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1.
Sci Total Environ ; 691: 64-70, 2019 Nov 15.
Artigo em Inglês | MEDLINE | ID: mdl-31319259

RESUMO

Molybdenum is an essential trace element for humans but can be harmful with excess assimilations or chronic exposures. In this study a polymer-functionalized nanocomposite (HFO-PsAX) was fabricated for selective adsorption of molybdate from aqueous solution. HFO-PsAX was prepared by grafting hydrous ferric oxide nanoparticles (HFOs) into the porous structure of a polystyrene anion exchanger (PsAX) by in situ synthesis method. The resultant HFO-PsAX exhibited greatly enhanced selectivity toward molybdate as compared with the matrix, PsAX, which is also a fair adsorbent for scavenging molybdate. The competitive abilities of the ubiquitous anions, i.e., chloride, carbonate, sulfate, and phosphate, on the adsorption of molybdate by HFO-PsAX followed the order: chloride < phosphate < carbonate < sulfate. The unexpectedly weak competitive ability of trivalent phosphate may be due to incompletely dissociated state and formation of molybdate-phosphate complexes. The optimal pH for the adsorption of molybdate was determined as pH≈4, which is associated with the dissociation constants of molybdic acid; certain adsorption capacities were also observed even under extremely alkaline condition (pH=14) for single-component molybdate solution. Temperature (10, 25, and 40°C) has negligible effect on the adsorption capacities by HFO-PsAX, and Freundlich model and Dubinin-Radushkevich (D-R), Temkin model can describe the adsorption isotherms well. The adsorption potential of Temkin model is calculated as ≈100J/mol, which is between those of physisorption and chemisorption process. Fixed-bed column adsorption experiments validated the potential of HFO-PsAX in treating Mo(VI) contaminated water for practical application, and the exhausted HFO-PsAX can be regenerated by a binary NaOH-NaCl solution (both 5% in mass) without loss in adsorption capacities.

2.
Sci Total Environ ; 687: 198-205, 2019 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-31207510

RESUMO

Paired electrolysis can take advantage of both anodic oxidation and cathodic reduction, and thus improve current efficiency for electrochemical wastewater treatment. In this work, differential control of anode/cathode potentials of paired electrolysis for simultaneous removal of chemical oxygen demand (COD) and total nitrogen (TN, including ammonia, nitrate, and nitrite) was studied. We first determined the optimal potentials for anodic oxidation of COD/NH4+ or cathodic reduction of NO3-/NO2- (minimization of over-oxidation or over-reduction) by preliminary cyclic voltammetry and constant-potential electrolysis experiments, i.e., 1.6 V for anodic oxidation and -1.26 V for cathodic reduction in this case. The optimal working potential of the cathode was achieved at appropriate current density in the paired electrolysis system, the working potential of the anode was independently controlled by adjusting the ratio of its surface area to that of the cathode. In this way, both the cathode and anode could work under optimal potentials. At an optimized cathodic current density of 5.0 mA cm-2 and cathode/anode surface area ratio of 2:1, the removal efficiencies of COD and TN from simulated wastewater reached 91.9% and 86.2%, respectively. Additionally, the developed paired electrolysis system was validated by treating an actual pharmaceutical wastewater, results for which showed that a total current efficiency of 84.8% was achieved, which was at least twice as high as that of traditional electrochemical processes.

3.
Chemosphere ; 201: 621-626, 2018 Jun.
Artigo em Inglês | MEDLINE | ID: mdl-29547852

RESUMO

Reverse osmosis concentrate (ROC) of printing and dyeing wastewater remains as a daunting environmental issue, which is characterized by high salinity, chemical oxygen demand (COD), chroma and low biodegradability. In this study electro-oxidation process (PbO2/Ti electrode) coupled with oxidation-reduction potential (ORP) online monitor was applied to treat such a ROC effluent. The results show that with the increase of specific electrical charge (Qsp), the removal efficiencies of COD, TN and chroma increased significantly at the incipience and then reached a gentle stage; the optimal total current efficiency (12.04 kWh m-3) was obtained with the current density of 10 mA cm-2 (Qsp, 3.0 Ah L-1). Meanwhile, some inorganic ions can be simultaneously removed to varying degrees. FTIR analyses indicated that the macromolecular organics were decomposed into smaller molecules. A multi-parameter linear relationship between ORP and Qsp, COD and Cl- concentration was established, which can quantitatively reflect the effect of current density, chloride ion concentration, pollutants and reaction time on the performance of the electro-oxidation system. As compared to a traditional constant-current system, the constant-ORP system developed in this study (through the back-propagation neural network [BPN] model with ORP monitoring) approximately reduced the energy cost by 24-29%. The present work is expected to provide a potential alternative in optimizing the electro-oxidation process.


Assuntos
Corantes/análise , Águas Residuárias/química , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Biodegradação Ambiental , Análise da Demanda Biológica de Oxigênio , China , Eletrodos , Filtração , Osmose , Oxirredução , Salinidade
4.
Environ Sci Technol ; 48(13): 7494-502, 2014 Jul 01.
Artigo em Inglês | MEDLINE | ID: mdl-24877792

RESUMO

Ionic organic contaminants (OCs) are a growing concern for water treatment and the environment and are removed inefficiently by many existing technologies. This study examined removal of anionic OCs by anion exchange resins (AXRs) as a promising alternative. Results indicate that two polystyrene AXRs (IRA910 and IRA96) have higher sorption capacities and selectivity than a polyacrylate resin (A860). For the polystyrene resins, selectivity follows: phenolates ≥ aromatic dicarboxylates > aromatic monocarboxylates > benzenesulfonate > aliphatic carboxylates. This trend can be explained based on hydration energy, the number of exchange groups, and aromaticity and hydrophobicity of the nonpolar moiety (NPM) of the anions. For A860, selectivity only varies within a narrow range (0.13-1.64). Despite the importance of the NPM of the anions, neutral solutes were sorbed much less, indicating synergistic combinations of electrostatic and nonelectrostatic interactions in the overall sorption. By conducting multiple linear regression between Abraham's descriptors and nature log of selectivity, induced dipole-related interactions and electrostatic interactions were found to be the most important interaction forces for sorption of the anions, while solute H-bond basicity has a negative effect. A predictive model was then developed for carboxylates and phenolates based on the poly parameter linear free energy relationships established for a diverse range of 16 anions and 5 neutral solutes, and was validated by accurate prediction of sorption of five test solutes within a wide range of equilibrium concentrations and that of benzoate at different pH.


Assuntos
Resinas de Troca de Ânions/química , Ânions/isolamento & purificação , Modelos Teóricos , Compostos Orgânicos/isolamento & purificação , Adsorção , Ânions/química , Interações Hidrofóbicas e Hidrofílicas , Compostos Orgânicos/química , Análise de Regressão , Soluções , Temperatura Ambiente , Água/química , Purificação da Água
5.
Environ Sci Technol ; 48(12): 6772-9, 2014 Jun 17.
Artigo em Inglês | MEDLINE | ID: mdl-24815932

RESUMO

The equilibrium Polanyi adsorption potential was reconstructed as ε = -RT ln(Ca(or H)/δ) to correlate the characteristic energy (E) of Polanyi-based models (qe = f[ε/E]) with the properties or structures of absorbates, where qe is the equilibriumn adsorption capacity, Ca(or H) is the converted concentration from the equilibrium aqueous concentration at the same activity and corresponds to the adsorption from the gas or n-hexadecane (HD) phase by the water-wet adsorbent, and "δ" is an arbitrary divisor to converge the model fitting. Subsequently, the modified Dubinin-Astakhov model based on the reconstructed ε was applied to aqueous adsorption on activated carbon, black carbon, multiwalled carbon nanotubes, and polymeric resin. The fitting results yielded intrinsic characteristic energies Ea, derived from aqueous-to-gas phase conversion, or EH, derived from aqueous-to-HD phase conversion, which reflect the contributions of the overall or specific adsorbate-adsorbent interactions to the adsorption. Effects of the adsorbate and adsorbent properties on Ea or EH then emerge that are unrevealed by the original characteristic energy (Eo), i.e., adsorbates with tendency to form stronger interactions with an adsorbent have larger Ea and EH. Additionally, comparison of Ea and EH allows quantitative analysis of the contributions of nonspecific interactions, that is, a significant relationship was established between the nonspecific interactions and Abraham's descriptors for the adsorption of all 32 solutes on the four different adsorbents: (Ea - EH) = 24.7 × V + 9.7 × S - 19.3 (R(2) = 0.97), where V is McGowan's characteristic volume for adsorbates, and S reflects the adsorbate's polarity/polarizability.


Assuntos
Modelos Teóricos , Adsorção , Alcanos/química , Carvão Vegetal/química , Nanotubos de Carbono/química , Polímeros/química , Soluções , Fuligem/química , Termodinâmica , Água/química
6.
Environ Sci Technol ; 46(12): 6806-14, 2012 Jun 19.
Artigo em Inglês | MEDLINE | ID: mdl-22578035

RESUMO

To obtain mechanistic insight into adsorption of phenolic compounds by two representative polymeric adsorbents, XAD-4 (polystyrene) and XAD-7 (polymethacrylate), a modified Polanyi-based Dubinin-Ashtakhov (D-A) model was developed based on a unique combination of the Polanyi theory, polyparameter linear energy relationships and infinitely dilute solution in n-hexadecane as the reference state. The adsorption potential in the D-A model ε = -RTln(C(w)/C(w) (sat)) was redefined by replacing the term (C(w)/C(w) (sat)) with the normalized equivalent concentration in n-hexadecane (CHD), where Cw is the aqueous equilibrium concentration and C(w) (sat) is the aqueous solubility of the solute. Using the new reference state allows quantitative comparison among various solutes. By fitting adsorption isotherms to the modified model using εHD = -RTln(CHD/10 000), a new normalizing factor (E(m)) was obtained to quantify the contributions of specific interactions (i.e., H-bonding, dipolar/polarizability, etc.) to the overall adsorption energy. Significant linear correlations were established between "A", the hydrogen-bond acidity, and "E(m)" for the investigated compounds, suggesting that, in addition to hydrophobic interactions, hydrogen-bonding is predominantly responsible for the adsorption of phenols by XAD-4 and XAD-7. Additionally, adsorption capacity and affinity of phenolates were significantly less than those of phenols; another model was proposed to accurately predict the effect of pH on the adsorption behavior of phenols.


Assuntos
Modelos Químicos , Polímeros/química , Adsorção
7.
J Environ Monit ; 12(1): 305-10, 2010 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-20082026

RESUMO

Selenite (SeO(3)(2-)) is an oxyanion of environmental significance due to its toxicity when taken in excess. In the present study, a hybrid adsorbent (HFO-201) was prepared by irreversibly impregnating hydrated ferric oxide (HFO) nanoparticles within a commercial available anion-exchange resin (D-201), and its adsorption towards selenite from water was investigated in batch and column tests. HFO-201 exhibited improved sorption selectivity toward selenite as compared to the polymeric anion exchanger D-201. Two possible adsorption interactions were responsible for selenite removal by HFO-201, the electrostatic interaction from the ammonium groups bound to the D-201 matrix, and the formation of inner-sphere complexes between the loaded HFO nanoparticles and selenite. In a wide pH range (i.e., 3-8), increasing solution pH was found to result in a decrease of selenite removal on HFO-201. Adsorption isotherms fit the Freundlich model well, and selenite adsorption increased with increasing ambient temperature, indicating its endothermic nature. Column adsorption tests suggested that satisfactory removal of selenite from 2 mg/L to less than 0.01 mg/L could be achieved by HFO-201 even in the presence of the commonly encountered anionic competition at greater concentration, with the treatment capacity of approximately 1200 bed volume (BV) per run, while that for D-201 was only less than 30 BV under otherwise identical conditions. Furthermore, the exhausted HFO-201 was amenable to efficient in situ regeneration with a binary NaOH-NaCl solution.


Assuntos
Compostos Férricos/química , Polímeros/química , Selenito de Sódio/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Amônia/química , Resinas de Troca de Ânions , Concentração de Íons de Hidrogênio , Cinética , Microscopia Eletrônica de Varredura , Nanopartículas/química , Tamanho da Partícula , Cloreto de Sódio/química , Hidróxido de Sódio/química , Selenito de Sódio/química , Eletricidade Estática , Termodinâmica , Poluentes Químicos da Água/química , Purificação da Água/instrumentação
8.
Water Res ; 44(3): 815-24, 2010 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-19906397

RESUMO

The present study developed a polymer-based hybrid sorbent (HFO-001) for highly efficient removal of heavy metals [e.g., Pb(II), Cd(II), and Cu(II)] by irreversibly impregnating hydrated Fe(III) oxide (HFO) nanoparticles within a cation-exchange resin D-001 (R-SO(3)Na), and revealed the underlying mechanism based on X-ray photoelectron spectroscopy (XPS) study. HFO-001 combines the excellent handling, flow characteristics, and attrition resistance of conventional cation-exchange resins with the specific affinity of HFOs toward heavy metal cations. As compared to D-001, sorption selectivity of HFO-001 toward Pb(II), Cu(II), and Cd(II) was greatly improved from the Ca(II) competition at greater concentration. Column sorption results indicated that the working capacity of HFO-001 was about 4-6 times more than D-001 with respect to removal of three heavy metals from simulated electroplating water (pH approximately 4.0). Also, HFO-001 is particularly effective in removing trace Pb(II) and Cd(II) from simulated natural waters to meet the drinking water standard, with treatment volume orders of magnitude higher than D-001. The superior performance of HFO-001 was attributed to the Donnan membrane effect exerted by the host D-001 as well as to the impregnated HFO nanoparticles of specific interaction toward heavy metal cations, as further confirmed by XPS study on lead sorption. More attractively, the exhausted HFO-001 beads can be effectively regenerated by HCl-NaCl solution (pH 3) for repeated use without any significant capacity loss.


Assuntos
Compostos Férricos/química , Metais Pesados/isolamento & purificação , Nanopartículas/química , Tamanho da Partícula , Espectroscopia Fotoeletrônica/métodos , Polímeros/química , Água/química , Adsorção , Cálcio/química , Cátions , Galvanoplastia , Meio Ambiente , Concentração de Íons de Hidrogênio , Resinas de Troca Iônica/química , Íons , Cinética , Nanopartículas/ultraestrutura , Soluções , Temperatura Ambiente , Fatores de Tempo , Eliminação de Resíduos Líquidos
9.
Water Res ; 43(17): 4421-9, 2009 Sep.
Artigo em Inglês | MEDLINE | ID: mdl-19615711

RESUMO

Phosphate originated from industrial effluents is one of the key factors responsible for eutrophication of the receiving waterways especially in the developing countries such as China. In the current study we proposed a novel process to immobilize nanoparticulate hydrated ferric oxide (HFO) within a macroporous anion exchange resin D-201, and obtained a hybrid adsorbent (HFO-201) for enhanced phosphate removal from aqueous system. The resulting HFO-201 possesses two types of adsorption sites for phosphate removal, the ammonium groups bound to the D-201 matrix and the loaded HFO nanoparticles. The coexisting sulfate anion strongly competes for ammonium groups, which bind phosphate through electrostatic interaction. However, it does not pose any noticeable effect on phosphate adsorption by the loaded HFO nanoparticles, which is driven by the formation of the inner-sphere complexes. Batch adsorption experiments also indicated that HFO-201 exhibits a little higher capacity for phosphate than the commercially available phosphate-specific adsorbent ArsenX(np), which possesses similar structure of HFO-201 and is produced by another patented technique. Fixed-bed column tests indicate that phosphate retention by HFO-201 from the synthetic waters results in the significant decrease of P from 2mg/L to less than 0.01 mg/L, with the treatment capacity of approximately 700 bed volume (BV) per run, while that for D-201 was less than 200 BV under otherwise identical conditions. Such satisfactory performance of the hybrid adsorbent is mainly attributed to the specific affinity of HFO toward phosphate as well as the Donnan membrane effect exerted by the anion exchanger support D-201. Moreover, the exhausted HFO-201 was amenable to efficient in situ regeneration with a binary NaOH-NaCl solution for repeated use without any significant capacity loss. Similar satisfactory results were also observed by using a phosphate-containing industrial effluent as the feeding solution.


Assuntos
Compostos Férricos/química , Resíduos Industriais , Nanopartículas , Fosfatos/isolamento & purificação , Polímeros/química , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Microscopia Eletrônica de Transmissão , Temperatura Ambiente
10.
Sci Total Environ ; 407(21): 5471-7, 2009 Oct 15.
Artigo em Inglês | MEDLINE | ID: mdl-19640564

RESUMO

In the current study, a new hybrid adsorbent HMO-001 was fabricated by impregnating nanosized hydrous manganese dioxide (HMO) onto a porous polystyrene cation exchanger resin (D-001) for enhanced lead removal from aqueous media. D-001 was selected as a support material mainly because of the potential Donnan membrane effect exerted by the immobilized negatively charged sulfonic acid groups bound to the polymeric matrix, which would result in preconcentration and permeation enhancement of lead ions prior to their effective sequestration by the impregnated HMO. HMO-001 was characterized by scanning electron micrograph (SEM), transmission electron micrograph (TEM), and X-ray diffraction (XRD). Lead adsorption onto HMO-001 was dependent upon solution pH due to the ion-exchange nature, and it can be represented by the Freundlich isotherm model and pseudo-first order kinetic model well. The maximum capacity of HMO-001 toward lead ion was about 395 mg/g. As compared to D-001, HMO-001 exhibited highly selective lead retention from waters in the presence of competing Ca(2+), Mg(2+), and Na(+) at much greater levels than the target toxic metal. Fixed-bed column adsorption of a simulated water indicated that lead retention on HMO-001 resulted in a conspicuous decrease of this toxic metal from 1 mg/L to below 0.01 mg/L (the drinking water standard recommended by WHO). The exhausted adsorbent particles are amenable to efficient regeneration by the binary NaAc-HAc solution for repeated use without any significant capacity loss. All the results validated the feasibility of HMO-001 for highly effective removal of lead from contaminated waters.


Assuntos
Chumbo/química , Compostos de Manganês/química , Óxidos/química , Poluentes Químicos da Água/química , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Microscopia Eletrônica de Varredura , Nanoestruturas , Poliestirenos/química , Purificação da Água/instrumentação
11.
J Hazard Mater ; 170(2-3): 824-8, 2009 Oct 30.
Artigo em Inglês | MEDLINE | ID: mdl-19493618

RESUMO

The present study reported synthesis of a new inorganic exchanger, i.e., zirconium hydrogen monothiophosphate [Zr(HPO3S)2, denoted ZrPS] and its selective sorption toward Pb(II), Cd(II) and Zn(II) ions. ZrPS sorption toward all the three metals is dependent upon solution pH due to the ion-exchange nature. As compared to another inorganic exchanger zirconium phosphate [Zr(HPO4)2, denoted ZrP], ZrPS exhibits highly selective sorption toward these toxic metals from the background of calcium ions at great levels. Such sorption preference is mainly attributed to the presence of -SH group in ZrPS, as further demonstrated by FT-IR analysis and XPS study. Moreover, ZrPS particles preloaded with heavy metals could be efficiently regenerated with 6M HCl for multiple use without any noticeable capacity loss. All the experimental results indicated that ZrPS is a promising sorbent for enhanced heavy metals removal from contaminated water.


Assuntos
Cádmio/isolamento & purificação , Chumbo/isolamento & purificação , Fosfatos/química , Poluentes Químicos da Água/análise , Poluição Química da Água/análise , Zinco/isolamento & purificação , Adsorção , Concentração de Íons de Hidrogênio , Troca Iônica , Tamanho da Partícula , Espectroscopia de Infravermelho com Transformada de Fourier , Difração de Raios X
12.
J Colloid Interface Sci ; 331(2): 453-7, 2009 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-19101673

RESUMO

Titanium phosphate (TiP) exhibits preferable sorption toward lead ion in the presence of competing calcium ions at high levels, however, it is present as fine or ultrafine particles and cannot be directly employed in fixed-bed or any flow-through systems due to the excessive pressure drop and poor mechanical strength. In the present study a new hybrid sorbent TiP-001 was fabricated by impregnating titanium phosphate (TiP) nanoparticles onto a strongly acidic cation exchanger D-001 for enhanced lead removal from waters. D-001 was selected as a host material mainly because of the Donnan membrane effect resulting from the immobilized sulfonic acid groups bound on the exchanger matrix, which would enhance permeation of the target metal cation prior to effective sequestration. TiP-001 was characterized by transmission electron micrograph (TEM), X-ray diffraction (XRD), and pH-titration. Batch and column sorption onto TiP-001 was assayed to evaluate its performance as compared to the host exchanger D-001. Lead sorption onto TiP-001 is a pH-dependent process due to the ion-exchange nature, and its sorption kinetics follows the pseudo-second-order model well. Compared to D-001, TiP-001 displays highly selective lead sorption in the presence of competing calcium cations at concentration of several orders higher than the target metal. Fixed-bed sorption of a synthetic feeding solution indicates that lead retention by TiP-001 results in a conspicuous decrease of this toxic metal from 0.50 to below 0.010 mg/L (drinking water standard recommended by WHO). Moreover, its feasible regeneration by dilute HCl solution also favors TiP-001 to be a feasible sorbent for enhanced lead removal from water.


Assuntos
Chumbo/química , Nanopartículas Metálicas/química , Titânio/química , Água/química , Cálcio/química , Concentração de Íons de Hidrogênio , Cinética , Nanopartículas Metálicas/ultraestrutura , Microscopia Eletrônica de Transmissão , Porosidade
13.
Environ Sci Technol ; 42(19): 7411-6, 2008 Oct 01.
Artigo em Inglês | MEDLINE | ID: mdl-18939579

RESUMO

As a family of hydrophobic ionizable organic compounds, aromatic sulfonates can be present at high levels in industrial wastewaters. They tend to exist as anions over a wide range of pH and cannot be effectively trapped by conventional adsorbents. In the current study, a recyclable acrylic ester polymer (NDA-801) was synthesized for effective removal of aromatic sulfonates from wastewater of high acidity (e.g., pH < 1) and inorganic salts (e.g., approximately 5-10% Na2SO4 in mass), for which sodium 2-naphthalene sulfonate (2-NS) was chosen as a representative target contaminant 2-NS uptake onto NDA-801 increased with the increasing acidity of the solution. The zeta potential of NDA-801 measured at different pH levels as well as batch 2-NS adsorption from methanol/water binary systems demonstrated the favorable roles of electrostatic and hydrophobic interaction in 2-NS adsorption. As compared to a granular activated carbon GAC-1, NDA-801 exhibited much higher removal efficiency and capacity of 2-NS in fixed-bed adsorption. Moreover, the exhausted NDA-801 beads by 2-NS can be completely regenerated by water wash for repeated use, which is more economically desirable than by other regenerants, such as NaOH solution. Continuous column adsorption-regeneration cycles indicated negligible capacity loss of NDA-801 during operation and further validated its feasibility for potential application in associated wastewater treatment.


Assuntos
Conservação dos Recursos Naturais , Hidrocarbonetos Aromáticos/isolamento & purificação , Naftalenossulfonatos/isolamento & purificação , Polímeros/química , Eliminação de Resíduos Líquidos , Poluentes Químicos da Água/isolamento & purificação , Absorção , Adsorção , Ésteres , Concentração de Íons de Hidrogênio , Cinética , Soluções , Sulfatos/química , Temperatura Ambiente , Termodinâmica , Purificação da Água
14.
Environ Sci Technol ; 42(11): 4140-5, 2008 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-18589978

RESUMO

A novel polymeric hybrid sorbent, namely ZrPS-001, was fabricated for enhanced sorption of heavy metal ions by impregnating Zr(HPO3S)2 (i.e., ZrPS) nanoparticles within a porous polymeric cation exchanger D-001. The immobilized negatively charged groups bound to the polymeric matrix D-001 would result in preconcentration and permeation enhancement of target metal ions prior to sequestration, and ZrPS nanoparticles are expected to sequester heavy metals selectively through an ion-exchange process. Highly effective sequestration of lead, cadmium, and zinc ions from aqueous solution can be achieved by ZrPS-001 even in the presence of competing calcium ion at concentration several orders of magnitude greater than the target species. The exhausted ZrPS-001 beads are amenable to regeneration with 6 M HCI solution for repeated use without any significant capacity loss. Fixed-bed column treatment of simulated waters containing heavy metals at high or trace levels was also performed. The content of heavy metals in treated effluent approached or met the WHO drinking water standard.


Assuntos
Cádmio/química , Resinas de Troca de Cátion/química , Chumbo/química , Nanopartículas/química , Purificação da Água/métodos , Zinco/química , Zircônio/química , Adsorção , Troca Iônica , Polímeros/química
15.
J Colloid Interface Sci ; 325(1): 41-7, 2008 Sep 01.
Artigo em Inglês | MEDLINE | ID: mdl-18556012

RESUMO

Removal of phthalate esters from water has been of considerable concern recently. In the present study, the adsorptive removal performance of diethyl phthalate (DEP) from water was investigated with the aminated polystyrene resin (NDA-101) and oxidized polystyrene resin (NDA-702). In addition, the commercial homogeneous polystyrene resin (XAD-4) and acrylic ester resin (Amberlite XAD-7) as well as coal-based granular activated carbon (AC-750) were chosen for comparison. The corresponding equilibrium isotherms are well described by the Freundlich equation and the adsorption capacities for DEP followed the order NDA-702 > NDA-101 > AC-750 > XAD-4 > XAD-7. Analysis of adsorption mechanisms suggested that these adsorbents spontaneously adsorb DEP molecules driven mainly by enthalpy change, and the adsorption process was derived by multiple adsorbent-adsorbate interactions such as hydrogen bonding, pi-pi stacking, and micropore filling. The information related to the adsorbent surface heterogeneity and the adsorbate-adsorbate interaction was obtained by Do's model. All the results indicate that heterogeneous resins NDA-702 and NDA-101 have excellent potential as an adsorption material for the removal of DEP from the contaminated water.


Assuntos
Carvão Vegetal/química , Ácidos Ftálicos/isolamento & purificação , Poliestirenos/química , Resinas Sintéticas/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Propriedades de Superfície , Termodinâmica
16.
J Hazard Mater ; 157(2-3): 293-9, 2008 Sep 15.
Artigo em Inglês | MEDLINE | ID: mdl-18249494

RESUMO

The removal of phenol from aqueous solution was examined by using a porous acrylic ester polymer (Amberlite XAD-7) as an adsorbent. Favorable phenol adsorption was observed at acidic solution pH and further increase of solution pH results in a marked decrease of adsorption capacity, and the coexisting inorganic salt NaCl exerts positive effect on the adsorption process. Adsorption isotherms of phenol were linearly correlated and found to be well represented by either the Langmuir or Freundlich isotherm model. Thermodynamic parameters such as changes in the enthalpy (DeltaH), entropy (DeltaS) and free energy (DeltaG) indicate that phenol adsorption onto XAD-7 is an exothermic and spontaneous process in nature, and lower ambient temperature results in more favorable adsorption. Kinetic experiments at different initial solute concentrations were investigated and the pseudo-second-order kinetic model was successfully represented the kinetic data. Additionally, the column adsorption result showed that a complete removal of phenol from aqueous phase can be achieved by XAD-7 beads and the exhausted adsorbent was amenable to an entire regeneration by using ethanol as the regenerant. More interestingly, relatively more volume of hot water in place of ethanol can also achieve a similar result for repeated use of the adsorbent.


Assuntos
Fenóis/isolamento & purificação , Polímeros/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Fenóis/química , Cloreto de Sódio/química , Soluções/química , Termodinâmica , Poluentes Químicos da Água/química
17.
J Colloid Interface Sci ; 318(2): 160-6, 2008 Feb 15.
Artigo em Inglês | MEDLINE | ID: mdl-18036605

RESUMO

In the current study, amorphous titanium phosphate (TiP) was prepared as an adsorbent for heavy metals from waters. Uptake of Pb(2+), Zn(2+), and Cd(2+) onto TiP was assayed by batch tests; a polystyrene-sulfonic acid exchanger D-001 was selected for comparison and Ca(2+) was chosen as a competing cation due to its ubiquitous occurrence in waters. The pH-titration curve of TiP implied that uptake of heavy metals onto TiP is essentially an ion-exchange process. Compared to D-001, TiP exhibits more preferable adsorption toward Pb(2+) over Zn(2+) and Cd(2+) even in the presence of Ca(2+) at different levels. FT-IR analysis of the TiP samples laden with heavy metals indicated that the uptake of Zn(2+) and Cd(2+) ions onto TiP is mainly driven by electrostatic interaction, while that of Pb(2+) ions is possibly dependent upon inner-sphere complex formation, except for the electrostatic interaction. Moreover, uptake of heavy metals onto TiP approaches equilibrium quickly and the exhausted TiP particles could be readily regenerated by HCl solution.


Assuntos
Cádmio/química , Chumbo/química , Titânio/química , Poluentes Químicos da Água/química , Zinco/química , Adsorção , Cálcio/química , Concentração de Íons de Hidrogênio , Magnésio/química , Tamanho da Partícula , Sódio/química , Espectroscopia de Infravermelho com Transformada de Fourier/métodos , Propriedades de Superfície , Água/química , Purificação da Água/métodos
18.
J Colloid Interface Sci ; 319(2): 392-7, 2008 Mar 15.
Artigo em Inglês | MEDLINE | ID: mdl-18155716

RESUMO

The adsorption equilibria of dimethyl phthalate (DMP) and diethyl phthalate (DEP) on two hyper-cross-linked polymer resins (NDA-99 and NDA-150) in aqueous solution were investigated at 298 K. And a coal-based granular activated carbon (AC-750) was chosen for comparison. All the adsorption equilibrium data of DMP were well fitted by the Polanyi-based isotherm modeling (Polanyi-Manes (PM) equation), and the characteristic curves of the three adsorbents were obtained. It is noteworthy that a reasonably good agreement was obtained between the combined micropore and mesopore volume of adsorbents and the corresponding adsorption volume capacity for phthalates. Compared to the granular activated carbon (AC-750), the greater adsorption performances of the two resins (NDA-99 and NDA-150) were assumed to result from their more abundant micro- and mesopore structure, where phthalates can be intensively adsorbed by pore-filling mechanism. According to the exponent b value of the PM equation, NDA-99 and NDA-150 show the more micro- and mesopore heterogeneity than AC-750. On the other hand, the functional groups on the adsorbent surfaces did not take a notable effect on the adsorption equilibria of phthalates. The theory equilibrium adsorption amounts of DEP, predicted by the specific characteristic curve of each adsorbent, agree well with the experimental ones, respectively. The characteristic curve of hyper-cross-linked polymer resins and its prediction of phthalates adsorption calculated by Polanyi-based isotherm modeling have a potential applicability for field applications.


Assuntos
Ácidos Ftálicos/isolamento & purificação , Purificação da Água/métodos , Adsorção , Carvão Vegetal/química , Modelos Químicos , Resinas Sintéticas/química
19.
Environ Sci Technol ; 41(14): 5057-62, 2007 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-17711223

RESUMO

In the present study we prepared a hyper-cross-linked polymeric adsorbent (NDA-701) possessing a uniquely bimodal pore size distribution for 4-nitrophenol (4-NP) adsorption from water. A macroporous polymeric adsorbent Amberlite XAD-4 and a granular activated carbon GAC-1 were chosen for comparison. NDA-701 exhibited better mechanical strength and higher capacity of 4-NP than XAD-4, which possibly resulted from its hyper-cross-linking nature and micropore structure, respectively. 4-NP adsorption isotherm onto NDA-701 is well described by the Freundlich model, and its better kinetics performance than GAC-1 resulted from its macropore structure. After adsorption NDA-701 was amenable to an entire regeneration by using NaOH solution as regenerant, whereas only approximately 75% regeneration efficiency was observed for GAC-1. Results of continuous fixed-bed runs in pilot and industrial scale demonstrated that NDA-701 is capable of completely removing 4-NP from chemical effluent with no capacity loss, and 4-NP can be readily recovered by further treatment of the concentrated regenerant solution. It is attractive that the value of the recovered 4-NP from chemical wastewater will even engender a surplus after countervailing all the operation cost during field application.


Assuntos
Nitrofenóis/química , Polímeros/química , Adsorção , Cinética , Microscopia Eletrônica de Varredura , Termodinâmica
20.
J Colloid Interface Sci ; 311(2): 382-90, 2007 Jul 15.
Artigo em Inglês | MEDLINE | ID: mdl-17433351

RESUMO

A hydrophilic hyper-cross-linked polymer resin (NDA-702) was synthesized, and the adsorption performance of dimethyl phthalate (DMP) on NDA-702 was compared with that on the commercial hydrophobic macroporous resin (Amberlite XAD-4) and granular activated carbon (AC-750). The kinetic adsorption of DMP onto NDA-702 and AC-750 is limited mainly by intraparticle diffusion and obeys the pseudo-second-order rate model, while the uptake on XAD-4 is limited mainly by film diffusion and follows the pseudo-first-order rate model. All the associated adsorption isotherms are well described by the Freundlich equation, and the larger uptake and stronger affinity of NDA-702 than AC-750 and XAD-4 probably result from the microporous structure, phenyl rings, and polar groups on NDA-702 polymer matrix. An interesting observation is that in the aqueous phase all the adsorbents spontaneously adsorb DMP driven mainly by enthalpy change, but the hydrophilic nature of NDA-702 and AC-750 surfaces results in less entropy change compared to hydrophobic XAD-4. Dynamic adsorption studies show that the high breakthrough and the total adsorption capacities of NDA-702 are 388 and 559 mg per gram dry resin at 313 K. Nearly 100% regeneration efficiency for the resin was achieved by methanol at 313 K.

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