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Removal Behavior of Cobalt from Aqueous Solutions by a Sodium-Modified Zeolitic Tuff Texto completo
2015
Solache-Ríos, M. | Olguín, M. T. | Martínez-Miranda, V. | Ramírez-García, J. | Zárate-Montoya, N.
The sorption behavior of cobalt by a sodium-modified zeolite-rich tuff was investigated using cobalt solutions prepared with water from the cooling system of a nuclear reactor. The sorption kinetics shows that the equilibrium was reached in less than 20 h. The isotherms showed that the sorption capacity of the sodium-modified zeolite-rich tuff for cobalt was 20.73 mg/g at 60 °C. The pH affects the sorption capacity of the sodium-modified zeolite-rich tuff for cobalt. The sorption capacity of the sodium-modified zeolite-rich tuff for cobalt was higher using nuclear purity water than water from other aqueous matrices.
Mostrar más [+] Menos [-]Monitoring Simulated Bioflocculation: Application of Micro-Flow Imaging Technology Texto completo
2015
Kollu, Kerim | Örmeci, Banu
Bioflocculation occurs in both engineered and natural systems and plays an important role in several water treatment processes as well as in pathogen transport and survival. In this study, bioflocculation was simulated in the laboratory to allow for well-controlled experiments. Escherichia coli and latex particles of varying sizes (3.2, 11 and 25 μm) were spiked into a buffer solution and were bioflocculated by adding alginate and varying amounts of calcium (0, 5, 10 and 15 mM). The extent of flocculation was determined by the calcium concentration, and the floc structure was modified by varying the particle size. The bioflocculation process was monitored with a dynamic particle analyzer, and the flocs formed were analyzed with respect to size, shape and porosity parameters. Larger flocs were observed to have a more heterogeneous structure with higher variation in shape and porosity compared to smaller flocs. Circularity and porosity parameters were shown to be strongly correlated with the calcium concentration. In addition, ultraviolet (UV) irradiation experiments were performed on flocculated and non-flocculated samples, and the inactivation data were assessed in light of floc characteristics determined with the particle analyzer.
Mostrar más [+] Menos [-]Aluminum Alginate–Montmorillonite Composite Beads for Defluoridation of Water Texto completo
2015
A novel alginate–montmorillonite biopolymer-clay composite bead formulation for water defluoridation was developed in this study. Montmorillonite was dispersed alginate solution, and the mixture was cross-linked in an aqueous solution of aluminum(III). The resulting cross-linked beads were characterized using FTIR, SEM, and mechanical measurements. In order to reveal the defluoridation capacity of the beads, batch adsorption experiments were carried out. Optimum conditions and effect of competing ions were investigated. Experimental data were modeled using several isothermal, kinetic, and thermodynamic models. Maximum Langmuir adsorption capacity was reached as 31.0 mg g⁻¹at 25 °C. It is also found that the adsorption is physical in nature and follows the Elovich kinetic model, and the fluoride removal efficiency is not affected by the presence of most competing anions. The results show that aluminum alginate–montmorillonite composite beads can be used as effective and natural sorbents for fluoride removal from water.
Mostrar más [+] Menos [-]Investigating the Use of Multi-Gaussian Nonlinear Regressions to Separate Collembolan Size Classes for Soil Quality Assessment Texto completo
2015
Marks, Evan A. N. | Molowny-Horas, Roberto | Domene, Xavier
Previous studies with bioindicator organisms have used somatic length distributions, i.e., population structure, to understand the effects of management, environment, or a potential contaminant on populations. We describe a statistical approach to separate somatic length classes of Folsomia candida juveniles as an endpoint for the assessment of changes in population structure. Reproduction-survival bioassays were carried out with five different biochars applied at increasing concentrations. Multi-Gaussian models parameterized juvenile size class cohorts, and the biomass of each size class cohort was estimated. Population structure was modified by both material type as well as concentration. Both biomass and population structure were sensitive to effects not reflected in juvenile number, the classic endpoint. Treatments with more size classes and larger individuals were taken to represent favorable conditions, and less size classes and smaller individuals indicated less favorable conditions. This extension of the standardized test provided additional information about the demography of the population.
Mostrar más [+] Menos [-]Copper Speciation in Soil: Time Evolution and Effect of Clay Amendment Texto completo
2015
Montenegro, Andrea C. | Ferreyroa, Gisele V. | Parolo, María E. | Tudino, Mabel B. | Lavado, Raúl S. | Molina, Fernando V.
Copper Speciation in Soil: Time Evolution and Effect of Clay Amendment Texto completo
2015
Montenegro, Andrea C. | Ferreyroa, Gisele V. | Parolo, María E. | Tudino, Mabel B. | Lavado, Raúl S. | Molina, Fernando V.
Copper bioavailability, specially to plants, is strongly dependent on its chemical form, as for most metals. Copper-contaminated soil can be treated in situ by the addition of minerals such as Na-bentonite, which mixed with surface soil, can transform this pollutant to non-bioavailable forms. In this work, shelter experiments were conducted to study the time evolution of Cu speciation, in pristine soil as well as in amended one. A selective sequential extraction method was employed to determine the metal speciation in the samples. The results show that the major metal fraction is the organic matter-bound one, whereas the exchangeable fraction is very low, even the first day after Cu addition. The time evolution shows a slow decrease of the organic-bound Cu and a corresponding increase of the most stable mineral fractions. With the addition of Na-bentonite to copper-contaminated soil, the most stable mineral fractions increase whereas the organic-bound one decreases, showing essentially similar time dependence of the several metal fractions. Sodium bentonite could be effectively used for remediation of soils polluted with Cu.
Mostrar más [+] Menos [-]Copper Speciation in Soil: Time Evolution and Effect of Clay Amendment Texto completo
2015
Montenegro, Andrea Constanza | Ferreyroa, Gisele Veronica | Parolo, Maria Eugenia | Tudino, Mabel Beatriz | Lavado, Raul Silvio | Molina, Fernando Víctor
Copper bioavailability, specially to plants, is strongly dependent on its chemical form, as for most metals. Copper-contaminated soil can be treated in situ by the addition of minerals such as Na-bentonite, which mixed with surface soil, can transform this pollutant to non-bioavailable forms. In this work, shelter experiments were conducted to study the time evolution of Cu speciation, in pristine soil as well as in amended one. A selective sequential extraction method was employed to determine the metal speciation in the samples. The results show that the major metal fraction is the organic matter-bound one, whereas the exchangeable fraction is very low, even the first day after Cu addition. The time evolution shows a slow decrease of the organic-bound Cu and a corresponding increase of the most stable mineral fractions. With the addition of Na-bentonite to copper-contaminated soil, the most stable mineral fractions increase whereas the organic-bound one decreases, showing essentially similar time dependence of the several metal fractions. Sodium bentonite could be effectively used for remediation of soils polluted with Cu. | Fil: Montenegro, Andrea Constanza. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; Argentina | Fil: Ferreyroa, Gisele Veronica. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina | Fil: Parolo, Maria Eugenia. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Patagonia Norte. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energias Alternativas. Universidad Nacional del Comahue. Instituto de Investigación y Desarrollo en Ingeniería de Procesos, Biotecnología y Energias Alternativas; Argentina | Fil: Tudino, Mabel Beatriz. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina | Fil: Lavado, Raul Silvio. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Parque Centenario. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales. Universidad de Buenos Aires. Facultad de Agronomía. Instituto de Investigaciones en Biociencias Agrícolas y Ambientales; Argentina | Fil: Molina, Fernando Víctor. Consejo Nacional de Investigaciones Científicas y Técnicas. Oficina de Coordinación Administrativa Ciudad Universitaria. Instituto de Química, Física de los Materiales, Medioambiente y Energía. Universidad de Buenos Aires. Facultad de Ciencias Exactas y Naturales. Instituto de Química, Física de los Materiales, Medioambiente y Energía; Argentina
Mostrar más [+] Menos [-]Biological Removal of Different Concentrations of Ibuprofen and Methylparaben in a Sequencing Batch Reactor (SBR) Texto completo
2015
Londoño, Yudy Andrea | Peñuela, Gustavo A
This study evaluated the behavior of a sequencing batch reactor (SBR) at laboratory-scale in removing the emerging contaminants, ibuprofen (IBP) and methylparaben (MPB), at different concentrations. Individual experiments were carried out for each pollutant and they were divided into six stages of operation, which included starting, load variation, and interim periods of system stabilization. The treated wastewater was synthetic, and it included the pollutions MPB or IBP, glucose as a co-substrate, macronutrients, and micronutrients. The inoculum used to start the reactor was an aerobic sludge from an SBR system used in the treatment of domestic wastewater, which presented with high-content organic material and featured good sedimentation characteristics. The removal percentages of the two compounds at concentrations of 300, 500, and 1000 μg/L were not similar. For MPB, high removal percentages (>96 %) were obtained, while for IBP, decreasing removal percentages were found with increases in analyte concentration, exhibiting average values of 51 ± 15.3, 26 ± 16.6, and 16 ± 5.4 %. Following the removal of IBP, this behavior showed pronounced effects in biomass inhibition during exposure to high concentrations of the pollutant.
Mostrar más [+] Menos [-]Nitrogen-Regulated Interactions Between Microcystis aeruginosa and Spiramycin Contaminant Texto completo
2015
Liu, Ying | Chen, Shi | Zhang, Jian | Gao, Baoyu
Nitrogen significantly regulated (p < 0.05) the effects of spiramycin on the growth and antioxidant responses of Microcystis aeruginosa as well as the biodegradation of spiramycin by M. aeruginosa during a 7-day exposure test. At a nitrogen level of 0.5 mg L⁻¹, the activities of superoxide dismutase and catalase were stimulated by 100–400 ng L⁻¹of spiramycin to protect algal cells from oxidative damage, resulting in alleviated toxicity of spiramycin and low malondialdehyde content in M. aeruginosa. The catalase activity was inhibited by 400 ng L⁻¹of spiramycin at higher nitrogen levels of 5–50 mg L⁻¹, leading to significant growth inhibition (p < 0.05) and higher malondialdehyde content through accumulation of hydrogen peroxide. Stimulated glutathione content and glutathione S-transferase activity were coupled to the biodegradation of spiramycin in M. aeruginosa. The 7-day biodegradation percentage of spiramycin varied from 8.9 to 29.6 %, which was enhanced by increased nitrogen concentration and decreased spiramycin concentration. Due to the regulation of algal growth, the toxicity of M. aeruginosa were significantly enhanced (p < 0.05) by 100 ng L⁻¹of spiramycin at a nitrogen concentration of 0.5 mg L⁻¹while significantly reduced (p < 0.05) by 400 ng L⁻¹of spiramycin at nitrogen levels of 5–50 mg L⁻¹, according to the luminescent bacteria test. Low concentration of coexisting spiramycin contaminant should be considered during the control of M. aeruginosa bloom, especially under nitrogen deficient condition.
Mostrar más [+] Menos [-]Enhanced Antibacterial Activity of Silver-Coated Kapok Fibers Through Dopamine Functionalization Texto completo
2015
Wang, Runkai | Shin, Chul ho | Park, Siho | Cui, Longzhe | Kim, Daeik | Pak, Chun-sŏk | Ryu, Moonhee
As a biopolymer-modified building block, a poly-dopamine layer can be utilized with a wide range of inorganic and organic materials for an adsorptive and microbial remediation. In this study, dopamine (DOPA) was used as a structural platform to bind silver onto the surface of kapok fibers, and a composite of surface-modified kapok fibers coated with DOPA along with silver were successfully manufactured. After a silver-coating process, a very strong antibacterial property was exhibited against Staphylococcus aureus with a high antibacterial efficiency, over 99 %, which could last for 48 h in peptone water. Enumeration determination was carried out in a spread plate method. For a comparative study, the antibacterial activity of raw kapok fibers and chemically enhanced kapok fibers with DOPA and silver was also evaluated. The results indicated that the chemically enhanced kapok fibers were very useful in controlling a microbial activity on a surface environment.
Mostrar más [+] Menos [-]Simultaneous Adsorption of Pb(Ii)-Cd(Ii), Pb(Ii)-Phenol, and Cd(Ii)-Phenol by Activated Carbon Cloth in Aqueous Solution Texto completo
2015
Arcibar-Orozco, Javier A. | Rangel-Mendez, Jose R. | Diaz-Flores, Paola E.
The aim of the present work was to determine the effect of the simultaneous adsorption of lead(II)-cadmium(II), lead(II)-phenol, and cadmium(II)-phenol by activated carbon cloths (ACCs). Three commercial ACCs were characterized and tested for individual metal adsorption, and competitive adsorption experiments were carried out with the best ACC (AW1104). The specific surface areas of all ACCs were >1000 m²/g, yet only AW1104 presented a high content of acidic sites (1.0 meq/g). Competitive adsorption experiments indicate that cadmium uptake is strongly affected by the presence of lead. This can be attributed either to a more favorable hydroxyl complexation of Pb(II) (that adsorbs strongly),or to the smallest hydrated radius of the Pb(II) molecule (that more easily diffuses). On the contrary, lead uptake was not considerably decreased in the presence of an equimolar cadmium concentration, indicating that AW1104 is more selective for Pb(II) than for Cd(II). Also, the presence of phenol causes a decrease in the heavy metal adsorption capacity, especially for cadmium (40 %). The former might be due to adsorbed phenol, which creates steric hindrance for cations to adsorb on specific oxygenated groups on the ACC. On the other hand, when heavy metals adsorb on the ACC surface, they stabilize the repulsive forces on the surface of the ACC for phenol adsorption, resulting in an increase of the adsorption capacity.
Mostrar más [+] Menos [-]Ecotoxicological Effects of an Arsenic Remediation Method on Three Freshwater Organisms—Lemna disperma, Chlorella sp. CE-35 and Ceriodaphnia cf. dubia Texto completo
2015
Rahman, M Azizur | Hogan, Donald | Duncan, Elliott | Doyle, Christopher | Rahman, Mohammad Mahmudur | Nguyen, T. V. | Lim, Richard P. | Maher, William | Naidu, R. | Krassoi, Rick | Vigneswaran, S. | Hassler, Christel
Chemical methods have been used for the remediation of arsenic (As)-contaminated water; however, ecological consequences of these methods have not been properly addressed. The present study evaluated the effects of the Fe-oxide-coated sand (IOCS) remediation method on As toxicity to freshwater organisms (Lemna disperma, Chlorella sp. CE-35, and Ceriodaphnia cf. dubia). The As removal efficiency by IOCS decreased substantially with time. The IOCS remediation method was less effective at suppressing the toxicity of Asⱽ than Asᴵᴵᴵ to L. disperma but was highly effective in reducing both the Asᴵᴵᴵ and Asⱽ toxicity to C. cf. dubia. The growth of Chlorella sp. was significantly higher (p < 0.05) in remediated and pre-remediated water than in controls (non-As-contaminated filtered Colo River water) for Asᴵᴵᴵ, while the opposite was observed for Asⱽ, indicating that Asⱽ is more toxic than Asᴵᴵᴵ to this microalga. Although the IOCS can efficiently remove As from contaminated water, residual As and other constituents (e.g. Fe, nitrate) in the remediated water had a significant effect on freshwater organisms.
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