h i g h l i g h t s ASGM-impacted soils from Davao de Oro, Philippines were evaluated. ASGM-impacted soils were highly contaminated with As, Pb and Zn. Cu, Pb, Zn and As in the contaminated soil came from sulphide minerals. Pb and Zn were strongly retained in the soils via adsorption to HFOs and clays. Cu and As release from the historic ASGM site exceeded environmental standards.

This study describes the effects of ceria (CeO 2) and dolomite [CaMg(CO 3) 2 ] additives on the pyrolysis behavior and fire resistive property of conventional intumescent flame retardant (IFR) coating system for I-beam steel substrate called ammonium polyphosphate-melamine-expandable graphite (APP-MEL-EG) system. The fire resistance of various formulations was evaluated using the standard vertical Bunsen burner fire test. Thermogravimetric analysis (TGA) was used to understand the degradation of coating formulations. Observations by scanning electron microscopy with energy dispersive X-ray spectroscopy (SEM-EDX) demonstrated that significant amounts of additives favored the formation of homogeneous compacted char structures, which were predominantly composed of carbon (C), phosphorus (P) and oxygen (O). These three main components of the char were also found to be in various binding combinations with other lighter elements like nitrogen (N) and hydrogen (H) as illustrated by the attenuated total reflectance Fourier transform infrared (ATR-FTIR) spectroscopy results. X-ray photoelectron spectroscopy (XPS) further suggest that polyethylene([(CH 2-C 2 H 2-CH 2) nÀ ]) free radicals were abundant on the char surface for the two best formulations and the binding energy of this radical promoted the formation of aromatic carbon chains that enhanced the char's thermal stability. This means that the selection of appropriate additives and combinations of flame-retardant ingredients could significantly change the morphology of the char layer and improve its thermal stability during fire exposure.

Multiple combinations of CeO2-Dolomite as fillers and Intumescent Flame Retardant (IFR) ingredients were used to optimize the intumescent coatings designed for I-beam steel substrates. The influenced of fillers and various combinations of flame-retardants on the fire protective performance of the coatings were evaluated using vertical Bunsen burner fire test and various characterization techniques. Formula C and Formula F having 1:1 and 2:2 CeO2-Dolomite ratio, obtained the lowest substrate temperature around 150oC and 150.4oC, respectively after 90 minutes fire exposure. Also, the morphological structures of intumescent char observed by SEM-EDX, demonstrated that Formula C and Formula F stimulated the formation of homogeneous and more compacted surface structure. X-ray photoelectron spectroscopy (XPS) provide the binding energies of C and O constituents, it was observed that [-(C2H4)n-] was the most important free radical as it could promote the formation of aromatic carbon chain in the char surface. Finally, the findings of this study revealed that the selection of appropriate fillers and combinations of flame-retardant ingredients significantly influenced the morphological structure of the char layer, of which, Formula C and Formula F produced a char with higher thermal stability, resulting to a more fire resistive IFR coating during fire exposure.

No abstract

Coal Fly Ash (CFA) is a hazardous waste from coal-fired power plants, but has increasingly become a popular supplementary cementitious material for cement in the construction industry. As a secondary resource of REE, its main advantage lies in its fine particle size that eliminates the need for costly and energy-intensive comminution. In this study, the potential of CFA from the Philippines as a secondary REE resource was investigated by direct leaching of REEs with hydrochloric acid (HCl). The CFA sample came from a coal-fired power plant with a circulating fluidized bed combustion (CFBC) technology. For the leaching tests, the effects of HCl concentration, leaching time and leaching temperature on REE extractions were elucidate optimized via Response Surface Methodology (RSM). The RSM results showed that the optimum leaching occurred at 3M HCl, 65 °C and 270 min with extractions of Nd, Er, Eu, Tb and Dy at 70.8%, 76.34%, 88.02%, 90.01% and 73.38%, respectively. According to these results, the CFA from the Philippines is a promising secondary resource of REE and the extraction method employed was effective in achieving a relatively high REE dissolution. Moreover, the empirical model that was established accurately predicted the dissolution of REE with an accuracy of 98.20%, 96.66%, 97.09%, 98.17% and 97.78% for Nd, Er, Eu, Tb and Dy, respectively.