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1.
Chemosphere ; 254: 126898, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957293

RESUMO

The utilization of Microcystis biomass is an urgent issue in the mitigation of cyanobacterial bloom. In this study, Microcystis-derived biochar (MB) and Fe3O4-modified biochar (Fe3O4/MB) were fabricated for the U(VI) elimination. The results showed that U(VI) sorption process by either MB or Fe3O4/MB was pH-dependent and ionic strength-independent. The maximum sorption capacity of MB was higher than that of Fe3O4/MB. According to the analysis of X-ray photoelectron spectroscopy, U(VI) sorption on both MB and Fe3O4/MB was mainly ascribed to the surface complexation between U(VI) and oxygen-containing functional groups on the surface of MB. Fe3O4 particles on the surface of MB didn't provide extra active sites for the sorption of U(VI), but it enabled the adsorbent to be magnetically separated. Five consecutive sorption/desorption cycles verified the good reusability of Fe3O4/MB in this study. Therefore, the investigation is not only meaningful for the utilization of nuisance biomass from cyanobacterial blooms, but also provides novel adsorbents for the U(VI) removal from aqueous solutions.


Assuntos
Carvão Vegetal/química , Eutrofização , Óxido Ferroso-Férrico/química , Microcystis/química , Urânio/análise , Poluentes Radioativos da Água/análise , Purificação da Água/métodos , Adsorção , Biomassa , Concentração de Íons de Hidrogênio , Fenômenos Magnéticos , Modelos Teóricos , Concentração Osmolar
2.
Chemosphere ; 254: 126899, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957294

RESUMO

In this study, the reduction of iron-carbon internal electrolysis was reinforced by persulfate for p-nitrophenol removal. The effects of persulfate dosage, initial pH and iron-carbon mass ratio were comprehensively studied in batch experiments. In the system of iron-carbon internal electrolysis coupled with persulfate, the iron-carbon internal electrolysis and persulfate had a significant mutual influence, exhibiting a wide range of pH in the treatment process. Moreover, the coupled system also showed the remarkable removal and degradation efficiency of p-nitrophenol according to the contrast experiments. The satisfactory results should be attributed to the potential reduction of iron-carbon internal electrolysis, which was stimulated by persulfate to transform the nitro group to the amine group, accompanying the subsequent oxidation. Furthermore, persulfate possessed the ability that the dynamically destructive effect on external and internal of Fe0 and the scavenging action on activated carbon, effectively strengthening the potential energy for release and transfer of reductive substances. Both HO• and SO4•- as the main free radicals were formed to mineralize the intermediates in the coupled system. These findings indicate that the system of iron-carbon internal electrolysis coupled with persulfate can be a promising strategy for the treatment of the toxic and refractory wastewater.


Assuntos
Carvão Vegetal/química , Eletrólise/métodos , Ferro/química , Nitrofenóis/análise , Sulfatos/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Modelos Teóricos , Nitrofenóis/química , Oxirredução , Águas Residuárias/química , Poluentes Químicos da Água/química
3.
Chemosphere ; 254: 126916, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957301

RESUMO

4-Nonylphenol (4-NP), a phenolic endocrine disruptor chemical (EDC), is known to have high toxicity to aquatic organisms and humans. The remediation of 4-NP-contaminated marine sediments was studied using red algae-based biochar (RAB) thermochemically synthesized from Agardhiella subulata with simple pyrolysis process under different temperatures of 300-900 °C in CO2 atmosphere. The RAB was characterized by XRD, Raman, FTIR spectroscopy, and zeta potential measurements. The calcium in RAB efficiently activated sodium percarbonate (SPC) to generate reactive radicals for the catalytic degradation of 4-NP at pH 9.0. The oxygen-containing functional groups reacted with H2O2, which increased the generation of reactive radicals under alkaline pH condition. Ca2+ ion was the active species responsible for 4-NP degradation. CaO/CaCO3 on RAB surface enhanced direct electron transfer, increased HO production, and 4-NP degradation in marine sediments. Langmuir‒Hinshelwood type kinetics well described the 4-NP degradation process. Remediation of contaminated sediments using RAB could be a sustainable approach toward closed-loop biomass cycling in the degradation of 4-NP contaminants.


Assuntos
Carvão Vegetal/química , Disruptores Endócrinos/análise , Recuperação e Remediação Ambiental/métodos , Sedimentos Geológicos/química , Fenóis/análise , Rodófitas/química , Poluentes Químicos da Água/análise , Biomassa , Carbonatos/química , Catálise , Humanos , Peróxido de Hidrogênio/química , Cinética
4.
Chemosphere ; 254: 126881, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32957288

RESUMO

Application of biochar (BC) derived from rice straw has generated increasing interest in long-term storage of soil organic carbon (SOC), however its carbon (C) sequestration potential vary widely among agricultural soils despite the same BC dose used. These discrepancies in the ability of soils to sequester C after BC application are poorly understood. Metabolic quotient (qCO2) is a reflection of "microbial efficiency" and linked to SOC turnover across ecosystems. Therefore, we investigated the SOC sequestration and qCO2 in a Yellow River alluvium paddy soil (YP) and a quaternary red clay paddy soil (QP) under rice-wheat annual rotation following 4-year of BC application rate of 11.3 Mg ha-1 per cropping season. BC application consistently brought 65.3 Mg C ha-1 into the soils over 4-year experimental period but increased SOC by 57.6 Mg C ha-1 in YP and 64.5 Mg C ha-1 in QP. Calculating SOC mass balance showed 11.7% of BC-C losses from YP and only 1.16% from QP. BC application stimulated the G+ bacterial, fungi, and actinomycetes by increasing O-alkyl C content in YP, while decreased the same microorganisms by decreasing anomeric C-H content in QP. Importantly, higher clay and amorphous Fe (Feo) contents in QP after BC application protected SOC from further decomposition, which in turn decreased microorganisms and resulted in higher SOC sequestration than YP. Our results indicated that soil properties controlled the extent of SOC sequestration after BC application and site-specific soil properties must be carefully considered to maximize long-term SOC sequestration after BC application.


Assuntos
Agricultura/métodos , Sequestro de Carbono , Carvão Vegetal/química , Carbono/metabolismo , Argila , Ecossistema , Oryza/metabolismo , Solo/química
5.
Bull Environ Contam Toxicol ; 105(4): 650-655, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-32889604

RESUMO

Biochar (char-product), generated by pyrolyzing organic materials, is produced for the intended use of land application to promote carbon sequestration, soil improvement and crop-yield. Despite the benefits biochar applications offers, scientific probing on impacts that may result from amendments with biochar is still fragmented. In this study, impact of biochar on Eudrilus eugeniae DNA was investigated. Rice-husk biochar was applied to soil at rates up to 80% d/w and earthworms were exposed for 35-day. Impact on DNA was measured using electrophoresis-gel-extraction-method. Data obtained showed that biochar application over 25% resulted in decreased survival. Electrophoresis-gel-analysis showed that DNA decreased from 450 to 300 bp in biochar soils (p = 0.002). Biochar rates (5%-25%) induced DNA damage. The DNA showed smeared bands or tail; indicating DNA degradation and/or damage. DNA damage is a clear evidence of negative impact of biochar(s) to soil-biota; suggesting that loading of soil with biochar could have serious consequences on soil-fauna.


Assuntos
Carvão Vegetal/toxicidade , Oligoquetos/fisiologia , Poluentes do Solo/toxicidade , Animais , Biota , Carvão Vegetal/química , Dano ao DNA , Oligoquetos/metabolismo , Oryza/metabolismo , Solo , Poluentes do Solo/análise
6.
Bull Environ Contam Toxicol ; 105(3): 422-427, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-32740746

RESUMO

This study explored the adsorption of representative non-steroidal anti-inflammatory drugs (NSAIDs), acetaminophen (AP), ibuprofen (IB), and salicylic acid (SA) by biochars. The sorption kinetics were fitted with six commonly used kinetic models, and the isotherm data was well described by both Langmuir and Freundlich models. Biochars of longer pyrolysis time showed better performance with the Langmuir maximum sorption capacities for AP, IB, and SA of 196 mg/g, 132 mg/g, and 48.8 mg/g, respectively. Variation in temperature hardly affected the adsorption performances, while the influence of pH exhibited pronounced dependency on physicochemical properties of both NSAIDs and biochars. Eighteen ball-milled (BM) biochars were then produced under different ball-milling conditions and examined for NSAIDs removal. Compared with unmilled biochars, BM-biochars produced under optimum conditions showed higher removal efficiencies. Electrostatic interaction and pore width of biochars greatly affected the NSAIDs adsorption onto biochars.


Assuntos
Anti-Inflamatórios não Esteroides/química , Carvão Vegetal/química , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Pirólise , Temperatura
7.
PLoS One ; 15(8): e0238105, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32853282

RESUMO

Biochar derived from straw is a potential low-cost adsorbent for metal ions and organic pollutants, but its practical application is still limited by the adsorption capacity. In this study, the correlation between the biochar's properties and pyrolysis temperature was explored. The adsorption mechanism was studied by monitoring the changes of biochar properties before and after adsorption using BET, SEM, XPS and FT-IR spectroscopy. The adsorption mechanism was revealed following the adsorption kinetics and the changes in biochar's properties before and after adsorption. The methylene blue (MB) and Pb2+ adsorption removal efficiency reached 95% at the initial concentration of 125 and 500 mg/L, respectively. Physisorption, chemisorption, and pore filling mechanisms determined the adsorption process of MB and Pb2+ on biochar. The Pb2+ adsorption process was highly affected by chemical co-precipitation at higher pyrolysis temperatures. The appearance of tar particles increased the adsorption rate of Pb2+. The biochar obtained at the pyrolysis temperature at 500, 800 and 900°C proved to be applicable for Pb2+ removal. Chemisorption and porosity dominated the MB adsorption, and biochars produced at pyrolysis temperatures of 200, 800 and 900°C are potential materials for MB removal. This study provides optimal pyrolysis conditions for transforming maize straw into valuable, low-cost materials for the removal of different pollutants.


Assuntos
Carvão Vegetal/química , Chumbo/química , Azul de Metileno/química , Zea mays/química , Adsorção , Cinética , Chumbo/isolamento & purificação , Azul de Metileno/isolamento & purificação , Pirólise , Propriedades de Superfície , Resíduos
8.
Ecotoxicol Environ Saf ; 205: 111028, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32829206

RESUMO

In this study, biochar-loading copper ions (Cu-BC), a novel composite for removing phenanthrene very efficiently from water, was prepared using the impregnation method. The performance of constructed wetlands (CWs) with these modified and original biochar as substrates was analyzed. CW with Cu-BC removed a large amount of phenanthrene (94.09 ± 3.02%). According to the surface characteristics analysis, Cu-BC can promote the removal of pollutants via complex absorption, hydrophobic adsorption, increasing the Lewis Pair and electrostatic attraction. Furthermore the higher nitrate removal rate in the treated system (91.11 ± 1.17%) was observed to have higher levels of bacterial metabolic diversity and denitrifier types. The phenanthrene accumulated in plants with this treatment system was enhanced by the role of copper in photosynthesis. It is able to boost the plant extraction of organic matter.


Assuntos
Carvão Vegetal/química , Cobre/química , Hidrocarbonetos Policíclicos Aromáticos/análise , Eliminação de Resíduos Líquidos/métodos , Poluentes Químicos da Água , Áreas Alagadas , Adsorção , Nitratos , Nitrogênio/metabolismo , Fenantrenos
9.
PLoS One ; 15(8): e0238154, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32853236

RESUMO

Black soldier fly (BSF) (Hermetia illucens L.) is one of the most efficient bio-waste recyclers. Although, waste substrate amendments with biochar or gypsum during composting process are known to enhance nutrient retention, their impact on agro-industrial waste have not been documented. Hence, this study focuses on a comparative effect of agro-industrial waste amended with biochar and gypsum on BSF larval performance, waste degradation, and nitrogen (N) and potassium retention in frass fertilizer. Brewery spent grain was amended with biochar or gypsum at 0, 5, 10, 15 and 20% to determine the most effective rates of inclusion. Amending feedstock with 20% biochar significantly increased wet (89%) and dried (86%) larval yields than the control (unamended feedstock). However, amendment with 15% gypsum caused decrease in wet (34%) and dried (30%) larval yields but conserved the highest amount of N in frass. Furthermore, the inclusion of 20% biochar recorded the highest frass fertilizer yield and gave a 21% increase in N retention in frass fertilizer, while biomass conversion rate was increased by 195% compared to the control. Feedstock amendment with 5% biochar had the highest waste degradation efficiency. Potassium content in frass fertilizer was also significantly enhanced with biochar amendment. At maturity, frass compost with more than 10% inclusion rate of biochar had the highest cabbage seed germination indices (>100%). The findings of this study revealed that initial composting of biochar amended feedstocks using BSF larvae can significantly shorten compost maturity time to 5 weeks with enhanced nutrient recycling compared to the conventional composting methods.


Assuntos
Carvão Vegetal/química , Larva/crescimento & desenvolvimento , Simuliidae/crescimento & desenvolvimento , Animais , Biomassa , Compostagem/métodos , Fertilizantes , Resíduos Industriais , Nitrogênio/química , Solo/química
10.
Ecotoxicol Environ Saf ; 205: 111169, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32827961

RESUMO

The characteristics and content of organo-mineral complex were confirmed to be changed in agriculture soils under the biochar application with long-term, but the resulting environmental effects in the retention and lasting of agrochemicals and xenobiotic pollutants is far from clear. In this study, biochar-soil composites were prepared by one-step dry ball-milling method, and a sorption case study was proceed to investigate the biochar incorporated affection in soils on the transport of dimethyl phthalate (DMP). More surface oxygen-containing functional groups on ball-milled biochar enhanced its complexation with soil minerals. Sorption isotherms of DMP onto the biochar-soil composites were well described by the Freundlich model, both heterogeneous surface and multilayer interactions occurred simultaneously. The kinetics of sorption could be simulated with the pseudo-second-order model (R2 > 0.98), while the average sorption energy (Ea) calculated from Dubinin-Radushkevich isotherms were found in the range of 3.83-5.60 kJ mol-1, which revealed that the sorption processes coexist of chemisorption and physisorption, and π-π electron donor-acceptor interaction, pore-filling and hydrophobic interactions could be identified as the main sorption mechanisms. Desorption of absorbed DMP appeared obvious nonlinear characteristics and lag effect, the calculated hysteresis index (HI) increased with the application of biochar into soil. Considering the phenomenon of biochar aging and soil complexation, it is important to verify how the transport and natural attenuation of contaminant will be influenced by biochar addition, especially the long-term effect in soil ecosystem.


Assuntos
Carvão Vegetal/química , Ácidos Ftálicos/análise , Poluentes do Solo/análise , Solo/química , Adsorção , Agricultura , Ecossistema , Ésteres , Cinética , Modelos Teóricos , Propriedades de Superfície
11.
Ecotoxicol Environ Saf ; 205: 111172, 2020 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-32846300

RESUMO

Following oil extraction in the wetland of the Yellow River Delta, heavy metal contamination of coastal saline-alkaline soil, especially with cadmium (Cd), has become a serious environmental problem in some regions. Biochar application has been proposed to remedy Cd-contaminated soil, but the remediation effect is related to preparation conditions of biochar (e.g., pyrolysis temperature and raw material) and soil properties. The invasive plant, Spartina alterniflora, produces a high amount of biomass, making it suitable for biochar production in coastal China. We investigated the effect of S. alterniflora-derived biochar (SDB) pyrolyzed at four temperatures (350, 450, 550, and 650 °C) crossed with three addition ratios (1, 5, and 10%) and control on Cd contamination of coastal saline-alkaline soil. Pyrolysis temperature affected pH, surface area, and functional groups of SDB. SDB markedly improved soil pH and soil organic matter, but the degree of improvement was affected by pyrolysis temperature and addition ratio. SDB significantly altered available Cd content in soil, but reduced it only at low pyrolysis temperatures (350 and 450 °C). Available Cd content had a positive correlation with soil pH (R2 = 0.298, P < 0.01), but was not related to salinity and soil organic matter content. Thus, SDB pyrolyzed at 350 °C with 5% addition was optimal for passivating Cd in coastal saline-alkaline soil, since available Cd content in soil decreased mostly (by 26.9%). These findings act as a reference for the development of an application strategy for SDB to ameliorate Cd-contaminated coastal saline-alkaline soil.


Assuntos
Cádmio/análise , Carvão Vegetal/química , Recuperação e Remediação Ambiental/métodos , Poaceae/química , Poluentes do Solo/análise , Solo/química , Álcalis/análise , Biomassa , China , Modelos Teóricos , Pirólise , Salinidade , Áreas Alagadas
13.
Bull Environ Contam Toxicol ; 105(2): 261-269, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32666192

RESUMO

Persistence and sorption behaviour of flubendiamide in two different Indian soils as affected by maize stalk biochar was studied. The persistence was more in West Bengal soil (178.6 days) than Sikkim soil (165.3 days) at 10 µg g-1 fortification level. Biochar amendment addition to soil at 5% enhanced the degradation process and half-life (T1/2) values were 103.5 and 117.4 days, respectively for biochar amended Sikkim and West Bengal soil. Sorption study through batch equilibrium method resulted the 4 h equilibrium time with adsorption 6.22% ± 0.16% and 5.26% ± 0.16% in Sikkim and West Bengal soil, respectively. Biochar addition at 5% increased the adsorption of flubendiamide to 8.12% ± 0.16% and 5.88% ± 0.16% indicating a greater influence in this process. The adsorption was more in biochar amended Sikkim soil than West Bengal soil. The values of desorption was slower than adsorption indicating a hysteresis effect having hysteresis coefficient (H1) ranges between 0.025 and 0.151 in two test soils.


Assuntos
Benzamidas/química , Carvão Vegetal/química , Recuperação e Remediação Ambiental/métodos , Poluentes do Solo/química , Sulfonas/química , Adsorção , Benzamidas/análise , Biomassa , Carvão Vegetal/economia , Solo , Poluentes do Solo/análise , Sulfonas/análise , Zea mays
14.
PLoS One ; 15(7): e0232811, 2020.
Artigo em Inglês | MEDLINE | ID: mdl-32614852

RESUMO

In the present work, the olive mill solid waste (OMSW)-derived biochar (BC) was produced at various pyrolytic temperatures (300-700°C) and characterized to investigate its potential negative versus positive application effects on pH, electrical conductivity (EC), and nutrients (P, K, Na, Ca, Mg, Fe, Mn, Zn, and Cu) availability in a calcareous loamy sand soil. Therefore, a greenhouse pot experiment with maize (Zea mays L.) was conducted using treatments consisting of a control (CK), inorganic fertilizer of NPK (INF), and 1% and 3% (w/w) of OMSW-derived BCs. The results showed that BC yield, volatile matter, functional groups, and zeta potential decreased with pyrolytic temperature, whereas BC pH, EC, and its contents of ash and fixed carbon increased with pyrolytic temperature. The changes in the BC properties with increasing pyrolytic temperatures reflected on soil pH, EC and the performance of soil nutrients availability. The BC application, especially with increasing pyrolytic temperature and/or application rate, significantly increased soil pH, EC, NH4OAc-extractable K, Na, Ca, and Mg, and ammonium bicarbonate-diethylenetriaminepentaacetic acid (AB-DTPA)-extractable Fe and Zn, while AB-DTPA-extractable Mn decreased. The application of 1% and 3% BC, respectively, increased the NH4OAc-extractable K by 2.5 and 5.2-fold for BC300, by 3.2 and 8.0-fold for BC500, and by 3.3 and 8.9-fold for BC700 compared with that of untreated soil. The results also showed significant increase in shoot content of K, Na, and Zn, while there was significant decrease in shoot content of P, Ca, Mg, and Mn. Furthermore, no significant effects were observed for maize growth as a result of BC addition. In conclusion, OMSW-derived BC can potentially have positive effects on the enhancement of soil K availability and its plant content but it reduced shoot nutrients, especially for P, Ca, Mg, and Mn; therefore, application of OMSW-derived BC to calcareous soil might be restricted.


Assuntos
Carvão Vegetal/farmacologia , Nutrientes/análise , Olea/química , Areia/química , Solo/química , Carvão Vegetal/química , Concentração de Íons de Hidrogênio , Minerais/metabolismo , Nutrientes/metabolismo , Fatores de Tempo , Zea mays/efeitos dos fármacos , Zea mays/crescimento & desenvolvimento , Zea mays/metabolismo
15.
Chemosphere ; 260: 127496, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32659541

RESUMO

Activated carbons have been reported to be useful for adsorptive removal of the volatile anaesthetic sevoflurane from a vapour stream. The surface functionalities on activated carbons could be modified through aqueous oxidation using oxidising solutions to enhance the sevoflurane adsorption. In this study, an attempt to oxidise the surface of a commercial activated carbon to improve its adsorption capacity for sevoflurane was conducted using 6 mol/L nitric acid, 2 mol/L ammonium persulfate, and 30 wt per cent (wt%) of hydrogen peroxide (H2O2). The adsorption tests at fixed conditions (bed depth: 10 cm, inlet concentration: 528 mg/L, and flow rate: 3 L/min) revealed that H2O2 oxidation gave desirable sevoflurane adsorption (0.510 ± 0.005 mg/m2). A parametric study was conducted with H2O2 to investigate the effect of oxidation conditions to the changes in surface oxygen functionalities by varying the concentration, oxidation duration, and temperature, and the Conductor-like Screening Model for Real Solvents (COSMO-RS) was applied to predict the interactions between oxygen functionalities and sevoflurane. The H2O2 oxidation incorporated varying degrees of both surface oxygen functionalities with hydrogen bond (HB) acceptor and HB donor characters under the studied conditions. Oxidised samples with enriched oxygen functionalities with HB acceptor character and fewer HB donor character exhibited better adsorption capacity for sevoflurane. The presence of a high amount of oxygen functional groups with HB donor character adversely affected the sevoflurane adsorption despite the enrichment of oxygen functional groups with HB acceptor character that have a higher tendency to adsorb sevoflurane.


Assuntos
Poluentes Atmosféricos/análise , Poluição do Ar/prevenção & controle , Anestésicos Inalatórios/análise , Carvão Vegetal/química , Oxigênio/química , Sevoflurano/análise , Adsorção , Ligação de Hidrogênio , Peróxido de Hidrogênio/química , Modelos Teóricos , Ácido Nítrico/química , Oxirredução , Porosidade , Propriedades de Superfície , Temperatura
16.
Chemosphere ; 260: 127500, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32688308

RESUMO

Lithium (Li+) is used in various applications involving pharmaceuticals, textile dyes, and batteries. Therefore, the demand for environmentally friendly and effective materials for Li+ uptake and recovery continues to increase. Herein, rice husk (RH) and coconut shell (CS) biomasses were used to fabricate honeycomb-networked biochar (BC) precursors via slow pyrolysis. RHBC- and CSBC-based MnO2 composites were synthesized by depositing MnO2 in various ratios onto RHBC and CSBC by varying the KMnO4 concentration (2%, 3%, and 4%), followed by simple ultrasonication and heat-treatment methodologies. The structural and physicochemical properties of all of the fabricated composites were analyzed using several different instrumental methods. The batch adsorption experiments were performed for comparative Li+-adsorption studies of RHBC-Mnx and CSBC-Mnx composites by optimizing several parameters (pH, adsorbent dose, Li+ initial concentration, and contact time). The comparative adsorption analysis revealed that the RHBC-Mnx composites exhibited stronger Li+-adsorption ability than the CSBC-Mnx composites and that increasing the MnO2 deposition to 3% in both cases led to maximum Li+ adsorption capacities (62.85 mg g-1 and 57.8 mg g-1), respectively. The kinetic studies show that Li+ adsorption proceeds through the pseudo-second-order mechanism. Li+ recovery was successfully carried out using HCl (eluting agent), thereby demonstrating the benefits of synthesized composites at the industrial scale. The current work indicates that the fabricated RHBC-Mnx and CSBC-Mnx composites may have potential for use as economical composites in eco-friendly applications such as Li+ adsorption and recovery from aqueous media.


Assuntos
Carvão Vegetal/química , Cocos/química , Lítio/análise , Compostos de Manganês/química , Oryza/química , Óxidos/química , Poluentes Químicos da Água/análise , Adsorção , Fontes de Energia Elétrica , Íons , Cinética , Resíduos Sólidos/análise
17.
Chemosphere ; 260: 127643, 2020 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-32683028

RESUMO

Effective treatment of 2,4-dichlorophenol (2,4-DCP) in wastewater is essential, as it could pose great threat to the environment. A hydrothermal biochar (hydrochar) was used to assist the electrochemical oxidation treatment of 2,4-DCP. The removal of 2,4-DCP using hydrochar in anode and cathode area with and without proton exchange membrane (PEM) under 3-9 V of electrolysis was investigated. Enhanced 2,4-DCP degradation in the anode area was achieved compared with the adsorption or electrolysis alone. The highest 2,4-DCP removal (∼76%) was obtained using the hydrochar in the anode area with PEM under 9 V. The mechanism for the 2,4-DCP removal during the electrolysis included adsorption by hydrochar and electrochemical degradation by the reactive oxygen species (ROS) generated by the electrode as well as the persistent free radicals (PFR) on hydrochar. The OH produced from anode was the predominant ROS contributing to the 2,4-DCP degradation under 9 V of electrolysis.


Assuntos
Carvão Vegetal/química , Clorofenóis/química , Poluentes Químicos da Água/química , Adsorção , Eletrodos , Eletrólise , Oxirredução , Fenóis , Águas Residuárias
18.
Ecotoxicol Environ Saf ; 201: 110873, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32544750

RESUMO

Batch experiments were conducted to examine the differential effects of biochar pyrolysis temperature and low-molecular-weight organic acids on the reduction of As(V) and Cr(VI) driven by Pennisetum hydridum biochar. The results showed that pyrolysis temperature significantly affected the reducing strength of the biochar. Biochar produced at 500 °C had a stronger electron-donating capacity than did the biochars produced at 300 and 700 °C. In the co-presence of the biochar and a low-molecular-weight organic acid, arsenic and chromium behaved differently. Oxalic acid and malic acid tended to have better effects on enhancing biochar-driven Cr(VI) reduction, as compared to citric acid while the opposite was observed for biochar-driven As(V) reduction. Biochar produced at 300 °C was more favourable for Cr(VI) reduction, as compared to the higher-temperature biochars while the opposite was observed for As(V) reduction in the presence of low-molecular-weight organic acids. This may make the lower-temperature biochar ideal for remediating contaminated soils containing both As(V) and Cr(VI) since it could maximize Cr(VI) reduction while minimizing As(V) reduction.


Assuntos
Arseniatos/metabolismo , Carvão Vegetal/química , Cromo/metabolismo , Poluentes do Solo/metabolismo , Biodegradação Ambiental , Ácido Cítrico/química , Malatos/química , Peso Molecular , Ácido Oxálico/química , Pirólise , Temperatura
19.
Ecotoxicol Environ Saf ; 201: 110825, 2020 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-32531575

RESUMO

Cotton-based adsorbents (CBAs) are promising materials for combating the problem of heavy metal pollution of environmental waters. This is ascribed to the low cost, abundance, biodegradability and efficiency of CBAs. Herein we review the adsorption of heavy metals (HMs) onto CBAs. We found that several surface modifications were employed to improve the efficiency of the CBAs. These modifications were effected via thermal, physical and chemical means to obtain activated carbons, biochars, ionic liquids, aerogels, hydrogels, chitosans and nanoparticle-derived CBAs. The CBAs exhibited maximum HMs uptake as low as 0.002 mg/g to as high as 505.6 mg/g. Although, the cotton-derived activated carbons and biochars exhibited enhanced HM uptake from that of the unmodified CBAs, they were less efficient than CBAs modified by other methods. Recent chemical, ionic liquid, chitosan and nano-derived CBAs were the most efficient, with high uptake and fast kinetic removal. However, the nanoparticle-based adsorbents are preferred to the chemically modified forms, due to the possibility of secondary pollution and the noxious effect of the latter to the environment. Findings showed that chemical treatment produced CBAs most efficient for As(V), Pb(II) and Fe(III), while ionic liquid CBA was more efficient for Cu(II) and Ni(II). Nano-based treatment was suitable for the uptake of Co(II), Zn(II), Pb(II) and Cd(II), while the chitosan based adsorbent was viable for Hg(II). Isotherm and kinetic evaluation of CBAs mostly conformed to the Langmuir and pseudo-second order models, respectively. Spontaneous adsorption of HMs onto CBAs was deduced from thermodynamic analysis, with endothermic and exothermic characteristics. Over 88% desorption of HMs was obtained from the CBAs studied with good average reusability from 3 to 20 cycles. We also discussed the directions for future research.


Assuntos
Gossypium/química , Metais Pesados/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Biodegradação Ambiental , Carvão Vegetal/química , Quitosana/química , Íons , Cinética , Termodinâmica
20.
Ecotoxicol Environ Saf ; 202: 110887, 2020 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-32585488

RESUMO

Chemical immobilization of heavy metals is a simple, low-cost, and environment-friendly technology for remediation of heavy metals contaminated soils. However, changes in environmental conditions, such as water management, acid deposition, temperature fluctuation, etc., might result in release of metal ions from the fixation sites, and the long-term stability of immobilization remediation is unclear. This study attempted to investigate the impact of water management strategies (wetting-drying cycle and dry cycle) on the stability of heavy metal immobilization by one-time application of biochar during 3 consecutive years of rice-wheat crop in Cu/Cd-contaminated soil. The transformation and accumulation of Cd and Cu in soil-crop system and the morphololgy and composition of biochar were analyzed. The results revealed that wetting-drying cycle and drying treatments reduced the contents of available Cd and Cu in soil by 15.9%-17.7% and 23.9%-31.5% and by 19.8%-62.7% and 16.1%-65.0%, as well as increased soil pH by 0.11-0.31 and 0.17-0.56, respectively. In the wetting-drying cycle treatment, biochar was more favorable for decrease in Cd and Cu accumulation in crop, when compared with that in dry treatment; however, the differences were insignificant in the subsequent years. Although the different water management strategies had no obvious effect on the soil total C, physicochemical analysis of the biochar collected after pot experiments indicated that the obvious structural decomposition of biochar in the drying treatment may have resulted in the release of heavy metals immobilized in biochar. These findings help in better understanding of the long-term immobilization mechanism of biochar in soil-plant system.


Assuntos
Agricultura/métodos , Cádmio/análise , Cobre/análise , Poluentes do Solo/análise , Carvão Vegetal/química , Poluição Ambiental/análise , Metais Pesados/análise , Oryza/química , Rotação , Solo/química , Triticum , Água/análise , Abastecimento de Água
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