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1.
Water Sci Technol ; 82(5): 877-886, 2020 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-33031067

RESUMO

Water pollution from antibiotics has attracted a lot of attention for its serious threat to human health. In this study, a magnetic adsorbent (zinc ferrite/activated carbon (ZnFe2O4/AC) was synthesized via microwave method to effectively remove gemifioxacin mesylate (GEM) and moxifloxacin hydrochloride (MOX). Based on the porosity of AC and the magnetism of ZnFe2O4, the resulting ZnFe2O4/AC has high adsorption capacities and can be easily separated from the solid-liquid system via a magnetic field. The largest adsorption capacities for GEM and MOX can reach up to 433.4 mg g-1 and 388.8 mg g-1, respectively, higher than those of reported adsorbents such as MIL-101 and MOF-808. Fastest adsorptions of GEM and MOX were found at 5 min, and solution pH and coexisting salts do not have a significant influence on the adsorption process. The adsorption mechanism analysis indicates that electrostatic interaction and H-bond interaction contribute to the effective adsorption.


Assuntos
Carvão Vegetal , Poluentes Químicos da Água , Adsorção , Antibacterianos , Magnetismo
2.
Water Sci Technol ; 82(7): 1296-1303, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33079710

RESUMO

Melamine foam is an important material in production and life. A series of porous carbon foams were obtained through a simple carbonization process of melamine foam at different temperatures. The carbon foams obtained at the carbonization temperature of 400 and 600 °C reveal a hydrophobic and even super-hydrophobic property (water contact angle larger than 150°) with a hexane adsorption much larger than that of melamine foam. However, the carbon foam obtained at the carbonization temperature of 800 °C reveals a super-hydrophilic property (water contact angle smaller than 5°) due to its severest shrinkage during the carbonization process. Interestingly, this series of carbon foams have an excellent performance in oil adsorption. However, the carbon membranes derived from the 800 °C carbon foam reveals oleophobicity under water (the adsorbed water at the surface was extremely important), which allows the penetration of water and blocks the infiltration of hexane at the same time. These different carbon forms have reversed applications in hexane/water separation.


Assuntos
Hexanos , Água , Adsorção , Carbono , Interações Hidrofóbicas e Hidrofílicas
3.
Water Sci Technol ; 82(7): 1327-1338, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33079713

RESUMO

Advanced oxidative processes (AOP) have been consolidated as an efficient treatment technique to degrade persistent contaminants. In addition to them, biosorption also emerges as a technique capable of removing both pollutants and intermediate products generated by other treatments such as AOP. Thus, this work evaluated the degradation and removal of the mixture of dyes Direct Red 23 and Direct Red 227 in aqueous solution (50 mg·L-1 of each). Preliminary tests showed that the photo-Fenton system under sunlight radiation was the most efficient, reaching a degradation ≥93%. For the adsorptive process using chicken eggshell, preliminary tests indicated that the ideal dosage of adsorbent was 8.0 g·L-1. For this process, a factorial design indicated the best working conditions, which demonstrated from the system adjusted well to the Elovich (kinetic) model and to the Freundlich and Sips models (equilibrium). When associating the two processes, AOP followed by adsorption achieved a total degradation/removal of ≈98% (for all λ) in a time of 60 min. Thus, the feasibility of the combined treatment is indicated.


Assuntos
Corantes , Têxteis , Adsorção , Animais , Concentração de Íons de Hidrogênio , Estresse Oxidativo
4.
Water Sci Technol ; 82(7): 1339-1349, 2020 Oct.
Artigo em Inglês | MEDLINE | ID: mdl-33079714

RESUMO

Flax straw biochar (FSBC)-supported nanoscale zero-valent iron (nZVI) composite (nZVI-FSBC) combining the advantages of nZVI and biochar was synthesized and tested for Cr(VI) removal efficiency from aqueous solution. Surface morphology and structure of FSBC and nZVI-FSBC were characterized by scanning electron microscopy, transmission electron microscopy, thermogravimetric analysis, X-ray diffraction (XRD), Fourier transform infrared (FTIR) spectroscopy, X-ray photoelectron spectroscopy (XPS), and Brunauer-Emmett-Teller techniques, which help to clarify the mechanism of Cr(VI) removal from aqueous solution. The adsorption of Cr(VI) onto FSBC and nZVI-FSBC was best described by the pseudo-second-order and the Sips model. Compared with FSBC, nZVI-FSBC remarkably improved the performance in removing Cr(VI) under identical experimental conditions. Due to the collaborative effect of adsorption and reduction of nZVI-FSBC, the adsorption capacity of nZVI-FSBC for Cr(VI) is up to 186.99 mg/g. The results obtained by XPS, XRD, and FTIR confirmed that adsorption and reduction dominated the processes of Cr(VI) removal by nZVI-FSBC. As a supporter, FSBC not only improved the dispersion of nZVI, but also undertook the adsorption task of Cr(VI) removal. The surface oxygen-containing functional groups of nZVI-FSBC mainly participated in the adsorption part, and the nZVI promoted the Cr(VI) removal through the redox reactions. These observations indicated that the nZVI-FSBC can be considered as potential adsorbents to remove Cr(VI) for environment remediation.


Assuntos
Ferro , Poluentes Químicos da Água , Adsorção , Carvão Vegetal , Cromo , Poluentes Químicos da Água/análise
5.
J Environ Qual ; 49(1): 50-60, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-33016368

RESUMO

Gatifloxacin (GAT) is a new generation fluoroquinolone antibiotic and its adsorption onto iron minerals influenced by coexisting trace elements [e.g., Cu(II)] has not been well investigated. To evaluate the adsorption behavior of GAT and Cu(II) onto goethite and hematite, the complexation constants of GAT with Cu(II) were determined using potentiometric titration, and the effects of Cu(II) concentration and solution pH on GAT adsorption were investigated using batch experiments. It was observed that GAT adsorption was negatively correlated with molar concentration ratio of Cu(II) to GAT. In our experimental pH range (i.e., 3.0-10.8), the calculated main species involved in GAT adsorption were Cu(GAT± )2+ and Cu(GAT± )2 2+ under acidic to neutral conditions, and formation of Cu(GAT- )2 (s) facilitated the removal of GAT from solution under alkaline condition. The adsorption data were well fitted by the Freundlich model and showed high nonlinearity. In adsorption onto goethite, the primary interactions shifted from electrostatic repulsion to formation of goethite-Cu(II)-GAT ternary surface complexes with increase of GAT concentration. For hematite, electrostatic repulsion was the main inhibiting mechanism and became stronger with increase of Cu(II) concentration. Our findings suggest that it is necessary to consider the complexation between GAT and coexisting metal cations in evaluating its transport in soils rich in different iron minerals.


Assuntos
Gatifloxacina , Minerais , Adsorção , Compostos Férricos , Compostos de Ferro
6.
J Environ Qual ; 49(3): 654-662, 2020 May.
Artigo em Inglês | MEDLINE | ID: mdl-33016401

RESUMO

Continuous-flow iron and bio-iron columns were used to evaluate the effects of seepage velocity and concentration on Cr(VI) removal from groundwater. Solid-phase analysis showed that microorganisms accelerated iron corrosion by excreting extracellular polymeric substances and generated highly reactive minerals containing Fe(II), which gave the bio-iron column a longer life span and enhanced capacity for Cr(VI) removal via enhanced adsorption and reduction by reactive minerals. The bio-iron column showed much higher Cr(VI) removal capacity than the iron column with increasing Cr(VI) loading, which was obtained by increasing the seepage velocity or influent Cr(VI) concentration from 95 to 1138 m yr-1 and from 5 to 40 mg L-1 , respectively. When the Cr(VI) loading varied in a range of 0 to 10 mg L-1 h-1 , the bio-iron column had a 60% longer longevity and one- to sixfold higher Cr(VI) elimination capacity than the iron column. This result indicated that, under fluctuating hydraulic conditions [e.g., seepage velocity and Cr(VI) concentration], the presence of microorganisms can significantly boost Cr(VI) removal using Fe0 -based permeable reactive barriers.


Assuntos
Água Subterrânea , Poluentes Químicos da Água/análise , Adsorção , Cromo , Ferro
7.
Sci Total Environ ; 741: 140216, 2020 Nov 01.
Artigo em Inglês | MEDLINE | ID: mdl-32886998

RESUMO

About 90% of the plastic garbage remains in terrestrial ecosystems, and increasing evidence highlights the exposure of crops to plastic particles. However, the potential bioaccumulation of microplastics by plants and their effects on plants' physiology remains unexplored. Here, we evaluated the adsorption, potential uptake, and physiological effects of polyethylene (PE) microbeads in an experimental hydroponic culture of maize. Using isotope analysis, taking advantage of the different carbon isotope composition (δ13C) of fossil-derived PE and C4 plants (e.g., maize), we estimated that about 30% of the carbon in the rhizosphere of microplastic-exposed plants was derived from PE. Still, we did not find evidence of PE translocation to the shoots. Plastic bioaccumulation in the rhizosphere caused a significant decline in transpiration, nitrogen content, and growth. Our results indicate that plastic particles may accumulate in the rhizosphere, impairing water and nutrient uptake, and eventually reaching root eaters. Due to the implications for food production and livestock feeding, our findings encourage further research on the mechanism leading to the bioaccumulation of microplastics on the surface of belowground tissues.


Assuntos
Polietileno , Poluentes Químicos da Água/análise , Adsorção , Ecossistema , Hidroponia , Microesferas , Plásticos , Zea mays
8.
J Environ Manage ; 263: 110368, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883474

RESUMO

Nowadays, alternative options to conventional wastewater treatment should be studied due to rising concerns emerged by the presence of pharmaceuticals compounds (PhCs) in the aquatic environment. In this work, a combined system including biological treatment by activated sludge plus adsorption with activated carbon is proposed to remove three selected drugs (acetaminophen (ACT), caffeine (CAF) and ibuprofen (IBU)) in a concentration of 2 mg L-1 of each one. For it three sequencing batch reactors (SBR) were operated. SBR-B treated a synthetic wastewater (SWW) without target drugs and SBR-PhC and SBR-PhC + AC operated with SWW doped with the three drugs, adding into SBR-PhC + AC 1.5 g L-1 of a mesoporous granular activated carbon. Results showed that the hybrid system SBR-activated carbon produced an effluent free of PhCs, which in addition had higher quality than that achieved in a conventional activated sludge treatment in terms of lower COD, turbidity and SMP concentrations. On the other hand, five possible routes of removal for target drugs during the biological treatment were studied. Hydrolysis, oxidation and volatilization pathways were negligible after 6 h of reaction time. Adsorption route only was significant for ACT, which was adsorbed completely after 5 h of reaction, while only 1.9% of CAF and 5.6% of IBU were adsorbed. IBU was the least biodegradable compound.


Assuntos
Eliminação de Resíduos Líquidos , Águas Residuárias , Adsorção , Reatores Biológicos , Esgotos
9.
J Environ Manage ; 263: 110415, 2020 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-32883481

RESUMO

Drinking water containing excess fluoride is a major health concern across the globe. The present study reports the feasibility of zirconium impregnated hybrid anion exchange resin (HAIX-Zr) for treating fluoride contaminated groundwater. The HAIX-Zr resin was prepared by impregnating ZrO2 nanoparticles on polymeric anion exchanger resin. Fluoride uptake by HAIX-Zr was quite rapid, 60% removal was obtained within 30 min. Kinetics of fluoride uptake by HAIX-Zr resin followed the pseudo-second-order kinetic model and adsorption data fitted best to Freundlich adsorption isotherm model. Maximum fluoride uptake capacity was observed as 12.0 mg/g. The defluoridation capacity of the resin decreases with increase in solution pH. The co-existing anions like chloride, phosphate, bicarbonate, nitrate, and sulphate at 100 mg/L concentration significantly affected fluoride removal and bicarbonate showed the highest interference. Continuous flow packed bed experiments were performed with real groundwater. To maintain a lower pH, weak acid cation exchange resin (INDION-236) was used before HAIX-Zr. It was observed that reducing the pH of the sample water to 4-4.5, increased the number of treated bed volumes fifteen times. Regeneration of fluoride-containing resin was done by passing 3% NaOH and 3% NaCl solution through an exhausted resin bed. The results revealed that HAIX-Zr can effectively remove fluoride from groundwater.


Assuntos
Água Subterrânea , Poluentes Químicos da Água/análise , Purificação da Água , Adsorção , Resinas de Troca de Ânions , Fluoretos , Concentração de Íons de Hidrogênio , Cinética , Zircônio
10.
Water Sci Technol ; 82(4): 651-662, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970618

RESUMO

The adsorption isotherms of Reactive Red 120 (RR-120) on Brazilian pine-fruit shell activated carbon, at six temperatures (298, 303, 308, 313, 318 and 323 K) and pH = 6, were determined and interpreted using a double layer model with one energy. A statistical physics treatment established the formulation of this model. Steric and energetic parameters related to the adsorption process, such as the number of adsorbed molecules per site, the receptor sites density and the concentration at half-saturation, have been considered. Thermodynamic potential functions such as entropy, internal energy and Gibbs free enthalpy are analyzed, and the choice of the models is based on assumptions in correlation with experimental conditions. By numerical fitting, the investigated parameters were deduced. The theoretical expressions provide a good understanding and interpretation of the adsorption isotherms at the microscopic level. We believe that our work contributes to new theoretical insights on the dye adsorption in order to know the physical nature of the adsorption process.


Assuntos
Carvão Vegetal , Triazinas , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Termodinâmica
11.
Water Sci Technol ; 82(4): 673-682, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970620

RESUMO

Loess is a typical natural mineral particle distributed widely around the world, and it is inexpensive, readily accessible, and harmless to the environment. In this study, loess was modified by surface grafting copolymerization of functional monomers, such as acrylic acid, N-vinyl pyrrolidone, and N,N-methylenebisacrylamide as a cross-linking agent, which afforded a novel loess-based grafting copolymer (LC-PAVP). After being characterized by scanning electron microscopy, thermal gravimetric analysis and Fourier-transform infrared spectroscopy, its adsorption capacity and mechanism of removing lead ions (Pb2+) were investigated. With the study of the optimal experimental conditions, it was demonstrated that the removal rate of Pb2+ by LC-PAVP can reach up to 99.49% in 60 min at room temperature. It was also found that the kinetic characteristics of the adsorption capacity due to the pseudo-second-order kinetic model and the thermodynamics conformed well with the Freundlich model. In summary, as a lost-cost and eco-friendly loess-based adsorbent, LC-PAVP is a good potential material for wastewater treatment.


Assuntos
Acrilatos , Poluentes Químicos da Água/análise , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Polímeros , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica , Águas Residuárias
12.
Water Sci Technol ; 82(4): 715-731, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970624

RESUMO

In the present work, native chitosan (Ch) along with its chemically and physico-chemically modified versions, namely sulphate cross-linked chitosan (SCC) and sulphate cross-linked chitosan-bentonite composite (SCC-B), were employed as potential adsorbents for the removal of an anionic dye, Alizarin Red S (ARS) from aqueous solutions. All three adsorbents were extensively characterized using techniques such as Fourier-transform infrared spectroscopy, scanning electron microscopy, energy dispersive X-ray, X-ray diffraction, Brunauer-Emmett-Teller analysis, thermogravimetric-differential thermal analysis, and pH point of zero charge. Various parameters were optimized, including pH of dye solution, contact time, adsorbent dose, initial adsorbate concentration and temperature of adsorption. Four adsorption isotherm models were studied and it was found that the Freundlich model was best-fit for all three systems. Maximum adsorption capacities towards adsorption of ARS were found to be 42.48, 109.12 and 131.58 mg g-1 for Ch, SCC and SCC-B, respectively. Kinetics of adsorption was examined by employing three well-known models in order to deduce the mechanism of adsorption. Thermodynamic studies show that the process is spontaneous and exothermic for all adsorbents employed. Furthermore, it was observed that for large sample volumes, the column adsorption method was more effective compared to the batch method.


Assuntos
Quitosana , Poluentes Químicos da Água , Adsorção , Antraquinonas , Humanos , Concentração de Íons de Hidrogênio , Cinética , Deficiência Energética Relativa no Esporte , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica
13.
Water Sci Technol ; 82(4): 732-746, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970625

RESUMO

The application of activated carbon fiber supported nanoscale zero-valent iron (ACF-nZVI) in the continuous removal of Cr(VI) and methyl orange (MO) from aqueous solution was studied in depth. The breakthrough curves of Cr(VI) in a fixed bed with ACF-nZVI were measured, and compared with those in the fixed bed with ACF. The catalytic wet peroxide oxidation (CWPO) process for MO was also carried out using ACF-nZVI after reacting with Cr(VI) in the same fixed bed. The results showed that the breakthrough time of ACF-nZVI was significantly longer than that of ACF. Higher pH values were unfavorable for the Cr(VI) removal. The breakthrough time increased with decreasing inlet Cr(VI) concentration or increasing bed height. The Yoon-Nelson and bed depth service time (BDST) models were found to show good agreement with the experimental data. The Cr(VI) removal capacity when using ACF-nZVI was two times higher than that when using ACF. Under the optimal empty bed contact time of 1.256 min, the fixed bed displayed high MO conversion (99.2%) and chemical oxygen demand removal ratio (55.7%) with low Fe leaching concentration (<5 mg/L) after continuous running for 240 min. After three cycles, the conversion of MO remained largely unchanged.


Assuntos
Carvão Vegetal , Poluentes Químicos da Água/análise , Adsorção , Compostos Azo , Fibra de Carbono , Cromo/análise , Ferro , Cinética
14.
Water Sci Technol ; 82(4): 747-758, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32970626

RESUMO

The eco-friendly and non-toxic natural organic substance, insolubilized humic acid (IHA), was used to remove Mn(II) from aqueous solutions. The adsorption characteristics were studied through a series of static adsorption tests. The results show that conditions such as the dose, the pH of the solution and the initial concentration of Mn(II) all affect removal efficiency, and the optimal pH value was 5.5. The sorption process for Mn(II) on IHA conforms to the pseudo-second-order adsorption kinetic model and intra-particle diffusion is not the only factor affecting the adsorption rate. Both Langmuir and Freundlich models can describe this adsorption behavior, and the experimental maximum adsorption capacity of IHA was 52.87 mg/g under optimal conditions. The thermodynamic analysis of adsorption shows that the adsorption process is a non-spontaneous endothermic physical reaction. Fourier transform infrared spectroscopy (FTIR), scanning electron microscopy (SEM) and energy-dispersive spectroscopy (EDS) were used to characterize the samples, it was found that as IHA successfully adsorbed Mn(II), the surface morphology of IHA changed after the adsorption reaction. The adsorption mechanism for Mn(II) on IHA is to provide electron pairs for carboxyl, phenolic hydroxyl and other functional groups to form stable complexes with Mn(II).


Assuntos
Poluentes Químicos da Água/análise , Adsorção , Substâncias Húmicas , Concentração de Íons de Hidrogênio , Cinética , Espectroscopia de Infravermelho com Transformada de Fourier , Termodinâmica
15.
Water Sci Technol ; 82(2): 242-254, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941166

RESUMO

Using waste pomelo peel as raw material, pomelo peel-based biochar (BC) was prepared by pyrolysis at 400 °C, and the pomelo peel-based biochar was prepared by loading γ-Fe2O3 onto the surface of the pomelo peel-based biochar by unlimited oxygen chemical precipitation. The results showed that the pomelo peel biochar loaded with γ-Fe2O3 had higher specific surface area and larger pore volume. The load of γ-Fe2O3 gives γ-Fe2O3@BC excellent magnetic separation ability, and its magnetic saturation intensity is as high as 30.60 emu/g. BC and γ-Fe2O3@BC were applied to remove norfloxacin (NOR) from a water body. It was found that the adsorption of NOR by both of them followed the pseudo-second-order kinetic model. The adsorption isotherm mainly conforms to the Sips model, and the adsorption process of NOR is a spontaneous endothermic reaction. The pH and ionic strength have a great influence on the adsorption of NOR by BC and γ-Fe2O3@BC, and they play a role mainly by influencing the morphology of NOR in water. The adsorption mechanism showed that cation exchange and hydrogen bonding were the main forces for BC to adsorb NOR. Moreover, the γ-Fe2O3 particles enhanced the hydrophobicity of the pomelo peel-based biochar, making the hydrophobicity become the main force for the adsorption of NOR by the γ-Fe2O3@BC. The adsorption-desorption experiment showed that after four cycles of recycling, the adsorption capacity of γ-Fe2O3@BC for NOR was still up to 61.43% of the initial adsorption capacity, and it had a good recycling property.


Assuntos
Norfloxacino , Poluentes Químicos da Água/análise , Adsorção , Carvão Vegetal , Cinética , Água
16.
Water Sci Technol ; 82(2): 255-265, 2020 Jul.
Artigo em Inglês | MEDLINE | ID: mdl-32941167

RESUMO

This study sought a new way to utilize sludge as a low cost and efficient adsorbent. Preparation of sludge adsorbent by hydrothermal carbonization was done at different temperatures (160-250 °C). Various characterization techniques were used in this study including elemental analysis, Fourier transform infrared spectroscopy (FT-IR), and X-ray photoelectron spectroscopy (XPS). The adsorption performance of the organic matter was analyzed by adsorption experiments with the endocrine disruptor bisphenol A (BPA). Results showed that as the hydrothermal temperature increased, the solid yield of hydrochar decreased from 84.73% to 55.19%, and the maximum specific surface area was 11.9 m2/g. Elemental analysis showed that the hydrochar contains more aromatic carbon than the raw sludge. It was found using the FT-IR and XPS that the hydrochar retains a large amount of oxygen-containing functional groups on the surface after hydrothermal treatment. Hydrochar can be used as an organic-pollutant adsorbent in water; it has a good adsorption effect on BPA and the removal rate can reach 96%. The adsorbed hydrochar can be hydrothermally retreated and returned to the sewage treatment plant for reuse.


Assuntos
Esgotos , Adsorção , Compostos Benzidrílicos , Fenóis , Espectroscopia de Infravermelho com Transformada de Fourier , Temperatura
17.
Water Sci Technol ; 82(3): 401-426, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32960788

RESUMO

Antibiotics are known as emergent pollutants because of their toxicological properties. Due to continuous discharge and persistence in the aquatic environment, antibiotics are detected almost in every environmental matrix. Therefore antibiotics that are polluting the aquatic environment have gained significant research interest for their removal. Several techniques have been used to remove pollutants, but appropriate technology is still to be found. This review addresses the use of modified and cheap materials for antibiotic removal from the environment.


Assuntos
Antibacterianos , Poluentes Químicos da Água/análise , Adsorção
18.
Water Sci Technol ; 82(3): 427-439, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32960789

RESUMO

The occurrence of organic micropollutants such as pharmaceutical drugs and hormones in the environment reflects the inefficiency of traditional wastewater treatment technologies. Biosorption is a promising alternative from a technical-economic point of view, so understanding the mechanisms of adsorption in new biosorbents is vital for application and process optimization. Within this context, this study aims to evaluate the mechanisms of adsorption and removal of synthetic and natural hormones by Pinus elliottii bark biosorbent (PS) compared to commercial granular activated carbon (GAC) through kinetic models, isotherm models, and thermodynamic models. The adsorbents were also characterized by morphology, chemical composition, functional groups, and point of zero charge. Characterization of the adsorbents highlights the heterogeneous and fibrous morphology and broader range of functional groups found for PS. Kinetic adjustments showed high accuracy for pseudo-second-order, Elovich, and intraparticle diffusion models, presenting multilinearity and evidencing multi-stage adsorption. The isotherms for PS followed high-affinity models, predominantly chemisorption, while those for GAC followed the Langmuir model, where physisorption predominates. These mechanisms were confirmed by thermodynamic models, which also indicated a higher dependence on temperature in the adsorption process. In the fortified water removal test, PS showed removal values higher than GAC, highlighting the advantages of this adsorbent.


Assuntos
Poluentes Químicos da Água/análise , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Lignina , Termodinâmica
19.
Water Sci Technol ; 82(3): 440-453, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32960790

RESUMO

A polyamine functionalized polystyrene resin (PSATA) was prepared via condensation reaction of acetylated polystyrene resin with triethylenetetramine, which, upon NaBH4 reduction, produced PSATAR. In comparison with the PSATA, the PSATAR with more flexible amine groups shows improved structural properties, and the equilibrium adsorption capacities of phenol, 2-nitrophenol (ONP) and 2,4-dinitrophenol (DNP) in wastewater were up to 1.073, 1.832 and 1.901 mmol/g, respectively. Their adsorption isotherms fit well with the Freundlich model, indicating a multilayer, heterogeneous adsorption nature. Kinetic studies indicated that the adsorption of phenolic compounds conforms to the pseudo-second-order kinetics with the adsorption rate controlled by film diffusion for ONP and DNP, and intra-particle diffusion in the later stage for phenol.


Assuntos
Poluentes Químicos da Água/análise , Purificação da Água , Adsorção , Cinética , Fenóis , Poliestirenos , Trientina , Águas Residuárias
20.
Water Sci Technol ; 82(3): 468-480, 2020 Aug.
Artigo em Inglês | MEDLINE | ID: mdl-32960792

RESUMO

In this work, a biosorbent was prepared by the ultrasound-acid treatment of Merremia vitifolia plant and tested for the removal of 2,4-dichlorophenoxyacetic acid (2,4-D), a phenoxy herbicide. Optimal values of five batch biosorption parameters namely stirring speed, contact time, biosorbent dosage, initial pH and initial adsorbate concentration were experimentally obtained in sequential manner for an enhanced biosorption capacity. The kinetics of the biosorption of 2,4-D were best described by the pseudo first order kinetic model (R2 = 0.99) and the biosorption equilibrium data were successfully fitted to the Langmuir adsorption isotherm (R2 = 0.99) with a maximum biosorption capacity of 66.93 mg g-1. The mechanism of biosorption was investigated using two intraparticle diffusion models (Weber and Boyd), Dubinin-Radushkevich isotherm model and electrostatic interactions. The presence of intraparticle and film diffusion limitations for the biosorption was confirmed along with the physical and chemical nature of the biosorption. The thermodynamic parameters of the biosorption were calculated using the equilibrium data obtained at four different temperatures. The entropy change for biosorption was found to be negative indicating the decreased randomness at the interface. Desorption studies were carried out using different solvents and the percentages of desorption were compared.


Assuntos
Convolvulaceae , Herbicidas , Poluentes Químicos da Água , Ácido 2,4-Diclorofenoxiacético , Adsorção , Biomassa , Concentração de Íons de Hidrogênio , Cinética , Termodinâmica
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