinity, structure, etc.) and thus conclude their contribution to the efficiency of their application with adsorbent material. As for the contaminants in water, the work focuses on fluoride, phosphates, nitrates, cadmium, nickel and pesticides, obtaining outstanding results for the nanoparticles of Ce-Ti @Fe3O4. In the case of gas treatment, on the one hand has developed a new nanomaterial based on magnetic nanoparticles stabilized in polyurethane sponges which present interesting results for the adsorption of methane and great applicability on a real scale. In addition, we have collaborated with the Institut Català de Nanotecnologia for the applicability of Metal Organic Frameworks in the oxidation of CO. Another application that has been given to magnetic nanoparticles has been its use to separate algae from wastewater treatment processes, in order to substitute the current sedimentation processes. With all this, the thesis offers a range of nanomaterials for different uses in environmental engineering, with the possibility of investigating and developing on its applicability on a large scale. To this end, different solutions are provided for the improvement of the environment

Environmental applications of engineered nanomaterials : synthesis and characterization /

Aquesta tesi es basa en el desenvolupament (síntesi) de diferents nanomaterials per a la seva aplicació com a materials adsorbents per a l'eliminació de contaminants en aigua (anions inorgànics, metalls pesats i pesticides) i per l'adsorció de gas metà. El desenvolupament dels diferents materials s'ha basat en una extensa recerca bibliogràfica de l'estat de l'art dels materials utilitzats actualment per a aquesta aplicació, i s'ha tractat de millorar l'eficiència del procés mitjançant l'ús de nanomaterials. Amb aquest objectiu s'han sintetitzat materials magnètics per diferents mètodes. En alguns casos, aquests han estat funcionalitzats amb grups orgànics per adaptar i/o millorar la seva funció d'adsorció o estabilitzar-los en suports (polímers, zeolites, esponges, etc.) per millorar la seva aplicació a una escala real en un futur. A més, es va desenvolupar un nou mètode per a la formació de nanopartícules core-shell amb un nucli de magnetita. Tots els nanomaterials sintetitzats s'han caracteritzat en profunditat, utilitzant les tècniques més avançades per a la caracterització dels nanomaterials. Tècniques com ara la microscòpia electrònica, difracció de raigs X, entre d'altres, permeten conèixer les característiques i propietats dels materials (mida, dispersió, estructura cristal·lina, etc.) i per tant concloure la seva contribució a l'eficàcia de cada un dels materials adsorbents. Pel que fa als contaminants en aigua, el treball se centra en el fluorur, el fosfat, el nitrat, els metalls cadmi i níquel i pesticides, destacant l'obtenció de resultats excepcionals per a les nanopartícules de Ce-Ti@Fe3O4. En el cas de tractament de gas, per una banda s'ha desenvolupat un nou nanomaterial basat en nanopartícules magnètiques estabilitzades en esponges de poliuretà que ha presentat resultats interessants per a l'adsorció de metà. A més, s'ha col·laborat amb la Institut Català de Nanotecnologia per a l'aplicabilitat dels Metal Organic Frameworks en l'oxidació de CO. Una altra aplicació que s'ha donat a les nanopartícules magnètiques ha estat la seva utilització en la separació de algues procedents de processos de tractament d'aigües, per tal de substituir el procés actual de decantació. Amb tot això, la tesi ofereix una gamma de nanomaterials per a diferents usos en enginyeria ambiental, amb la possibilitat d'investigar i desenvolupar en la seva aplicabilitat a gran escala. Amb aquesta finalitat, es proporcionen diferents solucions per a la millora del medi ambientThis thesis is based on the development (synthesis) of different nanomaterials for their application as adsorbent materials for the removal of pollutants from water (inorganic anions, heavy metals and pesticides) and for the adsorption of methane gas. The development of the different materials has been based on an extensive bibliographical search of the state of the art of the materials currently used for this application, and it has been tried to improve the efficiency of the process by using nanomaterials. Thus, magnetic (magnetite) nanoparticles are synthesized by different methods. These are functionalized with organic groups to adapt and/or improve their adsorption function or stabilize in supports (polymers, zeolites, sponges, etc.) to improve their application on a real scale. In addition, a new method for the formation of core-shell nanoparticles with a magnetite core is developed. All the synthesized nanomaterials have been characterized in depth, using the most advanced techniques for the characterization of nanomaterials. Techniques such as electron microscopy, X-ray diffraction, among others, allow to know the characteristics and properties of the materials (size, dispersion, crystallinity, structure, etc.) and thus conclude their contribution to the efficiency of their application with adsorbent material. As for the contaminants in water, the work focuses on fluoride, phosphates, nitrates, cadmium, nickel and pesticides, obtaining outstanding results for the nanoparticles of Ce-Ti @Fe3O4. In the case of gas treatment, on the one hand has developed a new nanomaterial based on magnetic nanoparticles stabilized in polyurethane sponges which present interesting results for the adsorption of methane and great applicability on a real scale. In addition, we have collaborated with the Institut Català de Nanotecnologia for the applicability of Metal Organic Frameworks in the oxidation of CO. Another application that has been given to magnetic nanoparticles has been its use to separate algae from wastewater treatment processes, in order to substitute the current sedimentation processes. With all this, the thesis offers a range of nanomaterials for different uses in environmental engineering, with the possibility of investigating and developing on its applicability on a large scale. To this end, different solutions are provided for the improvement of the environment

Conversion of Carbon Dioxide into Methanol Using Cu-Zn Nanostructured Materials as Catalysts

Nowadays, there is a growing awareness of the great environmental impact caused by the enormous amounts of carbon dioxide emitted. Several alternatives exist to solve this problem, and one of them is the hydrogenation of carbon dioxide into methanol by using nanomaterials as catalysts. The aim of this alternative is to produce a value-added chemical, such as methanol, which is a cheaply available feedstock. The development of improved materials for this conversion reaction and a deeper study of the existing ones are important for obtaining higher efficiencies in terms of yield, conversion, and methanol selectivity, in addition to allowing milder reaction conditions in terms of pressure and temperature. In this work, the performance of copper, zinc, and zinc oxide nanoparticles in supported and unsupported bimetallic systems is evaluated in order to establish a comparison among the different materials according to their efficiency. For that, a packed bed reactor operating with a continuous gas flow is used. The obtained results indicate that the use of bimetallic systems combined with porous supports, such as zeolite and activated carbon, is beneficial, thus improving the performance of unsupported materials by four times