Evaluation of the adsorption behavior and divalent metal ions removal efficiency of ceramic point-of-use water filter materials

Ceramic water filters (CWFs) are point-of-use devices mostly used in developing countries as a result of their effectiveness in the treatment of household water. However, there is a dearth of knowledge on the metal ions adsorption behavior of the filter materials. Therefore, this study investigates the adsorption behavior of the divalent metal ions using commercially available ceramic water filters as adsorbents, in a batch experiment and compared the data, to the extent of metal ion removal during filtration. The ceramic water filters were characterized with x-ray fluorescence spectrometer, x-ray powder diffractometer and fourier-transform infrared spectrophotometer. An adsorption batch experiment was conducted and filtration experiments were performed to determine the extent of divalent metal ions removed. The results of the study showed that divalent metal ions were adsorbed efficiently by ceramic water filters. The pseudo-second-order kinetic model best described the kinetic behavior of metal ion removal process. The extent of adsorption of ceramic water filters was in the range: 7.015-335.77 mgg-1. The adsorption patterns fitted the Freundlich isotherm model while the entropy, enthalpy, and Gibbs free energy, indicate that the processes for all CWF-adsorbents are endothermic, feasible and spontaneous. The kinetic and thermodynamic behavior of CWF-adsorbents indicate that the mechanism of the sorption process is chemisorption. There was a significant difference in the amount of divalent metal ions adsorbed in batch experiments compared to filtration experiments for ceramic water filter materials (Pot filter and candle filter). The metal ions adsorption potentials of ceramic water filters are found to be rate dependent; hence the rate of filtration must be of concern to manufacturers.