Water Defluoridation by Mexican Heulandite–clinoptilolite

Abstract

Fluorosis is caused by excess ingestion of fluoride. In this work, a natural Mexican zeolite (heulandite -clinoptilolite from Sonora) was evaluated for the sorption of fluoride ions from aqueous solutions and well-water. The effects of sodium, calcium, lanthanum, and europium in the crystalline network of this aluminosilicate, as well as, the effects of pH and particle size of the zeolite on the fluoride sorption were determined. It was found by x-ray diffraction, electronic microscopy, and IR that the structure of the material does not change after the retention of fluoride ions, and fluoride retention is not substantially affected by the cations (Na, Ca, La, and Eu) in the zeolite, the initial pH, or the particle size of the material studied. The K d values obtained from the zeolitic mineral treated with La and Eu are slightly different 3109 from those obtained from both the untreated zeolitic mineral and the material treated with Na and Ca.

Identification of selective ion-exchange resin for fluoride sorption

“…Comparison of these micrographs before and after fluoride sorption shows that there is no significant change in the morphology of the surface of the resins, as the concentrations of fluoride for the experimental study were very low. Similar results were observed by DiazNava et al [41]. …”

Adsorption equilibrium and kinetics of fluoride on sol–gel-derived activated alumina adsorbents

“…The city is located in northern Mexico, a region that has fluoride concentrations higher than the National and EPA's standards [2]. Analysis indicated that the groundwater has an average fluoride concentration of 6.95 mg/L.…”

“…Excessive fluoride in groundwater is also found in many regions worldwide. Many groundwater wells in the North-central part of Mexico contain fluoride in concentrations higher than 6 mg/L [2]. The maximum contaminant level (MCL) in drinking water in USA is 4.0 mg/L according to the drinking water standards set by the US Environmental Protection Agency, and the maximum acceptable concentration of fluoride in drinking water established by the World Health Organization is 1.5 mg/L.…”

Optimizing adsorption of fluoride from water by modified banana peel dust using response surface modelling approach

“…Many natural adsorbent materials were tried in the past to find out efficient and economically viable defluoridating agents such as activated alumina (Ghorai and Pant 2005), alumina-gibbsite (Mariappan et al 2003), activated carbon (Karthikeyan and Ilango 2007), calcite (Turner et al 2010), clay (Coetzee et al 2003), zeolite (Díaz-Nava et al 2007), activated charcoal (Daifullah et al 2007), bleaching earth (Mahramanlioglu et al 2002), red mud (Tor et al 2009), brick powder (Yadav et al 2006), sugarcane charcoal , waste tea ash (Mondal et al 2012a) and rice husk ash (Mondal et al 2012b).…”