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1.
J Colloid Interface Sci ; 574: 197-206, 2020 Aug 15.
Artigo em Inglês | MEDLINE | ID: mdl-32320855

RESUMO

Lanthanum (hydr)oxide-based materials are attractive as highly efficient adsorbents for phosphate removal from both sewage and lake environment. However, dissolved organic carbon (DOC) coexists in the waters and exact information is still lacking on how DOC influence the phosphate adsorption process. In this study, competitive adsorption of phosphate and DOC on lanthanum modified zeolite (LMZ) was investigated using humic acid as the representative. In LMZ, lanthanum hydroxide was shown to be the active ingredient accounting for >98% of the binding sites of both phosphate and DOC. Without competition, the maximum adsorption capacity of phosphate and DOC estimated from the Langmuir isotherm model was 52.25 and 41.32 mg/g, respectively. When coexisted, DOC did not affect the adsorption of phosphate while phosphate reduced the adsorption of DOC by ~40%. In addition, preloading LMZ with DOC had little effect on phosphate adsorption while coating with phosphate substantially lowered DOC adsorption. Furthermore, phosphate can release most of the adsorbed DOC (>60%), while DOC can not replace adsorbed phosphate (<2%). The adsorption kinetics of both phosphate and DOC was best described by the psudo-second-order model (r2 > 0.999). The adsorption of both phosphate and DOC increased with decreasing pH or increasing ionic strength. We proposed that phosphate was competitive than DOC for the ligand exchange sites of singly-coordinated hydroxyls, but DOC can be solely adsorbed onto the uncharged hydroxyls via hydrogen bonding.

2.
Environ Technol ; 41(5): 658-668, 2020 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-30074861

RESUMO

Monolayers of N-(2-aminoethyl)-3-aminopropyltrimethoxysilane have been established on magnetite nanoparticles to develop a novel magnetic adsorbent for fast decontamination of hexavalent chromium (Cr(VI)) from water. Results indicated that monolayer adsorption of the silane from water took place at low concentrations (<300 mg/L) and around 100% surface coverage was obtained at temperatures ≥90°C. The hydrolysed silane was anchored to the magnetite surface through condensation reactions between its silanol groups and the surface hydroxyl groups of magnetite. The functional amine groups were protonated by acid treatment for adsorbing Cr(VI). The monolayer of the silane on magnetite (MSM) with approximately 100% surface coverage showed extremely rapid adsorption kinetics for Cr(VI), such that the process was complete within 1 min. This enables the treatment of large amounts of sewage per unit time. The adsorption capacity for Cr(VI) was 8.0 mg/g, as estimated from the Langmuir isotherm model. The saturation magnetization of the MSM reached 64.16 emu/g, allowing easy magnetic recovery from water. In the presence of up to 50-fold molar excesses of chloride and nitrate anions, little effect on Cr(VI) removal was seen, but moderate and large impacts were observed with sulphate and hydroxyl anions, respectively. Desorption of adsorbed Cr(VI) and regeneration of the MSM were successfully achieved by NaOH and HCl treatments to deprotonate and protonate the amine groups, respectively. By selecting a silane with suitable functional groups, the surface properties may be tailored for a particular pollutant.


Assuntos
Nanopartículas de Magnetita , Compostos de Organossilício , Poluentes Químicos da Água , Purificação da Água , Adsorção , Cromo , Concentração de Íons de Hidrogênio , Cinética , Água
3.
Environ Int ; 134: 105322, 2020 Jan.
Artigo em Inglês | MEDLINE | ID: mdl-31739135

RESUMO

The separation of urine at source for phosphorus (P) recovery is attractive taking into account the high P concentration and small volume. However, the treatment of urine is still challenging due to its unpleasant odor and hygiene problems. Because the above problems could be solved by acidification to keep the pH of urine below 4, we propose a novel strategy to recover P from acidified urine using tailored hydrous zirconia-coated magnetite nanoparticles (Fe3O4@ZrO2). This strategy involves the selective adsorption of phosphate by easily separable and reusable Fe3O4@ZrO2, the desorption of adsorbed phosphate, and the precipitation of desorbed phosphate as calcium phosphate fertilizer. The results indicated that at pH 4, the P in synthetic urine was selectively adsorbed and could be exhausted using Fe3O4@ZrO2. Nearly all (>97.5%) of the sequestered P on the Fe3O4@ZrO2 nanoparticles was stripped using ≥1 M NaOH solution and ~100% of the stripped P was then successfully transformed into calcium phosphate, upon adding CaCl2 at pH >12 and a Ca/P molar ratio of 3. The liquid/solid (Fe3O4@ZrO2 particles) mixture could be conveniently separated for reuse using an external magnetic field. The reusability of the Fe3O4@ZrO2 nanoparticles in the extraction of P from synthetic urine was confirmed using five cycles of the adsorption-desorption process and their performance validated using real urine samples. The mechanism of phosphate adsorption was investigated using XPS, FTIR and zeta potential measurements, showing that phosphate was chemically adsorbed on the surface through direct coordination to zirconium atom via ligand exchange.

4.
Environ Sci Technol ; 53(21): 12449-12457, 2019 Nov 05.
Artigo em Inglês | MEDLINE | ID: mdl-31573182

RESUMO

Phosphorus-inactivating agents (PIAs) have increasingly been applied and extensively investigated to control internal phosphorus loading in lakes. However, little is known about the behavior of PIA-amended sediment in terms of phosphorus immobilization and release when the sediment is resuspended in the photic layer, whose environment differs from the lake bed. Lanthanum-modified bentonite (LMB) is a popular PIA product. In this study, the 33 day core incubation experiment under dark conditions showed that capping sediment with LMB efficiently decreased the concentration of total phosphorus, total dissolved phosphorus, and dissolved inorganic phosphorus (DIP) by 90, 87, and 99%, respectively. Resuspension into overlying water under light conditions at high pH, high dissolved organic carbon, and in the presence of algae significantly impedes the performance of LMB. However, the adoption of a higher LMB dose improved the performance, including a reduction in the phosphorus level and control of algal growth. The dynamics of the phosphorus migration when the LMB-inactivated sediment was resuspended into the photic zone mainly involves the release of DIP from the sediment and the uptake of DIP by algae and LMB. In conclusion, a higher dose is needed in the PIA (particularly Phoslock) application in shallow productive lakes where sediment resuspension occurs frequently.


Assuntos
Lagos , Poluentes Químicos da Água , Bentonita , Eutrofização , Sedimentos Geológicos , Fósforo
5.
Chemosphere ; 236: 124416, 2019 Dec.
Artigo em Inglês | MEDLINE | ID: mdl-31545207

RESUMO

The objective of this study was to develop a novel graphene oxide (GO)-based adsorbent by loading the cationic surfactant hexadecyltrimethylammonium bromide (HDTMA) to simultaneously scavenge copper ion, a charged species, and bisphenol A, an uncharged organic compound, from water. The HDTMA modification process was studied and the GO/HDTMA composites characterized using SEM (scanning electron microscopy), XRD (X-ray diffraction), XPS (X-ray photoelectron spectroscopy) and FTIR (Fourier Transform Infrared) spectroscopy. Within the concentration range of 6.4-11.5%, HDTMA caused the 2D GO sheets to form into solid 3D networks by reducing the repulsive forces and increasing the hydrophobic interactions between the adjacent GO sheets. The unique feature of this material is the simultaneous uptake of charged heavy metal ions and uncharged organic contaminants. The negative charges on GO results in the retention of heavy metal ions, while the hydrophobic phase created by the alkyl chain in HDTMA enables the adsorption of organic contaminants. The adsorption capacity of Cu2+ and bisphenol A reached 59.7 mg/g and 141.0 mg/g, respectively. The adsorption processes for both Cu2+ and bisphenol A were rapid, attaining ∼100% removal in 1 h and 2 h, respectively. Increasing the pH favored the adsorption of the two solutes. The presence of NaCl reduced the retention of Cu2+, but was beneficial for the adsorption of bisphenol A. The results demonstrate that the 3D structure and the adsorption of the target species can be achieved by tailoring the surface coverage of HDTMA on GO.


Assuntos
Compostos Benzidrílicos/isolamento & purificação , Cobre/isolamento & purificação , Grafite/química , Fenóis/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Adsorção , Cobre/química , Interações Hidrofóbicas e Hidrofílicas , Íons , Metais Pesados/isolamento & purificação , Espectroscopia Fotoeletrônica , Espectroscopia de Infravermelho com Transformada de Fourier , Tensoativos/química , Poluentes Químicos da Água/análise
6.
Huan Jing Ke Xue ; 40(5): 2295-2301, 2019 May 08.
Artigo em Chinês | MEDLINE | ID: mdl-31087869

RESUMO

Magnetite core/zirconia shell nanocomposite (abbreviated as Fe3O4@ZrO2 hereafter) was obtained using one-step co-precipitation method and its performance for removal of fluoride ion from water was studied. The results showed that the Langmuir maximum adsorption capacity of fluoride ion by Fe3O4@ZrO2 was 35.46 mg·g-1, which was far higher than those of magnetite, activated alumina and activated carbon. Studies of adsorption kinetics indicated that the adsorption of fluoride ion by Fe3O4@ZrO2 was fast and could be well described by the pseudo-second-order model. The adsorption process of fluoride ion was an endothermic reaction. The adsorption of fluoride ion by Fe3O4@ZrO2 decreased with increasing pH. Chloride, nitrate and sulfate anions, which commonly coexist in drinking water, had little effect on F- adsorption, although the coexistence of HCO3- and CO32- reduced the adsorption significantly by increasing the pH of the solution system. The fluoride adsorbed by Fe3O4@ZrO2 could be successfully desorbed with 1 mol·L-1 NaOH solution as desorption agent. The desorption rate reached 99.5%-99.6%. The F--desorbed Fe3O4@ZrO2 could be reused for the removal of F- after regeneration via restoring the protonation status of surface hydroxyl groups on hydrous zirconia. The removal efficiency of fluoride by Fe3O4@ZrO2 from actual well water was lower than that from pure water, but concentration limit for fluoride in drinking water could still be attained by increasing the dosage to a sufficiently high level. Fe3O4@ZrO2 is a promising material for fluoride removal due to its good performance, simple preparation method and easy separation from water by providing an external magnetic field.

7.
Sci Total Environ ; 682: 591-600, 2019 Sep 10.
Artigo em Inglês | MEDLINE | ID: mdl-31128372

RESUMO

Graphene materials are high-performance adsorbents for water and soil remediation, whose oxygen containing groups bind to metal ions intensely. In this study, we prepared carboxylated graphene oxide (GO-OCH2COOH) sponge and investigated the adsorption behaviors of Cu2+ on it by both experimental and computational approaches. Carboxylation largely improved the adsorption capacity from 23.8mg/g for graphene oxide (GO) sponge to 93.8mg/g for GO-OCH2COOH. The efficient adsorption was due to the strong interaction between Cu2+ and carboxyl groups (especially in -OCH2COOH form) according to the density functional theory calculation, while epoxy and hydroxyl groups contributed lowly. The fast adsorption process was achieved within 30min, corresponding to a large k2 value of pseudo-second order model (0.061mg/g/min). The adsorption was spontaneous and exothermic according to thermodynamics analyses. The binding strength of Cu2+ on GO-OCH2COOH was so strong that pH and ionic strength had mild impact. The strong binding sites were not recyclable, but the weaker ones (more than 40%) could be regenerated by simple washing. Our results highlighted the importance of chemical design in graphene adsorbents and the potential of GO-OCH2COOH in heavy metal fixation from water and soil.

8.
Huan Jing Ke Xue ; 40(1): 310-317, 2019 Jan 08.
Artigo em Chinês | MEDLINE | ID: mdl-30628288

RESUMO

We studied the loading of N-(2-Aminoethyl)-3-aminopropyl trimethoxy silane from aqueous solution as a monolayer on magnetite nanoparticles and examined the phosphate removal performance of the generated adsorbent (silane monolayer on magnetite nanoparticles, abbreviated as MSMNPs). The results indicate that silane monolayer adsorption on magnetite nanoparticles occurred at low concentrations (equilibrium silane concentration <300 mg·L-1) and a~100% surface monolayer coverage by silane could be established at a temperature ≥ 90℃ or a NaCl concentration ≥ 0.1 mol·L-1. The FTIR and XPS spectra indicate that hydrolyzed silane and magnetite nanoparticles are chemically linked. The loading of silane as a monolayer did not significantly change the saturation magnetization. The adsorption isotherm of phosphate based on MSMNPs fit the Langmuir model better, with a calculated maximum adsorption capacity reaching 7.59 mg·g-1. The adsorption and desorption of phosphate by MSMNPs are very fast, exceeding 90% within 30 min and reaching an equilibrium within 1 h. In conclusion, MSMNPs are novel adsorbents with easy separability, which enables the repeated use, and rapid adsorption and desorption of pollutants.

9.
Environ Pollut ; 247: 9-17, 2019 Apr.
Artigo em Inglês | MEDLINE | ID: mdl-30648618

RESUMO

Release of phosphorus (P) from sediment to overlying water has to be dealt with to address algal blooms in eutrophic lakes. In this study, the sediment from the Lake Taihu was amended with lanthanum modified zeolite (LMZ) to reduce P release under different pH, temperature and anaerobic conditions. LMZ performed well, to decreasing P concentration in Lake Taihu water in the presence of sediment. The EPC0 value, the critical P concentration at which there was neither P adsorption nor P release, was lowered by adding LMZ, suggesting that amendment with LMZ could diminish the risk of P release from the sediment. From the Langmuir isotherm model, the adsorption capacity of phosphate by LMZ was estimated to be 64.1 mgP/g. The LMZ-amended sediment had a higher content of stable P forms (HCl-P and Res-P) and a lower content of P forms with a high (NH4Cl-P and BD-P) or medium-high (NaOH-P and Org-P) risk of release, when compared with the original sediment. The fractionation simulates conditions which release potentially mobile P which can then be simply re-bound to LMZ. At high pH (>9.0), anaerobic condition or high temperature promoted the liberation of P from sediment. However, P release could be greatly inhibited by LMZ. In addition, although Mn2+ and NH4+ ions were released from sediment under the anaerobic condition, the release could also be hindered by adding LMZ. LMZ is a promising P inactivation agent to manage eutrophication in the sediment of Lake Taihu.


Assuntos
Sedimentos Geológicos/química , Fósforo/análise , Poluentes Químicos da Água/análise , Zeolitas/química , Adsorção , China , Recuperação e Remediação Ambiental , Eutrofização , Lagos/química , Lantânio , Fosfatos , Fósforo/química , Poluentes Químicos da Água/química
10.
J Colloid Interface Sci ; 517: 18-27, 2018 May 01.
Artigo em Inglês | MEDLINE | ID: mdl-29421677

RESUMO

Although graphene oxide (GO)-based materials are attractive media for water treatment, their separation from water for reuse remains a challenge. This study investigated the self-assembly of GO sheets in the presence of chitosan (CS), a natural polyaminosaccharide, into sponges. We found that about 93% of added CS could be combined with GO, regardless of the CS concentration. There exists an upper critical gelation limit, below which hydrogel forms and above which precipitation takes place. Results indicate that upon freeze-drying, a stable GO/CS sponge was generated only at a CS content of  ≥9%. Sponges with CS content between 9% and 41% had good filtering performance. The sponges were characterized with XRD, SEM and FTIR measurements and the interaction between GO and CS was analyzed. The GO/CS sponge with CS content of 9% had adsorption capacity of 275.5 mg/g for methylene blue (MB), a model dye molecule. Both electrostatic attraction and hydrophobic interactions are responsible for MB adsorption by GO/CS sponges. The GO/CS sponge could be regenerated for repeated use using 0.5 M NaOH solution as desorption reagent. Our fixed-bed column studies illustrate that the GO/CS sponge performed well as a filtering material for removing MB from water.

11.
Sci Total Environ ; 619-620: 42-48, 2018 Apr 01.
Artigo em Inglês | MEDLINE | ID: mdl-29136533

RESUMO

Eutrophication has become a worldwide environmental problem and removing phosphorus from water/wastewater before discharge is essential. The purpose of our present study was to develop an efficient material in terms of both phosphate adsorption capacity and magnetic separability. To this end, we first compared the performances of four spinel ferrites, including magnesium, zinc, nickel and copper ferrites. Then we developed a copper ferrite-based novel magnetic adsorbent, by synthesizing 1,6-hexamethylenediamine-functionalized copper ferrite(CuFe2O4) via a single solvothermal synthesis process followed by LaCl3 treatment. The materials were characterized with X-ray diffraction, transmission electron microscope, vibrating sample magnetometer, Fourier transform infrared spectra and N2 adsorption-desorption. The maximum adsorption capacity of our material, calculated from the Langmuir adsorption isotherm model, attained 32.59mg/g with a saturation magnetization of 31.32emu/g. Data of adsorption kinetics were fitted well to the psuedo-second-order model. Effects of solution pH and coexisting anions (Cl-, NO3-, SO42-) on phosphate adsorption were also investigated, showing that our material had good selectivity for phosphate. But OH- competed efficiently with phosphate for adsorption sites. Furthermore, increasing both NaOH concentration and temperature resulted in an enhancement of desorption efficiency. Thus NaOH solution could be used to desorb phosphate adsorbed on the material for reuse, by adopting a high NaOH concentration and/or a high temperature.

12.
Artigo em Inglês | MEDLINE | ID: mdl-29072622

RESUMO

Spongy graphene is a newly developed adsorbent of high performance for water treatment. Proper functionalization is an efficient approach to improve the adsorption capacity of graphene adsorbents. In this study, we prepared graphene oxide (GO), functionalized it with carboxyl groups to produce carboxylated GO (GO-COOH) dispersion, and lyophilized the GO-COOH dispersion to obtain the GO-COOH sponge. The adsorption isotherm, kinetics, thermodynamics, influencing factors, and regeneration of the adsorption of dye methylene blue (MB) on GO-COOH sponge were evaluated in batch experiments. The adsorption capacity of GO-COOH sponge was measured as 780 mg/g, which was nearly twice that of GO sponge (446 mg/g). The adsorption isotherm could be well described by the Freundlich model with a KF of 508 (L/mg)1/n. The adsorption kinetic was nicely fitted by pseudo-first-order model with a k1 of 0.00157·min-1. In thermodynamics analysis, the negative ΔG indicated the spontaneous nature of adsorption on GO-COOH sponge. The adsorption process was endothermic and was driven by the increase of entropy. Higher pH benefited the removal of MB by GO-COOH sponge and the ionic strength had no meaningful effect. The regeneration was poor due to the strong electrostatic interaction between MB and the GO-COOH sponge. The results collectively suggested that carboxylation increased the adsorption performance of GO sponge.


Assuntos
Corantes/química , Grafite/química , Azul de Metileno/química , Óxidos/química , Poluentes Químicos da Água/química , Purificação da Água/instrumentação , Adsorção , Concentração de Íons de Hidrogênio , Cinética , Concentração Osmolar , Termodinâmica , Purificação da Água/métodos
13.
Water Res ; 123: 1-11, 2017 10 15.
Artigo em Inglês | MEDLINE | ID: mdl-28641088

RESUMO

A unique sediment-capping agent consisting of a zeolite/hydrous zirconia composite (ZHZ) was developed and tested for P-immobilization in the overlying water and sediment cores from a freshwater pond. In the ZHZ, NaP1 zeolite was covered with hydrous zirconia, which existed as an amorphous phase. Experimental results in pond water indicated that ZHZ could efficiently remove soluble reactive phosphorus. The 28-day sediment incubation experiments showed that capping sediment with ZHZ resulted in a more efficient, rapid and sustained decrease in P concentration when compared with the traditional alum treatment method. Furthermore, ZHZ increased the sediment stability, resulting in the lowest turbidity, total phosphorus and soluble reactive phosphorus concentrations in overlying water following artificially induced resuspension of sediment. Phosphorus fractionation of sediment showed that the dominant P form transferred from HCl-extractable P to residual P, and the most release-sensitive P (labile P and reductant reactive P) was decreased after ZHZ application. Overall, ZHZ is a highly effective P-immobilization material. ZHZ has high potential as a sediment capping material to control internal P loading in eutrophic water bodies.


Assuntos
Fósforo/química , Poluentes Químicos da Água/química , Sedimentos Geológicos , Zeolitas , Zircônio
14.
Huan Jing Ke Xue ; 38(4): 1490-1496, 2017 Apr 08.
Artigo em Chinês | MEDLINE | ID: mdl-29965151

RESUMO

Zirconium modified diatomite was obtained by modifying raw diatomite with zirconium and the mass fraction of zirconia was 12.39% in the obtained material, which was proved to be amorphous via XRD. SEM images showed that porous floccules covered the surface of diatomite after modification and the specific surface area of the zirconium modified diatomite was 75.22 m2·g-1, larger than that of raw diatomite (14.00 m2·g-1). XPS spectra indicated that zirconia and diatomite were bonded together through chemical linkage, rather than physical deposition. The adsorption isotherm of phosphate by zirconium modified diatomite was fitted better to the Langmuir model with a calculated maximum adsorption capacity reaching 10.56 mg·g-1. The adsorption amount of zirconium oxide component in the material was estimated to be 81.67 mg·g-1 ZrO2, which was higher than that of pure zirconium oxides reported in previous studies. The adsorption amount of phosphate by zirconium modified diatomite decreased with the increase of pH. The adsorption was proved to be a ligand exchange process, supported by the XPS spectra of Zr3d region before and after adsorption. Chloride ion, sulfate ion and nitrate ion did not inhibit the adsorption of phosphate on the material, whereas coexistence of bicarbonate ions competed with phosphate ions to a certain extent. When treating eutrophic lake water with a phosphate concentration of 2 mg·L-1, the phosphate concentration level could meet the Ⅲ rank of Surface Water Environment Quality Standard of China by adopting the dosage of zirconium modified diatomite ≥1.25 g·L-1.

15.
Huan Jing Ke Xue ; 37(4): 1444-50, 2016 Apr 15.
Artigo em Chinês | MEDLINE | ID: mdl-27548967

RESUMO

A novel magnetic core/shell structured nano-particle Fe3O4@ SiO2phosphor-removal ahsorbent functionalized with hydrous aluminum oxides (Fe3O4@ SiO2@ Al2O3· nH2O) was synthesized. Fe3O4@ SiO2@ Al2O3· nH2O was characterized by XRD, TEM, VSM and BET nitrogen adsorption experiment. The XRD and TEM results demonstrated the presence of the core/shell structure, with saturated magnetization and specific surface area of 56.00 emu · g⁻¹ and 47.27 m² · g⁻¹, respectively. In batch phosphor adsorption experiment, the Langmuir adsorption maximum capacity was 12.90 mg · g⁻¹ and nearly 96% phosphor could be rapidly removed within a contact time of 40 mm. Adsorption of phosphor on Fe3O4@ SiO2@ Al2O3 · nH2O was highly dependent on pH condition, and the favored pH range was 5-9 in which the phosphor removal rate was above 90%. In the treatment of sewage water, the recommended dosage was 1.25 kg · t⁻¹. In 5 cycles of adsorption-regeneration-desorption experiment, over 90% of the adsorbed phosphor could be desorbed with 1 mol · L⁻¹ NaOH, and Fe3O4@ SiO2@ Al2O3· nH2O could be reused after regeneration by pH adjustment with slightly decreased phosphor removal rate with increasing recycling number, which proved the recyclability of Fe3O4@ SiO2@ Al2O3· nH2O and thereby its potential in recycling of phosphor resources.


Assuntos
Óxido de Alumínio/química , Óxido Ferroso-Férrico/química , Nanopartículas Metálicas/química , Fósforo/isolamento & purificação , Dióxido de Silício/química , Purificação da Água/métodos , Adsorção , Magnetismo , Reciclagem , Água , Poluentes Químicos da Água/isolamento & purificação
16.
Chemosphere ; 144: 1290-8, 2016 Feb.
Artigo em Inglês | MEDLINE | ID: mdl-26476050

RESUMO

A simple method to functionalize diatomite with hydrous iron oxide was attempted and its performance as a new active filtration material to remove and recover phosphate from water was investigated under varying solution conditions. The Langmuir phosphate adsorption capacity increased from 0.6 mgP/g for raw diatomite to 4.89, 14.71, 25.02 mgP/g for hydrous iron oxide modified diatomite (HIOMD), depending on the amount of iron loaded. Loading of hydrous iron oxide caused the increase in true and bulk density and a decline in filtration rate, but to a lesser extent. It was shown that the HIOMD product with suitable iron content could retain a good filtration performance with a greatly increased adsorption capacity for phosphate. The phosphate adsorption increased by decreasing pH and by increasing ionic strength at high pH levels. The adsorption process was interpreted by ligand exchange. Coexisting oxyanions of sulfate, nitrate, citrate, carbonate, silicate and humic acid showed different effects on phosphate fixation but it was presumed that their influence at their concentrations and pH levels commonly encountered in effluent or natural waters was limited, i.e., HIOMD had a reasonably good selectivity. Results in repeated adsorption, desorption and regeneration experiment showed that the adsorbed phosphate could be recovered and the material could be reused after regeneration. The column test showed that HIOMD could be potentially utilized as an adsorption filtration medium for phosphate removal and recovery from water.


Assuntos
Terra de Diatomáceas/química , Compostos Férricos/química , Nitratos/química , Fosfatos/análise , Poluentes Químicos da Água/análise , Purificação da Água/métodos , Adsorção , Filtração , Substâncias Húmicas/análise
17.
J Colloid Interface Sci ; 465: 76-82, 2016 Mar 01.
Artigo em Inglês | MEDLINE | ID: mdl-26641568

RESUMO

Hydrous lanthanum oxide was loaded onto the surface of Fe3O4@SiO2 core/shell magnetic nanoparticles to obtain an easily separable adsorbent (abbreviated as Fe-Si-La) for efficient separation of phosphate from water. Fe-Si-La was characterized with XRF, XRD, TEM, specific surface area and magnetization and their performance for phosphate removal was investigated. The Fe3O4@SiO2 core/shell structure was confirmed and the hydrous lanthanum oxide was successfully loaded onto its surface. The newly developed adsorbent had magnetization of 51.27emu/g. The Langmuir adsorption capacity of phosphate by Fe-Si-La reached 27.8mg/g by loading only 1mmol lanthanum per gram of magnetite. The adsorption was fast; nearly 99% of phosphate could be removed within 10min. The removal of phosphate was favored within the pH range 5.0-9.0. The adsorption on Fe-Si-La was not significantly influenced by ionic strength and by the coexistence of the anions of chloride and nitrate but sulfate, bicarbonate and humic acid showed slightly greater negative effects. Phosphate removal efficiency of higher than 95% was attained for real effluent of a wastewater treatment plant when the dose of adsorbent was >0.2kg/ton. The results showed that adsorbed phosphate could be nearly completely desorbed with NaOH solution for further use. In conclusion, Fe-Si-La is a promising adsorbent for the removal and recovery of phosphate from water.

18.
Artigo em Inglês | MEDLINE | ID: mdl-26301857

RESUMO

This study was undertaken to investigate the effectiveness of the hybrid adsorbent, which was synthesized from coal fly ash and was composed of lanthanum hydroxide and zeolite (La-ZFA), for phosphate removal from water. Long-term repeated adsorption tests for 30 days showed that the maximum removal capacity of the material reached 66.09 mg P/g. The fractionation of adsorbed phosphorus indicated that phosphate immobilized by La-ZFA was quite irreversible and was dominated by HCl-P fraction. It was suggested that the immobilization of phosphate was mainly attributed to lanthanum hydroxide and was slightly influenced by coexistence of other anions (Cl(-), NO3(-), SO4(2-), and HCO3(-)). At a La/P molar ratio between 1.5:1 and 2.0:1, a nearly complete removal (above 98%) of phosphate could be achieved. La-ZFA also exhibited great performance for removing phosphate from lake water (97.29%) as well as the effluent from wastewater treatment plant (97.86%), respectively. In addition, based on the results of the present study, it was believed that La-ZFA could be a potential material for phosphate removal in practical application.


Assuntos
Cinza de Carvão/química , Lantânio/química , Fosfatos/isolamento & purificação , Águas Residuárias/química , Poluentes Químicos da Água/isolamento & purificação , Purificação da Água/métodos , Zeolitas/química , Adsorção , Humanos , Lagos/química , Concentração Osmolar , Fosfatos/farmacocinética , Fósforo/isolamento & purificação , Água/química
19.
J Colloid Interface Sci ; 423: 13-9, 2014 Jun 01.
Artigo em Inglês | MEDLINE | ID: mdl-24703662

RESUMO

The traditional process of zeolite synthesis from coal fly ash produces large amount of waste alkaline solution, besides zeolite product. A novel hybrid sorbent, which was composed of zeolite and lanthanum hydroxide (La-ZFA), was produced by using soluble lanthanum chloride to react with waste alkaline solution after the traditional process. This study investigated the capability of phosphate removal by La-ZFA. The sorbent has a high phosphate removal capacity, with a sorption maximum of 71.94 mg/g, according to the Langmuir model. The removal of phosphate by La-ZFA performs well at a wide pH range, reaching>95% from pH 2.5 to pH 10.5 when initial P concentration<100 mg/L. Release of OH(-) during the interaction of phosphate with La-ZFA was observed. The formation of the monoclinic LaPO4 phase was identified by XRD analysis. The uptake of phosphate by La-ZFA was explained on the basis of the adsorption mechanism of the ligand exchange process. The sorbed phosphate could be recovered by hydrothermal treatment in 3M NaOH at 250°C, with a simultaneous regeneration of La-ZFA. Repeated sorption-desorption tests indicated that regenerated La-ZFA could be reused for phosphate removal. Therefore, synthesis of La-ZFA could impart additional function of phosphate removal to original zeolite, with the effective utilization of waste alkaline solution.

20.
Huan Jing Ke Xue ; 34(1): 231-6, 2013 Jan.
Artigo em Chinês | MEDLINE | ID: mdl-23487944

RESUMO

Activated alumina was studied for removing phosphate from water, and the recovery of adsorbed phosphate on activated aluminum oxide was also tested. Phosphate solution was prepared using distilled water, tap water and Luoshijiang River water, respectively. All the phosphate adsorption tests using activated alumina were proved to be well fitted with Langmuir isotherm and the respective maximum adsorption amount were 20.88, 32.15 and 29.85 mg x g(-1), respectively. The presence of electrolyte in water could be a positive factor for phosphate removal. As the pH value of phosphate solution became lower the Zeta potential of activated alumina increased, which could enhance the phosphate removal efficiency of activated alumina. The recovery tests indicated that NaOH (0.1 mol x L(-1)) solution could almost completely extract the phosphate adsorbed by activated alumina.


Assuntos
Óxido de Alumínio/química , Fósforo/isolamento & purificação , Poluentes Químicos da Água/isolamento & purificação , Adsorção , Fósforo/química , Hidróxido de Sódio/química , Poluentes Químicos da Água/química , Purificação da Água/métodos
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