RESUMEN
A novel mesoporous chitin blended MoO3-Montmorillonite nanocomposite was prepared through three-steps synthesis. First, chitin was extracted from prawn shell then MoO3-MMT was prepared, and lastly, chitin was blended with MoO3-MMT. Chitin-MoO3-MMT was applied for the removal of Cu(II) and Pb(II) from wastewater. XRD characterization revealed MoO3 solubility in MMT interlayers, SEM showed a nanocomposite formation with sharp nanorods like-structure and length ranging from 60 to 77.7 nm. FTIR exhibited fundamental changes in the surface functional groups after adsorption. XPS analysis before and after adsorption showed the domination of chemical bonding with N and O. N2 adsorption-desorption isotherm displayed H3-type hysteresis loop and a pore size diameter of 10.67 nm confirming the mesoporous nature. Adsorption efficiency was studied as a function of pH, time, metal concentration and adsorbent mass. Adsorption capacity (Qe) values were 19.03 and 15.92 mg.g-1 for Cu(II) and Pb(II) respectively. The metal surface coverage mapping was 1.87 × 10^19 and 4.34 × 10^18 atoms/m2 for Cu(II) and Pb(II) respectively. Adsorption followed Langmuir isotherm and pseudo-second-order (PSO) kinetics suggesting a monolayer chemisorption domination. Intraparticle diffusion (IPD) model showed a boundary layer control. Thermodynamically, the adsorption was spontaneous and endothermic with activation energies 25.94 and 29.37 kJ.mol-1 for Cu(II) and Pb(II) respectively.
Asunto(s)
Bentonita/química , Quitina/química , Cobre/química , Plomo/química , Molibdeno/química , Adsorción , Difusión , Concentración de Iones de Hidrógeno , Cinética , Microscopía Electrónica de Rastreo , Nanocompuestos/química , Tamaño de la Partícula , Espectroscopía Infrarroja por Transformada de Fourier , Propiedades de Superficie , Temperatura , Termodinámica , Aguas Residuales/química , Contaminantes Químicos del Agua/química , Purificación del Agua , Difracción de Rayos XRESUMEN
INTRODUCTION: In Egypt, the picture of threats to humans and the environment from the exposure to organic pollutants is still incomplete. Thus the objectives of this study were to assess the occurrence and distribution of polychlorinated biphenyls (PCBs), organochlorine pesticides, and chlorpyrifos in sediments and mussels of Abu Qir Bay and their risks for environment and human health. MATERIALS AND METHODS: Twenty-three different compounds organochlorines were determined in 20 surfacial sediment and 10 mussel samples by gas chromatography-electron capture detector. A Screening Level Ecological Risk Assessment (SLERA) and a Human Health Risk Assessment (HHRA) were performed with the data. RESULTS AND DISCUSSION: ΣDDT (DDT, DDE, DDD) (average concentration 27 µg/kg dw) dominated the detected organic pollutants in the sediments, followed by CHLs (chlordane, heptachlor, heptachloro epoxide), hexachlorocyclohexane, chlorpyrifos, endosulfane, dieldrine, Σ6 PCBs, aldrine, hexachlorobenzene, pentachlorobenzene, methoxychlor, and mirex. In general, concentrations of Σ6 PCBs in mussels were higher than their corresponding sediment concentrations reflecting their relatively high bioavailability and bioaccumulative potential. However, concentrations of the organochlorine pesticides in mussels were lower than their corresponding sediment samples. Nevertheless, the SLERA on the bay sediments revealed that adverse ecological effects to benthic species are expected to occur whereas the HHRA showed that adverse health effects are not expected to occur from the consumption of the mussels. CONCLUSIONS: With the help of a SLERA, it was possible to indicate which class of chlorinated organic compounds is of highest concern to assess and to improve the environmental quality of the bay. Monitoring of organochlorines and chlorpyrifos would be needed to control the future trend of pollution.
Asunto(s)
Bivalvos/química , Sedimentos Geológicos/química , Hidrocarburos Clorados/análisis , Insecticidas/análisis , Mariscos/análisis , Contaminantes Químicos del Agua/análisis , Animales , Clordano/análisis , Clordano/química , Clordano/toxicidad , Cloropirifos/análisis , Cloropirifos/química , Cloropirifos/toxicidad , Cromatografía de Gases , DDT/análogos & derivados , DDT/análisis , DDT/química , DDT/toxicidad , Dieldrín/análisis , Dieldrín/química , Dieldrín/toxicidad , Egipto , Hexaclorociclohexano/análisis , Hexaclorociclohexano/química , Hexaclorociclohexano/toxicidad , Humanos , Hidrocarburos Clorados/química , Hidrocarburos Clorados/toxicidad , Insecticidas/química , Insecticidas/toxicidad , Mar Mediterráneo , Bifenilos Policlorados/análisis , Bifenilos Policlorados/química , Bifenilos Policlorados/toxicidad , Medición de Riesgo/métodos , Contaminantes Químicos del Agua/química , Contaminantes Químicos del Agua/toxicidad , Calidad del AguaRESUMEN
The contamination of sediments and mussels sampled from Abu Qir Bay by polycyclic aromatic hydrocarbons (PAHs) was investigated. Concentrations of PAHs recorded in the bay sediments ranged from less than MDL to 2660 microg/kg dw. In general, concentrations of PAHs in mussels were higher than their corresponding sediment concentrations reflecting their great bioavailability (242-3880 microg/kg dw). The highest concentration was observed in the western part of the bay, a location affected by intensive shipping activities. The distribution pattern of PAHs was similar for mussels and sediments, particularly for sediments characterized by high contamination level, and they were dominated by the high molecular weight PAHs (4-6-rings). Applying different PAHs ratios, it was found that PAHs originated predominantly from the pyrogenic source either from the combustion of grass, wood and coal (majority of the samples) or from petroleum combustion (harbour area). The output of a Screening Level Ecological Risk Assessment (SLERA) on the bay sediments revealed that adverse ecological effects to benthic organisms are expected to occur in only one sample, and thus PAHs are not considered as contaminants of concern in Abu Qir Bay. Also adverse health effects are not expected to occur from the consumption of the investigated mussels with respect to PAHs in Abu Qir Bay.
Asunto(s)
Contaminantes Ambientales/análisis , Actividades Humanas , Hidrocarburos Policíclicos Aromáticos/análisis , Animales , Disponibilidad Biológica , Bivalvos/metabolismo , Ecosistema , Egipto , Salud Ambiental/métodos , Sedimentos Geológicos , Humanos , Mar Mediterráneo , Hidrocarburos Policíclicos Aromáticos/farmacocinética , Medición de RiesgoRESUMEN
In the last three decades, the industrial and human activities in the coastal area of Saudi Arabia have increased dramatically and resulted in the continuous invasion of different types of pollutants including heavy metals. Seven sediment cores were collected from three major industrialized areas; Jeddah, Rabigh and Yanbu, along the coast of Saudi Arabia to determine the spatial and temporal distribution of metals and to assess the magnitude of pollution and their potential biological effects. Sediments were analyzed for texture, calcium carbonate contents, organic matter and metals (Al, Fe, Mn, Cd, Cr, Cu, Ni, Pb and Zn). Some metals like, Cr, Mn, Ni and Zn, were enriched in the upper 15 cm of core samples (recent deposition of sediments). Cadmium concentrations showed high fluctuations with depth and reverse pattern to that for Al, Fe and Mn which indicated land based sources of this element to the studied areas. Elevated concentrations of lead were recorded in the bottom layers of cores in Jeddah that indicated the most dramatic increase in usage of gasoline in early 1970s. The calculated contamination factors (CF's) were found in the following sequences: Cd > Pb > Ni > Cu > Zn > Cr > Mn for all studied areas. Results of Pollution Load Index (PLI) revealed that Jeddah is the most polluted area, followed by Rabigh while Yanbu is the least contaminated area. Except for Ni, the concentrations of most metals in the majority of sediment samples were believed to be safe for living organisms. As no data were available on the concentration of metals in core sediments in the coastal area of Saudi Arabia, the results of this study would serve as a baseline against which future anthropogenic effects can be assessed.