A systematic mapping study on the development of permeable reactive barrier for acid mine drainage treatment

Acid mine drainage is a result of exposure of sulfide ore and minerals to water and oxygen. This environmental pollutant has been considered the second biggest environmental problem after global warming. On the other hand, permeable reactive barrier is an emerging remediation technology which can be used to treat acid mine drainage. However, the effectiveness of this proposed remediation technology greatly depends on the reactive media. Also, treatment of acid mine drainage using permeable reactive barrier is still in the infancy stage, and long-term performance is still unknown. Hence, this study was conducted to identify what have been studied, addressed and what are currently the biggest challenges and limitations on the use of permeable reactive barrier for acid mine drainage treatment. Through systematic mapping approach, the results have shown that the reactive media used in permeable reactive barrier can be categorized into five namely iron-based, organic-based, inorganic minerals-based, industrial waste-based, and combined media. The data revealed that majority of the papers which is about 40% use combined media as the reactive substrate. The future direction is toward the use of combined media as a reactive material for AMD treatment, for instance, use of geopolymer with mine tailings and silts as reactive media in combination with organic-based medi

Synthesis of geopolymer spheres with photocatalytic activity

Geopolymer is an emerging “green” cementitious material which has a potential to valorize waste such as rice hull ash (RHA). Geopolymer is a kind of alkali-activated material which forms from the reaction of alumino-silicates in an alkaline solution. This study uses RHA as the raw material for alkaline activator while metakaolin (MK) serves as a geopolymer precursor to synthesize the so-called geopolymer sphere. Then its capacity as a porous matrix was explored upon incorporation of TiO2 nanomaterial using horizontal vapor phase growth (HVPG) technique to enhance its photocatalytic property. Indication suggests that the synthesized MK-geopolymer spheres activated with RHA-based water glass solution (WGS) were comparable to that of commercial WGS. Furthermore, the geopolymer spheres were successfully coated with TiO2 in the form of nanocrystals. Its photocatalytic activity was evaluated in terms of methylene blue degradation. This material’s potential environmental application for water purification and wastewater treatment will be investigated for future works

Development and performance evaluation of abaca fiber reinforced fly ash based geopolymer composite

The use of natural fibers in reinforced composites to produce green materials is gaining more attention due to their attractive features such as low cost, low density and good mechanical properties, among others. This study thus investigates the potential of waste abaca (Manila hemp) fiber as reinforcing agent in geopolymer. Waste abaca fibers were subjected to different chemical treatments to modify the surface characteristics and to improve the adhesion with the fly ash-based geopolymer matrix. Test results confirmed that the chemical treatment removes the lignin, pectin and hemicellulose, as well as makes the surface rougher with the deposition of aluminum compounds. This improves the interfacial bonding between geopolymer matrix and the abaca fiber, while the geopolymer protects the treated fiber from thermal degradation. Samples of fly ash based geopolymer reinforced with fixed dose of chemically modified waste abaca fibers cured at different temperatures were synthesized and characterized in terms of compressive and flexural strengths. Then experimental thermal endurance of select composite was employed. Composites gained compressive strength after exposure to 200°C while retained its room-temperature compressive strength when exposed further up to 900°C. Furthermore, results indicated that flexural strength decreases with increasing exposure temperature. Scanning electron microscopy analyses were also performed to examine the microstructure of the geopolymer matrix and to investigate the failure mechanism in the fiber-geopolymer composite before and after exposure to elevated temperatures

A systematic mapping study on the development of permeable reactive barrier for acid mine drainage treatment

Acid mine drainage is a result of exposure of sulfide ore and minerals to water and oxygen. This environmental pollutant has been considered the second biggest environmental problem after global warming. On the other hand, permeable reactive barrier is an emerging remediation technology which can be used to treat acid mine drainage. However, the effectiveness of this proposed remediation technology greatly depends on the reactive media. Also, treatment of acid mine drainage using permeable reactive barrier is still in the infancy stage, and long-term performance is still unknown. Hence, this study was conducted to identify what have been studied, addressed and what are currently the biggest challenges and limitations on the use of permeable reactive barrier for acid mine drainage treatment. Through systematic mapping approach, the results have shown that the reactive media used in permeable reactive barrier can be categorized into five namely iron-based, organic-based, inorganic minerals-based, industrial waste-based, and combined media. The data revealed that majority of the papers which is about 40% use combined media as the reactive substrate. The future direction is toward the use of combined media as a reactive material for AMD treatment, for instance, use of geopolymer with mine tailings and silts as reactive media in combination with organic-based medi

Chemical treatment of waste abaca for natural fiber-reinforced geopolymer composite

The use of natural fibers in reinforced composites to produce eco-friendly materials is gaining more attention due to their attractive features such as low cost, low density and good mechanical properties, among others. This work thus investigates the potential of waste abaca (Manila hemp) fiber as reinforcing agent in an inorganic aluminosilicate material known as geopolymer. In this study, the waste fibers were subjected to different chemical treatments to modify the surface characteristics and to improve the adhesion with the fly ash-based geopolymer matrix. Definitive screening design of experiment was used to investigate the effect of successive chemical treatment of the fiber on its tensile strength considering the following factors: (1) NaOH pretreatment; (2) soaking time in aluminum salt solution; and (3) final pH of the slurry. The results show that the abaca fiber without alkali pretreatment, soaked for 12 h in Al2(SO4)3 solution and adjusted to pH 6 exhibited the highest tensile strength among the treated fibers. Test results confirmed that the chemical treatment removes the lignin, pectin and hemicellulose, as well as makes the surface rougher with the deposition of aluminum compounds. This improves the interfacial bonding between geopolymer matrix and the abaca fiber, while the geopolymer protects the treated fiber from thermal degradation. © 2017 by the authors

A systematic mapping and scoping review on geopolymer and permeable reactive barrier for acid mine drainage treatment research

Geopolymer has been recently gaining attention due to its excellent properties in various applications. It is an inorganic material that can be synthesized in the presence of a precursor rich in aluminosilica and an activator. This novel material also resembles the structure of a zeolite which makes it suitable in wastewater treatment applications. Meanwhile, one of the contributors to toxic metals in wastewater is the mining industry. The presence of these toxic metals in wastewater due to environmental impact brought by mining activities can contaminate both the ground and surface water. In addition, this could also cause environmental damage affecting the biodiversity around the area. One of the many challenges that the mining industry faces that contributes to environmental pollution is the generation of acid mine drainage. This is produced through further exposure of sulfide ore and other minerals to water and oxygen. On the other hand, the permeable reactive barrier is an emerging remediation technique that can be used to treat acid mine drainage. This paper reviews the current trend on geopolymer and permeable reactive barrier for acid mine drainage treatment research. This paper aims to identify the topics that have been studied and to elucidate the potential areas for research which could serve as a reference to future works. © 2020, Springer Nature Singapore Pte Ltd

Mechanical and thermal activation of nickel-laterite mine waste as a precursor for geopolymer synthesis

Geopolymer materials are increasing in scientific interest due to their flexibility in various applications. The geopolymer precursor is a mineral source with reactive Si and Al that is synthesized either mechanically or thermally to improve its cementitious activity. It was found out in previous literature that Nickel-laterite mine waste (NMW) is a prospective geopolymer precursor. However, this potentiality has not been explored in the Philippines, albeit the massive generation of NMW, which is merely dumped as a mining industry downstream process. This paper thus investigates the potential of the NMW as a raw material for geopolymer synthesis. Mechanical activation was performed using a ball mill with the following factors: ball-to-NMW ratio (4:1 and 10:1), mill speed (200 and 500 rpm), and grinding duration (30 and 120 minutes). Thermal activation was performed using a furnace treated at temperatures of 600, 700, and 800 °C. Response Surface Methodology (RSM) of the mechanical activation shows that a ball-to-NMW ratio of 10:1, mill speed of 443 rpm, and grinding duration of 120 minutes achieved optimized leachability of Si and Al. Thermal analysis results showed that NMW could be thermally activated from 600 to 800 °C. The results showed that both activation methods enhanced cementitious activity; hence, NMW could be utilized in geopolymer synthesis after thermal and mechanical activations. © 2020 The Author(s

Synthesis of geopolymer spheres with photocatalytic activity

Geopolymer is an emerging “green” cementitious material which has a potential to valorize waste such as rice hull ash (RHA). Geopolymer is a kind of alkali-activated material which forms from the reaction of alumino-silicates in an alkaline solution. This study uses RHA as the raw material for alkaline activator while metakaolin (MK) serves as a geopolymer precursor to synthesize the so-called geopolymer sphere. Then its capacity as a porous matrix was explored upon incorporation of TiO2 nanomaterial using horizontal vapor phase growth (HVPG) technique to enhance its photocatalytic property. Indication suggests that the synthesized MK-geopolymer spheres activated with RHA-based water glass solution (WGS) were comparable to that of commercial WGS. Furthermore, the geopolymer spheres were successfully coated with TiO2 in the form of nanocrystals. Its photocatalytic activity was evaluated in terms of methylene blue degradation. This material’s potential environmental application for water purification and wastewater treatment will be investigated for future works

Chemical stability and leaching behavior of one-part geopolymer from soil and coal fly ash mixtures

Aluminosilicate minerals have become an important resource for an emerging sustainable material for construction known as geopolymer. Geopolymer, an alkali-activated material, is becoming an attractive alternative to Portland cement because of its lower carbon footprint and embodied energy. However, the synthesis process requires typically a two-part system for alkali activation wherein the solid geopolymer precursor is mixed with aqueous alkali solutions. These alkali activators are corrosive and may be difficult to handle in the field-scale application. In this study, a one-part geopolymer in which coal fly ash was mixed with solid alkali activators such as sodium hydroxide and sodium silicate to form a powdery cementitious binder was developed. This binder mixed with soil only requires water to form the soil-fly ash (SO-CFA) geopolymer cement, which can be used as stabilized soil for backfill/foundation. This geopolymer product was then evaluated for chemical stability by immersing the material with 5% by weight of sulfuric acid solution for 28 days. Indication suggests that the geopolymer exhibited high resistance against acid attack with an observed increase of unconfined compressive strength even when the immersion time in acidic solution was increased to 56 days. The mineralogical phase, microstructure, and morphology of the material were characterized by X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, and scanning electron microscopy with energy-dispersive X-ray spectroscopy (SEM-EDX), respectively. Results not only confirmed the formation of gypsum due to acid attack but also indicated the dissolution of anorthite and albite that may have caused the microstructure to be composed of sodium aluminosilicate hydrate (N–A–S–H) and calcium (alumino) silicate hydrate (C(–A)–S–H) with poly(ferro-sialate-siloxo) and poly(ferro-sialate-disiloxo) networks. A column leaching test with deionized water was also performed on the soil-fly ash geopolymer to study the leachability of metals in the material. Results showed that arsenic exhibits higher mobility in the geopolymer as compared to that of cadmium, chromium, and lead. © 2018 by the authors. Licensee MDPI, Basel, Switzerland

A Perception Study of an Integrated Water System Project in a Water Scarce Community in the Philippines

The Integrated Water System (IWS) offers alternative water and sanitation services that can potentially benefit rural communities experiencing water scarcity. The IWS described in this study comprises three systems: The Rainwater Harvesting System (RWHS), Water Treatment System (WTS), and Eco-Toilet System (ETS). RWHS and WTS make use of rainwater, which can be utilized for several domestic uses, especially during wet season. ETS has several benefits to users including promotion of environmental and public health, as well as food security. Despite the potential benefits of the IWS components, the perceived acceptance of its users threatens the success of its implementation. This study focuses on determining the significant factors that can influence the social acceptance of IWS in the Municipality of Mulanay, Quezon Province, Philippines. This study considers behavioral intention as an indicator of social acceptance of the IWS components. The framework of this study is based on the combined technology acceptance model and theory of planned behavior (C-TAM-TPB) concept. C-TAM-TPB was analyzed using Partial Least Square–Structural Equation Modeling (PLS–SEM). The result of the C-TAM-TPB evaluation reveals that the user’s attitude towards use (ATU), including its significant predictors, can promote behavioral intention towards use of the IWS components. This study can further improve the development of IWS projects