Investigating the Adsorption of Humic Acid from Water Using CTS/PAM and CTS/PAM/EDTA Adsorbents

In recent decades, reports from around the globe indicate an increase in natural organic matters (NOMs) in surface waters, which has a negative impact on drinking water purification and causes problems such as the taste and color of water, reducing the amount of dissolved oxygen in water, causing membrane fouling in the filtration process, and acting as a precursor for the formation of an antiseptic by-product. This work used the adsorption process to evaluate the elimination of natural organic compounds in aquatic environments. Ethylenediaminetetraacetic acid (EDTA) as a crosslinker for chitosan (CTS) and N, N-methylenebisacrylamide as a crosslinker for polyacrylamide (PAM) were used to prepare humic acid (HA) adsorbents utilizing a two-step procedure. The FTIR spectroscopy proved the EDTA cross-linking agent was effective with the semicrosslinking CTS/PAM hydrogel. CTS/PAM/EDTA double network (DN) hydrogel exhibited a higher HA adsorption capacity ( <a:math xmlns:a="http://www.w3.org/1998/Math/MathML" id="M1"><a:msub><a:mrow><a:mi>q</a:mi></a:mrow><a:mrow><a:mi mathvariant="normal">e</a:mi></a:mrow></a:msub></a:math> = 107.7 mg/g) than CTS/PAM ( <d:math xmlns:d="http://www.w3.org/1998/Math/MathML" id="M2"><d:msub><d:mrow><d:mi>q</d:mi></d:mrow><d:mrow><d:mi mathvariant="normal">e</d:mi></d:mrow></d:msub></d:math> = 59.3 mg/g) at pH = 7 and an initial concentration of 60 mg·L−1 during 60 min. Also, results demonstrate that CTS/PAM/EDTA DN hydrogels showed faster adsorption kinetics than CTS/PAM.