RESUMO
Groundwater samples from eight deep drinking water wells that cover three aquifers in Chihuahua City, northern Mexico, were fully characterized. Water is naturally contaminated with arsenic, fluoride, and uranium, according to the Environmental Protection Agency (EPA) and local standards. The results from the Geochemist's Workbench (GWB) program revealed that the minerals in equilibrium with the groundwater were calcite and dolomite, while others, such as fluoride, schoepite, rutherfordite and K(UO2)(AsO4), were also dissolved. The hydrogeochemical characterization of water samples indicates that they were sodium bicarbonate-type water samples at neutral to slightly alkaline pH (7.6-8.3). A batch equilibrium sorption procedure was implemented using natural groundwater, a synthesized chitosan network (net-CS) and a chitosan binary network grafted with N-vinylcaprolactam/N-N-dimethylacrylamide (net-CS)-g-NVCL/DMAAm hydrogels. Isotherms and kinetics sorption tests were evaluated. The adsorption capacity of net-CS hydrogels for As ions was 0.0022 mg/g and F ions 0.15 mg/g after 50 h. Scanning electron microscopy coupled with energy-dispersive spectroscopy (SEM-EDS) was used to investigate the hydrogel surface before and after the sorption process, and TGA was used to evaluate the stability of the adsorbents. Freundlich adsorption isotherm constants for As and F ions indicate heterogeneous sorption and the mechanism of retention by physisorption.
Assuntos
Arsênio , Quitosana , Água Subterrânea , Poluentes Químicos da Água , Adsorção , Arsênio/análise , Fluoretos , Hidrogéis , Concentração de Íons de Hidrogênio , Cinética , México , Poluentes Químicos da Água/análiseRESUMO
Management of municipal solid waste (MSW) has become a significant environmental problem, especially in fast-growing cities. The amount of waste generated increases each year and this makes it difficult to create solutions which due to the increase in waste generation year after year and having to identify a solution that will have minimum impact on the environment. To determine the most sustainable waste management strategy for Chihuahua, it is first necessary to identify the nature and composition of the city's urban waste. The MSW composition varied considerably depending on many factors, the time of year is one of them. Therefore, as part of our attempt to implement an integral waste management system in the city of Chihuahua, we conducted a study of the characteristics of MSW composition for the different seasons. This paper analyzes and compares the findings of the study of the characterization and the generation of solid waste from households at three different socio-economic levels in the city over three periods (April and August, 2006 and January, 2007). The average weight of waste generated in Chihuahua, taking into account all three seasons, was 0.592 kg capita(-1) day(-1). Our results show that the lowest income groups generated the least amount of waste. We also found that less waste was generated during the winter season. The breakdown for the composition of the waste shows that organic waste accounts for the largest proportion (45%), followed by paper (17%) and others (16%).
Assuntos
Resíduos/estatística & dados numéricos , México , Estações do Ano , Fatores Socioeconômicos , População UrbanaRESUMO
The characterization of urban solid waste generation is fundamental for adequate decision making in the management strategy of urban solid waste in a city. The objective of this study is to characterize the waste generated in the households of Chihuahua city, and to compare the results obtained in areas of the city with three different socioeconomic levels. In order to identify the different socioeconomic trends in waste generation and characterization, 560 samples of solid waste were collected during 1 week from 80 households in Chihuahua and were hand sorted and classified into 15 weighted fractions. The average waste generation in Chihuahua calculated in this study was 0.676 kg per capita per day in April 2006. The main fractions were: organic (48%), paper (16%) and plastic (12%). Results show an increased waste generation associated with the socioeconomic level. The characterization in amount and composition of urban waste is the first step needed for the successful implementation of an integral waste management system.