PHOSPHATE ION ADSORPTION USING ZEOLITE FLY ASH PREPARED BY A SIMPLE REFLUX TECHNIQUE
Galuh Yuliani*), Asep Ahid, Maryono and Agus Setiabudi

Chemistry Department, Universitas Pendidikan Indonesia

Abstract

Fly ash is solid waste produced on coal combustion processes that owing to its high silica and alumina contents has been a promising source for zeolite precursor. Due to increasing problems related to fly ash accumulation in coal power stations, its utilization is becoming a great interest for many researchers. Hence, this research aims to explore a simple reflux method for zeolite synthesis from this waste materials and utilize the resulting product to adsorb phosphate ion from aqueous solution. The zeolite is prepared by a 1 h reflux method at 150oC to a mixture of fly ash and alkaline solution of NaOH, followed with gentle heating at 90oC for 24 h using an oven. The zeolite product was then analyzed using FTIR, XRD, XRF, BET, and SEM. The FTIR spectra show characteristics vibrations of Si-O-Si or Al-O-Al stretching in tetrahedral [SiO4]4- or [AlO4]5- at 985 cm-1, Al-O-Si stretching at 663 cm-1, Al-O or Si-O bending at 455 cm-1. The BET analysis shows that the surface area increased sharply from 6.9 m2/g for fly ash to 34.1 m2/g for zeolite. The XRD analysis indicated the formation of sodium aluminum silicate hydrate as sodalite zeolite (JCPDS Card No. 31-1271). The zeolite utilization as adsorbent for phosphate ions in aqueous solution was quantified using a UV-Vis spectrophotometer adopting Fardiaz method. It was found that the adsorption capacity for phosphate absorption was 11.8 mg/g within the optimum contact time of 25 mins. The adsorption data was analyzed using Langmuir and Freundlich adsorption isotherms. Based on the obtained correlation factors (R2), the absorption data follows Freundlich model, signifying a possible of multilayer adsorption due to physical interaction between adsorbent and adsorbate molecules.

Keywords: adsorption- phosphate ions- fly ash- zeolite synthesis-

Topic: Environmental Chemistry and Engineering