ABSTRACT
117 The efficacy of aluminum (hydr) oxide coated pumice (AOCP) for water defluoridation, has been assessed and demonstrated under batch experimental conditions. The aims of the study reported in this chapter were to; (i) investigate the suitability of AOCP under dynamic conditions in laboratory-scale column experiments, which is a more appropriate approach for generating useful information for the design of full scale water treatment systems and, (ii) explore the potential for the regeneration of exhausted AOCP for re-use, as that can contribute to its economic viability. AOCP was capable of reducing model water with fluoride concentration of 5.0 ± 0.2 mg/L to < 1.5 mg/L (WHO guideline), under continuous flow conditions. An empty bed contact time (EBCT) of 24 min wasfound a suitable guide contact time for design purposes, with respect to optimal use of AOCP fluoride adsorption capacity. Using Pearson’s chi-square goodness-of- fit method, the Thomas and Adams-Bohart models were found capable of describing the breakthrough experimental data, and also the bed depth service time (BDST) model, based on the coefficient of determination (R 2 ). In contrast to the regeneration of most adsorbents, it was found that the fluoride adsorption capacity of exhausted AOCP after the first cycle of regeneration was not only fully (100%) restored, but increased by more than 30% (compared to that of fresh AOCP) under batch conditions and more than 50% under continuous flow conditions, suggesting the usefulness of the regeneration concept/approach. This may presumably contribute to the economic viability of AOCP for water defluoridation.
