The Experts below are selected from a list of 3477 Experts worldwide ranked by ideXlab platform
Xiangfeng Kong - One of the best experts on this subject based on the ideXlab platform.
-
Phosphogypsum stabilization of bauxite residue conversion of its alkaline characteristics
Journal of Environmental Sciences-china, 2019Co-Authors: Shengguo Xue, Graeme J Millar, Chuxuan Li, Meng Li, Jun Jiang, Xiangfeng KongAbstract:Abstract Reduction of the high alkalinity of bauxite residue is a key problem to solve to make it suitable for plant growth and comprehensive utilization. In this study, Phosphogypsum, a waste product from the phosphate fertilizer industry, was used to drive the alkaline transformation of the bauxite residue. Under optimal water washing conditions (liquid/solid ratio of 2 mL/g, 30°C, 24 hr), the impact of quantity added, reaction time and reaction mechanism during Phosphogypsum application were investigated. Phosphogypsum addition effectively lowered pH levels and reduced the soluble alkalinity by 92.2%. It was found that the concentration of soluble Na and Ca ions in the supernatant increased gradually, whilst the exchangeable Na+ and Ca2 + in solid phase changed 112 mg/kg and 259 mg/kg, respectively. Ca2 + became the dominant element in the solid phase (Phosphogypsum addition of 2%, liquid/solid ratio of 2 mL/g, 30°C, 12 hr). X-ray diffraction data indicated that cancrinite and hydrogarnet were the primary alkaline minerals. SEM images suggested that Phosphogypsum could promote the formation of stable macro-aggregates, whilst the content of Ca2 + increased from 5.6% to 18.2% and Na reduced from 6.8% to 2.4%. Treatment with Phosphogypsum could significantly promote the transformation of alkalinity cations by neutralization, precipitation and replacement reactions. This research provided a feasible method to promote soil formation of bauxite residue by Phosphogypsum amendment.
-
Phosphogypsum stabilization of bauxite residue conversion of its alkaline characteristics
Journal of Environmental Sciences-china, 2019Co-Authors: Shengguo Xue, Graeme J Millar, Chuxuan Li, Meng Li, Jun Jiang, Xiangfeng KongAbstract:Abstract Reduction of the high alkalinity of bauxite residue is a key problem to solve to make it suitable for plant growth and comprehensive utilization. In this study, Phosphogypsum, a waste product from the phosphate fertilizer industry, was used to drive the alkaline transformation of the bauxite residue. Under optimal water washing conditions (liquid/solid ratio of 2 mL/g, 30°C, 24 hr), the impact of quantity added, reaction time and reaction mechanism during Phosphogypsum application were investigated. Phosphogypsum addition effectively lowered pH levels and reduced the soluble alkalinity by 92.2%. It was found that the concentration of soluble Na and Ca ions in the supernatant increased gradually, whilst the exchangeable Na+ and Ca2 + in solid phase changed 112 mg/kg and 259 mg/kg, respectively. Ca2 + became the dominant element in the solid phase (Phosphogypsum addition of 2%, liquid/solid ratio of 2 mL/g, 30°C, 12 hr). X-ray diffraction data indicated that cancrinite and hydrogarnet were the primary alkaline minerals. SEM images suggested that Phosphogypsum could promote the formation of stable macro-aggregates, whilst the content of Ca2 + increased from 5.6% to 18.2% and Na reduced from 6.8% to 2.4%. Treatment with Phosphogypsum could significantly promote the transformation of alkalinity cations by neutralization, precipitation and replacement reactions. This research provided a feasible method to promote soil formation of bauxite residue by Phosphogypsum amendment.
Carlos Ruiz Canovas - One of the best experts on this subject based on the ideXlab platform.
-
leaching of rare earth elements rees and impurities from Phosphogypsum a preliminary insight for further recovery of critical raw materials
Journal of Cleaner Production, 2019Co-Authors: S Chapron, Guilhem Arrachart, Carlos Ruiz Canovas, Stephane PelletrostaingAbstract:Abstract Phosphogypsum is a pollutant waste generated by the fertilizer industry. Managing this pollutant is challenging due to the large volumes generated worldwide. A promising route is the valorization of Phosphogypsum to recover rare earth elements. However, optimized recovery schemes are needed to create a cost-effective and environmentally friendly process. This paper studies the extraction efficiency of rare earth elements from Phosphogypsum and the release of impurities during leaching in a variety of solutions and different working conditions. The best leaching performance was obtained using a 3 M nitric acid (above 80%) solution that achieved a dissolution rate of 63% of the gypsum originally present. In contrast, using 0.5 M sulfuric acid extracted between 46% and 58% of the rare earth elements contained in Phosphogypsum, dissolving less than 6% of the gypsum. This higher dissolution of gypsum led to a higher release of impurities by nitric acid. Increasing reaction times from 2 h to 8 h yielded an improvement of leaching efficiency of around 8% for both leaching solutions, while also promoting an increase of 6% in the release of impurities. Adding DTPA resulted in poor leaching performance (from 13% to 22%). Pretreating Phosphogypsum with water can remove a significant fraction of the impurities without scavenging rare earth elements. Mineralogical and chemical evidence suggests unreacted phosphate and fluoride are the most probable minerals hosting rare earth element minerals in Phosphogypsum. The results of this study could contribute to optimizing recovery methods to extract rare earth elements from Phosphogypsum worldwide, thus helping achieve the goals of the circular economy.
Rafael Perezlopez - One of the best experts on this subject based on the ideXlab platform.
-
fractionation and fluxes of metals and radionuclides during the recycling process of Phosphogypsum wastes applied to mineral co2 sequestration
Waste Management, 2015Co-Authors: M Contreras, M.j. Gázquez, A Santos, Rafael Perezlopez, Luis Esquivias, Victor Moralesflorez, Juan Pedro BolívarAbstract:The industry of phosphoric acid produces a calcium-rich by-product known as Phosphogypsum, which is usually stored in large stacks of millions of tons. Up to now, no commercial application has been widely implemented for its reuse because of the significant presence of potentially toxic contaminants. This work confirmed that up to 96% of the calcium of Phosphogypsum could be recycled for CO2 mineral sequestration by a simple two-step process: alkaline dissolution and aqueous carbonation, under ambient pressure and temperature. This CO2 sequestration process based on recycling Phosphogypsum wastes would help to mitigate greenhouse gasses emissions. Yet this work goes beyond the validation of the sequestration procedure; it tracks the contaminants, such as trace metals or radionuclides, during the recycling process in the Phosphogypsum. Thus, most of the contaminants were transferred from raw Phosphogypsum to portlandite, obtained by dissolution of the Phosphogypsum in soda, and from portlandite to calcite during aqueous carbonation. These findings provide valuable information for managing Phosphogypsum wastes and designing potential technological applications of the by-products of this environmentally–friendly proposal.
-
assessment of Phosphogypsum impact on the salt marshes of the tinto river sw spain role of natural attenuation processes
Marine Pollution Bulletin, 2011Co-Authors: Aguasanta M Sarmiento, Julio Castillo, Rafael Perezlopez, J.m. NietoAbstract:Abstract About 120 Mton of Phosphogypsum from the fertiliser industry were stack-piled on the salt-marshes of the Tinto river (Spain). This paper investigates the capacity of salt-marshes to attenuate contamination due to downward leaching from Phosphogypsum. Solids and pore-waters were characterized at different depths of the pile to reach the marsh-ground. In superficial zones, metals were highly mobile, and no reduced sulphur was found. However, pollutant concentration decreased in the pore-water in deeper oxygen-restricted zones. Metal removal occurred by precipitation of newly formed sulphides, being this process main responsible for the contamination attenuation. Pyrite-S was the main sulphide component (up to 2528 mg/kg) and occurred as framboids, leading to high degrees of pyritization (up to 97%). The sulphidization reaction is Fe-limited; however, excess of acid-volatile sulphide over other metals cause precipitation of other sulphides, mainly of Cu and As. This decrease in metal mobility significantly minimises the impact of Phosphogypsums on the salt-marshes.
-
dynamics of contaminants in Phosphogypsum of the fertilizer industry of huelva sw spain from phosphate rock ore to the environment
Applied Geochemistry, 2010Co-Authors: I Lopezcoto, J L Aguado, Juan Pedro Bolívar, José Miguel Nieto, Rafael Perezlopez, M SantistebanAbstract:Abstract The dynamics of trace elements from phosphate rock ore to the environment in a phosphoric acid plant located in SW Spain and the impact of Phosphogypsum wastes were investigated through total digestion and BCR-sequential extraction. Based on total concentration, element transfer factors as criteria for examining the potential environmental risk of waste with respect to ore rock were calculated, and it was observed that most trace elements are only transferred into Phosphogypsum at rates of 2–12%. However, based on those concentrations that are likely to be most readily mobile in the environment, Phosphogypsum acts as a higher emission source of contaminants than the original rock. About 100 million tonnes of Phosphogypsum are stack-piled in a dump of 1200 ha over salt-marshes of an estuary formed by the confluence of the Tinto and Odiel rivers. Phosphogypsum has been applied, at the recommended rate of 20–25 t/ha since 1978–2001, to improve fertility and reduce Na saturation in agricultural soils of the Guadalquivir river valley (140 km 2 ). Phosphogypsum capacity as a source of mobile contaminants in three environmental scenarios (water leaching, exposure to oxidising and reducing conditions) was quantified by combining sequential extraction and waste mass. The amounts of mobile contaminants that could be released for every tonne of Phosphogypsum are approximately 7 × 10 2 g Sr, 1.1 × 10 2 g Fe, 55 g Y, 30 g Ce, 12 g Cr, 11 g Ti, 5 g Zn, 4 g each of Cu and Pb, 3 g each of V and Cd, 2 g each of As and Ni and 1 g U. Multiplying these amounts by 100 Mt and 20–25 t/ha, it is possible to calculate risk assessments of Phosphogypsum for both estuarine zones, e.g. in a hypothetical stack collapse and waste spilling, and agricultural soils, respectively.
Yiming Wang - One of the best experts on this subject based on the ideXlab platform.
-
effects of Phosphogypsum and superphosphate on compost maturity and gaseous emissions during kitchen waste composting
Waste Management, 2015Co-Authors: Fan Yang, Hong Shi, Guoxue Li, Yiming WangAbstract:Highlights: • Effect of Phosphogypsum and superphosphate on composting gas emissions was studied. • The reduction mechanisms of composting gas were clarified in this study. • No negative effect was caused on maturity with Phosphogypsum and superphosphate. • CH{sub 4} and NH{sub 3} emission was decreased with Phosphogypsum and superphosphate addition. • GHG decreased by 17.4% and 7.3% with Phosphogypsum and superphosphate addition. - Abstract: This study investigated the effects of Phosphogypsum and superphosphate on the maturity and gaseous emissions of composting kitchen waste. Two amended compost treatments were conducted using Phosphogypsum and superphosphate as additives with the addition of 10% of initial raw materials (dry weight). A control treatment was also studied. The treatments were conducted under aerobic conditions in 60-L reactors for 35 days. Maturity indexes were determined, and continuous measurements of CH{sub 4}, N{sub 2}O, and NH{sub 3} were taken. Phosphogypsum and superphosphate had no negative effects on compost maturity, although superphosphate inhibited the temperature rise in the first few days. The addition of Phosphogypsum and superphosphate drastically reduced CH{sub 4} emissions (by 85.8% and 80.5%, respectively) and decreased NH{sub 3} emissions (by 23.5% and 18.9%, respectively). However, a slight increase in N{sub 2}O emissions (by 3.2%more » and 14.8%, respectively) was observed. Composting with Phosphogypsum and superphosphate reduced total greenhouse gas emissions by 17.4% and 7.3% respectively.« less
-
effects of Phosphogypsum and superphosphate on compost maturity and gaseous emissions during kitchen waste composting
Waste Management, 2015Co-Authors: Fan Yang, Hong Shi, Yiming WangAbstract:This study investigated the effects of Phosphogypsum and superphosphate on the maturity and gaseous emissions of composting kitchen waste. Two amended compost treatments were conducted using Phosphogypsum and superphosphate as additives with the addition of 10% of initial raw materials (dry weight). A control treatment was also studied. The treatments were conducted under aerobic conditions in 60-L reactors for 35 days. Maturity indexes were determined, and continuous measurements of CH4, N2O, and NH3 were taken. Phosphogypsum and superphosphate had no negative effects on compost maturity, although superphosphate inhibited the temperature rise in the first few days. The addition of Phosphogypsum and superphosphate drastically reduced CH4 emissions (by 85.8% and 80.5%, respectively) and decreased NH3 emissions (by 23.5% and 18.9%, respectively). However, a slight increase in N2O emissions (by 3.2% and 14.8%, respectively) was observed. Composting with Phosphogypsum and superphosphate reduced total greenhouse gas emissions by 17.4% and 7.3% respectively.
Barbara Paci Mazzilli - One of the best experts on this subject based on the ideXlab platform.
-
Phosphogypsum recycling in the building materials industry: assessment of the radon exhalation rate
Journal of Environmental Radioactivity, 2017Co-Authors: M.p. Campos, L. J.p. Costa, M. B. Nisti, Barbara Paci MazzilliAbstract:Phosphogypsum can be classified as a Naturally Occurring Radioactive Material (NORM) residue of the phosphate fertilizer industry. One of the main environmental concerns of its use as building material is the radon exhalation. The aim of this study is to measure the radon exhalation rate from plates and bricks manufactured with Phosphogypsum from three installations of the main Brazilian producer, Vale Fertilizantes, in order to evaluate the additional health risk to dwellers. A simple and reliable accumulator method involving a PVC pipe sealed with a PVC pipe cover commercially available with CR-39 radon detector into a diffusion chamber was used for measuring radon exhalation rate from Phosphogypsum made plates and bricks. The radon exhalation rate from plates varied from 0.19 ± 0.06 Bq m−2h−1, for Phosphogypsum from Bunge Fertilizers, from 1.3 ± 0.3 Bq m−2h−1, for Phosphogypsum from Ultrafertil. As for the bricks, the results ranged from 0.11 ± 0.01 Bq m−2h−1, for Phosphogypsum from Bunge Fertilizers, to 1.2 ± 0.3 Bq m−2h−1, for Phosphogypsum from Ultrafertil. The results obtained in this study for the radon exhalation rate from Phosphogypsum plates and bricks are of the same order of magnitude than those from ordinary building materials. So, it can be concluded that the recycling of Phosphogypsum as building material is a safe practice, since no additional health risk is expected from the radiological point of view.
-
Lixiviation of natural radionuclides and heavy metals in tropical soils amended with Phosphogypsum
Journal of Environmental Radioactivity, 2015Co-Authors: M. B. Nisti, C.r. Saueia, L.h. Malheiro, G.h. Groppo, Barbara Paci MazzilliAbstract:Abstract The main phosphate industries in Brazil are responsible for the annual production of 5.5 million tons of a residue (Phosphogypsum), which is stored in stacks. The presence of radionuclides and metals puts restrictions on the use of Phosphogypsum in agriculture. To assure a safe utilization, it is important to estimate the lixiviation of the radionuclides ( 238 U, 226 Ra, 210 Pb, 210 Po, 232 Th and 228 Ra) and metals (As, Cd, Cr, Ni, Se, Hg and Pb) present in Phosphogypsum. For this purpose, an experiment was carried out, in which columns filled with sandy and clay Brazilian typical soils mixed with Phosphogypsum were percolated with water, to achieve a mild extraction of these elements. The results obtained for the concentration of the radionuclides and metals in the leachate were low; giving evidence that, even when these elements are present in the Phosphogypsum, they do not contribute to an enhancement of their content in water.
-
rare earth elements as tracers of sediment contamination by Phosphogypsum in the santos estuary southern brazil
Applied Geochemistry, 2007Co-Authors: Sonia Maria Barros De Oliveira, P S C Silva, Déborah Inês Teixeira Fávaro, Barbara Paci Mazzilli, C.r. SaueiaAbstract:In the Cubatao region, southern Brazil, sediments are transported by several rivers from the Serra do Mar Ridge into the Santos estuary. Fertilizer plants have been operating along the margins of one of these rivers (Mogi River) producing a large volume of Phosphogypsum, which is stockpiled in nearby areas. Surface sediments of the Mogi River were sampled upstream and downstream in relation to the point where the effluents of the Phosphogypsum piles flow into the drainage system. In the vicinity of this point one sediment core was collected. Results show that REE, Ba, Zr and Th concentrations in the non-contaminated sediments are of the same order as those present in the upper continental crust. The contaminated samples present a composition affected by that of the Phosphogypsum, marked by a higher concentration of these elements and a stronger degree of REE fractionation. These Phosphogypsum characteristics are inherited from the Catalao igneous phosphate ore and were moderately modified by the industrial process of phosphoric acid production. The Phosphogypsum signal decreases rapidly downstream, pointing to a limited area of influence of the stacks. The deepest sediments of the core are also free of contamination, representing a time interval prior to the deposition of Phosphogypsum wastes on the banks of the estuary.