IMOBILISASI ASAM SALISILAT, ASAM GALAT DAN ASAM HUMAT PADA MAGNETIT SERTA APLIKASINYA UNTUK ADSORPSI [AuCl4]-

MAYA RAHMAYANTI, 1. Prof. Drs. Sri Juari Santosa, M.Eng, Ph. D. ; 2. Dr. Sutarno, M.Si.

2016 | Disertasi | S3 Kimia

Emas adalah salah satu logam yang paling banyak kegunaannya dan telah digunakan sebagai unit pertukaran dan penyimpan kekayaan untuk jangka waktu lama. Saat ini emas telah banyak dimanfaatkan dalam bidang teknologi tinggi termasuk elektronik, telekomunikasi, aerospace, teknik kimia dan industri medis. Pada studi ini, magnetit terimobilisasi asam salisilat, asam galat dan asam humat (Mag-SA, Mag-GA dan Mag-HA) disintesis untuk adsorpsi [AuCl4]- . Imobilisasi asam salisilat, asam galat dan asam humat pada magnetit telah dilakukan menggunakan metode kopresipitasi dengan dan tanpa melibatkan gelombang ultrasonik. Immobilisasi dilakukan melalui metode satu tahap dan metode dua tahap. Karakterisasi material hasil sintesis dilakukan menggunakan spektrofotometer Fourier Transform Infrared (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) dan Vibrating Sample Magnetometer (VSM). Material hasil sintesis selanjutnya digunakan untuk adsorpsi [AuCl4]-. Adsorpsi [AuCl4]- pada Mag-SA, Mag-GA dan Mag-HA dikaji dengan mempelajari pengaruh keasaman medium terhadap adsorpsi [AuCl4]-, menentukan model kinetika adsorpsi dan model isotherm adsorpsi. Hasil karakterisasi menunjukkan bahwa keberadaan gelombang ultrasonik menurunkan nilai saturasi magnetisasi dari adsorben dan memperkecil ukuran kristal adsorben. Ukuran kristal dan nilai saturasi magnetisasi material hasil sintesis dengan metode satu tahap lebih kecil dari pada ukuran kristal dan nilai saturasi magnetisasi material hasil sintesis dengan metode dua tahap. Kajian adsorpsi menunjukkan bahwa adsorpsi [AuCl4]- pada Mag-SA, Mag-GA dan Mag-HA berlangsung optimum pada pH 3. Kinetika adsorpsi [AuCl4]- pada semua adsorben mengikuti kinetika adsorpsi pseudo orde dua Ho. Isoterm adsorpsi [AuCl4]- pada semua adsorben mengikuti isoterm Langmuir, kecuali pada Mag-GA yang disintesis melalui satu tahap, isoterm adsorpsinya mengikuti isoterm Freundlich. Hasil karakterisasi adsorben setelah adsorpsi menunjukkan bahwa proses adsorpsi diikuti dengan reduksi Au(III) menjadi Au(0).

Gold is one of the most useful metals and has been used as unit of exchange and store of wealth for over a long period. Nowadays gold has been highly utilized in high-tech fields including electronic, telecomunication, aerospace, chemical engineering and medical industry. In this study, magnetite-immobilized salicylic acid, gallic acid and humic acid (Mag-SA, Mag-GA and Mag-HA) were synthesized for adsorption of [AuCl4]-. Immobilization of salicylic acid, gallic acid and humic acid onto magnetite were carried out using co-precipitation method with and without the involvement of ultrasonic waves then applied for [AuCl4]- adsorption. Immobilization was done through the one-stage and two-stages methods. Characterization of the synthesized materials was performed using a Fourier Transform Infrared (FTIR) spectrophotometer (FTIR), X-Ray Diffraction (XRD), Scanning Electron Microscopy (SEM) and Vibrating Sample Magnetometer (VSM). Adsorption of [AuCl4]- onto Mag-SA, Mag-GA and Mag-HA were studied by first examining the effect of the acidity of the medium and followed by determining the model of adsorption kinetics and adsorption isotherm. The results showed that ultrasonic waves decreased the value of the saturation magnetization of the adsorbents and reduced the size of the adsorbent crystals. Crystal size and saturation magnetization of the one-step-synthesized material were smaller than the two-step-synthesized material. Adsorption of [AuCl4]- onto Mag-SA, Mag-GA and Mag-HA was found to be optimum at pH 3. The adsorption kinetic of [AuCl4]- onto all adsorbents could be described well by pseudo second order kinetic model. The adsorption isotherm [AuCl4]- onto all adsorbents agreed well with Langmuir isotherm model, except for the adsorption isotherms of [AuCl4]- onto the one-step-synthesized Mag-GA that agreed well with Freundlich isotherm model. The characterization result confirmed that the adsorption of Au(III) by Mag-SA, Mag-GA and Mag-HA was accompanied by reduction of Au(III) to Au(0).

Kata Kunci : Mag-SA, Mag-GA, Mag-HA, adsorpsi, [AuCl4]-