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1.
PLoS One ; 15(8): e0236718, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32797052

RESUMO

High-flow low-expansion backfill materials have been developed to improve difficult slurry pipeline transport and poor roof-contact effect of many filling materials. The fly ash content was fixed at 80%, with 8.5% - 9.5% mineral powder content, 8.5% - 9.5% lime, 2% - 3% desulfurized gypsum, 0.9% - 1.2% sodium carbonate, and 0.01% - 0.02% aluminum powder content. The prepared backfill material processed good fluidity, with the expansion rate of the hardened material reaching 2% - 3%, and compressive strength on 90 d reaching 4 MPa-5.5 MPa. SEM observations indicated that as the aluminum content increased, ettringite on bubble walls transformed from a fine-needle to needle-rod shape. Secondly, the hydration products of the system were mainly hydrated calcium silicate gel and ettringite, which interconnected and promoted the formation of the structure. The backfill material has extensive sources of raw materials, low cost, simple filling process, and good filling effect.


Assuntos
Cinza de Carvão/química , Mineração , Compostos de Cálcio/química , Sulfato de Cálcio/química , Óxidos/química , Água/química
2.
PLoS One ; 15(6): e0234045, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32544208

RESUMO

A study was conducted to determine the impact of applying different sources of Mg, namely kieserite, ground magnesium limestone (GML) and Mg-rich synthetic gypsum (MRSG) on an acid tropical soil, oil palm growth and production. Besides high amount of Mg and Ca, MRSG contains S. Exchangeable Ca in the untreated soil of the plantation was 0.64 cmolc kg-1, but its critical level to sustain oil palm growth was 0.9 cmolc kg-1. MRSG was applied in the plantation as Mg-fertilizer; however, since Ca is also a limiting nutrient, oil palm growth was correlated (r = 0.69) with Ca supplied by the MRSG. Mg needed to sustain oil palm production is normally supplied by kieserite. Its requirement can be met at a lower cost compared to that of the kieserite by using MRSG. Due to MRSG treatment, exchangeable Ca in the soil increased steadily to satisfy the requirement of oil palm for fruit bunches production. From the glasshouse and field study, it was observed that MRSG applied at 1.5 times the recommended rate gave results comparable to that of the kieserite. MRSG treatment resulted in the increase of soil pH to >5 that precipitated Al3+ as inert Al-hydroxides, which eventually enhanced oil palm seedlings growth. Thus, MRSG can also replace GML to increase soil pH and satisfy the Ca and Mg requirement of oil palm. It can be concluded that MRSG has the potential to be used as a source of Mg as well as Ca for oil palm grown on acidic soil.


Assuntos
Sulfato de Cálcio/química , Sulfato de Cálcio/farmacologia , Magnésio/química , Magnoliopsida/efeitos dos fármacos , Magnoliopsida/crescimento & desenvolvimento , Solo/química , Calibragem , Concentração de Íons de Hidrogênio , Plântula/efeitos dos fármacos , Plântula/crescimento & desenvolvimento
3.
Ecotoxicol Environ Saf ; 201: 110847, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32554203

RESUMO

Bauxite residues (BR), commonly named red muds, are the saline-sodic waste produced during the extraction of alumina from bauxite. In this study, four kinds of BR were mixed at increasing concentrations with two soils in a mesososm experiment. Unamended BR from Provence (PRO) and Guinea (GUI) bauxite were selected, and Modified Bauxite Residues from PRO and GUI (MBR-PRO and MBR-GUI) were obtained by gypsum application and repeated leaching, in order to reduce their pH, electrical conductivity (EC) and exchangeable sodium percentage (ESP). Several indicators of microbial community functions and structure (growth of culturable bacteria; enzymatic activities; C-sourced substrates degradation (Biolog®); bacteria and fungi PCR-RFLP fingerprints) were measured after 35 days of incubation. Results showed that PRO residue had stronger negative effects than GUI on all the tested indicators. Residues modified by gypsum addition (MBR-PRO, MBR-GUI) were equally or sometimes less harmful compared to unamended residues. Microbial activities (bacterial growth and enzyme activities) were more inhibited than the diversity of microbial functions (Biolog®), and the structure of bacterial and fungal communities was not affected by increasing concentrations of bauxite residues. EC and ESP were the main factors explaining the inhibition of microbial activities, although the origin of bauxite residue is of great importance too.


Assuntos
Óxido de Alumínio/toxicidade , Sulfato de Cálcio/toxicidade , Microbiota/efeitos dos fármacos , Microbiologia do Solo , Poluentes do Solo/toxicidade , Solo/química , Óxido de Alumínio/análise , Óxido de Alumínio/química , Bactérias/efeitos dos fármacos , Bactérias/crescimento & desenvolvimento , Sulfato de Cálcio/análise , Sulfato de Cálcio/química , Fungos/efeitos dos fármacos , Fungos/crescimento & desenvolvimento , Poluentes do Solo/análise , Poluentes do Solo/química
4.
Chemosphere ; 255: 126936, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32417511

RESUMO

Transforming gypsum into α-calcium sulfate hemihydrate (α-HH) provides a promising utilization pathway for the abundant amount of chemical gypsum. The transformation follows the route of "dissolution-recrystallization", during which the arsenic pollutant in gypsum is released into the solution, and hence raises the possibility of being distributed into the product of α-HH, a potential harm that has always been neglected. Investigation of the transformation process at neutral pH revealed that the arsenate ions in solution were distributed into α-HH and generated an enrichment of arsenic by 4-6 times. Arsenate ions distributed into α-HH by substitution for lattice sulfate, adsorption on α-HH facets and occupation for surface sulfate sites. While at higher concentrations, calcium arsenate coprecipitated with α-HH or even crystallized independently. Increasing temperature accelerated the phase transformation and restrained arsenate migration into α-HH due to the lag of distribution balance. The pH of solution modulated the dominant arsenate species and decreasing pH weakened arsenate substitution capacity for sulfate in α-HH. This work uncovers arsenate distribution mechanism during the transformation of gypsum into α-HH and provides a feasible method to restrain arsenate distribution into product, which helps to understand arsenate behavior in hydrothermal solution with high concentration of sulfate minerals and provides a guidance for controlling pollutants distribution into product.


Assuntos
Sulfato de Cálcio/química , Modelos Químicos , Adsorção , Arseniatos/química , Arsênico , Compostos de Cálcio/química , Concentração de Íons de Hidrogênio , Sulfatos
5.
Chemosphere ; 256: 127138, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32450348

RESUMO

The present work investigates hazardous elements and nanomineralogical assemblages of phosphogypsum waste from an abandoned phosphate fertilizer industry located in Santa Catarina state (Brazil). Correlations between the chemical composition, nanominerals, and ultrafine particles are discussed. Multifaceted physical-geochemical study provided a careful understanding of the nanomineralogical assemblage of the phosphogypsum waste. The electron beam investigation revealed the presence of many hazardous elements in the ultrafine particles. Cr, Pb, Mn, Se, Sr, and Zr, among others, were found in individual ultrafine particles and nanominerals in all studied samples. Besides that, rare earth elements were found in different concentration ranges, being Ce, La, and Nd, the rare earth elements, found in the higher concentrations, above 900 mg kg-1. The data supplied by this article are important to characterize the phosphogypsum waste, assessing the potential hazard to the environment and human health, and also, provides information to enable the designing of alternatives to manage this waste.


Assuntos
Sulfato de Cálcio/química , Monitoramento Ambiental , Fertilizantes/análise , Metais Pesados/análise , Metais Terras Raras/análise , Fósforo/química , Brasil , Humanos , Material Particulado/análise , Fosfatos/análise
6.
Chemosphere ; 250: 126290, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32120149

RESUMO

Arsenic- and trace metals-bearing gypsum (As-gypsum) is one of the major hazardous solid wastes produced from metallurgical industry that poses a serious threat to the environment. However, the method for effective extraction of As and trace metals from As-gypsum is still lacking. In this study, simultaneous extraction of As and trace metals from a hydrometallurgical As-gypsum via hydrothermal recrystallization in acid solution was investigated. The effects of the type (H2SO4 vs HCl) and concentration of acid, and temperature on extraction efficiency were assessed. The results showed that 99% As, >92% Cu and >96% Zn could be extracted from the As-gypsum during hydrothermal treatment in 6 mol L-1 H2SO4 at 90 and 120 °C, but Pb and Cd could not be extracted efficiently. The results of hydrothermal treatment in HCl solutions demonstrated that higher HCl concentration and temperature significantly enhanced the extraction efficiency and 100% As, Cu2+, Zn2+, Pb2+ and >90% Cd were removed from the As-gypsum after treatment in 6 mol L-1 HCl, at 120 °C, for 12 h. X-ray diffraction (XRD), scanning electron microscopy (SEM), Fourier transform infrared spectroscopy (FTIR), and Raman spectroscopy results revealed that dissolution-recrystallization of gypsum is the key process for the removal of the incorporated As and trace metals. Thermodynamic modelling indicated that the released HAsO42-/Me2+ transformed into H3AsO4/MeCln(2-n) (1 ≤ n ≤ 4) species in HCl solution, hence inhibiting their reincorporation into the recrystallization products via isomorphic substitution for SO42-/Ca2+. This work provides a simple and effective method for detoxification and reclamation of As-gypsum.


Assuntos
Arsênico/química , Arsênico/toxicidade , Sulfato de Cálcio/química , Resíduos Perigosos , Inativação Metabólica , Metalurgia , Metais , Metais Pesados/química , Oligoelementos/química , Difração de Raios X
7.
Ecotoxicol Environ Saf ; 194: 110384, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-32126412

RESUMO

Electrolytic manganese residue (EMR) contains a large amount of NH4+-N and Mn2+ and can negatively impact the environment. A stabilization treatment of soluble contaminants in the EMR is necessary for its reuse and safe stacking. This study presents experimental results for the stabilization of NH4+-N and Mn2+ in the EMR using phosphogypsum leachate as a low-cost phosphate source and MgO/CaO (PLMC) process. The results demonstrated that the stabilization efficiency of NH4+-N and Mn2+ was 93.65% and 99.99%, respectively, under the following conditions: a phosphogypsum leachate dose of 1.5 mL g-1, an added MgO dose of 0.036 g g-1, an added CaO dose of 0.1 g g-1 and a reaction time of 2 h. The stabilization effect of the PLMC process was higher and more cost effective than that of using Na3PO4·12H2O and MgO/CaO. The concentration of NH4+-N and Mn2+ in the leaching liquor decreased to 80 mg L-1 and 0.5 mg L-1, respectively, after the stabilization under the optimum conditions. The stabilization characteristics indicated that NH4+-N was stabilized to form NH4MgPO4·6H2O (struvite) and that Mn2+ was stabilized to form Mn5(PO4)2(OH)4, Mn3(PO4)2·3H2O and Mn(OH)2. PO43--P, F-, and heavy metal ions of the phosphogypsum leachate were removed from the leaching liquor and stabilized in the treated EMR.


Assuntos
Compostos de Cálcio/química , Sulfato de Cálcio/química , Óxido de Magnésio/química , Manganês/análise , Óxidos/química , Fósforo/química , Amônia/análise , Amônia/química , Eletrólise , Eletrólitos , Poluentes Ambientais/análise , Poluentes Ambientais/química , Resíduos Industriais/análise , Manganês/química , Solubilidade , Estruvita/análise , Estruvita/química
8.
Chemosphere ; 248: 125979, 2020 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-32028158

RESUMO

In China, the amount of phosphogypsum (PG) has exceeded 250 million tons with more than 55 million tons of growth rates each year. As the micro constituent, fluorine and phosphorus restrict the resourceful disposal of PG. This paper focused on chemical looping gasification (CLG) which used PG as an oxygen carrier, systematically investigated the gasification performance and chemical behavior of fluorine and phosphorus contained in PG during CLG process. Main conclusions are as follows. The main pollutant of chemical looping gasification process was HF, which was transformed from NaF. Phosphorus transformed from water-soluble phosphorus (Ca(H2PO4)2, Ca(HPO4)) into insoluble Ca3(PO4)2.20 reducing-oxidizing cycles were investigated, and a less and less fluorine content in oxygen carrier was found because its phase transformation from solid NaF to gaseous HF, and the phosphorus content in oxygen carrier changed slightly under the current conditions. The Ca3(PO4)2 particle layers existed in both the middle of the reduced solid particles and the middle of the cycled oxygen carrier particles, confirmed to actually act as a glue between the particles. Furthermore, transformation routes of fluorine and phosphorus during the CLG process were discussed and the generation of syngas in CLG process needed to be purified.


Assuntos
Sulfato de Cálcio/química , Flúor/química , Fósforo/química , China , Fluoretos , Gases , Oxigênio/química , Água
9.
Environ Pollut ; 258: 113790, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31918063

RESUMO

In situ immobilization of heavy metals in contaminated soils using industrial by-products is an attractive remediation technique. In this work, titanium gypsum (TG) was applied at two levels (TG-L: 0.15% and TG-H: 0.30%) to simultaneously reduce the uptake of cadmium (Cd), lead (Pb) and arsenic (As) in rice grown in heavy metal contaminated paddy soils. The results showed that the addition of TG significantly decreased the pH and dissolved organic carbon (DOC) in the bulk soil. TG addition significantly improved the rice plants growth and reduced the bioavailability of Cd, Pb and As. Particularly, bioavailable Cd, Pb and As decreased by 35.2%, 38.1% and 38.0% in TG-H treatment during the tillering stage, respectively. Moreover, TG application significantly reduced the accumulation of Cd, Pb and As in brown rice. Real-time PCR analysis demonstrated that the relative abundance of sulfate-reducing bacteria increased with the TG application, but not for the iron-reducing bacteria. In addition, 16S rRNA sequencing analysis revealed that the relative abundances of heavy metal-resistant bacteria such as Bacillus, Sulfuritalea, Clostridium, Sulfuricella, Geobacter, Nocardioides and Sulfuricurvum at the genus level significantly increased with the TG addition. In conclusion, the present study implied that TG is a potential and effective amendment to immobilize metal(loid)s in soil and thereby reduce the exposure risk of metal(loid)s associated with rice consumption.


Assuntos
Arsênico/isolamento & purificação , Cádmio/isolamento & purificação , Sulfato de Cálcio/química , Chumbo/isolamento & purificação , Poluentes do Solo/isolamento & purificação , Titânio/química , Bactérias/classificação , Oryza , RNA Ribossômico 16S , Microbiologia do Solo
10.
Food Chem ; 310: 125983, 2020 Apr 25.
Artigo em Inglês | MEDLINE | ID: mdl-31835225

RESUMO

In this study, the effects of the addition of various polysaccharides (konjac gum, gellan gum, and curdlan gum) on the rheological and textural properties of calcium sulfate-induced soy protein isolate gels were investigated. The incorporation of konjac gum and curdlan gum at 0.3 and 0.5% (w/v) concentrations and gellan gum at 0.5% concentration significantly enhanced (P < 0.05) the hardness and water-holding capacity of the resultant gels. The increased elastic moduli during and after gelation, reinforced fracture stress, and lowered onset gelling temperature indicated that the addition of the abovementioned polysaccharides strengthened gel structures and accelerated gelation. Confocal laser scanning microscopy analysis revealed that the polysaccharides also improved gel microstructures, with the gels containing konjac gum displaying the highest homogeneity. The findings of this study may provide important information for the development of innovative soy protein isolate-based gel products with improved texture.


Assuntos
Sulfato de Cálcio/química , Polissacarídeos/química , Proteínas de Soja/química , Amorphophallus/química , Módulo de Elasticidade , Géis/química , Polissacarídeos Bacterianos/química , Reologia , Proteínas de Soja/isolamento & purificação , Temperatura , Água/química , beta-Glucanas/química
11.
Chemosphere ; 239: 124823, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31726520

RESUMO

Several studies have demonstrated that gypsum (CaSO4·2H2O) and calcite (CaCO3) can be important hosts of arsenic in contaminated hydrogeological systems. However, the extent to which microbial reducing processes contribute to the dissolution and transformation of carbonate and sulfate minerals and, thereby, to arsenic mobilization is poorly understood. These processes are likely to have a strong impact on arsenic mobility in iron-poor environments and in reducing aquifers where iron oxyhydroxides become unstable. Anoxic batch bioassays with arsenate (As(V)) coprecipitated with calcite, gypsum, or ferrihydrite (Fe(OH)3) were conducted in the presence of sulfate or molybdate to examine the impact of bioprocesses (i.e. As(V), sulfate, and Fe(III)-reduction) on arsenic dissolution, speciation, and eventual remineralization. Microbial reduction of As(V)-bearing calcite caused an important dissolution of arsenite, As(III), which remained in solution up to the end of the experiment (30 days). The reduction of As(V) from gypsum-As(V) also led to the release of As(III), which was subsequently remineralized, possibly as arsenic sulfides. The presence of sulfate triggered arsenic dissolution in the bioassays with ferrihydrite-As(V). This study showed that although gypsum and calcite have a lower capacity to bind arsenic, compared to iron oxides, they can play a critical role in the biogeochemical cycle of arsenic in natural calcareous and gypsiferous systems depleted of iron since they can be a source of electron acceptors for reducing bioprocesses.


Assuntos
Arsênico/química , Bactérias/metabolismo , Carbonato de Cálcio/química , Sulfato de Cálcio/química , Compostos Férricos/química , Arseniatos/química , Arsenicais/química , Arsenitos/química , Carbonatos/química , Água Subterrânea/química , Ferro/química , Molibdênio/química , Oxirredução , Solubilidade , Sulfatos/química , Sulfetos/química
12.
Environ Pollut ; 258: 113729, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31855679

RESUMO

Next to the city of Huelva (SW of Spain), around 100 Mt of phosphogypsum (PG) are stored in stacks on the salt-marshes of the Tinto River estuary covering a surface of about 1000 ha. Due to the high content of 238U series natural radionuclides of the PG, its acidic nature (pH about 3), and the fact that PG stacks were disposed without any kind of isolation from the substrate, they could produce a potential radioactive impact into the underlying sediments. The aim of this work is to assess the pollution of the underlying sediments by natural radionuclides coming from the PG stacks. To this end, seven cores were taken, and PG and sediments samples collected at different depths were analysed. The activity concentrations of the main long half-live natural radionuclides of interest were determined by applying both gamma-ray and alpha-particle spectrometry radiometric techniques. The results of this study showed that the first decimeters of salt-marsh sediment act as a "barrier" for the radionuclides coming from the PG stacks decreasing rapidly its activity concentration in depth, affecting mainly sediments located in the first 20 cm below the contact due to mixing processes. While 230Th, 226Ra and 210Pb pollution is mainly restricted to the first 20 cm of sediments, U-isotopes can reach higher depths (up to around 50 cm) by leaching processes due to their lower reactivity and higher concentration in the polluted leachates. The obtained results have high relevance for the design of the perimeter channel which is projected to build in the restoration project, suggesting that should has around 1 m deep under the base of the PG stacks, to ensure the full collection of polluting leachates, and to prevent their release into the estuary of the Tinto River.


Assuntos
Sulfato de Cálcio/química , Fósforo/química , Radioisótopos/análise , Poluentes Radioativos do Solo/análise , Áreas Alagadas , Sedimentos Geológicos/química , Espanha
13.
Environ Sci Pollut Res Int ; 27(2): 1348-1358, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31749009

RESUMO

A combined amendment (CF) consisting of 90% calcium sulfate (CaSO4) and 10% ferric oxide (Fe2O3) was used to investigate the feasibility, active principles, and possible mechanisms of the immobilization of heavy metals in paddy soil. A soil incubation experiment, two consecutive pot trials, and a field experiment were conducted to evaluate the effectiveness and persistence of CF on metal(loid) immobilization. Soil incubation experiment results indicated that the application of CF significantly decreased the concentrations of cadmium (Cd), lead (Pb), and arsenic (As) in soil solution. CF treatments simultaneously reduced the accumulation of Cd, Pb, and As in two consecutive pot trials. The total Cd, Pb, and As concentrations in the rice grains were respectively 0.02, 2.08, and 0.62 mg kg-1 in the control treatment in the second year, which exceeded the safety limits of contaminants in food products in China. However, a high amount of CF amendment (CF-H, 0.3%) effectively decreased Cd, Pb, and As by 75.0%, 75.5%, and 46.8%, respectively. Further, with the CF amendment, the bioavailable Cd and Pb in the soil and the accumulation of Cd, Pb, and As in rice grain in the field experiment were also significantly decreased. The concentrations of Cd, Pb, and As in grains were respectively 0.02, 0.03, and 0.39 mg kg-1 in the control treatment in the field experiment, which decreased to 0.01, 0.01, and 0.22 mg kg-1 with CF addition, suggesting that grains produced in the field could pose less health risk. In conclusion, these results implied that CF was an effective and persistent combined amendment to immobilize heavy metals in soil and thereby can reduce the exposure risk of metal(loid)s associated with rice consumption.


Assuntos
Arsênico/isolamento & purificação , Cádmio/metabolismo , Sulfato de Cálcio/química , Recuperação e Remediação Ambiental/métodos , Compostos Férricos/química , Chumbo/metabolismo , Oryza/química , Poluentes do Solo/metabolismo , Solo/química , Arsênico/análise , Biodegradação Ambiental , Cádmio/análise , Sulfato de Cálcio/análise , China , Grão Comestível/química , Compostos Férricos/análise , Chumbo/análise , Oryza/metabolismo , Poluentes do Solo/análise , Poluentes do Solo/química
14.
Orthop Surg ; 12(1): 295-303, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31863648

RESUMO

OBJECTIVES: To analyze the optimum particle size or formula ratio of surgical-grade calcium sulfate (CS) for appropriate compressive strength, setting time, and vitro degradation rate. METHODS: Three types of calcium sulfate hemihydrate (CSH) particles with diameters of 0-37.5 µm, 37.5-75 µm, and >75 µm were screened. Based on formulation ratio of different particles, this topic is divided into 10 groups by the unconstrained third-order simplex lattice mixing design scheme in formula design experiment. The optimum formulation ratio of particle diameter for compressive strength, solidification time, and degradation rate in vitro was analyzed. RESULTS: When the percentage of the particle diameter of CS with 0-37.5 µm, 37.5-75 µm and >75 µm are 55.0%, 17.4%, and 27.6% respectively, the compressive strength of the test sample is the highest, which is 14.16 MPa. When the percentage of the particle diameter of CS with 0-37.5 µm, 37.5-75 µm, and >75 µm are 0.00%, 0.00%, and 100.00% respectively, the initial setting time of the sample is the longest, which is 410.0 s. When the percentage of the particle diameter of CS with 0-37.5 µm, 37.5-75 µm, and >75 µm are 0.00%, 0.00%, and 100.00% respectively, the final setting time of the sample is the largest, and the final setting time of the sample is 460.00 s. When the percentage of the particle diameter of CS with 0-37.5 µm, 37.5-75 µm, and >75 µm are 0.00%, 0.00%, and 100.00% respectively, the degradation rate of the sample in vitro is the slowest, which is 18.8%. CONCLUSION: The morphological structure of surgical-grade CS can affect compressive strength, setting time, and in vitro degradation rate. Surgical CS should be prepared based on different uses.


Assuntos
Materiais Biocompatíveis/química , Substitutos Ósseos/química , Sulfato de Cálcio/química , Força Compressiva , Tamanho da Partícula , Materiais Biocompatíveis/síntese química , Substitutos Ósseos/síntese química , Humanos , Teste de Materiais
15.
Chemosphere ; 241: 124824, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-31590026

RESUMO

Waste management and global warming are the two challenging issues of the present global scenario. Increased human population has set the platform for rapid industrialization and modern agriculture. The industries such as energy, steel, and fertilizers play a significant role in improving the social, and economic status of human beings. The industrial production of energy (that involves combustion of coal), production of steel items and diammonium ammonium fertilizer generate a huge amount of wastes such as fly ash (FA), steel slag (SS) and phosphogypsum (PG), respectively. Inappropriate dumping of any kind of waste poses a threat to the environment, therefore, scientific management of waste is required to reduce associated environmental risks. These wastes i.e. SS, FA, and PG being rich sources of oxides of calcium (CaO), silicon (SiO2), iron (FeO), and aluminum (Al2O3), etc. may affect the release of greenhouse gases from the soil. The information associated with the application of FA, SS, and PG onto the paddy fields and their impacts on methane and nitrous oxide emissions are highly fragmented and scarce. The present review extensively and critically explores the available information with respect to the effective utilization of FA, SS, and PG in paddy cultivation, their potential to mitigate greenhouse gases emission and their associated mechanisms. The fine grid assessment of these waste management provides new insight into the next level research and future policy options for industries and farmers.


Assuntos
Recuperação e Remediação Ambiental/métodos , Gases de Efeito Estufa/química , Resíduos Industriais , Oryza , Gerenciamento de Resíduos/métodos , Sulfato de Cálcio/química , Cinza de Carvão/química , Fertilizantes , Fósforo/química , Aço/química
16.
Chemosphere ; 242: 125174, 2020 Mar.
Artigo em Inglês | MEDLINE | ID: mdl-31675582

RESUMO

Salt marshes are natural deposits of heavy metals in estuarine systems, where sulphide precipitation associated with redox changes often results in a natural attenuation of contamination. In the present study, we focus on the effects of variable redox conditions imposed to a highly-polluted phosphogypsum stack that is directly piled over the salt marsh soil in the Tinto River estuary (Huelva, Spain). The behaviour of contaminants is evaluated in the phosphogypsum waste and in the marsh basement, separately, in controlled, experimentally-induced oscillating redox conditions. The results revealed that Fe, and to a lesser extent S, control most precipitation/dissolution processes. Ferric iron precipitates in the form of phosphates and oxyhydroxides, while metal sulphide precipitation is insignificant and appears to be prevented by the abundant formation of Fe phosphates. An antagonistic evolution with changing redox conditions was observed for the remaining contaminants such as Zn, As, Cd and U, which remained mobile in solution during most of experimental run. Therefore, these findings revealed that high concentrations of phosphates inhibit the typical processes of immobilisation of pollutants in salt-marshes which highlights the elevated contaminant potential of phosphogypsum wastes on coastal environments.


Assuntos
Sulfato de Cálcio/química , Estuários , Oxirredução , Fósforo/química , Monitoramento Ambiental/métodos , Ferro/química , Metais Pesados/análise , Fosfatos/química , Rios , Espanha , Poluentes Químicos da Água/análise , Áreas Alagadas
17.
Chemosphere ; 239: 124741, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31518921

RESUMO

In many parts of the world, wastewater irrigation has become a common practice because of freshwater scarcity and to increase resource reuse efficiency. Wastewater irrigation has positive impacts on livelihoods and at the same time, it has adverse impacts related to environmental pollution. Hydrochemical processes and groundwater behaviour need to be analyzed for a thorough understanding of the geochemical evolution in the wastewater irrigated systems. The current study focuses on a micro-watershed in the peri-urban Hyderabad of India, where farmers practice intensive wastewater irrigation. To evaluate the major factors that control groundwater geochemical processes, we analyzed the chemical composition of the wastewater used for irrigation and groundwater samples on a monthly basis for one hydrological year. The groundwater samples were collected in three settings of the watershed: wastewater irrigated area, groundwater irrigated area and upstream peri-urban area. The collected groundwater and wastewater samples were analyzed for major anions, cations and nutrients. We systematically investigated the anthropogenic influences and hydrogeochemical processes such as cation exchange, precipitation and dissolution of minerals using saturated indices, and freshwater-wastewater mixtures at the aquifer interface. Saturation indices of halite, gypsum and fluorite are exhibiting mineral dissolution and calcite and dolomite display mineral precipitation. Overall, the results suggest that the groundwater geochemistry of the watershed is largely controlled by long-term wastewater irrigation, local rainfall patterns and water-rock interactions. The study results can provide the basis for local decision-makers to develop sustainable groundwater management strategies and to control the aquifer pollution influenced by wastewater irrigation.


Assuntos
Irrigação Agrícola/métodos , Água Subterrânea/química , Águas Residuárias , Ânions/análise , Carbonato de Cálcio/química , Sulfato de Cálcio/química , Cátions/análise , Meio Ambiente , Monitoramento Ambiental/métodos , Água Doce/química , Água Subterrânea/análise , Hidrologia/métodos , Índia , Magnésio/química , Salinidade , Poluentes Químicos da Água/análise , Poluentes Químicos da Água/química , Qualidade da Água
18.
Genomics ; 112(1): 981-989, 2020 01.
Artigo em Inglês | MEDLINE | ID: mdl-31220587

RESUMO

Phosphogypsum (PG) is an acidic by-product from the phosphate fertilizer industry and it is characterized by a low nutrient availability and the presence of radionuclides and heavy metals which pose a serious problem in its management. Here, we have applied Illumina MiSeq sequencing technology and five bioinformatics pipelines to explore the phylogenetic communities in Tunisian PG. Taking One Codex as a reference method, we present the results of 16S-rDNA-gene-based metataxonomics abundances with four other alternative bioinformatics pipelines (MetaGenome Rapid Annotation using Subsystem Technology (MG-RAST), mothur, MICrobial Community Analysis (MICCA) and Quantitative Insights into Microbial Ecology (QIIME)), when analyzing the Tunisian PG. Importantly, based on 16S rDNA datasets, the functional capabilities of microbial communities of PG were deciphered. They suggested the presence of PG autochthonous bacteria valorizable into (1) removal of radioactive elements and toxic heavy metals, (2) promotion of plant growth, (3) oxidation and (4) reduction of sulfate. These bacteria can be explored further for applications in the bioremediation of by-products, like PG, by different processes.


Assuntos
Bactérias/metabolismo , Sulfato de Cálcio , Fósforo , Bactérias/classificação , Bactérias/genética , Bactérias/isolamento & purificação , Biodegradação Ambiental , Sulfato de Cálcio/química , Sulfato de Cálcio/metabolismo , Biologia Computacional , Sequenciamento de Nucleotídeos em Larga Escala , Microbiota , Fósforo/química , Fósforo/metabolismo , Análise de Sequência de DNA , Software , Tunísia
19.
Mater Sci Eng C Mater Biol Appl ; 106: 110175, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31753362

RESUMO

Resorbable bioceramics offer advantages in healing bone defects due to their degradation capability. Degradation rates differ significantly from one bioceramic to another; nevertheless, the degradation rate should match the growth rate of new bone. In the present study, a head-to-head comparison of the degradation rate of calcium sulfate and tricalcium phosphate is conducted. First, the degradation behaviors of calcium sulfate and tricalcium phosphate are evaluated separately. The comparison indicates that the degradation rate of calcium sulfate is one order of magnitude faster than that of tricalcium phosphate. Along with a fast degradation rate, the formation of calcium phosphate on the surface of calcium sulfate pellets is also faster. A core-shell roll composed of a calcium sulfate core and a tricalcium phosphate shell is also prepared. After soaking the core-shell roll in phosphate buffered saline solution for 24 h, calcium phosphate precipitates form only on the surface of core, the part containing calcium sulfate anhydrite.


Assuntos
Materiais Biocompatíveis/química , Fosfatos de Cálcio/química , Cerâmica/química , Sulfato de Cálcio/química
20.
Radiat Prot Dosimetry ; 187(4): 509-517, 2019 Dec 31.
Artigo em Inglês | MEDLINE | ID: mdl-31650175

RESUMO

The objective of this paper is to study the effect of consecutive heating of TL elements of a thermoluminescence dosemeter (TLD) card in hot N2 gas-based TLD badge reader. The effect is studied by theoretical simulations of clamped heating profiles of the discs and resulting TL glow curves. The simulated temperature profile accounts for heat transfer to disc from hot gas as well as radiative and convective heat exchanges between the disc and the surrounding. The glow curves are simulated using 10 component glow peak model for CaSO4:Dy using the simulated temperature profile. The shape of the simulated glow curves and trend in total TL signal of the three discs were observed to match closely with the experimental observations when elevated surrounding temperature was considered for simulation. It is concluded that the readout (heating) of adjacent TLD disc affects the surrounding temperature leading to the changes in temperature profile of the next disc.


Assuntos
Sulfato de Cálcio/química , Disprósio/química , Temperatura Alta , Compostos de Lítio/química , Dosimetria Termoluminescente/instrumentação , Dosimetria Termoluminescente/métodos , Humanos , Termodinâmica
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