Distribution of heavy metals and metalloid in surface sediments of heavily-mined area for bauxite ore in Pengerang, Malaysia and associated risk assessment

A detailed investigation has been conducted to evaluate the distribution of heavy metals and metalloid in the surface sediments of a bauxite mining area in association with the potential ecological and human health risk. Field sampling was carried out within the Pengerang bauxite mining areas, including mine tailings, ex-mining pond and streams. Distribution of heavy metals (Al, Cd, Co, Cr, Cu, Fe, Mn, Pb, Sr, Zn) and metalloid such as As in sediments indicated that Fe and Al constituted the greatest portion of metal elements in the sediment while Pb and Cu were found exceeding the recommended guideline values at some locations. Assessment of potential ecological risk (PERI) demonstrated low to medium ecological risk in the metal-contaminated sediments with Cd, As and Pb have generally greater risk compared to other metals, contributing the most to the total risk index (RI). The sediment enrichment factor (EF) indicated no enrichment of most metals while Pb and As at some locations were classified as having minor and moderately to severe enrichment. The geo-accumulation index (Igeo) and contamination factor (CF) indicated that the sediments were classified uncontaminated with respect to most metals. Assessment of potential human health risk revealed that the hazard index (HI) values of the carcinogenic and non-carcinogenic risks were an order of magnitude higher among children compared to adults. There were no significant non-carcinogenic risk due to metals and metalloid in the study area as HIs <1. However, the lifetime cancer risk (LCR) for As is relatively higher than other metals and falls within tolerable LCR for regulatory purposes. Therefore, this study has highlighted the implication on potential ecological and human health risks of heavy metal occurrence in sediments of bauxite mining areas thus indicating the importance of geomorphological changes due to land exploitation for mining sector

Potential of soil, sludge and sediment for mineral carbonation process in Selinsing Gold Mine, Malaysia

Soil, sludge and sediment that are rich in alkaline earth silicates play significant roles as passive agents for removing carbon dioxide through mineral carbonation process. This study was conducted to characterize the mineralogical component and chemical composition of gold mining wastes and to identify the availability of natural silicate minerals as a feedstock for the mineral carbonation process. Particle-size distribution analysis was performed, and pH of the soil, sludge, and sediment were determined, whereas the mineralogical component and chemical composition of the samples were also analyzed. Results demonstrated that the presence of sepiolite and chlorite-serpentine in the stockpile and mine tailings can sequester carbon dioxide into magnesium carbonates, while the presence of stilpnomelane in the stockpile can be sequestered into iron carbonate. The presence of large amounts of small-size particles (silt fraction) in sludge (78.23%) at the mine tailings was identified to have higher surface area to absorb carbon dioxide. pH conditions of sludge (pH 7.9) and sediment (pH 8.3) from the mine tailings were favorable to enhance carbonate precipitation. Therefore, gold mine wastes have shown the potential for passive sequestration of carbon dioxide, thus, providing more insights into the enhancement of mineral carbonation process and the potential of natural silicate minerals

The mineralogy and chemical properties of sedimentary waste rocks with carbon sequestration potential at the Selinsing gold mine, Pahang

Waste rocks are a non-economical by-product of mining operations, which can lock up carbon dioxide into a carbonate form and thereby help reduce greenhouse gases emissions. The aims of this research are to determine the mineral and chemical composition of the sedimentary waste rocks of gold mines and to classify the potential of silicate minerals to be a feedstock for carbonation mineralization. The sampling was undertaken at the Selinsing gold mine, where waste rocks were collected from the waste dump, stockpiles, the borrow pit, and the main pit. The mineralogical and chemical component of the sedimentary waste rocks were explored using X-ray diffraction and energy dispersive X-ray spectroscopy. The findings indicated that the presence of divalent cations, of 55.12% for CaO, 9.09% for MgO, and 16.24% for Fe2O3 from gold mine waste, capable of sequestering carbon dioxide into calcium, magnesium and iron carbonates, respectively, through carbonation of mineral. The domination of silicate minerals such as quartz, muscovite, kaolinite, chlorite, albite, and carbonate minerals such as calcite, have been found to be widespread in sedimentary waste rocks. However, the natural silicates (chlorite, muscovite) and carbonates (calcite) are potential minerals which can be consumed as feedstock for carbonation processes because they contain the magnesium, iron, and calcium elements which can form stable carbonates in the presence of carbon dioxide. The mineralogy and chemical composition of sedimentary waste rocks from the Selinsing gold mine provides a better understanding of the future carbonation reaction to sequester more carbon dioxide in response to climate change

Phytoremediation potential of vetiver grass (Vetiveria zizanioides) for treatment of metal-contaminated water

Phytoremediation using vetiver grass (Vetiveria zizanioides) has been regarded as an effective technique for removing contaminants in polluted water. This study was conducted to assess the removal efficiency of heavy metals (Cu, Fe, Mn, Pb, Zn) using vetiver grass (VG) at different root lengths and densities and to determine metals uptake rate by plant parts (root and shoot) between treatments (low and high concentration). Removal efficiency for heavy metals in water by VG is ranked in the order of Fe>Pb>Cu>Mn>Zn. Results showed that VG was effective in removing all the heavy metals, but removals greatly depend on root length, plant density and metal concentration. Longer root length and higher density showed greater removals of heavy metals due to increased surface area for metal absorption by plant roots. Results also demonstrated significant difference of heavy metals uptake in plant parts at different concentrations indicating that root has high tolerance towards elevated concentration of heavy metals. However, the effects were less significant in plant shoot suggesting that metals uptake were generally higher in root than in shoot. The findings have shown potential of VG in phytoremediation for heavy metals removal in water thus providing significant implication for treatment of metal-contaminated water

Carbon Sequestration of Limestone Mine Waste through Mineral Carbonation and Utilization as Supplementary Cementitious Material

This study highlights the potential of limestone mine waste for mineral carbonation and its potential as supplementary cementitious material. Mineralogical and chemical composition analysis of limestone mine waste sample were performed, and mineral carbonation experiment was conducted under ambient pressure and temperature. The effect of particle size and pH condition was investigated to observe the influence of the parameters on carbonation efficiency. The limestone mine wastes were identified to have potential for carbon sequestration due to its high calcium oxide content alongside magnesium oxide which are derived from Ca- and Mg-carbonate minerals. It can be seen from this study that smaller particle size and pH 10 condition were ideal for the carbonation process. The end product of calcium carbonate proved that mineral carbonation occurred during the reaction, indicating the potential of the mine waste as feedstock for mineral carbonation. Additionally, the use of limestone mine waste can also be regarded as supplementary cementitious material due to its chemical composition while at the same time serves as potential storage and sink for sequestered carbon dioxide

Carbon sequestration of mining waste in reducing carbon dioxide emission through mineral carbonation

The process of extracting minerals from mining operation emits high carbon dioxide emission in the atmosphere. However, large quantities of waste materials produced from the mining operation can be utilized for carbon sequestration by mineral carbonation process. Therefore, this study was conducted to; (1) evaluate the potential characteristics of mining wastes such as gold, limestone and iron ore mine wastes for carbon sequestration; (2) enhance mineral carbonation process at varying particle size, temperature and pH in sequestering more carbon dioxide in carbonate form and; (3) develop potential application of mining wastes for long term carbon storage in brick production. Rock, soil, sludge and sediment samples were collected and analyzed for their characteristics including pH, particle-size distribution, mineralogical composition, morphological structure and chemical composition by integrating X-ray diffraction, scanning electron miscroscopy and energy dispersive X-ray analyses. The mineral carbonation experiment was conducted using mining waste at different particle size, temperature and pH. Brick production incorporating mining waste was produced at different mix design ratio and the effects of carbonation time and curing periods on carbon dioxide uptake were measured. Findings suggest that gold mine was identified as the source of MgO and Fe2O3 due to the presence of magnesium-iron silicate minerals; limestone mine as the source of CaO due to high availability of calcium-bearing mineral; and iron mine contains iron-calcium-magnesium silicate minerals as the source of Fe2O3, CaO and MgO that can be used as feedstock for mineral carbonation process. Iron mining waste was further evaluated for mineral carbonation due to variety of potential minerals and has the highest average divalent cation content. The effect of mineral carbonation using iron mining waste shows that smaller size particles (<38 μm) have achieved a higher calcium, iron and magnesium carbonation efficiency of 3.81%, 6.66% and 6.43%, respectively. As the temperature increased at 200°C, the maximum calcium, iron and magnesium carbonation efficiency of 4%, 5.82% and 5.62%, respectively were obtained. Increasing the pH at pH 12 resulted in greater calcium, iron and magnesium carbonation efficiency of 5.56%, 5.85% and 5.83%, respectively. Acceptable carbonation efficiency was achieved under the favorable conditions of ambient pressure. The incorporation of different types of mine waste indicates good durability of bricks, where limestone mine waste bricks have reduced water absorption and improved compressive strength of up to 0.52% and 40.23 N/mm2, respectively. Iron mine waste bricks show higher carbon dioxide uptake averaging 0.63%. Various mix design ratio and curing period are the most significant factors that affect the water absorption of carbonated brick specimens, while carbonation time had increased the compressive strength of brick specimens. Low carbon dioxide uptake can be improved by increasing the percentage of mining waste used up to 60% and lengthening the carbonation time up to 3 hours. Therefore, utilization of mining wastes as feedstock for mineral carbonation process can be regarded as a solution for waste minimization issue and seems to be an environmentally beneficial approach in reducing carbon dioxide emissions. This would be useful in promoting sustainable use of natural resources and for future mitigation strategies of mining-related issues

Application of theory of planned behavior in measuring the behavior to reduce plastic consumption among students at Universiti Putra Malaysia, Malaysia

This study was conducted to identify the relationship between variables that affect behavioral intention among UPM students in reducing plastic consumption. A survey was done using validated questionnaire and distributed among 393 respondents of UPM students. The study revealed that perceived behavioral control (PCB) shows the highest relationship with behavior compared to other variables. There was statistically significant of behavior difference between genders. However, there was no statistically significant difference of behavior between level of education and stream of study (science and social science)

Evaluating capacity building of the local community towards environmental conservation in an estuarine community, Kong Kong Laut, Johor

Key community-based environmental conservation programmes in Kong Kong Laut, Johor include the river and mangrove ecosystem conservation and management programme. The overall aim of conserving the ecosystem and encouraging local community participation in the programme is to promote the existing eco-tourism potential of the area. This paper entails the outcomes of community-based activities aimed at building the capacities of local communities through community mobilisation, awareness creation and capacity building (i.e. transferred knowledge and skills). Findings indicate that there have been improvements in the river water quality status within the ecosystems over the course of a one-year project, despite relatively small participation among the local communities in the conservation programme. However, it was evident that active participation from a minority group of the local community has contributed to significant human and social capital, suggesting that community empowerment might be crucial for future development. Despite this, a school outreach programme on waste minimisation within the community demonstrated an encouraging level of participation among school children and teachers. The major challenge to maintaining continuous efforts to conserve their environment is the simultaneous developments taking place close to the river and mangrove ecosystems. While it remains a challenge to all the stakeholders, collaborative efforts among the local communities and the university, school, government agencies and private sector have made it possible to strategise for more future approaches that will benefit the whole community

Mineral carbonation of sedimentary mine waste for carbon sequestration and potential reutilization as cementitious material

This study highlights the importance of mineralogical composition for potential carbon dioxide (CO2) capture and storage of mine waste materials. In particular, this study attempts to evaluate the role of mineral carbonation of sedimentary mine waste and their potential reutilization as supplementary cementitious material (SCM). Limestone and gold mine wastes were recovered from mine processing sites for their use as SCM in brick-making and for evaluation of potential carbon sequestration. Dominant minerals in the limestone mine waste were calcite and akermanite (calcium silicate) while the gold mine waste was dominated by illite (iron silicate) and chlorite-serpentine (magnesium silicate). Calcium oxide, CaO and silica, SiO2, were the highest composition in the limestone and gold mine waste, respectively, with maximum CO2 storage of between 7.17 and 61.37%. Greater potential for CO2 capture was observed for limestone mine waste as due to higher CaO content alongside magnesium oxide. Mineral carbonation of the limestone mine waste was accelerated at smaller particle size of < 38 μm and at pH 10 as reflected by the greater carbonation efficiency. Reutilization of limestone mine waste as SCM in brick-making exhibited greater compressive strength and lower water absorption compared to the bricks made of gold mine waste. The gold mine waste is characterized as having high pozzolanic behaviour, resulting in lower carbonation potential. Therefore, it has been noticeable that limestone mine waste is a suitable feedstock for mineral carbonation process and could be reutilized as supplementary cementitious material for cement-based product. This would be beneficial in light of environmental conservation of mine waste materials and in support of sustainable use of resources for engineering construction purposes

Carbon dioxide sequestration of iron ore mining waste under low-reaction condition of a direct mineral carbonation process

Mining waste that is rich in iron-, calcium- and magnesium-bearing minerals can be a potential feedstock for sequestering CO2 by mineral carbonation. This study highlights the utilization of iron ore mining waste in sequestering CO2 under low-reaction condition of a mineral carbonation process. Alkaline iron mining waste was used as feedstock for aqueous mineral carbonation and was subjected to mineralogical, chemical, and thermal analyses. A carbonation experiment was performed at ambient CO2 pressure, temperature of 80 °C at 1-h exposure time under the influence of pH (8–12) and particle size (< 38–75 µm). The mine waste contains Fe-oxides of magnetite and hematite, Ca-silicates of anorthite and wollastonite and Ca-Mg-silicates of diopside, which corresponds to 72.62% (Fe2O3), 5.82% (CaO), and 2.74% (MgO). Fe and Ca carbonation efficiencies were increased when particle size was reduced to < 38 µm and pH increased to 12. Multi-stage mineral transformation was observed from thermogravimetric analysis between temperature of 30 and 1000 °C. Derivative mass losses of carbonated products were assigned to four stages between 30–150 °C (dehydration), 150–350 °C (iron dehydroxylation), 350–700 °C (Fe carbonate decomposition), and 700–1000 °C (Ca carbonate decomposition). Peaks of mass losses were attributed to ferric iron reduction to magnetite between 662 and 670 °C, siderite decarbonization between 485 and 513 °C, aragonite decarbonization between 753 and 767 °C, and calcite decarbonization between 798 and 943 °C. A 48% higher carbonation rate was observed in carbonated products compared to raw sample. Production of carbonates was evidenced from XRD analysis showing the presence of siderite, aragonite, calcite, and traces of Fe carbonates, and about 33.13–49.81 g CO2/kg of waste has been sequestered from the process. Therefore, it has been shown that iron mining waste can be a feasible feedstock for mineral carbonation in view of waste restoration and CO2 emission reduction