Adsorption studies for the simultaneous removal of arsenic and selenium using naturally prepared adsorbent materials     

L. D. Mafu  T. A. M. Msagati  B. B. Mamba 《International Journal of Environmental Science and Technology》2014,11(6):1723-1732

The adsorption properties of eggshell membranes (ESM), eggshells (ES) and orange peels (OP) were studied for the removal of arsenic (total As) and selenium (total Se). The effect of chemical treatment of these adsorbents by HNO₃ and NaOH was also investigated using Fourier transform infrared spectroscopy (FT-IR). Analysis of the FT-IR spectra showed that treatment with NaOH and HNO₃ had an effect on the functional groups present in the materials and also on the adsorption by extension. Thermal analysis showed that ES were more thermally stable than the others with no water molecules in their matrix, which could have caused a substantial weight loss at around 70 °C. In terms of adsorption capacities, chemical treatment increased the adsorption capacities of ESM and OP achieving up to 170 μg g^?1 (As) and 160 μg g^?1 (Se), and 120 μg g^?1 (As) and 70 μg g^?1 (Se), respectively, with not much activity for ES in terms of adsorption. The two adsorbents (NaOH-treated OP and ESM) were then tested in environmental water samples and the results showed that 68.9 % of As and 74.8 % of Se, and 54.1 % of As and 47.3 % of Se were removed from domestic wastewater samples investigated using OP and ESM, respectively. Moreover, better selectivities towards the compounds of interest were achieved.  相似文献   

Hydrological and geotechnical investigations of mass movements in an equatorial city (Yaoundé, Cameroon)     

Benjamin Ngounou Ngatcha  Georges Emmanuel Ekodeck  Mamba Mpele  Perpétue Espérance Ntana 《Environmental Earth Sciences》2011,62(8):1733-1747

In the present study, mass movements (landslide and mudslide) bound to a gully located at Mendong, a suburb of Yaoundé in Cameroon were examined using hydrological, geotechnical and geomorphological observations. The data indicate that water is an important causative factor of mass movements in the area studied. In fact, the water flow (waste water and runoff) provokes the saturation of materials at the slope foot. These materials lose their mechanical qualities and some deep ruptures generate landslide. During the rainy season, when the cumulative rainfall is more than 200 mm, these landslides are accompanied by mudslides that generate disturbances on the infrastructure situated around the gully and farther downstream. The economic and environmental damages resulting from the Mendong mass movements are considerable, such as degradation of the topography, losses in farm land, transportation and downstream sedimentation in a pond situated at the slope foot, loss of life and damage to the economy. All this calls for a multidisciplinary and integrated approach to hazard assessment and risk mitigation, which included data collection and interpretation, growing public and authority awareness, and preventing or reducing runoff and waste water flows by proper management and drainage.  相似文献