Publication: Crosslinked polyacrylamide/ polyethylenimine containing nano-hydroxyapatite/cellulose hybridization for the adsorption of lead ions in aqueous solution
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Date
2024-07-01
Authors
Ng, Chi Loon
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Abstract
The increasing pollution of wastewater with heavy metals has become a significant human and environmental concern. The need for efficient adsorbents to
remove these pollutants is critical. This study aims to develop an adsorbent system with the combination of a crosslink and hybrid fillers system that can effectively adsorb heavy metals from water. A polymer nanocomposite adsorbent system made from 70 wt% of polyacrylamide (PAM), 30 wt% of polyethylenimine (PEI) containing 3 phr of nanohydroxyapatite (nHA), and 15 phr of cellulose (Cel) was successfully crosslinked with N,N methylenebisacrylamide (MBA) and prepared via solution casting. The PAM/PEI/MBA and the nanocomposites were characterized via several techniques such as water absorption swelling test, thermogravimetric analysis (TGA) and field emission scanning electron microscopy (FESEM). The effects of the addition of different amounts of crosslinker (1 phr and 10 phr) on the adsorption capacities were explored. The adsorption capacity of PAM/PEI/Cel/nHA/MBA 10% was shown to be higher than PAM/PEI/Cel/nHA/MBA 1%. The study examined the impact of pH, initial heavy metal concentration, and contact time on adsorption. The results revealed that the optimal pH for adsorption is 5. Additionally, it was found that the adsorption capacity increases with the initial concentration of heavy metals. Furthermore, a longer contact time also enhances the adsorption capacity. The highest adsorption capacity attained was 404.5 mg/g at pH = 5, an initial concentration of 100 ppm, and 2 hours of contact time using 10 mg of absorbent. The isotherm of the crosslinked nanocomposite PAM/PEI/Cel/nHA/MBA 10% was examined with Langmuir and Freundlich isotherms while the kinetics were examined with pseudo-first-order kinetic and pseudo-second order kinetic. The result showed that it obeys the Freundlich isotherm and pseudo-second order kinetics, with R² values of 0.9991 and 0.9976, respectively, showing a multilayer chemisorption adsorption process.