Fluoride removal with extra low energy reverse osmosis membranes: three years of large scale field experience in Finland

Coagulation behaviors of aluminum salts towards fluoride: Significance of aluminum speciation and transformation

“…The Al species were analyzed by the ferron colorimetric method [23]. Al a , Al b , and Al c corresponded to monomeric, medium polymer, and large polymer species and/or solid-phase Al(OH) 3 , respectively.…”

“…On the other hand, the hydrolysis of Al salts tends to form a series of Al species with different structures, charges, and polymerization character [14], and the diversity of Al species possibly impacts the interaction between fluoride and different Al species thereafter. PACl as polymeric species of Al salt shows superiority in removing particulate and organics as compared to traditional monomeric Al such as AlCl 3 , and PACl exhibits inherent advantages less independence on pH [15], less alkalinity consumption [16], and less sludge production [17]. However, its superiority in terms of fluoride removal as compared to AlCl 3 and the mechanisms involved in has rarely been investigated.…”

“…Our previous study indicates that the formation of Al-F complexes involves the removal of fluoride by AlCl 3 , and this effect benefits fluoride removal to a large extent as compared to Al (OH) 3 adsorption [7]. The transformation of different fluoride species, i.e., free fluoride, complexed fluoride (Com-F), and adsorbed fluoride, plays a determining role and is highly dependent on solution pH and the ratio of fluoride to Al (R F:Al ) [8,13].…”

“…However, the long-term excessive intake of fluoride via drinking water can lead to the wide occurrence of dental and skeletal fluorosis [2], of which over 500 million people are suffering from fluorosis globally [3]. The removal of fluoride from drinking water has received great attention in the past several decades.…”

“…The removal of fluoride from drinking water has received great attention in the past several decades. Defluoridation can be achieved by different processes such as adsorption [4][5][6], (electro)-coagulation [7][8][9], ion-exchange [10], membrane separation [3], and the Nalgonda process [11]. Among these technologies, coagulation is widely applied due to its simplicity and high efficiency.…”