KINETICS AND ISOTHERM STUDIES OF Pb(II) IMPRINTED CARBOXYMETHYL CHITOSAN–PECTIN-PEGDE

Abstract

Pectin and chitosan are biomaterials that capable to act as biosorbent. Pectin has active groups, such as carboxyl, methoxyl, and hydroxyl (OH), while chitosan has amine group (–NH2) and hydroxyl (OH) as the active site metal ion absorber. Integration of two biopolymers is conducted by using a suitable cross-linker agents that are expected to form stable and more organized structure. This structure facilitate metal ions to enter and to form chelation reaction. Thus, it has great capacity for metal adsorption. A modified natural adsorbent pectin-chitosan has been synthesized by reacting of -OH group among pectin (Pec) and chitosan with Poly(ethylene glycol) Diglycidyl Ether (PEGDE) crosslinker agent to form a stable and an acidic medium-resistance adsorbent. Prior to increasing the active group of the adsorbent, chitosan was attached with acetate to form Carboxymethyl Chitosan (CMC). Furthermore, the CMC-Pec-PEGDE adsorbent was imprinted with Pb (II) to afford Pb(II) imprinted-CMC-Pec-PEGDE adsorbent in order to improve the selective sorption of Pb(II) metal ion. All of the functional groups attached on the synthesized adsorbents were characterized by Fourier Transform Infrared (FT-IR) Spectrometry. The kinetics and thermodynamics bath sorption of Pb(II) on Pb(II) imprinted-CMC-Pec-PEGDE film adsorbent have been investigated including the optimal condition for adsorption. The pseudo first-order and second-order kinetic model were investigated in order to determine the adsorption mechanism. The results indicated that all of the three adsorbent, CMC, CMC-Pec-PEGDE, and Pb(II) imprinted-CMC-Pec-PEGDE followed a pseudo-second-order kinetic model. Furthermore, adsorption studies of Pb(II) ion on CMC and CMC–Pec-PEGDE found to follow Langmuir adsorption while on imprinted-CMC-Pec-PEGDE followed Freundlich adsorption isotherm. The adsorption isotherm parameters of CMC and CMC-Pec-PEGDE adsorbents were ΔG° of 24.8 and 23.1 kJ mol-1, respectively. While Pb(II) imprinted-CMC-Pec-PEGDE followedisotherm model with ΔG° of 9.6 kJ mol-1.