Heavy metals are well recognized as potential health hazards as they can neither be degraded nor biologically detoxified. Discharge of heavy metals such as Chromium, copper, cadmium, lead, … etc. in wastewater can be toxic to aquatic life and render natural waters as they become unsuitable for human consumption due to their tendency to accumulate in living organisms. Chromium compounds present at high concentrations in wastewater discharged from industrial sites such as tanneries can be lethal to marine species. This paper focuses the light on the potential use of cement kiln dust (CKD) collected from Al-Mergheb Portland Cement Factory at Al-Khoms, Libya, as an adsorbent to remove chromium [Cr (III)] from tanning wastewater, collected from two local tanneries, under kinetic and equilibrium conditions. Adsorption capacity of CKD is evaluated according to different adsorbent doses and temperatures of the tested wastewater samples. Two samples of 2336 and 4320 mg/l of Cr (III) initial concentrations were investigated by batch process. Collected data were tested against three mathematical models, Simple first order model, Lagergren's model and Ritchie's model. Though the preliminary testing was achieved at ambient temperature, the effect of temperature on adsorption capacity was conducted experimentally as the best fit model was identified and presented as a relationship between temperature and equilibrium rate constant.
The study concludes that CKD is an effective adsorbent to remove Cr (III) from tannery wastewater and the percentage removal of Cr(III) depends on the adsorbent dose, such that optimum removal of Cr (III) occurs at ambient temperature, 1200 rpm agitation rate, 60 min. contact time and a pH value of 0.5. Ritchie's kinetic model offers the best fit of the kinetic behavior of the system. A linear relationship between the equilibrium rate constant of Ritchie's model and the system temperature suggests that the adsorption process is controlled by an endothermic reaction; however, an efficient Cr (III) removal can be achieved at ambient temperature.
The present study reveals a feasible practical use of Portland Cement Kiln Dust as a low cost adsorbent to remove Cr(III) from wastewater.
تاريخ النشر
09/03/2009
الناشر
the 11th International Conference on Environmental Science and Technology (CEST2009)Chania, Crete, Greece
علي يوسف عكاشة | Aly Y. Okasha | 9474