Fluoride Adsorption onto Acid-Treated Diatomaceous Mineral from Kenya

Abstract

Acid treated diatomaceous earth (ATDE) from a mining site in Kenya was evaluated for its removal of F from aqueous solutions using adsorption batch experiments. The effect of initial F concentration, adsorbent dosage, contact time, temperature, pH and competing anions was studied. The adsorption process was very fast reaching an initial equilib- rium in just 10 min. Fluoride adsorption onto ATDE increased strongly from just about 40% to over 92% when the solution temperature was raised from 293 to 303 K. The process was however, almost unresponsive to pH changes drop- ping by a margin of < 1% from 98.8% to 98% when the solution pH was raised from 1.59 to 6.89. It was obvious therefore that increase in concentration of OH<sup>-</sup> ions does not affect F adsorption onto ATDE. More so apart from the Cl<sup>-</sup> ions which marginally reduced F adsorption onto ATDE, there was no obvious effect of the SO<sub>4</sub><sup>2-</sup> , NO<sub>3</sub><sup>-</sup> and PO<sub>4</sub><sup>3-</sup> ions on F uptake by ATDE. Complete F removal (100% adsorption) could be achieved at 400 mg/L initial F concentra- tions using 0.5 g/mL ATDE batch loading ratio at 303 - 313 K and pH = 3.4 ± 0.2. The F adsorption iso- therm was well correlated to the Freundlich and Langmuir models and could be classified as H-Type according to Giles classification of isotherms. The maximum Langmuir F adsorption capacity of ATDE was 51.1 mg/g. It has been demonstrated that a diatomaceous mineral from Kenya could be use as an inexpensive adsorbent for the removal of F ions from aqueous streams

Synthesis and performance evaluation of Al/Fe oxide coated diatomaceous earth in groundwater defluoridation: Towards fluorosis mitigation

“…The percent fluoride removal decreased with increasing initial fluoride concentration. [20,21] This could have been because the mass of adsorbent was constant while there was an increase in the initial concentration of adsorbate. There would therefore be an increase in the equilibrium concentration of unadsorbed fluoride.…”

Carbon-Based Materials for De-Fluoridation of Water: Current Status and Challenges

“…More than 260 million people around the world is affecting by the excess fluoride concentration in groundwater [1]. Only in India, more than 60 million people are at risk of developing fluorosis from fluoride contaminated drinking water [2,3]. Water is the primary major source of fluoride in daily intake by human beings.…”

Removal of Fluoride from Aqueous Solutions by Adsorption Using a Siliceous Mineral of a Kenyan Origin

“…To verify the performance of M1 for practical applications in defluoridation of water, up-flow column adsorption experiments were conducted in Pyrex TM columns using high F water samples containing about 5-90 mg/L F from natural sources in Elementaita-Gilgil Area, Nakuru County, Kenya [33]. The fluoride adsorption data from the column experiments were then analyzed using the Thomas model [58] in the form:…”

“…The effect of adsorption parameters including: time of contact, batch adsorbent loading, competing ions, pH, and temperature on F adsorption onto M1 was evaluated and equilibrium isotherms used to determine the adsorption capacity and to elucidate the mechanism for F adsorption. The batch adsorption results were then verified for practical application on high fluoride water from a natural source from Elementaita-Gilgil, Nakuru County, Kenya, using column experiments [33].…”