Abstract
Humic acid (HA) impairs water quality due to its reactivity with many substances present in water. During the drinking-water treatment process and water distribution via water supply system, HA present in water may react with chlorine and other disinfects <br /> producing harmful disinfection by-products (DBPs), which are categorized by the International Agency for Research on Cancer (IARC) in groups 2A (probably carcinogenic to humans) or 2B (possibly carcinogenic to humans). Several studies have investigated and reported increased HA removal by iron-coated sorbents. Therefore, the aim of this study was to examine the removal of HA from water by two commercially available bituminous coal-based activated carbons (ACs), Cullar D (Cm) and Hydraffin 30N (Hm). Prior to testing the chosen adsorbents were chemically modified according to two protocols: (1) oxidation by acid mixture (m1), and (2) oxidation with acid mixture followed by iron-ions impregnation (m2). The batch adsorption tests were used to test their efficiency in HA removal under various values of process parameters (initial HA concentration, pH, contact time, adsorbent mass, and temperature). The results showed that up to 96 % of HA removal can be obtained by Cullar D modification Cm1, while maximum uptake of HA by Hydraffin 30N modification was achieved with Hm1 (62.1 %). After surface saturation with Fe3+ –ions (m2), both activated carbons showed similar and lower performances in HA removal (Cm2 up to 66.5 %, and Hm2 up to 50.3 %). FTIR analysis confirmed differences in modified AC structures, as well as favorable structure of Cm1 for HA adsorption.
Highlights
Natural organic matter (NOM) is a complex mixture mostly consisting of the following humic substances: humin, humic acid (HA), and fulvic acid
HNO3 and H2SO4 as strong oxidants, increased the amount of oxygen in the functional groups of the sample. This was evident by the observed bands that had formed after acid treatment at 2800–3200 cm−1 belonging to O–H, and at 1650–1750 cm−1 belonging to C–O and C=O groups
The significant increase of adsorption capacities have been reported after chemical modification of low-cost materials, especially those conducted in aim of adsorbent iron-coating
Summary
Natural organic matter (NOM) is a complex mixture mostly consisting of the following humic substances: humin, humic acid (HA), and fulvic acid. Humic acid is one of the main constituents of NOM, and together with fulvic acid presents up to 80 % of the dissolved organics in natural waters. M. Habuda-Stanić et al, Adsorption of Humic Acid from Water... Present in treated drinking water, HA reacts with chlorine and chlorine-based disinfects producing several different compounds, such as trihalomethanes (THMs), haloacetic acids (HAAs) and haloketones, classified as disinfection by-products (DBPs), which the International Agency for Research on Cancer (IARC) has categorized as probably carcinogenic to humans (group 2A) or possibly carcinogenic to humans (group 2B). HA can bind molecules of pesticides and heavy metals on its surface, and, natural organic matter, and HA as part of them, should be removed during drinking-water treatment.[1]
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