Effective removal of heavy metals from water by apatitic tricalcium phosphate subjected to different thermal treatments


In this study, tricalcium phosphate was prepared through a fast precipitation route at room temperature and then subjected to heat treatments within the temperature range of 100 degrees C-900 degrees C. Based on Fourier-transform infrared spectroscopy and X-ray diffraction studies, the powders heated below 600 degrees C were assigned to apatitic tricalcium phosphate (TCPa) whereas the calcination at 900 degrees C led to beta-tricalcium phosphate (beta-TCP) formation. The dried and calcined powders were tested as sorbents for cadmium in an aqueous medium. Their depolluting performance just slightly decreased with raising calcination temperature due to concomitant reductions in specific surface area (S-BET) and total volume of pores (V-p). Accordingly, the dried sample (TCPa100) was selected to study the adsorption of relevant pollutant Cd2+ ions found in wastewaters. The adsorption capacity qe was found to be 450 mg g(-1) at 25 degrees C, and increased to 493 mg g(-1) by the rise in temperature to 45 degrees C, indicating the endothermic nature of the adsorption process. In addition, the adsorption equilibrium was better described by the Freundlich model (R-2 = 0.9823), followed by Dubinin-Kaganer-Radushkevich (R-2 = 0.9739) and Langmuir model (R-2 = 0.9357). The morphological changes induced from this interaction were highlighted by scanning electron microscopy and transmission electron microscopy observations. Furthermore, the TCPa100 removal efficiency of aqueous heavy metals such as lead (Pb2+), copper (Cu2+) and zinc (Zn2+) from contaminated waters was evinced for single and multi-component pollution systems.




Engineering, Chemical; Water Resources


Jebri, S; Ferreira, JMD; Khattech, I

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