Adsorptive mitigation of fluoride ions using aluminosilicate adsorbents: A state-of-the-art review

Abstract

Water is a vital resource for life, and its pollution is a great threat. The growth of industrialization and population has increased environmental pollution. Fluorine is popularly known as a double-edged sword, as it is one of the 14 essential elements required in limited amounts, but consumption beyond certain limits can be fatal. Sources of fluoride contamination are natural as well as anthropogenic. According to World Health Organization, water containing more than 1.5 mg of fluoride per liter is unsafe for human consumption. Thus the control of fluoride contamination is highly sought after. Defluoridation of water can be done with various methods, viz., ion exchange, electrocoagulation, adsorption, membrane separation, and precipitation. Out of these, adsorption is considered the most encouraging because of its low operational cost, manageable operating conditions, high adsorption capacity, and low cost of adsorbent synthesis. This review focuses on defluoridation applications with three major classes of aluminosilicate adsorbents, viz., zeolite, geopolymer, and clay. The review also discusses new synthesis strategies and characterization techniques to understand the morphology and suitability of the adsorbents towards defluoridation applications. At last, a brief overview of the effects of the associated operating parameters, viz., adsorbent dosage, operation temperature, solution pH, time of adsorption, and adsorption temperature, is also provided.

Keywords

• Fluoride adsorption
• Aluminosilicate adsorbent
• Zeolite
• Geopolymers
• Clay
• Review