In this study, the thermal degradation and pyrolysis of hospital plastic waste consisting of polyethylene (PE), polystyrene (PS), and polypropylene (PP) were investigated using TG-GC/MS. The identified molecules with the functional groups of alkanes, alkenes, alkynes, alcohols, aromatics, phenols, CO and CO2 were found in the gas stream from pyrolysis and oxidation, and are chemical structures with derivatives of aromatic rings. They are mainly related to the degradation of PS hospital waste, and the alkanes and alkenes groups originate mainly from PP and PE-based medical waste. The pyrolysis of this hospital waste did not show the presence of derivatives of polychlorinated dibenzo-p-dioxins and polychlorinated dibenzofurans, which is an advantage over classical incineration methodologies. CO, CO2, phenol, acetic acid and benzoic acid concentrations were higher in the gases from the oxidative degradation than in those generated in the pyrolysis with helium. In this article, we propose different pathways of reaction mechanisms that allow us to explain the presence of molecules with other functional groups, such as alkanes, alkenes, carboxylic acids, alcohols, aromatics and permanent gases.
Coagulation processes are widely used for water treatment, mainly with chemical coagulants. In this research, starch derived from a residue (plantain peel, Musa paradisiaca) was used as a starting point for a chemical modification. Through acetylation, its chemical structure was modified and characterized by Infrared Spectrophotometry, for its evaluation as a coadjuvant in coagulation operations to reduce the turbidity of raw water. Two experimental designs were developed to evaluate the incidence of modified starch as the main coagulant or in conjunction with a conventional coagulant (Al2(SO4)3), at different Al2(SO4)3 / acetylated starch ratios, in jar-test experiments. In the first experimental design, with the acetylated starch as the main coagulant, turbidity removal percentages reached 47.93% (average value, 41.18%). For the Al2(SO4)3 / acetylated starch coagulation process, 98.91% turbidity removal was reached in the second experimental design (average value, 97.16%). The incidence on turbidity in a jar-test of starch chemical substitution degree and the Al2(SO4)3 / Acetylated starch ratio was investigated using ANOVA analysis. There was a great incidence of the chemical substitution degree and the concentration of acetylated starch used, when modified starch was used as the main coagulant. For the second experimental design, the Al2(SO4)3 / Acetylated starch relationship had a greater incidence on the turbidity removal. Thus, modified starch obtained from plantain peel waste is a promising coadjuvant material for water coagulation processes.
A spatial characterization was undertaken to demonstrate the presence of hexavalent chromium (Cr (VI)) in surface waters (maximum depth of 0.5 m) in the Ciénaga de las Quintas mangrove swamp, located in the city of Cartagena de Indias, Colombia. This characterization was geostatistical in nature, an approach that is little used in such studies, although it offers two‐dimensional profiles of the concentration of relevant contaminants (hexavalent chromium in this case) with concentrations between 3 and 9.2 μg/L. Sampling was carried out systematically on a square grid with a cell size of one ha (100 m × 100 m). To corroborate the relationship between the sample positions and concentrations, the Euclidean distance matrices of each variable were calculated previous step for conducting the Mantel test, which indicated a positive correlation between the distance and concentration of hexavalent chromium (R = 0,1674: p value = 0.1275). The Moran Index was also calculated for Cr (VI). The experimental semivariogram (γ)was also calculated and fit to the exponential theoretical model, with a correlation coefficient of 99.4%. Using this analytical model of variance, predictions of Cr (VI) concentrations were made for unsampled locations, using the Kriging method with a new mesh side of only 10 m. This approach indicated the new mesh points exhibiting the higher concentrations coincided with locations in the swamp that receiving sewage effluents from the Bazurto public grocery market and the Chinatown neighbourhood. The Cr (VI) contamination was of anthropogenic origin because its concentration displays a gradient from the zone of human activities to the Cartagena de Indias bay.
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