Factors affecting the leaching of lead from UPVC pipes.
This paper summarizes the results of a series of studies on the various factors that affect the leaching of lead from unplasticized poly(vinyl chloride) (UPVC) pipes. Factors that were studied include temperature, pH and extractants. Results showed that, for a given UPVC pipe, the rate of leaching of lead depended primarily on temperature and the nature of extractants. While the rate of leaching of lead was quite low with distilled water, it was very much enhanced by the presence of low concentration of anions such as Cl(-), HPO inf4 (sup2-) HCO inf3 (sup-) , NO inf3 (sup-) , SO inf4 (sup2-) and EDTA. EDTA, being a strong complexing agent, was most effective. Rates of leaching were found to be higher at elevated temperature except in the cases of HPO inf4 (sup2-) and EDTA. Effect of pH was not pronounced. The temperature at which the UPVC pipes were extruded was found to affect the rate of leaching of lead. Pipes extruded at 190°C were found to have lower rate of leaching than those extruded at 180°C and 170°C. Analysis of the pipes by Scanning Electron Microscopy showed that the distribution of lead in the pipes extruded at 190°C was more uniform than those extruded at 170°C.
Department of Chemistry, National University of Singapore, Kent Ridge, 0511, Republic of Singapore.
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Koh
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Wong
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Gan
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Yap