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1.
J Colloid Interface Sci ; 614: 603-616, 2022 May 15.
Artigo em Inglês | MEDLINE | ID: mdl-35123214

RESUMO

This is the first report of the metal Fe-Ti oxide/biochar (Fe2TiO5/BC) composite for simultaneous removal of aqueous Pb2+, Cr6+, F- and methylene blue (MB). Primary Fe2TiO5 nano particles and aggregates were dispersed on a high surface area Douglas fir BC (∼700 m2/g) by a simple chemical co-precipitation method using FeCl3 and TiO(acac)2 salts treated by base and heated to 80 °C. This was followed by calcination at 500 °C. This method previously was used without BC to make the neat mixed oxide Fe2TiO5, exhibiting a lower energy band gap than TiO2. Adsorption of Cr(VI), Pb(II), fluoride, and MB on Fe2TiO5/BC was studied as a function of pH, equilibrium time, initial adsorbate concentration, and temperature. Adsorption isotherm studies were conducted at 5, 25, and 45 ℃ and kinetics for all four adsorbates followed the pseudo second order model. Maximum Langmuir adsorption capacities for Pb2+, Cr6+, F- and MB at their initial pH values were 141 (pH 2), 200 (pH 5), 36 (pH 6) and 229 (pH 6) mg/g at 45 ℃ and 114, 180, 26 and 210 mg/g at 25 ℃, respectively. MB was removed from the water on Fe2TiO5/BC by synergistic adsorption and photocatalytic degradation at pH 3 and 6 under UV (365 nm) light irradiation. Cr6+, Pb2+, F-, and MB each exhibited excellent removal capacities in the presence of eight different competitive ions in simulated water samples. The removal mechanisms on Fe2TiO5/BC and various competitive ion interactions were proposed. Some iron ion leaching at pH 3 catalyzed Photo-Fenton destruction of MB. Fe2TiO5, BC, and Fe2TiO5/BC bandgaps were studied to help understand photocatalysis of MB and to advance supported metal oxide photodegradation using smaller energy band gaps than the larger bandgap of TiO2 for water treatment. A long range goal is to photocatalytically destroy some sorbates with adsorbents to avoid the need for regeneration steps.


Assuntos
Azul de Metileno , Poluentes Químicos da Água , Adsorção , Carvão Vegetal , Cromo/análise , Fluoretos , Ferro , Cinética , Chumbo , Óxidos , Titânio , Poluentes Químicos da Água/análise
2.
Chemosphere ; 292: 133355, 2022 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-34929276

RESUMO

This study compared the lead (Pb2+) immobilization efficacy of biochar-supported phosphate to conventional in-situ heavy metal immobilization methods (with lime, neat biochar and phosphate). The biochar-supported phosphate was obtained by treating Douglas fir biochar (BC) with anhydrous calcium chloride and potassium dihydrogen phosphate. The amount of Pb2+ immobilized was determined by comparing the concentration of ammonium nitrate extractable Pb2+ lead from lead-spiked soil (without amendment) to that of a 30 d incubation with (a) lead-spiked soil plus 5% (wt./wt.) biochar supported-phosphate, (b) lead-spiked soil plus 5% (wt./wt.) untreated Douglas fir biochar, (c) lead-spiked soil plus 5% (w/w) lime and (d) lead-spiked soil plus 5% (wt./wt.) potassium dihydrogen phosphate. The control (lead-spiked soil without amendment) produced the largest quantity (96.08 ± 9.22 mg L-1) of NH4NO3-extractable Pb2+, while lead-spiked soil treated with 5% (wt./wt.) biochar-supported phosphate resulted in the lowest quantity of NH4NO3 extractable Pb2+ (0.3 ± 0.2 mg L-1). The mechanism for immobilization of Pb2+ by BP occurs at pH < 7 through dissolution of hydroxyapatite embedded in BP during modification, followed by precipitation of insoluble Pb10(PO4)6(OH)2. The residual lead fraction in the lead-spiked soil increased by 20.9% following amendment with BP. These results indicate that biochar-supported phosphate is a candidate to reduce lead mobility (bioavailability) in polluted soil. This amendment may lower Pb2+ uptake into plants while minimizing the potential for water contamination due to Pb2+mobility.


Assuntos
Pseudotsuga , Poluentes do Solo , Carvão Vegetal , Chumbo , Fosfatos , Solo , Poluentes do Solo/análise
3.
J Environ Manage ; 296: 113186, 2021 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-34256294

RESUMO

Biochar adsorbents can remove environmental pollutants and the remediation of Cr(VI) and nitrate are considered. Cr(VI) is a proven carcinogen causing serious health issues in humans and nitrate induced eutrophication causes negative effect on aquatic systems around the world. Douglas fir biochar (DFBC), synthesized by fast pyrolysis during syn gas production, was treated with aniline. Then, a polyaniline biochar (PANIBC) composite containing 47 wt% PANI was prepared by precipitating PANI on DFBC surfaces by oxidative chemical polymerization of aniline in 2M HCl. PANIBC exhibited a point of zero charge (PZC) of 3.0 and 8.2 m2/g BET (N2) surface area. This modified biochar was characterized by thermogravimetric analysis (TGA), scanning electron microscopy (SEM) morphology and surface elements, and oxidation states by X-ray photoelectron spectroscopy (XPS). PANIBC exhibited positive surface charge below pH 3, making it an outstanding adsorbent, for Cr(VI) removal. Cr(VI) and nitrate removal mechanisms are presented based on XPS analysis. DFBC and PANIBC Cr(VI) and nitrate adsorption data were fitted to Langmuir and Freundlich isotherm models with maximum Langmuir adsorption capacities of 150 mg/g and 72 mg/g, respectively. Cr(VI) and nitrate removal at pH 2 and 6 were evaluated by reducing the amount of PANI (9 wt%) dispersed on to DFBC. Adsorption capacities verses temperature studies revealed that both Cr(VI) and nitrate adsorption are endothermic and thermodynamically favored. Regeneration studies were conducted on both DFBC and PANIBC using 0.1M NaOH and PANIBC exhibited excellent sorption capacities for Cr(VI) and nitrate in lake water samples and in the presence of competitive ions.


Assuntos
Cromo , Poluentes Químicos da Água , Adsorção , Compostos de Anilina , Carvão Vegetal , Cromo/análise , Humanos , Concentração de Íons de Hidrogênio , Cinética , Nitratos , Água , Poluentes Químicos da Água/análise
4.
Sci Total Environ ; 773: 145631, 2021 Jun 15.
Artigo em Inglês | MEDLINE | ID: mdl-33940740

RESUMO

Aqueous phosphate uptake is needed to reduce global eutrophication. Negatively charged adsorbent surfaces usually give poor phosphate sorption. Chemically- and thermally-modified lignite (CTL) was prepared by impregnating low-cost lignite (RL) with Ca2+ and Mg2+ cations, basified with KOH (pH Ì´ 13.9), followed by a 1 h 600 °C pyrolysis under nitrogen. CTL has a positive surface (PZC = 13) due to basic surface Ca and Mg compounds, facilitating the aqueous phosphate uptake. CaCO3, MgO, Ca(OH)2, and Mg(OH)2 surface phases with 0.22 µm particle sizes were verified by XRD, XPS, SEM, TEM, and EDX before and after phosphate uptake. Higher amounts of these mineral phases promoted more CTL phosphate uptake than raw lignite (RL) and thermally treated lignite (TL) without Ca/Mg modification. Phosphorous uptake by Ca2+/Mg2+ occurs not by classic adsorption but by stochiometric precipitation of Mg3(PO4)2, MgHPO4, Ca3(PO4)2, and CaHPO4. This offers the potential of substantial uptake capacities. CTL's phosphate removal is pH-dependent; the optimum pH was 2.2. Water-washed CTL exhibited a maximum Langmuir phosphate uptake capacity of 15.5 mg/g at pH 7, 6 and 14 times higher than that of TL and RL, respectively (particle size <150 µm, adsorbent dose 50 mg, 25 mL of 25-1000 ppm phosphate concentration, 24 h, 25 °C). The unwashed CTL exhibited a maximum Langmuir phosphate removal capacity (80.6 mg/g), 5.2-times greater than the washed CTL (15.5 mg/g). Insoluble Ca2+ and Mg2+ phosphates/hydrophosphate particles dominated CTL's phosphate removal. Phosphates were recovered from both exhausted unwashed and washed CTL better in HCl than in NaOH. P-laden washed CTL exhibited a slow phosphate leaching rate under initial pH of 6.5-7.5 (52-57% over 20 days) after phosphate uptake, indicating it could serve as a slow-release fertilizer. Unwashed CTL retained more phosphates than washed CTL (cumulative qe for 4 cycles = 391.8 mg/g vs 374.7 mg/g) and potentially improves soil fertility more.

5.
Environ Res ; 201: 111218, 2021 10.
Artigo em Inglês | MEDLINE | ID: mdl-33965387

RESUMO

Environmental (pH, temperature ionic strength, cations, anions) and process (pyrolysis temperature, particle size, adsorbent dosage, initial concentration) parameters were evaluated for ciprofloxacin and acetaminophen sorption onto a series of sustainable banana peel biochars. Ciprofloxacin and acetaminophen were chosen as model pharmaceuticals for removal owing to their worldwide presence in aquatic systems. After pyrolytic preparation from 450 to 750 °C, the biochars were qualitatively and quantitatively characterized by physicochemical, morphological, mineralogical and elemental analyses. Batch sorption studies were employed to evaluate the pH effects from 2 to 10, biochar pyrolysis temperatures (450, 550, 650, and 750 °C), particle sizes (30-50, 50-100, 100-150 BSS mesh), adsorbent dosages (0.5, 1.0, 2.0 g/L), adsorbate concentrations (0.5-200 ppm) and uptake temperatures (10, 25, 40 °C) on sorption efficiency. Maximum pharmaceutical sorption is achieved by the biochar prepared at 750 °C. Sorption rate increased with decrease in biochar particle size from 30 to 50 to 100-150 BSS mesh. Relationships between biochar properties and their sorptive potential showed positive correlations with surface area, total pore volume, %C, %ash and C/N molar ratios. Sorption data was modelled using different isotherm models and both kinetic and thermodynamic equations. Maximum Langmuir capacities of ciprofloxacin and acetaminophen on BPBC750 were 23.3 and 40.8 mg/g at 10 °C; 21.0 and 49.93 mg/g at 25 °C and 20.42 and 57.3 mg/g at 45 °C, respectively. Langmuir isotherm fittings and thermodynamic parameters confirmed the exothermic sorption (for ciprofloxacin) and endothermic sorption (for acetaminophen). The role of ionic strength, cations and anions on pharmaceuticals sorption were evaluated. H-bonding, π-π-interactions and pore diffusion were major contributors to pharmaceutical sorption.


Assuntos
Musa , Acetaminofen , Adsorção , Carvão Vegetal , Ciprofloxacina
6.
Small ; 17(34): e2007840, 2021 08.
Artigo em Inglês | MEDLINE | ID: mdl-33899324

RESUMO

A noticeable interest and steady rise in research studies reporting the design and assessment of smart adsorbents for sequestering aqueous metal ions and xenobiotics has occurred in the last decade. This motivates compiling and reviewing the characteristics, potentials, and performances of this new adsorbent generation's metal ion and xenobiotics sequestration. Herein, stimuli-responsive adsorbents that respond to its media (as internal triggers; e.g., pH and temperature) or external triggers (e.g., magnetic field and light) are highlighted. Readers are then introduced to selective adsorbents that selectively capture materials of interest. This is followed by a discussion of self-healing and self-cleaning adsorbents. Finally, the review ends with research gaps in material designs.


Assuntos
Recuperação e Remediação Ambiental , Poluentes Químicos da Água , Purificação da Água , Adsorção , Metais , Poluentes Químicos da Água/análise
7.
J Colloid Interface Sci ; 597: 182-195, 2021 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33866210

RESUMO

Phosphate is a primary plant nutrient, serving integral role in environmental stability. Excessive phosphate in water causes eutrophication; hence, phosphate ions need to be harvested from soil nutrient levels and water and used efficiently. Fe-Mg (1:2) layered double hydroxides (LDH) were chemically co-precipitated and widely dispersed on a cheap, commercial Douglas fir biochar (695 m2/g surface area and 0.26 cm3/g pore volume) byproduct from syn gas production. This hybrid multiphase LDH dispersed on biochar (LDHBC) robustly adsorbed (~5h equilibrium) phosphate from aqueous solutions in exceptional sorption capacities and no pH dependence between pH 1-11. High phosphate Langmuir sorption capacities were found for both LDH (154 to 241 mg/g) and LDH-modified biochar (117 to 1589 mg/g). LDHBC was able to provide excellent sorption performance in the presence of nine competitive anion contaminants (CO32-, AsO43-, SeO42-, NO3-, Cr2O72-, Cl-, F-, SO42-, and MoO42-) and also upon remediating natural eutrophic water samples. Regeneration was demonstrated by stripping with aqueous 1 M NaOH. No dramatic performance drop was observed over 3 sorption-stripping cycles for low concentrations (5 ppm). The adsorbents and phosphate-laden adsorbents were characterized using Elemental analysis, BET, PZC, TGA, DSC, XRD, SEM, TEM, and XPS. The primary sorption mechanism is ion-exchange from low to moderate concentrations (10-500 ppm). Chemisorption and stoichiometric phosphate compound formation were also considered at higher phosphate concentrations (>500 ppm) and at 40 °C. This work advances the state of the art for environmentally friendly phosphate reclamation. These phosphate-laden adsorbents also have potential to be used as a slow-release phosphate fertilizer.


Assuntos
Poluentes Químicos da Água , Adsorção , Carvão Vegetal , Hidróxidos , Cinética , Fosfatos , Água , Poluentes Químicos da Água/análise
8.
Environ Res ; 192: 110283, 2021 01.
Artigo em Inglês | MEDLINE | ID: mdl-33022217

RESUMO

Biochar-based hybrid composites containing added nano-sized phases are emerging adsorbents. Biochar, when functionalized with nanomaterials, can enhance pollutant removal when both the nanophase and the biochar surface act as adsorbents. Three different pine wood wastes (particle size < 0.5 mm, 10 g) were preblended with 1 wt% of three different graphenes in aqueous suspensions, designated as G1, G2, and G3. G1 (SBET, 8.1 m2/g) was prepared by sonicating graphite made from commercial synthetic graphite powder (particle size 7-11 µm). G2 (312.0 m2/g) and G3 (712.0 m2/g) were purchased commercial graphene nanoplatelets (100 mg in 100 mL deionized water). These three pine wood-graphene mixtures were pyrolyzed at 600 °C for 1 h to generate three graphene-biochar adsorbents, GPBC-1, GPBC-2, and GPBC-3 containing 4.4, 4.9, and 5.0 wt% of G1, G2, and G3 respectively. Aqueous Cu2+ adsorption capacities were 10.6 mg/g (GPBC-1), 4.7 mg/g (GPBC-2), and 5.5 mg/g (GPBC-3) versus 7.2 mg/g for raw pine wood biochar (PBC) (0.05 g adsorbent dose, Cu2+ 75 mg/L, 25 mL, pH 6, 24 h, 25 ± 0.5 °C). Increased graphene surface areas did not result in adsorption increases. GPBC-1, containing the lowest nanophase surface area with the highest Cu2+ capacity, was chosen to evaluate its Cu2+ adsorption characteristics further. Results from XPS showed that the surface concentration of oxygenated functional groups on the GPBC-1 is greater than that on the PBC, possibly contributing to its greater Cu2+ removal versus PBC. GPBC-1 and PBC uptake of Cu2+ followed the pseudo-second-order kinetic model. Langmuir maximum adsorption capacities and BET surface areas were 18.4 mg/g, 484.0 m2/g (GPBC-1) and 9.2 mg/g, 378.0 m2/g (PBC). This corresponds to 3.8 × 10-2 versus 2.4 × 10-2 mg/m2 of Cu2+ removed on GPBC-1 (58% more Cu2+ per m2) versus PBC. Cu2+ adsorption on both these adsorbents was spontaneous and endothermic.


Assuntos
Grafite , Pinus , Poluentes Químicos da Água , Adsorção , Carvão Vegetal , Cobre , Cinética , Água , Poluentes Químicos da Água/análise , Madeira/química
9.
Sci Total Environ ; 765: 142698, 2021 Apr 15.
Artigo em Inglês | MEDLINE | ID: mdl-33097261

RESUMO

The year 2020 brought the news of the emergence of a new respiratory disease (COVID-19) from Wuhan, China. The disease is now a global pandemic and is caused by a virus named SARS-CoV-2 by international bodies. Important viral transmission sources include human contact, respiratory droplets and aerosols, and through contact with contaminated objects. However, viral shedding in feces and urine by COVID-19-afflicted patients raises concerns about SARS-CoV-2 entering aquatic systems. Recently, targeted SARS-CoV-2 genome fragments have been successfully detected in wastewater, sewage sludge and river waters around the world. Wastewater-based epidemiology (WBE) studies can provide early detection and assessment of COVID-19 transmission and the growth of active cases within given wastewater catchment areas. WBE surveillance's ability to detect the growth of cases was demonstrated. Was this science applied throughout the world as this pandemic spread throughout the globe? Wastewater treatment efficacy for SARS-CoV-2 removal and risk assessments associated with treated water are reported. Disinfection strategies using chemical disinfectants, heat and radiation for deactivating and destroying SARS-CoV-2 are explained. Analytical methods of SARS-CoV-2 detection are covered. This review provides a more complete overview of the present status of SARS-CoV-2 and its consequences in aquatic systems. So far, WBE programs have not yet served to provide the early alerts to authorities that they have the potential to achieve. This would be desirable in order to activate broad public health measures at earlier stages of local and regional stages of transmission.


Assuntos
COVID-19 , Infecções por Coronavirus , Coronavirus , China/epidemiologia , Humanos , SARS-CoV-2
10.
Chemosphere ; 269: 128409, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33069440

RESUMO

Biochar has become a popular research topic in sustainable chemistry for use both in agriculture and pollution abatement. To enhance aqueous Cr(VI), Pb(II) and Cd(II) removal efficiency, high surface area (535 m2/g) byproduct Douglas fir biochar (DFBC) from commercial syn-gas production obtained by fast pyrolysis (900-1000 °C, 1-10 s), was subjected to a KOH activation. KOH-activated biochar (KOHBC) underwent a remarkable surface area increase to 1049 m2/g and a three-fold increase in pore volume (BET analysis). Batch sorption studies on KOHBC verses pH revealed that the highest chromium, lead and cadmium removal capacities occurred at pH 2.0, 5.0 and 6.0, respectively. KOHBC exhibited much higher adsorption capacities than unactivated DFBC. Heavy metal loadings onto KOHBC were characterized by scanning electron microscopy, transmission electron microscopy and X-ray photoelectron spectroscopy. Sorption of Cr(VI), Pb(II) and Cd(II) all followed pseudo-second order kinetics and the Langmuir adsorption model. The highest Langmuir adsorption capacities at the respective pH's of maximum adsorption were 140.0 mg g-1 Pb(II), 127.2 mg g-1 Cr(VI) and 29.0 mg g-1 Cd(II). Metal ions spiked into natural and laboratory waste water systems exhibited high sorption capacities. Desorption studies carried out using 0.1 M HCl revealed that Pb(II) adsorption onto the KOHBC surface is reversible. Portions of Cd(II) and Cr(VI) adsorbed strongly onto KOHBC were unable to be desorbed by 0.1 M HCl and 0.1 M NaOH.


Assuntos
Pseudotsuga , Poluentes Químicos da Água , Adsorção , Cádmio , Carvão Vegetal , Cromo/análise , Concentração de Íons de Hidrogênio , Cinética , Chumbo , Poluentes Químicos da Água/análise
11.
J Colloid Interface Sci ; 587: 767-779, 2021 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-33309243

RESUMO

Commercialization of novel adsorbents technology for providing safe drinking water must consider scale-up methodological approaches to bridge the gap between laboratory and industrial applications. These imply complex matrix analysis and large-scale experiment designs. Arsenic concentrations up to 200-fold higher (2000 µg/L) than the WHO safe drinking limit (10 µg/L) have been reported in Latin American drinking waters. In this work, biochar was developed from a single, readily available, and taxonomically identified woody bamboo species, Guadua chacoensis. Raw biochar (BC) from slow pyrolysis (700 °C for 1 h) and its analog containing chemically precipitated Fe3O4 nanoparticles (BC-Fe) were produced. BC-Fe performed well in fixed-bed column sorption. Predicted model capacities ranged from 8.2 to 7.5 mg/g and were not affected by pH 5-9 shift. The effect of competing matrix chemicals including sulfate, phosphate, nitrate, chloride, acetate, dichromate, carbonate, fluoride, selenate, and molybdate ions (each at 0.01 mM, 0.1 mM and 1 mM) was evaluated. Fe3O4 enhanced the adsorption of arsenate as well as phosphate, molybdate, dichromate and selenate. With the exception of nitrate, individually competing ions at low concentration (0.01 mM) did not significantly inhibit As(V) sorption onto BC-Fe. The presence of ten different ions in low concentrations (0.01 mM) did not exert much influence and BC-Fe's preference for arsenate, and removal remained above 90%. The batch and column BC and BC-Fe adsorption capacities and their ability to provide safe drinking water were evaluated using a naturally contaminated tap water (165 ± 5 µg/L As). A 960 mL volume (203.8 Bed Volumes) of As-free drinking water was collected from a 1 g BC-Fe fixed bed. Adsorbent regeneration was attempted with (NH4)2SO4, KOH, or K3PO4 (1 M) strippers. Potassium phosphate performed the best for BC-Fe regeneration. Safe disposal options for the exhausted adsorbents are proposed. Adsorbents and their As-laden analogues (from single and multi-component mixtures) were characterized using high resolution XPS and possible competitive interactions and adsorption pathways and attractive interactions were proposed including electrostatic attractions, hydrogen bonding and weak chemisorption to BC phenolics. Stoichiometric precipitation of metal (Mg, Ca and Fe) oxyanion (phosphate, molybdate, selenate and chromate) insoluble compounds is considered. The use of a packed BC-Fe cartridge to provide As-free drinking water is presented for potential commercial use. BC-Fe is an environmentally friendly and potentially cost-effective adsorbent to provide arsenic-free household water.


Assuntos
Arsênio , Sasa , Poluentes Químicos da Água , Purificação da Água , Adsorção , Arsênio/análise , Carvão Vegetal , Compostos Férricos , Ferro , Cinética , Transferência de Tecnologia , Poluentes Químicos da Água/análise
12.
ACS Omega ; 5(27): 16366-16378, 2020 Jul 14.
Artigo em Inglês | MEDLINE | ID: mdl-32685799

RESUMO

Pine needle litter in Himalayan forests leads to forest fires, ground water recharge inhibition, soil acidification and contamination, and stops the growth of grass and plants. This study provides a possible solution for pine needle litter problem by converting it to biochar. Pine needle litter lying on the ground for approximately a month was collected from the Himalayan region. The pine needle litter biochars were generated using slow pyrolysis (residence time, 30 min; heating rate, 10 °C/min) at 350, 450, 550, 650, and 750 °C. Finally, pine needle litter biochar prepared at 550 °C (PNBC550) was selected for sorptive removal of aqueous lead both in batch and column studies. The PNBC550 was characterized for proximate and elemental compositions, crystallinity, surface area, morphology, and functional groups. A BET surface area of 230.9 m2/g was obtained for PNBC550. Batch sorption studies were carried out to study (1) the adsorption versus pH studies (at pH 2 to 7), (2) isotherms (at 10, 25, and 35 °C) to evaluate the temperature effect on the sorption efficiency, and (3) kinetics to reveal the effect of time, adsorbent dose, and initial concentration on the reaction rate. Increasing pyrolysis temperature raised lead sorption up to 550 °C. Lead adsorption increased considerably as pH rose from 2 to a maximum adsorption around pH 5 and above. The sorption data were fitted using different isotherm models and kinetic equations. The Langmuir adsorption capacity increased from 22.93 mg/g at 10 °C to 40.43 mg/g at 35 °C, showing that adsorption was endothermic. Fixed-bed studies were conducted at room temperature with an initial lead concentration of 7.85 mg/L and 4.0 g of PNBC550 at initial pH 5.0 and a flow rate of 3 mL/min. Desorption studies conducted under the same experimental conditions found about 90-93% lead recovery. Development of high-efficiency biochars for lead remediation provides a sustainable solution for the Himalayan pine needle litter problem. The biochars also possess the possible potential for aqueous removal of other metal cations.

13.
Chemosphere ; 258: 127336, 2020 Nov.
Artigo em Inglês | MEDLINE | ID: mdl-32563916

RESUMO

Modification of commercially available Douglas fir biochar (BC) by iron oxide nanoparticle precipitation from aqueous Fe2+/Fe3+ salt solutions upon NaOH treatment generated a hybrid adsorbent (MBC) that removed three common emerging aqueous contaminants, a stimulant (caffeine) and two anti-inflammatory drugs (ibuprofen and acetylsalicylic acid) through batch sorption. Fe3O4 particles (12.3 ± 7.1 nm diameter fundamental particles with aggregates 1-17 µm diameter) dispersed on the biochar surface provided magnetization and created new adsorption sites for the contaminant uptake. These smaller quasi-spherical, octahedral Fe3O4 particles as well as the spindle-like Fe2O3 particles were observed with scanning electron microscopy (SEM) images of MBC, and the composition was confirmed by X-ray powder diffraction (XRD). Adsorption features were evaluated using Langmuir and Freundlich isotherm models. The Langmuir adsorption capacities on MBC at 35 °C have increased from 24.6 ± 0.4 to 75.1 ± 1.8 mg/g for caffeine, 17.5 ± 0.4 to 39.9 ± 1.2 mg/g for ibuprofen and 106.2 ± 2.8 to 149.9 ± 4.5 mg/g for acetylsalicylic acid after Fe3O4 modification. Fast adsorption resulted in equilibrium within 5 min. MBC has potential as a low cost, green adsorbent for pharmaceutical mitigation from water with high adsorption capacities and fast kinetics. The Douglas fir biochar is a byproduct waste from a syn-gas from wood production process covering its production costs.


Assuntos
Carvão Vegetal , Compostos Férricos/química , Magnetismo , Preparações Farmacêuticas/isolamento & purificação , Águas Residuárias/química , Purificação da Água/métodos , Adsorção , Cinética , Pseudotsuga , Poluentes Químicos da Água/isolamento & purificação
14.
ACS Omega ; 5(6): 2575-2593, 2020 Feb 18.
Artigo em Inglês | MEDLINE | ID: mdl-32095682

RESUMO

Rice and wheat husks were converted to biochars by slow pyrolysis (1 h) at 600 °C. Iron oxide rice husk hybrid biochar (RHIOB) and wheat husk hybrid biochar (WHIOB) were synthesized by copyrolysis of FeCl3-impregnated rice or wheat husks at 600 °C. These hybrid sorbents were characterized using X-ray photoelectron spectroscopy, X-ray diffraction, scanning electron microscopy (SEM), SEM-energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, transmission electron microscopy, physical parameter measurement system, and Brunauer-Emmett-Teller (BET) surface area techniques. Fe3O4 was the predominant iron oxide present with some Fe2O3. RHIOB and WHIOB rapidly chemisorbed As(III) from water (∼24% removal in first half an hour reaching up to ∼100% removal in 24 h) at surface Fe-OH functions forming monodentate ≡Fe-OAs(OH)2 and bidentate (≡Fe-O)2AsOH complexes. Optimum removal occurred in the pH 7.5-8.5 range for both RHIOB and WHIOB, but excellent removal occurred from pH 3 to 10. Batch kinetic studies at various initial adsorbate-adsorbent concentrations, temperatures, and contact times gave excellent pseudo-second-order model fits. Equilibrium data were fitted to different sorption isotherm models. Fits to isotherm models (based on R 2 and χ2) on RHIOB and WHIOB followed the order: Redlich-Peterson > Toth > Sips = Koble-Corrigan > Langmuir > Freundlich = Radke-Prausnitz > Temkin and Sips = Koble-Corrigan > Toth > Redlich-Peterson > Langmuir > Temkin > Freundlich = Radke-Prausnitz, respectively. Maximum adsorption capacities, Q RHIOB 0 = 96 µg/g and Q WHIOB 0 = 111 µg/g, were obtained. No As(III) oxidation to As(V) was detected. Arsenic adsorption was endothermic. Particle diffusion was a rate-determining step at low (≤50 µg/L) concentrations, but film diffusion controls the rate at ≥100-200 µg/L. Binding interactions with RHIOB and WHIOB were established, and the mechanism was carefully discussed. RHIOB and WHIOB can successfully be used for As(III) removal in single and multicomponent systems with no significant decrease in adsorption capacity in the presence of interfering ions mainly Cl-, HCO3 -, NO3 -, SO4 2-, PO4 3-, K+, Na+, Ca2+. Simultaneous As(III) desorption and regeneration of RHIOB and WHIOB was successfully achieved. A very nominal decrease in As(III) removal capacity in four consecutive cycles demonstrates the reusability of RHIOB and WHIOB. Furthermore, these sustainable composites had good sorption efficiencies and may be removed magnetically to avoid slow filtration.

15.
ACS Appl Mater Interfaces ; 12(8): 9248-9260, 2020 Feb 26.
Artigo em Inglês | MEDLINE | ID: mdl-31990524

RESUMO

Oil spills cause massive loss of aquatic life. Oil spill cleanup can be very expensive, have secondary environmental impacts, or be difficult to implement. This study employed five different adsorbents: (1) commercially available byproduct Douglas fir biochar (BC) (SA ∼ 695 m2/g, pore volume ∼ 0.26 cm3/g, and pore diameter ∼ 13-19.5 Å); (2) BC modified with lauric acid (LBC); (3) iron oxide-modified biochar (MBC); (4) LBC modified with iron oxide (LMBC); and (5) MBC modified with lauric acid (MLBC) for oil recovery. Transmission, engine, machine, and crude oils were used to simulate oil spills and perform adsorption experiments. All five adsorbents adsorbed large quantities of each oil in fresh and simulated seawater with only a slight pH dependence, fast kinetics (sorptive equilibrium reached before 15 min), and high regression fits to the pseudo-second-order kinetic model. The Sips isotherm model oil sorption capacities for these sorbents were in the range ∼3-11 g oil/1 g adsorbent. Lauric acid-decorated (60-2 wt %) biochars gave higher oil adsorption capacities than the undecorated biochar. Lauric acid enhances biochar hydrophobicity and its water contact angle and reduces water influx into biochar's porosity preventing it from sinking in water for 3 weeks. These features were observed even at 2% wt of lauric acid (sinks only after 2 weeks). Magnetization by magnetite nanoparticle deposition onto BC and LBC allows the recovery of the exhausted adsorbent by a magnetic field as an alternative to filtration. Oil sorption was endothermic. Recycling was demonstrated after toluene stripping. The oil-laden adsorbents' heating values were obtained, suggesting an alternative use of these spent adsorbents as a low-cost fuel after recovery, avoiding waste disposal costs. The initial and oil-laden adsorbents were characterized by scanning electron microscopy, transmission electron microscopy, energy-dispersive X-ray spectroscopy, Fourier transform infrared spectroscopy, X-ray diffraction, Brunauer-Emmet-Teller surface area, contact angle, thermogravimetric analyses, differential scanning calorimetry, vibrating sample magnetometry, elemental analysis, and X-ray photoelectron spectroscopy.

16.
Sci Total Environ ; 706: 135943, 2020 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-31862592

RESUMO

Discarded bamboo culms of Guadua chacoensis were used for biochar remediation of aqueous As(V). Raw biochar (BC), activated biochar (BCA), raw Fe3O4 nanoparticle-covered biochar (BC-Fe), and activated biochar covered with Fe3O4 nanoparticles (BCA-Fe) were prepared, characterized and tested for As(V) aqueous adsorption. The goal is to develop an economic, viable, and sustainable adsorbent to provide safe arsenic-free water. Adsorbents were characterized using scanning electron microscopy (SEM) and energy dispersive analysis by X-ray (SEM-EDX), transmission electron microscopy (TEM) and energy dispersive X-ray spectroscopy (TEM-EDS), X-ray photoelectron spectroscopy (XPS), X-ray powder diffraction (XRD), Brunauer-Emmett-Teller surface area measurements (SBET), point of zero charge determinations (PZC), and elemental analysis. Activation with KOH increased the O/C ratio and the surface area of BC from 6.7 m2/g to 1239.7 m2/g (BCA). As(V) sorption equilibrium was achieved within <2 h for all four adsorbents and kinetics followed the pseudo-second-order model. At a 10 mg/L initial As(V) concentration, BC-Fe achieved a 100% removal (5 mg/g) over a pH 5 to 9 window. Sorption was endothermic on all four adsorbents and the capacities rose with the increasing temperature. Langmuir capacities at 40 °C for BC, BCA, BC-Fe, and BCA-Fe were 256, 217, 457, and 868 mg/g, respectively, and capacities were compared with other sorbents. Breakthrough fixed-bed column sorption was carried out for BC and BC-Fe producing 6.6 mg/g and 13.9 mg/g bed capacities, respectively. Potassium phosphate was a better As stripping agent than sodium bicarbonate. Performance of the adsorbents in an As(V)-spiked natural water and a naturally As(V)-contaminated domestic water were assessed. Robust arsenate sequestration occurred generating As-safe water (As <0.01 mg/L), despite the presence of competing ions. Stoichiometric precipitation of iron-arsenate complexes triggered by iron dissolution was also established.


Assuntos
Sasa , Purificação da Água , Adsorção , Arsênio , Carvão Vegetal , Compostos Férricos , Cinética , Nanopartículas Metálicas , Poluentes Químicos da Água
17.
Sci Total Environ ; 694: 133427, 2019 Dec 01.
Artigo em Inglês | MEDLINE | ID: mdl-31756815

RESUMO

Providing drinking water with safe arsenic levels in Latin American (LA) countries (a total of 22 countries) is a major current challenge. Arsenic's presence in water has been neglected for many decades since it was first reported ~100 years ago in Argentina. The major arsenic source in this region is geogenic. So far, arsenic has been reported in 15 LA countries. Arsenic concentrations in drinking water have been reported up to >200 fold (2000 µg/L) the WHO limit of 10 µg/L. About 14 million people in the arsenic affected LA countries depend on contaminated water characterized by >10 µg/L of arsenic. Low-cost, easy to use, efficient, and sustainable solutions are needed to supply arsenic safe water to the rural and peri-urban population in the affected areas. In the present study, >250 research articles published on various emerging technologies used for arsenic remediation in rural and peri-urban areas of LA countries are critically reviewed. Special attention has been given to arsenic adsorption methods. The manuscript focuses on providing insights into low cost emergent adsorbents with an implementation potential in Latin America. Natural, modified and synthetic adsorbents used for arsenic decontamination were reviewed and compared. Advantages and disadvantages of treatment methods are summarized. Adsorbent selection criteria are developed. Recommendations concerning emerging adsorbents for aqueous arsenic removal in LA countries have also been made.


Assuntos
Arsênio/análise , Água Potável/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , América Latina , Poluição da Água
18.
J Environ Manage ; 250: 109429, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31491719

RESUMO

Magnetic Fe3O4/Douglas fir biochar composites (MBC) were prepared with a 29.2% wt. Fe3O4 loading and used to treat As(III)-contaminated water. Toxicity of As(III) (inorganic) is significantly greater than As(V) and more difficult to remove from water. Removal efficiency was optimized verses pH, contact time and initial concentration. Column sorption and regeneration were also studied. Adsorption kinetics data best fitted the pseudo second order model (R2 > 0.99). Adsorption was analyzed with three isotherm models at 20, 25 and 40 °C. The Sips isotherm showed the best fit at 25 °C with a 5.49 mg/g adsorption capacity, which is comparable with other adsorbents. MBC gave faster kinetics (~1-1.5 h) at pH 7 and ambient temperature than previous adsorbents. The Gibbs free energy (ΔG) of this spontaneous As(III) adsorption was -35 kJ/mol and ΔH = 70 kJ/mol was endothermic. Experiments were performed on industrial and laboratory wastewater samples in the presence of other co-existing contaminants (pharmaceutical residues, heavy metals ions and oxi-anions). The composite reduced the arsenic concentrations below the WHO's safe limit of 0.2 mg/L for waste water discharge. X-ray photoelectron spectroscopy (XPS) studies found As(III) and less toxic As(V) on Fe3O4 surfaces indicating adsorbed (or adsorbing) As(III) oxidation occurred upon contact with O2 and possibly dissolved Fe(III) or upon drying under oxic conditions. Under anoxic conditions magnetite to maghemite transformation drives the oxidation. A pH-dependent surface chemisorption mechanism was proposed governing adsorption aided by XPS studies vs pH.


Assuntos
Arsênio , Pseudotsuga , Poluentes Químicos da Água , Purificação da Água , Adsorção , Carvão Vegetal , Compostos Férricos , Óxido Ferroso-Férrico , Concentração de Íons de Hidrogênio , Cinética , Água
19.
Chem Rev ; 119(6): 3510-3673, 2019 03 27.
Artigo em Inglês | MEDLINE | ID: mdl-30830758

RESUMO

In the last few decades, pharmaceuticals, credited with saving millions of lives, have emerged as a new class of environmental contaminant. These compounds can have both chronic and acute harmful effects on natural flora and fauna. The presence of pharmaceutical contaminants in ground waters, surface waters (lakes, rivers, and streams), sea water, wastewater treatment plants (influents and effluents), soils, and sludges has been well doccumented. A range of methods including oxidation, photolysis, UV-degradation, nanofiltration, reverse osmosis, and adsorption has been used for their remediation from aqueous systems. Many methods have been commercially limited by toxic sludge generation, incomplete removal, high capital and operating costs, and the need for skilled operating and maintenance personnel. Adsorption technologies are a low-cost alternative, easily used in developing countries where there is a dearth of advanced technologies, skilled personnel, and available capital, and adsorption appears to be the most broadly feasible pharmaceutical removal method. Adsorption remediation methods are easily integrated with wastewater treatment plants (WWTPs). Herein, we have reviewed the literature (1990-2018) illustrating the rising environmental pharmaceutical contamination concerns as well as remediation efforts emphasizing adsorption.


Assuntos
Recuperação e Remediação Ambiental/métodos , Preparações Farmacêuticas/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Animais , Tratamento Farmacológico/estatística & dados numéricos , Água Subterrânea , Humanos , Preparações Farmacêuticas/administração & dosagem , Preparações Farmacêuticas/química , Poluentes Químicos da Água/química , Poluição Química da Água/estatística & dados numéricos
20.
Environ Res ; 169: 434-444, 2019 02.
Artigo em Inglês | MEDLINE | ID: mdl-30530083

RESUMO

Carbon dot- and magnetite-modified magnetic carbon nanotubes (CMNTs) were synthesized and evaluated for carbamazepine removal from water. The adsorbent was characterized by multiple modern surface and microstructure analyzing techniques. CMNTs were composed of three components including carbon dots (CDs), carbon nanotubes (CNTs) and magnetite. CDs and CNTs introduce abundant carboxyl groups onto CMNTs and magnetite allows rapid magnetic separation of the adsorbent realizable after batch adsorption. This adsorbent has a moderately high adsorption capacity of 65 mg-carbamazepine/g-adsorbent at pH 7.0 ±â€¯0.2, which is superior to many reported adsorbents. Carbamazepine was uptaken well in a wide pH range, regardless of the surface charging of CMNTs. Its adsorption on CMNTs was quite fast and reached 80% of removal during the initial 3 h. The mass transfer within CMNTs and the time-dependent utilization, exhaustion and depletion of the adsorption capacity were successfully described using a simplified homogeneous surface diffusion model (HSDM). The surface diffusion coefficients (Ds) rose with increasing initial carbamazepine concentrations. After six regeneration and recycle experiments, the capacity loss of CMNTs was less than 2.2% at the conditions tested. FTIR spectra showed the characteristics of the components. Raman spectra implied a π-π electron donor-acceptor (EDA) interaction during adsorption. This work proposed a method of combining π-bond-rich materials (CNTs and CDs) and magnetite to make separable composite adsorbents with high affinity interactions between carbamazepine and carbon materials. The prepared adsorbent is attractive for carbamazepine removal due to its good performance, moderate cost, ease of separation, and ability to regenerate.


Assuntos
Carbamazepina/análise , Nanotubos de Carbono , Poluentes Químicos da Água , Purificação da Água , Adsorção , Fenômenos Magnéticos , Água
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