A tool for realistic study of nanoparticulate coal rejects

Pollution caused by hazardous and carcinogenic inorganic elements and organic compounds from coal may be more severe when coupled by other sources of pollution. In addition, the modes of occurrence of potential hazardous elements (PHEs) in coal cleaning rejects (CCRs) have been widely investigated using different methods, including statistical methods, which, however, in some cases resulted in misleading interpretations. In order to verify this potential problem and find an effective solution, we selected a data set, which contained comprehensive analyses of CCRs. The secondary products in sulphides-bearing coal mine rejects were studied in demand to determine their geochemical and ecological structures and to assess their position in the reduction of PHEs in the nature. A zone located in south Brazil, which is the major coal power plant in South America, can be given as an example of such a problem. In this work, a novel methodology for the analysis of PHEs in soils and sediments is proposed for this affected coal area. The analytical method combining X-Ray Diffraction (XRD) and advanced electron microscopies shows the importance of nanomineralogy in understanding different circumstances of coal contamination. Several ultrafine-nanoparticles (UNPs) were identified in the sampled soils and river sediments together with the PHEs. A decrease in PHEs was identified in association with UNPs. However, still further investigations are required with regard to the mobility of PHEs in water, atmosphere, soils, and sediments. The site studied around the coal power plant showed the highest sorption capacity possibly due to the high retention ability of components of soil and sediments such as carbon and clay. These observations of the coal-derived nanoparticles confirm their capability of regulating the mobility of hazardous elements, implying the need for restoring complex abandoned coal areas.

PURIFICAÇÃO ÁCIDO-BASE EXPERIMENTAL DE CASCAS DE ARROZ CARBONIZADAS: EXPLORANDO SUA EFICÁCIA NA ADSORÇÃO DE RESÍDUOS NÃO VALORIZADOS DA INDÚSTRIA DE ARROZ

The burning of rice husks produces natural silica and generates charcoal with excellent properties for the adsorption of different pollutants. The objective of this study was to enhance the adsorption properties of this industrial residue from burning rice husk through acid and base purifications. The raw coal (RC) was initially modified with HCl(aq.) and then with NaOH(aq.), and subsequently renamed MC. Efficiency was verified by the adsorption of methylene blue (MB) dye, considering a concentration of 10 mg L-1, dosage of 0.05 g L-1, pH 6.7, and 120 min. MB removal was 78% for RC and 97% for MC, with experimental capacities of 144.78 mg g-1 and 180.78 mg g-1, respectively. The kinetics were better adjusted by Avrami (R2 0.99, error <2.8%). The properties of charcoal improved with the modification, presenting a more porous structure, greater surface area and functional groups that contributed to adsorption, proving that simple purification methods, such as acid-base purification, can be crucial for waste reuse.  A queima da casca de arroz produz sílica natural e gera um carvão com excelentes propriedades para adsorção de diferentes poluentes. O objetivo deste trabalho foi aprimorar as propriedades de adsorção desse resíduo carbonizado através de purificação ácida e básica. O carvão bruto (RC) foi modificado, primeiramente com HCl(aq.) e em seguida com NaOH(aq.), sendo re-nomeado MC. A eficiência foi investigada pela adsorção do corante azul de metileno (MB), considerando concentração 10 mg L-1, dosagem 0,05 g L-1, pH 6,7, e 120 min. A remoção de MB foi de 78% para RC e 97% para MC, com capacidades experimentais de 144,78 mg g-1 e 180,78 mg g-1, respectivamente. As cinéticas foram melhor ajustadas por Avrami (R2 0,99, erro <2,8%). As propriedades do carvão melhoraram com a modificação, apresentando estrutura mais porosa, maior área superficial e grupos funcionais que contribuíram para a adsorção, provando que métodos simples de purificação podem ser cruciais para a reutilização de resíduos. &nbsp

Nanomineralogy of evaporative precipitation of efflorescent compounds from coal mine drainage

Efflorescent nanophases (NPs) are found as a transitory accumulation of potentially hazardous elements (PHEs), particularly in tropical climates. The central objective of this study was to investigate the distribution of PHEs with NPs through the evaporative formation structures (EFS) of enormously PHEs-rich coal-mine drainages (CMD). The EFS were studied in natural coal mine drainage for five months in order to determine their geochemical and ecological structures and to assess their position in the reduction of PHEs in nature. The largest coal-fired power plant in South America, located in south Brazil, is used as an example of such a problem. In this work, a novel methodology for the analysis of PHEs in CMD precipitates is proposed for this affected coal area. The analytical method, combining X-Ray Diffraction (XRD) and advanced electron microscopies, shows the importance of nanomineralogy in understanding different circumstances of coal contamination. Several ultrafine-nanoparticles (UNPs) were identified in the sampled soils and river sediments together with the PHEs. A decrease in PHEs was identified in association with UNPs. However, further investigations are required with regard to the mobility of PHEs in water, atmosphere, soils, and sediments. The EPS was thoroughly studied, acquiring suitable understanding with investigational facts for Ca and Fe-sulphates, pickeringite, and several amorphous phases

Development of a biosponge based on Luffa cylindrica and crosslinked chitosan for Allura red AC adsorption

A new bioadsorbent from Luffa cylindrica and cross-linked chitosan was proposed in the present study. Luffa was used as a natural support medium for chitosan crosslinked with glutaraldehyde (LCsG) and epichlorohydrin (LCsE). Biosponges were applied to remove Allura red from aqueous solutions. LCsG and LCsE were produced using different concentrations of chitosan (1%, 3% and 5% (m v−1)) and crosslinking agents (0.5%, 1.0% and 1.5% (v v−1)). Based on the FT-IR spectra, functional groups characteristic of chitosan crosslinked with glutaraldehyde and epichlorohydrin confirmed the crosslinking. In addition, the biosorbent revealed highly efficient functional groups and morphology with irregularities favorable for adsorption. It was found that the increase in the percentage of glutaraldehyde and epichlorohydrin increased the sample's swelling degree, and the degree of cross-linking was greater than 80% for all LCsG. The results regarding the degree of swelling and degree of crosslinking corroborated with the evaluation of the biosponge's adsorptive potential. The Sips model predicted the equilibrium isotherms, with a maximum adsorption capacity of 89.05 mg g−1 for LCsG and 60.91 mg g−1 for LCsE. The new procedure was successful. Luffa was excellent support for chitosan, resulting in an attractive, low-cost bioadsorbent, preventing renewable sources

Nanoparticles and interfaces with toxic elements in fluvial suspended sediment

Studies examining nanoparticles (NPs) and hazardous elements (HEs) contained in suspended sediments (SSs) are vital for watershed administration and ecological impact evaluation. The biochemical consequence of titanium-nanoparticles (Ti-NPs) from SSs in Colombia's Magdalena River was examined utilizing an innovative approach involving nanogeochemistry in this study. In general, the toxicity and the human health risk assessment associated with the presence of some Ti-NPs + HEs in SSs from riverine systems need to be determined with a robust analytical procedure. The mode of occurrence of Ti-NPs, total Ti and other elements contained within SSs of the Magdalena River were evaluated through advanced electron microscopy (field emission scanning electron microscope-FE-SEM and high resolution transmission electron microscope-HR-TEM) coupled with an energy dispersive X-ray microanalysis system (EDS); X-Ray Diffractions (XRD); and inductively coupled plasma-mass pectrometry (ICP-MS). This work showed that enormous quantities of Ti-NPs were present in the river studied and that they displayed diverse eochemical properties and posed various possible ecological dangers. Ti-NP contamination indices must be established for measuring the environmental magnitudes of NP contamination and determining contamination rank among rivers. Finally, SS contamination guidelines must be recommended on an international level. This study contributes to the scientific understanding of the relationship of HE and Ti-NP dynamics from SSs in riverine systems around the world

Functionalization of corn stover with 3-aminopropyltrietoxysilane to uptake Reactive Red 141 from aqueous solutions

An alternative and low-cost adsorbent (CS–APTES) was developed by the functionalization corn stover (CS) with 3-aminopropyltrietoxysilane (APTES) using a simple method. Several analytical techniques were used to prove the functionalization and then, CS–APTES was employed to adsorb Reactive Red 141 (RR141) dye from aqueous solutions. The functionalization with APTES caused an increase of 15 times in the adsorption capacity. The adsorption of RR141 on CS–APTES was favored at pH 3.0 using a dosage of 3.0 g L–1. The adsorption equilibrium was reached within 4 h, being the process thermodynamically favorable, endothermic, and controlled by chemisorption. The maximum adsorption capacity was 15.65 mg g–1. CS–APTES was efficient to treat a colored effluent containing various ions and molecules. The use of 10 g L–1 of CS–APTES was sufficient to decolorize more than 98% of this effluent. It was concluded that CS–APTES can be easily prepared from CS, generating an efficient and low-cost adsorbent which, in turn, is able to treat colored effluents

Nanomineralogy of mortars and ceramics from the Forum of Caesar and Nerva (Rome, Italy): The protagonist of black crusts produced on historic buildings

The recent focus of the impacts of atmospheric pollution on effective conservation methods for historic structures of great cultural heritage has been shown to be of critical importance for preservation. This work focuses on medieval Roman mortars and ceramics from the historic Forum of Caesar and Nerva, in Rome, Italy, and analyzes the urgency of repair of defects in rendered façades based on the inspection of surfaces where defects were detected, defining a methodology to predict the repair urgency of defects and building elements. X-ray spectroscopy (EDS), field emission scanning electron microscopy (FE-SEM), high-resolution transmission electron microscopy (HR-TEM), and X-ray powder diffraction (XRD) analyses are well equipped to study mineralogy, ultra-fine particles, and nanoparticles (NPs, minerals and amorphous phases) that are present in medieval Roman ruins. Applied analysis of ruin-derived mortar and ceramics detected the presence of materials, primarily constituted of quartz, alumino-silicates, Fe-hydr/oxides, portions of amorphous phases, calcareous minerals, pyroxene, and carbonaceous materials. The Forum of Caesar and Nerva are two of the greatest remaining symbols of historic Roman construction. Many compounds recognized by XRD can be revealed by advanced microscopies and vice versa. The incidence of NPs containing potentially toxic elements (PTEs), and numerous carbonaceous complexes linked with building material alterations due to moisture and atmospheric contamination were also discovered. This study assesses the philosophies of preservation and culture, while considering the exhaust emitted by vehicular traffic in order to propose a justifiable and effective method to best conserve historic Roman structures located in high traffic areas

The impact of air pollution on the rate of degradation of the fortress of Florianópolis Island, Brazil

The study of the prevalence of agglomerated nanoparticles (ANPs) containing potentially hazardous elements (PHEs) in the atmosphere is an emerging field of research. As such, the development of effective analytical procedures for the documentation of ANPs in air dust is vital for the evaluation of human health consequences. X-ray powder diffraction (XRD), Raman spectroscopy (RS), Mossbauer spectroscopy (MS) and advanced microscopy (AM) analyses of levels of pollutant concentration have been completed for many years in buildings worldwide. The chemical and mineralogical features of the Fortress of Nossa Senhora da Conceição de Araçatuba in the Brazilian state of Santa Catarina were utilized to catalog the geologic makeup of the structure's raw materials. Analyses of diverse categories of historical building were developed and performed to show the incidence of normal and anthropogenic compounds with PHEs. These geochemical effects and the subsequent fate and transport of nanoparticulate and colloidal (1–1000 nm) compounds in the atmosphere have remained a focus of study for many years. However, the data published in the scientific literature is nowhere near adequate to generate an exhaustive standard of the performance, fate, and transport of natural and anthropogenic ANPs in the atmosphere. Studies to date do provide a preliminary argument for the human health risk calculations from historical buildings due to ANPs. Thus, the geochemical makeup of ANPs and their position in collected nanomineral–organic accumulations may offer some insight into their source. Our ability to detect such ANPs may decrease over time due to the tendency of historical buildings to accrete sludge over the years. The occurrence of PHEs in atmospheric ANPs has not formerly been recognized on the island environment examined in this study. However, it has been shown that it presents a clear and present danger to the preservation of historical monuments

An eco-friendly and low-cost strategy for groundwater defluorination: adsorption of fluoride onto calcinated sludge

The excess of fluoride ions (F−) in water for human supply is a serious public health. The recommended concentration of F− ions by the World Health Organization (WHO) is 1.5 mg L-1. Several groundwater sources around the world contain high F− concentrations, and require treatment before human consumption. It was developed an eco-friendly and low-cost strategy for groundwater defluorination, i.e., adsorption onto calcinated sludge. This strategy was efficient at pH of 5.5 and using 5 g L-1 of calcinated sludge. The groundwater attained the WHO standard within 60 min. The kinetic model of pseudo-second-order obtained a better adjustment to the experimental data. The equilibrium curve at 25 °C was better represented by the Tóth model. The maximum adsorption capacity was 2.04 mg g-1. Therefore, adsorption using calcinated sludge can be considered as an eco-friendly and low-cost strategy for groundwater defluorination

Identification of mercury and nanoparticles in roots with different oxidation states of an abandoned coal mine

The morphology and composition of roots with different degrees of oxidation as a function of time were evaluated aiming to identify possible hazardous elements and nanoparticles. The roots were obtained from an abandoned coal mine located in the city of Criciúma, Santa Catarina, Brazil. From the roots, analyses were performed to identify nanoparticles (NPs) and ultrafine particles (UFPs), containing possible hazardous elements (PHEs) that cause potential environmental risks and impacts on human health. The identification of nanoscale materials requires greater robustness, so advanced integrated techniques have been used. The characterization of different types of roots was done by using focused ion beam (FIB), to evaluate nano-compound assemblies with high-resolution transmission electron microscopy/energy dispersive spectroscopy (HR-TEM/EDS). The results showed the presence of NPs containing Hg, Co, Cr, Ni, and V. The presence of these elements has increased consistently with the increase of C concentration in the roots, suggesting that the PHEs were gradually released from organic matter and inorganic minerals of coal. However, even with their decrease in roots, it was found that these elements still remained in the soil in significant quantities, even after 15 years of inactivation of the coal mine