Synthesis of Na-A zeolite from water treatment residue using hydrothermal and microwave techniques

Abstract Na-A zeolite was synthesized from water treatment residue (WTR) using hydrothermal and microwave techniques. WTR was brought from Metropolitan Waterworks Authority (Thailand) and was activated by firing at 700 °C for 3 h in an electric furnace. The activated WTR was reacted with 3 M NaOH solution in a reactor under a controlled temperature of 80, 90 and 100 °C for 8, 10, 12, and 14 h. SEM (Scanning electron microscopy) images reveal the cubic crystal of zeolite. The highest cation exchange capacity (CEC) was obtained from sample synthesized at 90 °C for 14 h and gave the CEC value of 3.14 meq/g Ca2+. For the microwave technique, the raw materials were reacted at 80 90 and 100°C for 30, 60, and 120 min. Results showed that the sample obtained at 80 °C for 30 min represented the highest CEC value of 0.29 meq/g Ca2+.</jats:p

Properties of hydroxyapatite based geopolymer synthesized from bituminous fly ash

Abstract This research studied the engineering properties of hydroxyapatite based on fly ash-geopolymer as a biomaterial. The ratio of Na2O/SiO2 and K2O/SiO2 at 0.15 0.20 0.25 0.30 by mole, 2.5 5.0 7.5, 10 wt.% of calcium phosphate and heat treatment at 500°C, 600°C and 700°C for 2 hours were used to studied changed of compressive strength and crystalline phase in samples. The results observed highest 28-days compressive strength of 21.99 and 19.14 MPa for 0.20 by mole of Na2O/SiO2 and 0.15 by mole of K2O/SiO2, respectively. When calcium phosphate (CP) was added in fly ash-geopolymer, the optimum ratio of CP was found in 2.5 wt.% that have unconfined compressive strength (UCS) of 19.03 and 13.60 MPa for NaOH and KOH activator. After heat treatment of geopolymer at 500°C, the maximum compressive strength at 9.09 MPa and 22.76 MPa for each activator was obtained. Finally, the XRD resulted show hydroxyapatite, mullite quartz and sodium aluminum silicate peaks in both fly ash-geopolymer with NaOH and KOH and 2.5% CP.</jats:p

Properties of hydroxyapatite-based geopolymer synthesized from calcined kaolin

Abstract This research synthesized the geopolymer from calcined kaolin (600°C for 2 h in a muffle furnace) using sodium hydroxide (NaOH) and potassium hydroxide (KOH) as alkali activators. Calcium phosphate (CP) and heat treatment were introduced to study their effects on the unconfined compressive strength (USC) and crystalline phases formation of kaolin-based geopolymer. Results showed that the highest USC strength at 28 days of geopolymer was obtained from 0.4 moles of Na2O/SiO2 and K2O/SiO2 and gave strength of 12.95 and 11.56 MPa, respectively. The USC of geopolymer was observed to decrease with the addition of CP. The amounts of 5 wt.% of CP gave a 28-day strength of kaolin-based geopolymer containing NaOH and KOH activators at 9.95 and 8.88 MPa, respectively. The CP-doped geopolymers were then heated at temperatures of 500, 600, and 700°C for 2 h Results indicated that heat treatment at 600°C gave the highest USC of CP-doped geopolymer containing NaOH and KOH equal to 7.61 and 4.61 MPa, respectively with the appearance of hydroxyapatite, muscovite, and quartz in the XRD diffractograms.</jats:p

Comparative study on the preparation of belite cement from nano-silicas extracted from different agricultural wastes with calcium carbide residue

Belite cement was prepared using nano-silicas extracted from three different agricultural wastes–black rice husk ash (BRHA), bagasse ash (BA), and palm oil fuel ash (POFA)–which were reacted at 1200 − 1400 °C with CaC2 residue as calcium source. The product was compared with that from CaCO3. Nano-silica extracted from BRHA was of very fine particle size (surface area 312.4 m2/g and V/S ratio 0.35 × 106 cm) and being highly reactive, forms β-C2S at lower firing temperatures; however, at higher temperatures, less-desirable γ-polymorphs are formed. Nano-silica extracted from POFA contains Na2O, Al2O3, and K2O impurities, which stabilize the β and α-forms and delay the transformation to γ-phase. This is reflected in relatively high compressive strength at firing temperature above 1200 °C, compared to other mixtures. Thus, these results indicate that the best combination of these waste materials for the preparation of belite cement phases is POFA ash and CaC2 residue

Hydration study of ordinary portland cement in the presence of zinc ions

Hydration products of Portland cement pastes, hydrated in water and in the presence of zinc ions were studied comparatively at different ages. Hydration products were studied by X ray diffractions (XRD) and infrared spectroscopy (IR). Although IR is not frequently used in cement chemistry, it evidenced a new phase Ca(Zn(OH)3)2. 2H2O formed during cement hydration in the presence of zinc. The significant retardation of early cement hydration in the presence of zinc is assessed in detail by differential calorimetry as a complement to the study carried out by IR and XRD, providing evidence that permits to evaluate the kinetic of the early hydration