SINTESIS MCM-41 DAN NH2-MCM-41 SEBAGAI ADSORBEN Hg(II) DALAM MEDIUM AIR

SUTARDI, S.Si, Prof. Dr. Sri Juari Santosa, M.Eng.

2011 | Tesis | S2 Ilmu Kimia

Telah dilakukan sintesis MCM-41 dan NH2-MCM-41 sebagai adsorben Hg(II) dalam medium air. Sintesis MCM-41 dilakukan melalui proses hidrotermal campuran Na2SiO3 dan setiltrimetilammonium bromida (CTAB) dengan pengaturan pH = 10 menggunakan larutan H2SO4 1 M. Sintesis NH2-MCM-41 dilakukan dengan merefluks campuran MCM-41 dan (3-aminopropil)- trimetoksisilan (APTMS) dalam toluena pada temperatur 60 oC selama 12 jam. Padatan hasil sintesis dikarakterisasi dengan metode spektrofotometri inframerah (FTIR), difraksi sinar-X (XRD), mikroskop elektron transmisi (TEM) dan fisisorpsi isotermal gas N2 menggunakan gas sorption analyzer berdasarkan persamaan BET. Padatan MCM-41 dan NH2-MCM-41 hasil sintesis digunakan untuk mengadsorb ion Hg(II) dalam medium air pada berbagai variasi pH, waktu kontak, dan konsentrasi Hg(II). Hasil analisis FTIR menunjukkan adanya gugus Si-OH dan Si-O-Si pada struktur MCM-41 dan NH2-MCM-41. Keberadaan gugus fungsional aminopropil yang teramati pada spektra NH2-MCM-41, menunjukkan bahwa proses penjangkaran telah berhasil dilakukan. Pola difraktogram sinar-X dan hasil foto TEM untuk MCM-41 dan NH2-MCM41 menunjukkan struktur pori heksagonal yang seragam. Hasil analisis fisisorpsi gas N2 dengan metode BET menunjukkan bahwa setelah proses penjangkaran, ukuran luas permukaan, diameter pori, dan volume total pori mengecil. Hasil kajian adsorpsi Hg(II) oleh padatan MCM-41 dan NH2-MCM-41 menunjukkan bahwa adsorpsi maksimal terjadi pada pH = 4. Kajian kinetika adsorpsi Hg(II) oleh MCM-41 mengikuti kinetika orde satu dengan harga k1 1,73 x 10-3 menit-1 dan oleh NH2-MCM-41 mengikuti kinetika adsorpsi orde dua dengan harga k2 sebesar 3,97 x 10-5 (g/mol.menit). Padatan NH2-MCM-41 memiliki kapasitas adsorpsi yang lebih besar, yakni 63,29 mg/g (3,16 x 10-4 mol/g) dibandingkan MCM-41 yang hanya 14,21 mg/g (7,09 x 10-5 mol/g), artinya modifikasi MCM-41 menjadi NH2-MCM-41 terbukti mampu meningkatkan kapasitas adsorpsi terhadap Hg(II).

Synthesis of MCM-41 and NH2-MCM-41 as adsorbents of Hg(II) in aqueous solution had been done. MCM-41 was synthesized through hydrothermal process used Na2SiO3 solution and cethyltrimethylammonium bromide (CTAB) adjusted at pH = 10 by using 1 M H2SO4 solution. NH2-MCM-41 was made by refluxing a mixture of MCM-41 and (3-aminopropyl)trimethoxysilane (APTMS) in toluene at temperature of 60 oC for 12 h. The solid products were characterized by infrared spectrofotometry (FTIR), X-ray diffraction (XRD), Tranmission Electron Microscope (TEM), and N2 physisorption method using a gas sorption analyzer based on the BET equation. The synthesized MCM-41 and NH2-MCM-41 were applied as adsorbents of Hg(II) in aqueous solution at various pH, contact time, and concentration of Hg (II). Characterization of solid products by using FTIR spectroscopy showed the existence of Si-OH and Si–O–Si groups in both MCM-41 and NH2-MCM-41 structure. Observed aminopropyl groups in NH2-MCM-41 spectra indicated that the enchoring process was successful. Both the XRD pattern and TEM image displays consistency results that MCM-41 and NH2-MCM-41 had an ordered hexagonal pore structure. Results of N2 physisorption analysis showed that after anchoring process, the size of BET surface area, pore diameter, and total pore volume were decreases. The adsorption study of Hg (II) on solid MCM-41 and NH2-MCM-41 showed the maximum adsorption occurs at pH = 4. The adsorption kinetics study of Hg (II) using MCM-41 coincide well the first order kinetic with value of k1 1.73 x 10-3 minute-1, while adsorption of Hg(II) using NH2-MCM-41 coincide well the second order kinetic with value of k2 3.97 x 10-5 (g/mol.minute). NH2-MCM-41 possesed greater adsorption capacities, i.e. 63,29 mg/g (3,16 x 10-4 mol/g) than MCM-41, i.e. 14,21 mg/g (7,09 x 10-5 mol/g), it means that modification of MCM-41 to NH2-MCM-41 was proved to increase the adsorption capacity for Hg(II).

Kata Kunci : MCM-41, NH2-MCM-41, kinetika, kapasitas, adsorpsi Hg(II).