Preparation of Zeolite A from Coal Fly Ash as Adsorbent for Ni(II) and Zn(II)

Abstract

Fly ash is waste of coal that can be converted into zeolite. Zeolite A was synthesized from fly ash by fusion of NaOH:fly ash, namely 0.8:1, 1:1, 1.2:1, and 1.4:1 at fusion temperature and reaction time of 450, 550, and 650 ºC for 30, 60, 120, and 180 minutes followed by hydrothermal treatment. NaOH:fly ash ratio of 0.8:1 with fusion temperature of 450 ºC for 30 minutes exhibited the highest cation exchange capacity of 138 mek/100 g. Characterization using X-ray diffraction showed a similarity in term of diffraction peaks of zeolite synthetic with a typical peak PCDFWIN program database file number 39-0222 which is assigned as zeolite A [Na96Al96Si96O384.216H2O]. Capacity adsorption of zeolite synthetic was tested to ions Ni(II) and Zn(II) with fly ash as an adsorbent for comparison. The adsorption parameters were pH, contact time, and initial concentration. The best adsorption conditions for the zeolites synthetic and fly ash towards Zn(II) was obtained at pH 6, contact time 150 minutes, and initial concentration of 150 ppm. The best adsorption conditions for the zeolites synthetic towards Ni(II) was obtained at pH 4, contact time 30 minutes, and intial concentration of 60 ppm, whereas for fly ash was obtained at pH 6, contact time 60 minutes, and initial concentration of 60 ppm. The capacity adsorption of the synthetic zeolite towards Ni(II) and Zn(II) has a value greater than that of the fly ash.

Abu layang merupakan limbah batu bara yang dapat dikonversi menjadi zeolit. Zeolit A disintesis dari abu layang dengan ragam peleburan NaOH:abu layang, yaitu 0.8:1, 1:1, 1.2:1, dan 1.4:1 pada suhu dan waktu peleburan 450, 550, dan 650 ºC selama 30, 60, 120, dan 180 menit diikuti perlakuan hidrotermal. Nisbah NaOH:abu layang 0.8:1 dengan suhu peleburan 450 ºC selama 30 menit memiliki kapasitas tukar kation tertinggi sebesar 138 mek/100 g. Pencirian dengan difraksi sinar-X menunjukkan kesamaan puncak difraksi zeolit sintetik dengan puncak khas basis data program PCDFWIN nomor arsip 39-0222 yang merupakan zeolit A [Na96Al96Si96O384.216H2O]. Zeolit sintetis diuji kemampuan adsorpsinya terhadap ion Ni(II) dan Zn(II) dengan abu layang sebagai adsorben pembandingnya. Parameter adsorpsi yang digunakan, ialah pH, waktu kontak, dan konsentrasi awal. Kondisi adsorpsi terbaik untuk zeolit sintetis dan abu layang terhadap Zn(II) diperoleh pada pH 6, waktu kontak 150 menit, dan konsentrasi awal 150 ppm. Kondisi adsorpsi terbaik untuk zeolit sintetis terhadap Ni(II) diperoleh pada pH 4, waktu kontak 30 menit, dan konsentrasi 60 ppm, sedangkan untuk abu layang pada pH 6, waktu kontak 60 menit, dan konsentrasi 60 ppm. Kapasitas adsorpsi zeolit sintetis terhadap Ni(II) dan Zn(II) memiliki nilai kapasitas yang lebih besar dibandingkan abu layang.