Natural contamination of world groundwater supplies with arsenic of volcanic origin has become a complicated and growing problem given current shortage of water. Maintenance cost of treatments that are based on ion ex...Natural contamination of world groundwater supplies with arsenic of volcanic origin has become a complicated and growing problem given current shortage of water. Maintenance cost of treatments that are based on ion exchange and reverse osmosis is considered high, in addition to the high production of sludge with such methods. On the other hand, efficiency of treatments employing coagulation/filtration is usually relative, depending on the method of application. Currently, emerging treatments that use nanotechnology are gaining relevance, due to their high efficiency and low cost. These methods are highly selective, with minimum generation of toxic wastes, as long as particle release into the environment is kept under control to avoid health risks. The present study developed filters with magnetic nanoparticles of Fe<sub>3</sub>O<sub>4</sub> (magnetite) supported on porous silica (Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>) at a mass ratio of 2:1. The nanoparticles were synthetized by co-precipitation of Fe(II) and Fe(III) using NH<sub>4</sub>OH<sub>(ac)</sub> under inert atmosphere. Average sizes of 15 nm were obtained, measured by means of Transmission Electronic Microscopy (TEM) and characterized by X-ray Powder Diffraction (XRD);the magnetic power was qualitatively determined. The efficiency of the composite material (Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>) was determined in a prototype laboratory with a height of 60 cm and a diameter of 5 cm, assembled with five filters of the composite material, with 1 g each filter. The filters were wrapped in resistant water-porous fabric to favor continuous flow at a ratio of 0.015 L/min. The test was performed with arsenic solutions at (43.7 ± 2.1 μg/L), similar to the amount present in water supplies currently treated in Costa Rica. The removal was completed in 7 minutes with 0 N.T.U and less than 10 μg/L arsenic concentration (maximum limit allowed in Costa Rica), quantified by Atomic Absorption Spectrometry with Hydride Generation. After the reaction filters, the prototype was assembled with cleaning filters at a ratio of 1:8. The final way out was through a magnetized tube to ensure that no nanoparticles were released outside with the water, thus contributing to nanotoxicology safety for people and the environment.展开更多
Helicobacter pylori (H. pylori) is bacteria considered to be present in half of the population and it is a public health problem worldwide. Most patients infected with H. pylori show no clinical symptoms;nonetheless, ...Helicobacter pylori (H. pylori) is bacteria considered to be present in half of the population and it is a public health problem worldwide. Most patients infected with H. pylori show no clinical symptoms;nonetheless, approximately 10% to 20% of these patients will develop peptic ulcers and 1% will develop gastric cancer. The International Agency for Research on Cancer has classified H. pylori as a Group 1 carcinogen, recognized as the only bacteria capable of producing cancer. Samples of drinking water (n = 44) from aqueducts with chlorination treatment in selected areas with high prevalence of gastric cancer were analyzed in Costa Rica. Samples of drinking water from Panamá (n = 44) from aqueducts supplying untreated water for human consumption in the province of Chiriquí were also analyzed. The molecular marker of H. pylori, glmM, was used, and to optimize the Real Time PCR (qPCR) technique, annealing temperature, concentration of primers and probe were standardized;also, by analyzing different standard curves, the best reaction conditions that allowed detecting and quantifying the gene were determined. The LightCycler® 480 II (LC480II) equipment from Roche Diagnostics GmbH was used, as well as the Absolute Quantification Analysis by means of the Second Derivative Maximum Method. In the case of the samples from Costa Rica, it was determined that 79.5% were positive for H. pylori;removing outlier high average, quantification of bacteria was determined in 3.6 × 103 copies/100 mL. For Panamá it was determined that 86% of the samples were found positive for the presence of H. pylori;removing outlier high average quantification of bacteria was determined at 3.3 × 102 copies/100 mL. The difference in values between the aqueducts in both countries revealed an environmental distribution of the bacteria of epidemiological interest in each case.展开更多
文摘Natural contamination of world groundwater supplies with arsenic of volcanic origin has become a complicated and growing problem given current shortage of water. Maintenance cost of treatments that are based on ion exchange and reverse osmosis is considered high, in addition to the high production of sludge with such methods. On the other hand, efficiency of treatments employing coagulation/filtration is usually relative, depending on the method of application. Currently, emerging treatments that use nanotechnology are gaining relevance, due to their high efficiency and low cost. These methods are highly selective, with minimum generation of toxic wastes, as long as particle release into the environment is kept under control to avoid health risks. The present study developed filters with magnetic nanoparticles of Fe<sub>3</sub>O<sub>4</sub> (magnetite) supported on porous silica (Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>) at a mass ratio of 2:1. The nanoparticles were synthetized by co-precipitation of Fe(II) and Fe(III) using NH<sub>4</sub>OH<sub>(ac)</sub> under inert atmosphere. Average sizes of 15 nm were obtained, measured by means of Transmission Electronic Microscopy (TEM) and characterized by X-ray Powder Diffraction (XRD);the magnetic power was qualitatively determined. The efficiency of the composite material (Fe<sub>3</sub>O<sub>4</sub>@SiO<sub>2</sub>) was determined in a prototype laboratory with a height of 60 cm and a diameter of 5 cm, assembled with five filters of the composite material, with 1 g each filter. The filters were wrapped in resistant water-porous fabric to favor continuous flow at a ratio of 0.015 L/min. The test was performed with arsenic solutions at (43.7 ± 2.1 μg/L), similar to the amount present in water supplies currently treated in Costa Rica. The removal was completed in 7 minutes with 0 N.T.U and less than 10 μg/L arsenic concentration (maximum limit allowed in Costa Rica), quantified by Atomic Absorption Spectrometry with Hydride Generation. After the reaction filters, the prototype was assembled with cleaning filters at a ratio of 1:8. The final way out was through a magnetized tube to ensure that no nanoparticles were released outside with the water, thus contributing to nanotoxicology safety for people and the environment.
文摘Helicobacter pylori (H. pylori) is bacteria considered to be present in half of the population and it is a public health problem worldwide. Most patients infected with H. pylori show no clinical symptoms;nonetheless, approximately 10% to 20% of these patients will develop peptic ulcers and 1% will develop gastric cancer. The International Agency for Research on Cancer has classified H. pylori as a Group 1 carcinogen, recognized as the only bacteria capable of producing cancer. Samples of drinking water (n = 44) from aqueducts with chlorination treatment in selected areas with high prevalence of gastric cancer were analyzed in Costa Rica. Samples of drinking water from Panamá (n = 44) from aqueducts supplying untreated water for human consumption in the province of Chiriquí were also analyzed. The molecular marker of H. pylori, glmM, was used, and to optimize the Real Time PCR (qPCR) technique, annealing temperature, concentration of primers and probe were standardized;also, by analyzing different standard curves, the best reaction conditions that allowed detecting and quantifying the gene were determined. The LightCycler® 480 II (LC480II) equipment from Roche Diagnostics GmbH was used, as well as the Absolute Quantification Analysis by means of the Second Derivative Maximum Method. In the case of the samples from Costa Rica, it was determined that 79.5% were positive for H. pylori;removing outlier high average, quantification of bacteria was determined in 3.6 × 103 copies/100 mL. For Panamá it was determined that 86% of the samples were found positive for the presence of H. pylori;removing outlier high average quantification of bacteria was determined at 3.3 × 102 copies/100 mL. The difference in values between the aqueducts in both countries revealed an environmental distribution of the bacteria of epidemiological interest in each case.
