Suspension Sorbents for Removal of Arsenic Compounds and Humates From Water

Abstract

This paper is devoted to the features of the synthesis and applications of suspension iron(III)-based sorbents in water treatment. The problems of toxic impurities of the drinking water, especially soluble arsenic compounds or different organic disinfection by-products, are very acute not only for Ukraine, but for many other countries too. So, it is very important to find simple and effective method to treat polluted natural waters to the required quality. The comparison of different treatment methods for removal of arsenic compounds and humates was made, as a result of which it was determined that the usage of adsorbents, especially fine particle iron-based sorbents, is very effective in natural organic matter removal and some other pollutants. Fine particle iron-based adsorbents are effective for arsenic removal due to its chemical structure. These materials removed arsenic compounds by chemisorption processes and immobilization of arsenate and arsenite ions in the insoluble form of ferric arsenate. Thus, the aim of the work was to develop the adsorbent for effective removal of arsenic compounds and humates from natural waters. We synthesized 7 suspension iron(III)-based sorbents by homogeneous precipitation from FeCl3 solution by thermal hydrolysis of urea. The efficiency of synthesized samples was checked by adsorption tests (humates and arsenite removal) and capillary suction time test. Iron(III) oxyhydroxide was the main phase of the most effective fine particle adsorbents. Applications on natural water showed that the synthesized iron(III) oxyhydroxide effectively removed arsenic compounds not only from model waters, but also from natural water with reaching of regulatory requirements.

Development of iron-containing sorption materials for water purification from arsenic compounds

“…A simple and effective way to separate finely dispersed adsorbents from water is to use microfiltration membranes. SFU series sorbents not only show high efficiency in the removal of arsenic compounds, but, according to previous studies [7], they demonstrate the ability to remove humates from water and protect the microfiltration membrane from colloidal fouling. As a result, the finely dispersed sorption material properties were fully implemented in the developed flow sheet (Fig.…”

“…According to the data of preliminary studies [7], the sorption materials of SFU series are characterized by particles of spherical shape and almost the same size, which is positive when used in the sorption-membrane treatment method. This homogeneity of the formed particles is explained by the fact that in the case of homogeneous precipitation, the particles are slowly formed from a solution with an equable concentration of the precipitant and are not further subjected to any destructive processes.…”

“…The efficiency of SFU series adsorbents in relation to arsenate and arsenite ions was determined on model solutions with different arsenic contents (500, 2000, 4000, 10000, 12000, and 15000 μg/l). The adsorbent dose was selected according to previous studies [7] and amounted to 50 mg/l. All SFU series samples showed similar sorption properties against arsenate and arsenite ions (Fig.…”

“…Irrational water resources usage leads to a significant increase in the content of natural organic substances in surface waters, which contributes to an increase in the tap water color index and the formation of carcinogenic disinfection by-products [6,7]. It should be noted that in natural waters arsenic compounds exist not only in the form of arsenates, arsenites or their methylated forms, but also as complexes with humic substances [8,9].…”