The Potential of Minjingu Phosphate Rock for Water Defluoridation

Abstract

In some parts of Tanzania, fluoride ion concentrations in potable water are higher than recommended by WHO. Consequently, searches for economically and technically viable strategies are required to address this problem. This work aims to determine the potential of phosphate rock mined from Minjingu area in Northern Tanzania as water de-fluoridatant. The results obtained are reported herein. The rock particles were chemically activated and then characterised by XRF, XRD and nitrogen physisorption. Results showed that the main component of chemically activated rock particles was calcium hydroxyapatite with Ca/P ratio of 1.55 whereas the main component of non-activated particles was calcium fluoroapatite (Ca/P ratio of 1.66). The results also indicated that activated rock material was mesoporous with a BET surface area of 57.4 m2/g. Results for water defluoridation showed that the material had a fluoride ion percentage removal of about 90%, when the adsorbent dose was 8 g, contact time of 30 minutes, initial fluoride ion concentration 5 mg/L, pH values of 6.0 to 7.2 and batch volume of 50 mL. The material could be regenerated using 1% NaOH and reused in the water defluoridation process. Therefore, Minjingu Phosphate Rock (MPR) is potential water de-fluoridatant.