Geopolymer has been widely used as adsorbent for heavy metals and dyes. Modification on geopolymer surface with cationic surfactant can improve the anion exchange capacity of geopolymer. In this paper, fly ash-based geopolymer had been modified with cetyltrimethylammonium bromide (CTAB) which is...

Fly ash which is solid waste can be used as an adsorbent for wastewater treatment. Alkali modification and alkali activation on fly ash can increase the adsorption capacity of fly ash. In this study, alkali modified fly ash and alkali activated fly ash were used as Zn(II) ions adsorbents. The effect of adsorption time and initial concentration of Zn(II) ions was studied, as well as the kinetics and isotherm adsorption. The results showed that the removal efficiency of Zn(II) ions by alkali activated fly ash is higher than that by alkali modified fly ash. The adsorptions of Zn(II) ions by alkali modified fly ash and by alkali activated fly ash have reached equilibrium after two hours. The increase of initial concentration of Zn(II) ions would decrease the removal efficiency with both alkali modified fly ash and alkali activated fly ash. Adsorptions of Zn(II) ions by both alkali modified fly ash and alkali activated fly ash tend to follow pseudo second order kinetics model and Langmuir isotherm model with maximum adsorption capacity of 62.696 mg/g and 66.667 mg/g, respectively.

This paper describes the adsorption of Cu2+ and Fe2+ ions, common heavy metals found in industrial wastewater, by a fly ash-based geopolymer in batch adsorption experiments. Kinetics studies showed that the adsorption of each ion followed a pseudo-second order reaction. Moreover, adsorption isotherm of Cu2+ and Fe2+ ions followed the Langmuir model. Monolayer adsorption capacities were approximately 53.76 mg/g for Cu2+ ion and 52.63 mg/g for Fe2+ ion, respectively.

Geopolymer as a Portland cement substitute had been synthesized from alkaline activation of co-combustion residuals of bamboo and kaolin. Types of used alkaline activators were NaOH solution, KOH solution, a mixture of NaOH solution-water glass, and a mixture of KOH solution-water glass. Geopolymer with NaOH solution as activator had a compressive strength which was higher compared to geopolymer with KOH solution as an activator. However, geopolymer with NaOH solution-water glass as activator had a compressive strength which was lower compared to geopolymer with KOH solution-water glass as activator either at room temperature curing or at a curing temperature of 60 °C. The use of water glass with NaOH or KOH solution as activator could increase the compressive strength of geopolymer and yielded geopolymer having more dense and more homogeneous microstructure seen from SEM images. XRD patterns revealed the presence of sodium aluminosilicate hydrate in geopolymer with NaOH solution and NaOH solution-water glass as activators, and potassium aluminosilicate hydrate in geopolymer with KOH solution and KOH solution-water glass as activators. Furthermore, FTIR spectra indicated asymmetrical vibration of Si(Al)-O at around 1008 cm-1 related to geopolymer product.

Geopolymer is anorganic polymer which can be used to heavy metal removal through adsorption process. Geopolymer can be produced from raw material containing alumino-silicate oxide such as fly ash which is solid waste from coal combustion. In this study, geopolymer was prepared from fly ash with alkali activation process using mixture of 10 N NaOH solution and Na-Silicate solution. Fly ash-based geopolymer was then applied as adsorbent for different heavy metals removal, i.e. Cu²⁺, Fe²⁺, Mn²⁺, Zn²⁺, in aqueous solutions. Removal efficiencies were calculated from changes of heavy metal concentration determined by Atomic Absorption Spectroscopy (AAS) analysis. Characterization of fly ash- based geopolymer covered Brunauer-Emmett-Teller (BET) surface area analysis and Scanning Electron Microscope- Energy Dispersive X-Ray (SEM-EDX) analysis. The results showed that fly ash-based geopolymer could adsorb heavy metals with better removal efficiency compared to the raw fly ash.