Complexation ability of modified Na-Humate and its application in removal of toxic metals from water

Abstract

Efficiency of an amine modified Na-Humate (Na-Hum), which was isolated from coal mine in Karaganda/Kazakhstan, was explored as a sorbent for removal of toxic metal ions from water. Na-Hum was immobilized with ethylene diamine to get a suitable adsorbent called modified humate (Mod-Hum). Pseudo-first-order and pseudo-second-order kinetic models gave the best correlation at the suitable pH. The experimental results were calculated according to the related adsorption formulas, which were then depicted in tables and graphics. The amount of toxic metal ions remained in the solution after treating with Mod-Hum was measured by atomic absorption spectroscopy. The process parameters such as mixing time, temperature, and pH during the adsorption were investigated to find optimum sorption capacity. The results after adsorption were compared to determine the differences between natural (Na-Hum) and the modified matter (Mod-Hum). The complexation ability of compounds by exchange of Na-Hum and Mod-Hum with several metal ions such as Cu(CH₃COO)₂·H₂O, Co(CH₃COO)₂·4H₂O, Ni(CH₃COO)₂·4H₂O, and Cd(CH₃COO)₂·2H₂O was also investigated. All obtained compounds were characterized by several techniques such as FTIR, TGA/DTA, and SEM-EDAX, elemental analysis and XRD. The adsorption studies with both Na-Hum and Mod-Hum clearly demonstrated that Na-Humate treated with amine is a more efficient adsorbent than the natural form. In addition, Mod-Hum fitted better with pseudo-first-order model and removed water contaminants such as Cu, Co, Ni, and Cd more effectively, which was attributed to higher reactivity of N and O donor sites of the adsorbent toward toxic metals.

Keywords:

• Na-Humate
• Adsorption
• Complexation
• Modification

Acknowledgment

Support for analysis and research by the Dicle University Science and Technology Research Center (DUBTAM) is gratefully acknowledged.