제주 스코리아로부터 합성한 제올라이트를 고분자 Polysulfone 및 PAN로 고정화한 비드에 의한 수 중 중금속 이온의 흡착 특성

Abstract

In order to examine the adsorption characteristics of heavy metal ions (Ni^(2+), Zn^(2+), and Cr^(3+)) from aqueous solutions, the Jeju scoria found in large amounts in Jeju Island, was synthesized via fusion/hydrothermal method, and the synthesized zeolite (syn-zeolite) was immobilized with polysulfone (PS) and polyacrlonitrile (PAN). The prepared PS-syn-zeolite beads and PAN-syn-zeolite beads were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectrometer (FT-IR), thermo gravimetric analysis (TGA), and scanning electron microscope (SEM). The PS-syn-zeolite beads and PAN-syn-zeolite beads were optimal at the conditions of 1.25 g of PS and 1.5 g of syn-zeolite, and of 1.0 g of PAN and 2.0 g of syn-zeolite, respectively. The adsorption of Ni^(2+), Zn^(2+), and Cr^(3+) by PS-syn-zeolite beads and PAN-syn-zeolite beads increased with time and reached to equilibrium after 60 min for Ni^(2+) and Zn^(2+), and 90-120 min for Cr^(3+) in case of syn-zeolite in powder state, and after 48 hr in case of PS-syn-zeolite beads and PAN-syn-zeolite beads. The adsorption of Ni^(2+), Zn^(2+), and Cr^(3+) by syn-zeolite, PS-syn-zeolite beads and PAN-syn-zeolite beads were fitted to pseudo-first-order model and to Langmuir adsorption model. Each of the maximum adsorption capacities by PS-syn-zeolite beads and PAN-syn-zeolite beads was calculated from Langmuir isotherms as 31.35 mg/g zeolite (9.32 mg/g bead) and 33.0 mg/g zeolite (6.27 mg/g bead) for Ni^(2+), 60.24 mg/g zeolite (16.53 mg/g bead) and 81.3 mg/g zeolite (15.77 mg/g bead) for Zn^(2+), and 27.02 mg/g zeolite (8.1 mg/g bead) and 27.25 mg/g zeolite (4.76 mg/g bead) for Cr^(3+). Compared theses results with those calculated for syn-zeolite in powder state (40.32 mg/g for Ni^(2+), 119.05 mg/g for Zn^(2+), and 37.45 mg/g for Cr^(3+)), the adsorption capacities by the former gained 78% and 82% for Ni^(2+), 51% and 68% for Zn^(2+), and 72% and 73% for Cr^(3+), respectively. Each of the distribution coefficients (K_(d)) of Ni^(2+), Zn^(2+), and Cr^(3+) in the presence of coexisting ions (Na^(+), K^(+), Ca^(2+), Mg^(2+)) by PS-syn-zeolite beads and PAN-syn-zeolite beads was 5.1 times, 8.6 times and 4.0 times and more, compared with those of coexisting ions, indicating that the removal of the former in the presence of the latter by PS-syn-zeolite beads and PAN-syn-zeolite beads carries out more selectively. Finally, any sign of zeolite leakage or damage of the beads was not detected even after five adsorption-desorption cycles, while the adsorption capacities of Ni^(2+), Zn^(2+), and Cr^(3+) by PS-syn-zeolite beads and PAN-syn-zeolite beads were stably maintained.