Novel triethylenetetramine functionalized absorbent from polyacrylonitrile for heavy metal ion adsorption

The contamination of water recourses by heavy metal is a serious worldwide environmental problem[1]. Recently, much attention has been paid to the synthesis and applications of chelating sorbents based on natural and synthetic materials in removal of harmful contaminants from aqueous media. Polyacrylonitrile is one of the promising candidates because it can be easily obtained and many derivatives can be prepared using hydroxyl or amine residue [2]. Several functional groups such as diethylene-triaminetetraacetic, monoethanolamine, diethylenetriamine and Ethylenediaminetetraacetic acid have been used for metal ions adsorption[3]. In this study we have developed a simple method for functionalizing of polyacrylonitrile (PAN) with two volume percent (50 and 100) of triethylenetetramine (PAN–TETA 50 and 100). The evolved surface characteristics and surface reactions of PAN–TETA and their metal complexes were investigated by FT-IR and scanning electron microscope. The prepared resins were applied to remove Zn (II) from aqueous solutions. The optimization of experimental conditions and parameters including initial pH, adsorbent dose, contact time, initial metal ion concentration for the removal of Zn (II) were investigated. Adsorption increased with increasing metal ions concentration, initial pH, and temperature. Pseudo first-order, pseudo-second-order models were considered to evaluate the rate parameters. The adsorption followed pseudo-second-order kinetic model with correlation coefficients greater than 0.993. Attempts were made to fit the isothermal data using Langmuir, Freundlich and Temkin equations. The maximum adsorption capacity of 102.16 mg g−for zinc ions were achieved in pH=6. Thermodynamic parameters of ΔG°, ΔH° and ΔS° indicated the adsorption process was spontaneous and endothermic.