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•Bamboo based biochar/montmorillonite composite preparation.•Porous biochar acted as support to host particles of montmorillonite.•The composite exhibited much better compared to raw ...biochar via nitrates removal.
Biochar is a promising immobilization tool for various contaminants in liquid wastes, aqueous solutions and soils. To further improve the sorption characteristics, a biochar/montmorillonite composite was produced and synthesized in an experimental pyrolysis reactor, using bamboo as biomass feedstock. The composite was characterized by physico-chemical and structural methods (FTIR, SEM, SEM/EDX, SSA, Low temperature nitrogen adsorption method). Based on these methods, the successful preparation of a bamboo based biochar/montmorillonite composite preparation has been demonstrated. The particles of montmorillonite were distributed across the biochar surface. The adsorption studies for removal nitrates from aqueous solutions were investigated by a batch method at laboratory temperatures. The experimental data were fitted by three adsorption models (Langmuir, Freundlich and DR; R2 > 0.93). The maximum adsorption capacity achieved by biochar at pH 4, was about 5 mg g−1 and by biochar/montmorillonite composite 9 mg g−1. The results suggest that the bamboo-based biochar/montmorillonite composite can be used effectively in the treatment of industrial effluents or waste water containing anionic pollutants such as nitrates.
Methylene blue (MB) is one of the most widely studied organic molecules in the treatment of wastewater. Sorption, biodegradation, photodegradation, electrochemical oxidation, ozonation, and other ...advanced oxidative processes are frequently used to remove this dye from water solutions. The unexpected degradation of MB adsorbed on magnetic biochar from aqueous solution was observed. We found that the conditions of handling, such as drying temperature and storage period, substantially influenced the stability of the dye fixed on the (magnetic) carbon adsorbents. Twelve substances were identified by mass spectrometry as products of decomposition, mostly demethylated, oxidated, and hydroxylated substances. The decomposition of MB was further investigated using non-magnetic carbon biochars and aluminosilicate mineral zeolite. Our findings of the spontaneous decomposition of MB and the identification of the species of degradation offer a new approach to evaluate the mechanism of adsorption, the process of regeneration, and the toxicity of treated solutions.
Large amounts of coal combustion products (as solid products of thermal power plants) with different chemical and physical properties cause serious environmental problems. Even though coal fly ash is ...a coal combustion product, it has a wide range of applications (e.g., in construction, metallurgy, chemical production, reclamation etc.). One of its potential uses is in zeolitization to obtain a higher added value of the product. The aim of this paper is to produce a material with sufficient textural properties used, for example, for environmental purposes (an adsorbent) and/or storage material. In practice, the coal fly ash (No. 1 and No. 2) from Czech power plants was firstly characterized in detail (X-ray diffraction (XRD), X-ray fluorescence (XRF), scanning electron microscopy with energy dispersive X-ray analysis (SEM-EDX), particle size measurement, and textural analysis), and then it was hydrothermally treated to synthetize zeolites. Different concentrations of NaOH, LiCl, Al
O
, and aqueous glass; different temperature effects (90-120 °C); and different process lengths (6-48 h) were studied. Furthermore, most of the experiments were supplemented with a crystallization phase that was run for 16 h at 50 °C. After qualitative product analysis (SEM-EDX, XRD, and textural analytics), quantitative XRD evaluation with an internal standard was used for zeolitization process evaluation. Sodalite (SOD), phillipsite (PHI), chabazite (CHA), faujasite-Na (FAU-Na), and faujasite-Ca (FAU-Ca) were obtained as the zeolite phases. The content of these zeolite phases ranged from 2.09 to 43.79%. The best conditions for the zeolite phase formation were as follows: 4 M NaOH, 4 mL 10% LiCl, liquid/solid ratio of 30:1, silica/alumina ratio change from 2:1 to 1:1, temperature of 120 °C, process time of 24 h, and a crystallization phase for 16 h at 50 °C.
Gadolinium oxymolybdate, Gd
2
MoO
6
(monoclinic,
C
2/
c
) was prepared via nonconventional mechanochemical/thermal process from powdered oxide precursors (Gd
2
O
3
and (NH
4
)
2
MoO
4
). The effect ...of mechanical activation via high-energy ball milling on the reactivity of the stoichiometric Gd
2
O
3
+ (NH
4
)
2
MoO
4
mixture was studied by thermal analysis (TG-DSC) and Fourier-transform infrared spectroscopy. While thermal treatment of nonactivated mixture leads only to decomposition of (NH
4
)
2
MoO
4
and formation of Gd
2
O
3
–MoO
3
system, mechanical activation provides enough energy for a chemical reaction between both reactants. The product with an average crystallite size of approximately 1 μm shows a well-faceted morphology. The investigation of magnetic properties revealed antiferromagnetic coupling, which is attributed to exchange interactions.
Availability of water may influence activities of all living organisms, including cyanobacterial communities. Filamentous cyanobacterium Nostoc commune is well adapted to wide spectrum of ecosystems. ...For this reason, N. commune had to develop diverse protection strategies due to exposition to regular rewetting and drying processes. Few studies have been conducted on activities, by which cyanobacteria are trying to avoid water deficit. Therefore, the present study using physiological and morphological parameters is focused on comparison between European and Antarctic ecotypes of N. commune during rewetting. Gradual increase of FV/FM ratios, as the markers of active PS II, demonstrated the recovery processes of N. commune colonies from Europe as well as from Antarctica after time dependent rehydration. During the initial hours of rewetting, there was lower content of soluble proteins in colonies from Antarctica in comparison to those from Europe. Total content of nitrogen was higher in European ecotypes of N. commune. Significantly higher frequency of occurrence of heterocysts in Antarctic ecotypes was observed. The heterocyst cells were significantly longer in Antarctic ecotypes rather than European ecotypes of N. commune.
The continued decrease in water quality requires new advances in the treatment of wastewater, including the preparation of novel, effective, environmentally friendly, and affordable sorbents of toxic ...pollutants. We introduce a simple non-conventional mechanochemical synthesis of magnetically responsive materials. Magnetic lignite and magnetic char were prepared by high-energy ball co-milling from either raw Slovak lignite or coal-based char together with a ferrofluid. The products were characterised by X-ray diffraction, electron microscopy,
Fe Mössbauer spectroscopy, X-ray photoelectron spectroscopy (XPS), volumetric magnetic susceptibility, and low-temperature nitrogen adsorption, and both magnetic carbons were comparatively tested as potential sorbents of As(V) oxyanions and Cd(II) cations in aqueous solutions. The magnetic char was an excellent sorbent of As(V) oxyanions (
= 19.9 mg/g at pH 3.9), whereas the magnetic lignite was less effective. The different sorption properties towards arsenic anions may have been due to different oxidation states of iron on the surfaces of the two magnetic composites (determined by XPS), although the overall state of iron monitored by Mössbauer spectroscopy was similar for both samples. Both magnetic composites were effective sorbents for removing Cd(II) cations (
(magnetic lignite) = 70.4 mg/g at pH 6.5;
(magnetic char) = 58.8 mg/g at pH 6.8).
Agricultural waste biomass is often used to produce activated carbon with high specific surface area, high degree of porosity and excellent sorption properties. Many researchers used chemical ...activation in connection with single-stage or two-stage pyrolysis. Therefore, the aim of this work was to compare both methods. The first method covered direct chemical activation of biomass with a single pyrolytic step. The second procedure consisted of two-stage pyrolysis (after first pyrolysis the char was chemically activated and pyrolysed secondly). Significant differences in morphology, textural properties, organic structure and crystallinity of prepared activated carbons were observed. Activated carbons were tested as a sorbent of Cd2+ from water. Textural analysis showed that the volume of micropores in sample after two-stage pyrolysis was more than four times higher in comparison with single-stage. The value of external surface area related with presence of mesopores was similar for both activated carbons (Sext(single-stage) = 48.1 m2/g; Sext(two-stage) = 50.3 m2/g). The study of ACs sorption capacity was performed as exemplified by cadmium. The experiments evaluated using Langmuir and Freundlich models showed that AC prepared by two-stage pyrolysis has more than three times higher sorption capacity, i.e. 107.5 mg Cd/g comparing to single-stage one, where the sorption capacity of 32.8 mg Cd/g was attained. Thus, loading of environment by cadmium and its uptake by various sorbents are also discussed and compared.
•Single-stage pyrolysis was compared with two-stage pyrolysis process to obtain chemically activated carbon from waste biomass.•Significant differences in morphology, textural properties, organic structure and crystallinity were observed.•From the viewpoint of cadmium sorption, two-stage pyrolysis is much more effective in comparison to the single-stage.
•Magnetic biochar prepared from biomass waste by microwave pyrolysis/precipitation.•Non-stoichiometric nano-maghemite enhances surface texture.•Magnetic biochar as an effective adsorbent of arsenic ...and methylene blue.•Short microwave irradiation increases the arsenic desorption rate.•Degradation of methylene blue by microwave regeneration controlled by HPLC/ESI-MS.
The application of microwave irradiation for rapid synthesis of magnetic biochar from agricultural waste with the subsequent modification of carbon matrix by magnetic nanoparticles was performed. The magnetic biochar was characterized by 57Fe Mössbauer spectroscopy, X-ray diffraction, a low-temperature nitrogen adsorption method, and electron microscopy. Except of magnetic properties, modification of biochar brings surface texture increase (SBET = 21.1 m2/g for char precursor versus 139.1 m2/g for magnetic biochar), and therefore better adsorption properties. The magnetic biochar was tested as an adsorbent of As5+ oxyanion and methylene blue (MB) to study the sorption mechanism and regeneration process. Magnetic biochar is the excellent adsorbent of arsenic (Qm = 24.9 mg/g; pH = 3.8). In the regeneration procedure, fast-acting microwave irradiation (10 s) significantly increases the value of the As5+ desorption rate constant as well as the initial desorption rate. The adsorption of MB on the magnetic biochar (Qm = 55.0 mg/g; pH = 10.2) was realized to study microwave-induced thermal regeneration. After short microwave treatment (30 s), a degradation of MB was observed (no absorption in the UV/VIS spectrum), whereas six degradation products were detected (HPLC/ESI-MS) and proposed formulas were revealed. Longer irradiation (60 s) caused total degradation of MB.
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The contribution deals with an evaluation of atmospheric deposition monitoring in 2001–2009 which was realised in the vicinity ofsiderite mining and processing works. Besides of gaseous emissions the ...works also produced the solid compounds of iron oxides and otherheavy metals. The iron ore plant worked up to August 2008. The atmospheric deposition (wet and dry) was determined by the modified bulkdeposition methodology. The samples were collected from seventeen monitoring sites, which are located maximally up to 8 km from the mainpollution source. Together with the deposition fluxes of heavy metals (Fe, Mn, Zn, Pb, Cu,Cr, Cd, As), the mineralogical composition,dispersion and size characteristics of solid particles were studied in selected samples. The volume content of respirable solid particles withthe diameter under 5 μm was from 6.7 to 13.2 %. Nanoparticles with the average hydrodynamic diameter in the interval of 242–558 nm werefound. High values of the deposition (median) of iron - 4111 mg.m-2.year -1, manganese - 236.6 mg.m-2.year -1 and especially toxic arsenic -8.05 mg.m-2.year -1 were measured in the area of Nižná Slaná in the years 2001–2008 and compared with other areas. A correlation betweenemissions of solid pollutants in particular years and the deposition for these metals was observed. In 2009, after shutdown of the works,a decrease of values at the most contaminated sites of deposition by arsenic, manganese and iron about 90 % was recorded. Sucha significant change was not recorded for other studied metals.
Purpose
To evaluate the ecological risk, physico-chemical properties, and the impact of anthropogenic sources on permanent eighteen samples of grass vegetation soils (PGVS) and agricultural soils ...(AS) near the U.S. Steel company in Košice city, Eastern Slovakia.
Methods
In this study, permanent grass vegetation soils (PGVS) and agricultural soils (AS) samples were analyzed. Samples were taken from the following localities (
L
):
PGVS
1a-1c
; AS
1a-1c
from U.S. Steel-slag heap (
L
1
),
PGVS
2a-2c
; AS
2a-2c
from Gomboš (
L
2
),
PGVS
3a-3c
; AS
3a-3c
from U.S. Steel plant (main gate of U.S. Steel) (
L
3
). The physico-chemical properties were determined using methods, such as thermal analysis (TG, DTG/DTA), X-ray fluorescence spectrometry (XRF), CHNS spectrometry, granulometry, and X-ray powder diffractometry (XRPD).
Results
The environmental quality index of Cd and Co in all samples was found to be ˃3 and indicated high pollution of the studied area by these elements. This assumption was confirmed by XRF spectrometry. For all the analyzed samples, the permitted limits for the elements Cd, Cr, and Co were largely exceeded, that also corresponded to the area from which they were taken. In all the studied samples, the C, H, N, and S concentrations were higher in the permanent grass soil samples than the concentrations in agricultural soil samples. The quartz was found as the major mineral; the others such as chlorite, albite, muscovite, or microcline were detected in smaller amounts. All samples were thermaly stable up to 40 °C.
Conclusions
In the surveyed area, the major source of heavy metal pollution was from industrial discharge. This demonstrates that effective management strategies could be developed to safeguard the environmental quality of agricultural soils and permanent grass vegetation in the studied area.
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