Cd²⁺ and Cr³⁺ Cation Immobilization by Using Geopolymer Based on PT. IPMOMI Fly Ash

Abstract:

This study investigates the immobilization of Cd²⁺ and Cr³⁺ by using geopolymer paste based on PT. IPMOMI fly ash. The best composition of geopolimers paste was determined based on the highest magnitude of its 7 days compressive strength. Geopolymer pastes were prepared by varying SiO₂/Al₂O₃ and Na₂O/SiO₂ molar ratio of the starting materials. X-Ray Diffraction (XRD) and Scanning Electron Microscope (SEM) were employed to examined these compositions. The molar ratio of SiO₂/Al₂O₃ 6.46 was found to produce the highest compressive strength of the resulting geopolymer paste, i.e 25 MPa and increased to 33.17 MPa by adjusting the ratio of Na₂O/SiO₂ to 0.65. Cd²⁺ and Cr³⁺ cations were added into geopolymers resin at the level of 1000 – 16000 ppm (mg/kg fly ash) and it was found to improve their compressive strength. The addition of 4000 ppm of Cd²⁺ increased the compressive strength to 38.6 MPa while the inclusion of 6800 ppm of Cr³⁺ reached 47.83 MPa. Further addition of cations reduced these values and the lowest compressive strength was observed on the addition of 16000 ppm of Cd²⁺ and Cr³⁺, i.e 8.65 MPa and 4.39 MPa, respectively. Leaching test was conducted by using Inductively Coupled Plasma-Optical Emission Spectroscopy (ICP-OES) and the distribution of heavy metal cations were examined by using SEM-EDX. The results showed that geopolymer pastes were able to immobilize Cr³⁺ at the studied level as there was no trace of Cr³⁺ detected after 6.5 hours of leaching. Geopolymer pastes were also found to completely immobilize Cd²⁺ at the level of 1000 ppm albeit the addition of 16000 ppm results in 6.26% leached out of this cation.

• Periodical: Materials Science Forum (Volume 841)
• Pages: 186-192
• DOI: https://doi.org/10.4028/www.scientific.net/MSF.841.186
• Online since: January 2016
• Authors: Hamzah Fansuri*, I’Is M. Anisatun, Anif Fatmawati, Wahyu Prasetyo Utomo, Warih Supriadi, Ridho Bayuaji, Subaer Subaer
• Keywords: Compressive Strength, Fly Ash, Geopolymer, Heavy Metal, Immobilization, SEM-EDX, XRD

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