Removal of Fluoride from Drinking Water by Sorption Using Diatomite Modified with Aluminum Hydroxide

Abstract

Exposure to fluoride beyond the recommended level for longer duration causes both dental and skeletal fluorosis. Thus, the development of cost-effective, locally available, and environmentally benign adsorbents for fluoride removal from contaminated water sources is absolutely required. In the present study, diatomaceous earth (diatomite) locally available in Ethiopia, modified by treating it with an aluminum hydroxide solution, was used as an adsorbent for fluoride removal from aqueous solutions. Adsorption experiments were carried out by using batch contact method. The adsorbent was characterized using FT-IR spectroscopy. Effects of different parameters affecting efficiency of fluoride removal such as adsorbent dose, contact time, initial fluoride concentration, and pH were investigated and optimized. The optimum adsorbent dose, contact time, initial fluoride concentration, and pH values were 25 g/L, 180 min, 10 mg/L, and 6.7, respectively. The performance of the adsorbent was also tested under optimum conditions using groundwater samples taken from Hawassa and Ziway. Langmuir and Freundlich isotherm models were applied to describe the equilibrium data. Compared to Langmuir isotherm (R2 = 0.888), the Freundlich isotherm (R2 = 0.985) model was better fitted to describe the adsorption characteristics of fluoride on Al-diatomite. The Langmuir maximum adsorption capacity was 1.67 mg/g. The pseudosecond-order model was found to be more suitable than the pseudofirst-order to describe the adsorption kinetics. The low correlation coefficient value of R2 = 0.596 for the intraparticle diffusion model indicates that the intraparticle diffusion model does not apply to the present studied adsorption system. The maximum fluoride removal was observed to be 89.4% under the optimum conditions which indicated that aluminum hydroxide-modified diatomite can be used as efficient, cheap, and ecofriendly adsorbents for the removal of fluoride from contaminated water.

Electrocoagulation as a Promising Defluoridation Technology from Water: A Review of State of the Art of Removal Mechanisms and Performance Trends

“…It should be pointed out that any solid analysis did not present in order to support the aforementioned removal mechanisms expressed by Equations ( 14)- (16).…”

“…Incident of crippling fluorosis, thyroid disorder, infertility in women, cancer, and Alzheimer's syndrome Different processes have been evaluated to reduce high fluoride concentrations in water and, consequently, to prevent hazardous health effects. Some examples of examined technologies include adsorption [11][12][13], chemical precipitation using lime or magnesium salts [14,15], co-precipitation and adsorption through coagulation-flocculation with alum [16,17], ion exchange [18,19], electrodialysis [20][21][22], and electrocoagulation [23,24]. Amongst these technologies, electrocoagulation (EC) has emerged in recent decades as a suitable alternative compared to the conventional coagulation process.…”

Bone char from an invasive aquatic species "devilfish" as a sustainable adsorbent for the removal of fluoride in water for human consumption

“…Fluoride pollution of water is a major issue worldwide (Akafu et al 2019;Fan et al 2019;Kumar et al 2019;Medellin-Castillo et al 2020). In drinking water, a fluoride concentration between 0.5 to 1.0 mg L -1 can be considered beneficial to teeth and bones (Abeykoon et al 2020;Medellín-Castillo et al 2020;Quintáns-Fondo et al 2019).…”

“…Various technologies are available for the removal of fluorides, including precipitation, coagulation, reverse osmosis, ion exchange, and adsorption. Of all methods, adsorption is highly effective and economical for the reduction of excess fluoride in water (Abeykoon et al 2020;Akafu et al 2019;Alkurdi et al 2019;Assaoui et al 2020;Emmanuel et al 2018;Fan et al 2019), and it uses a variety of adsorbent materials, including clay, soil, organic matter, alumina, zeolites, nanomaterials, activated carbon and bone char (Alkurdi et al 2019;Teusner et al 2016). Bone chars have been widely considered in fluoride removal and have gained considerable attention due to their cheapness, high availability, easy preparation and high adsorption capacity (Alkurdi et al 2019;Medellin-Castillo et al 2020).…”

Acid Modification of Diatomite-Based Sorbents

“…The raw and modified diatomite was effective for all pollutants, particularly, for inorganic pollutants, such as Fe: 34-68%, Cu about 65%, Pb: 55-80% [13]. In [14], the authors stated that diatomite modified with aluminium hydroxide was found as an efficient adsorbent for defluoridation of liquid and groundwater. The maximal purification of water from fluoride and adsorption capacity was 89% and 1.67 mg/g, respectively.…”