Diatomite or diatomaceous earth (DE) is one of materials which can be used as an adsorbent to treat heavy metal ions from waste water, even there are many factories used it to clean the water for drinking. However, natural DE (raw DE) has very low adsorption capacity because of low specific surface area. In this work, natural DE from Lam Dong province, Viet Nam was demagnetized to remove iron and activated by HCl solution for 90 minutes with concentration of 10% at room condition. Adsorbent capacity was evaluated using As solution and the results show that the activated diatomite has adsorption capacity three times higher than that of raw DE, and the specific surface area of activated diatomite was increased 47.5% with the main chemical composition of 90.8% SiO2 and high porosity

Climate change is recognized as a global problem and even the industrial and construction sectors are trying to reduce the green-house gas emissions, especially on CO2 emissions. In Vietnam, the coal-fired thermal power plants are discharging millions of tons of CO2 and coal ash annually. This coal ash is comprised of about 80% of fly ash and the rest is bottom ash. This study would like to introduce one of the potential solutions in a carbon-constrained society that would not only manage the fly ash but also utilized this as raw material for green materials through geopolymerization. The geopolymer-based material has lower energy consumption, minimal CO2 emissions and lower production cost as it valorizes industrial waste. The fly ash containing high alumino-silicate resources from a coal-fired power plant in Vietnam was mixed with sodium silicate and sodium hydroxide solutions to obtain the geopolymeric pastes. The pastes were molded in 10x10x20cm molds and then cured at room temperature for 28 days. The 28-day geopolymer specimens were carried out to test for engineering properties such as compressive strength (MPa), volumetric weight (kg/m3), and water absorption (kg/m3). The microstructure analysis was also conducted for this eco-friendly materials using X ray diffraction (XRD), and Fourier Transform Infrared Spectroscopy (FTIR), Scanning Electron Microscope (SEM), Differential Thermal Analysis - Thermal Gravimetric Analysis (DTA-TGA).

Calcium hydroxyapatite (also known as hydroxyapatite - HA), formula Ca5(PO4)3(OH) or Ca10(PO4)6(OH)2, is a double salt of tri - calcium phosphate and calcium hydroxide. And apatite exists naturally in the form of fluorine-apatite Ca10(PO4)6F2. In human and animal body, HA is the main component in bone (accounting for 65-70% weight) and teeth (99%). In this study, calcium hydroxide (Ca(OH)2) and phosphoric acid (H3PO4) were used as raw materials to produce hydroxyapatite (HA). The hydroxyapatite was synthesized by hydrothermal method. Physico-chemical and microstructural properties of the HA were characterized by X-ray diffraction (XRD), Fourier-transform infrared spectroscopy (FTIR), Brunnaeur-Emmett- Teller (BET) analysis and Scanning Electron Microscope (SEM) and compared with standard sample of HA. For lead treatment in wastewater, adsorption of HA was tested by measuring concentration of lead of the adsorption process. In which, Pb is one of the toxicity heavy metals that caused many dangerous diseases and threatening human health and life.