Adsorption of Fluoride from Aqueous Solution and Groundwater onto Activated Carbon of Avocado Seeds

In the East African Rift Valley, groundwater is severely polluted with fluoride ion which causes a scarcity of water supplies and public health problems. This study is aimed at investigating the adsorption performance of activated carbon of avocado seeds (ACAS) in fluoride removal from aqueous solution and groundwater. The batch adsorption experiments were carried out by varying the contact time, solution pH, agitation speed, adsorbent dose, and initial fluoride concentration at constant room temperature using the fluoride ion-selective electrode method. Adsorption of fluoride onto ACAS reached its equilibrium condition at the contact time of 60 min under the stirring rate of 200 rpm, pH 6, and ACAS dose 1.9 g/100 mL with an initial fluoride concentration of 5.2 mg/L. Maximum adsorption efficiency was found to be 86%, whereas the fluoride removal from groundwater was 72% under the same experimental condition. The experimental data were well fitted with the Langmuir model with a maximum adsorption capacity of 1.2 mg/g, whereas the kinetic model was well described by a pseudo-second-order model at R-2 0.99. Generally, the research findings showed that activated carbon can be employed as an alternative adsorbent for fluoride remediation from domestic water supplies.