Surface charge, secondary adsorption- desorption and form distribution of Cu2+ and Zn2+ in Ultisols and Alfisols having adsorbed phosphate were studied by potentiometric titration, adsorption equilibrium and sequentia...Surface charge, secondary adsorption- desorption and form distribution of Cu2+ and Zn2+ in Ultisols and Alfisols having adsorbed phosphate were studied by potentiometric titration, adsorption equilibrium and sequential extraction method, respectively. The soil surface negative charges increased whereas the amount of positive charges decreased with increase of P adsorbed. The soil secondary adsorption capacity for Cu2+ and Zn2+ was positively significantly correlated with the amount of P adsorbed by the soils, which could be described by the Langmuir equation. The amounts of Cu2+ and Zn2+ desorption from soils were decreased after P adsorption by the soils and the relationship between them was linear. After the soils adsorbed P, form distribution of Cu2+ and Zn2+ in soils changed remarforbly.展开更多
A group of Zn-Al layered double hydroxides (LDHs) were synthesized at different temperatures from 25-90 °C in order to investigate the influence of synthesis temperature on characteristics of the LDHs and their p...A group of Zn-Al layered double hydroxides (LDHs) were synthesized at different temperatures from 25-90 °C in order to investigate the influence of synthesis temperature on characteristics of the LDHs and their phosphate adsorption behaviour. The results reveal that an increase in the synthesis temperature generally improves the specific surface area of the sample and the phosphate adsorption capacity. The significantly enhanced crystallin- ity of the Zn-Al-30, synthesized at 30 °C, leads to a remarkable decrease in the specific surface area and consequently a poor phosphate adsorption capacity. It is suggested that the surface adsorption plays an important role in the phosphate uptake by the Zn-Al LDHs. Zn-Al-70 presents a relatively higher crystallinity and a lower specific surface area, compared with Zn-Al-60 and Zn-Al-80, but the highest phosphate adsorption capacity, indicating that surface adsorption is only one of the pathways for phosphate removal. The phosphate adsorption by the Zn-Al follows a pseudo-second-order kinetic equation. The adsorption isotherms fit Langmuir models, and the maximum a dsorption capacities of the Zn-Al-25, Zn-Al-50 and Zn-Al-70 are estimated to be 17.82, 21.01 and 27.10 mg·g-1 adsorbent, respectively.展开更多
The phosphate adsorption and surface charge characteristics of the tropical and subtropical soils derived from different parent materials in China were determined, and their relations to soil mineralogy were analysed....The phosphate adsorption and surface charge characteristics of the tropical and subtropical soils derived from different parent materials in China were determined, and their relations to soil mineralogy were analysed.The results showed that all soil phosphate adsorption curves were well fitted by Freundlich equation and Langmuir equation. The maximum buffering capacity of P ranged from 66 to 9880 mg kg-1, with an increasing order of purple soil, skeletal soil, red soil, lateritic red soil, yellow soil and latosol; and the highest value was 149 times the lowest value, which indicated great differences among these soils in phosphate adsorption and supplying characteristics. The pHo (zero point of charge) values obtained by salt titrationpotential titration varied from 3.03 to 5.49, and the highest value was found in the latosol derived from basalt whereas the lowest value was found in the purple soil. The correlation analysis indicated that the main minerals responsible for phosphate adsorption in the soils were gibbsite, amorphous iron oxide and kaolinite; and the pHo was mainly controlled by kaolinite, gibbsite and oxides.展开更多
A series of lanthanum doped meosoporous MCM-41 （LaxM41, x is Si/La molar ratio） was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N2 adsorption/desorp...A series of lanthanum doped meosoporous MCM-41 （LaxM41, x is Si/La molar ratio） was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N2 adsorption/desorption technique. The content of La in the materials was determined by ICE It was found that the La content of La25M41, La50M41 and La100M41 was 7.53%, 3.89% and 2.32%, respectively. The phosphate adsorption capacities increased with increasing amount of La incorporation. With 0.40 g La25M41 99.7% phosphate could be removed. The effects of Si/La molar ratio, LaxM41 dose, pH, initial concentration of phosphate solution, co-ions on phosphate adsorption were also evaluated. The phosphate adsorption kinetics of LaxM41 could be well-described by the pseudo second-order model, and Langmuir isotherm fit equilibrium data much better than the Freundlich isotherm.展开更多
The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsor...The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsorption on Al-oxide-typed surfaces between pH 3.5 to pH 5.5 as suspension pH changed from 2 to 9, but the adsorption amount of phosphate decreased continually as pH rose on Fe-oxide typed surfaces. The adsorption amount of phosphate and the maximum phosphate adsorption pH decreased in the order of yellow-red soil > lateritic red soil > red soil > paddy soil, which was coincided with the content order of amorphous Al oxide. The removement of organic matter and Fe oxide made the maximum phosphate adsorption pH rise from 4.0 to 5.0 and 4.5, respectively. The desorption curves with pH of four soils showed that phosphate desorbed least at pH 5. Generally the desorption was contrary to the adsorption with pH changing. There was a good accordance between adsorption or desorption and the concentration of Al in the suspension. The possible mechanisms of phosphate adsorption are discussed.展开更多
Phosphate is one of the most predominant pollutants in natural waters. Laboratory experiments were conducted to investigate the phosphate adsorption performance of a（NFS） made from drinking water treatment residuals...Phosphate is one of the most predominant pollutants in natural waters. Laboratory experiments were conducted to investigate the phosphate adsorption performance of a（NFS） made from drinking water treatment residuals. The adsorption of phosphate on the NFS fitted well with the Freundlich isotherm and pseudo second-order kinetic models. At p H 7.0, the maximum adsorption capacity of 1.03 mg/g was achieved at 15°C corresponding to the wastewater temperature in cold months, and increased notably to 1.31 mg/g at 35°C.Under both acidic conditions（part of the adsorption sites was consumed） and basic conditions（negative charges formed on the surface of NFS, which led to a static repulsion of PO43-and HPO42-）, the adsorption of phosphate was slightly inhibited. Further study showed that part of the adsorption sites could be recovered by 0.25 mol/L Na OH. The activation energy was calculated to be above 8.0 k J/mol, indicating that the adsorption of phosphate on NFS was probably a chemical process. Considering the strong phosphate adsorption capacity and recoverability, NFS showed great promise on enhancing phosphate removal from the secondary treated wastewater in the filtration process.展开更多
The types, contents and morphologies of crystalline Fe oxides and their relations to phosphate adsorptionon the clay fractions in soils with variable charge in southern China were investigated by means of XRD, TEM,EMA...The types, contents and morphologies of crystalline Fe oxides and their relations to phosphate adsorptionon the clay fractions in soils with variable charge in southern China were investigated by means of XRD, TEM,EMA and chemical analysis methods.Results indicated that the types and contents of crystalline Fe oxidesvaried with the soils examined. The dominant crystalline Fe oxide was hematite in the latosols and goethitesin the red soils.In yellow-brown soils, the only crystalline Fe oxide was goethite.The difference between Aldand Alo came mainly from the Al substituting for Fe in the pe oxides. The crystal morphology of goethiteappeared mainly as subrounded flat or iso-dimensional rather than acicular particles. Hematites occurredin plates of various thickness. Their MCDa/MCDc ratios in the latosols and red soils were generally above1.5 and below 1.5, respectively. The MCD values of goethites and hematites were 15-25nm and 20-35nm,and their specific surface areas were 80-120m￣2/g and 35-75m￣2/g, respectively.The goethite crystals weregenerally smaller. Variations of the total amounts of crystalline Fe oxi es in clay fractions were not related tophosphate adsorption. The types, contents and morphologies of crystalline Fe oxides in the soils remarkablyaffected phosphate adsorption characteristics of the soils. The phosphate adsorption of goethite was muchgreater than that of hematite. The higher the MCD /MCDc rotio of hematite, the lower the phosphateadsorption.展开更多
Chemical forms of the phosphate adsorbed on goethite surfaces and characteristics of the coordinategroups which exchange with P on goethite surfaces in solutions with different pll values were investigated.Results sho...Chemical forms of the phosphate adsorbed on goethite surfaces and characteristics of the coordinategroups which exchange with P on goethite surfaces in solutions with different pll values were investigated.Results showed that the chemical forms of P on goethite surfaces changed from the dominance of monodentatecorrdination to that of bidentate one with increasing pH of the solution. By influencing types of phosphateions in solutions, pH affected the chemical forms of P on goethite surfaces. The amount of OH￣- displacedby phosphate on goethite surfaces was the most at pH 7.0, the second at pH 9.0, and the least at pH 4.5.展开更多
The removal of phosphate from wastewater using traditional biological or precipitation methods is a huge challenge.The use of high-performance adsorbents has been shown to address this problem.In this study,a novel co...The removal of phosphate from wastewater using traditional biological or precipitation methods is a huge challenge.The use of high-performance adsorbents has been shown to address this problem.In this study,a novel composite adsorbent,composed of dolomite-doped biochar and bentonite(DO/BB),was first synthesized via co-pyrolysis.The combination of initial phosphate concentration of 100 mg/L and 1.6 g/L of DO/BB exhibited a high phosphate-adsorption capacity of 62 mg/g with a removal efficiency of 99.8%.It was also stable in complex water environments with various levels of solution pH,coexisting anions,high salinity,and humic acid.With this new composite,the phosphate concentration of the actual domestic sewage decreased from 9 mg/L to less than 1 mg/L,and the total nitrogen and chemical oxygen demand also decreased effectively.Further,the cross-flow treatment using a PVC membrane loaded with DO/BB(PVC-DO/BB),decreased the phosphate concentration from 1 to 0.08 mg/L,suggesting outstanding separation of phosphate pollutants via a combination of adsorption and separation.In addition,the removal of phosphate by the PVC-DO/BB membrane using NaOH solution as an eluent was almost 90%after 5 cycles.The kinetic,isotherm and XPS analysis before and after adsorption suggested that adsorption via a combination of electrostatic interaction,complexation and precipitation contributed to the excellent separation by the as-obtained membranes.展开更多
Herein,a Fe^(3+)-loaded aminated polypropylene fiber has been reported as an efficient phosphate adsorbent.The remarkable phosphate removal ability of the fiber is due to Fe^(3+)immobilization,and it demonstrates a ma...Herein,a Fe^(3+)-loaded aminated polypropylene fiber has been reported as an efficient phosphate adsorbent.The remarkable phosphate removal ability of the fiber is due to Fe^(3+)immobilization,and it demonstrates a maximum adsorption capacity of 33.94 mg·P·g^(–1).Adsorption experiments showed that the fiber is applicable over a wide pH range from 2 to 9.Furthermore,the adsorption kinetics and isotherm data were consistent with the pseudo-second-order and Langmuir adsorption models,respectively.The adsorption equilibrium of the fiber for phosphate was reached within 60 min,indicating an efficient monolayer chemisorption process.Moreover,the adsorbent maintained prominent phosphate removal in the presence of competitive ions such as NO_(3)^(–)and Cl^(–),exhibiting high selectivity.More importantly,the fiber demonstrated excellent reusability(5 times)and low adsorption limit below 0.02 mg·P·g^(–1).In addition,the phosphate removal efficiency of the fiber can exceed 99%under continuous flow conditions.The adsorption mechanism was studied by X-ray photoelectron spectroscopy,showing that the adsorption of phosphate on the fiber mainly depended on the chemical adsorption of the modified Fe^(3+).Overall,this study proves that the fiber possesses many advantages for phosphate removal,including high adsorption efficiency,lower treatment limit,good recyclability,and environmental friendliness.展开更多
Cationic hydrogels have received great attention to control eutrophication and recycle phosphate.In this study,a type of La(OH)_(3) loaded magnetic MAPTAC-based cationic hydrogel(La(OH)_(3)@MMCH)was developed as a pot...Cationic hydrogels have received great attention to control eutrophication and recycle phosphate.In this study,a type of La(OH)_(3) loaded magnetic MAPTAC-based cationic hydrogel(La(OH)_(3)@MMCH)was developed as a potential adsorbent for enhanced phosphate removal from aqueous environment.La(OH)_(3)@MMCH exhibited high adsorption capacity of 105.72±5.99 mg P/g,and reached equilibrium within 2 hr.La(OH)_(3)@MMCH could perform effectively in a wide pH range from 3.0 to 9.0 and in the presence of coexisting ions(including SO_(4)^(2-),Cl^(-),NO_(3)^(-),HCO_(3)^(-),SiO_(4)^(4-) and HA).The adsorption-desorption experiment indicated that La(OH)_(3)@MMCH could be easily regenerated by using NaOH-NaCl as the desorption agent,and 73.3%adsorption capacity remained after five cycles.Moreover,La(OH)_(3)@MMCH was employed to treat surface water with phosphate concentration of 1.90 mg/L and showed great removal efficiency of 95.21%.Actually,MMCH showed high surface charge density of 34.38-59.38 meq/kg in the pH range from 3.0 to 11.0 and great swelling ratio of 3014.57%within 24 h,indicating that MMCH could produce the enhanced Donnan membrane effect to pre-permeate phosphate.Furthermore,the bifunctional structure of La(OH)_(3)@MMCH enabled it to capture phosphate through electrostatic attraction and ligand exchange.All the results prove that La(OH)_(3)@MMCH is a promising adsorbent for eutrophication control and phosphate recovery.展开更多
Zeolite （Na） modified by self-synthesized nano-Fe particles was used as infiltration media to adsorb phosphate in rainwater runoff. The adsorption capacities increased up to 75 times that of natural zeolite at a sat...Zeolite （Na） modified by self-synthesized nano-Fe particles was used as infiltration media to adsorb phosphate in rainwater runoff. The adsorption capacities increased up to 75 times that of natural zeolite at a saturated equilibrium phosphate concentration of 0.42 mg/L. The correlation of capacity and material-specific surface area indicated that specific surface area was not the key factor contributing to the capacity improvement. SEM and XRD analysis showed that chemical reaction between Fe and P to form new products like cacoxenite is the main reason for the increased capacity, and that the method of adding metal ions or particles to improve the adsorption capacity for phosphate is feasible.展开更多
This study was performed to investigate the removal of phosphate from domestic wastewater using a modified steel slag as the adsorbent. The adsorption effects of alkalinity, salt, water,and thermal modification were i...This study was performed to investigate the removal of phosphate from domestic wastewater using a modified steel slag as the adsorbent. The adsorption effects of alkalinity, salt, water,and thermal modification were investigated. The results showed that thermal activation at 800℃ for 1 hr was the optimum operation to improve the adsorption capacity. The adsorption process of the thermally modified slag was well described by the Elovich kinetic model and the Langmuir isotherm model. The maximum adsorption capacity calculated from the Langmuir model reached 13.62 mg/g. Scanning electron microscopy indicated that the surface of the modified slag was cracked and that the texture became loose after heating. The surface area and pore volume did not change after thermal modification. In the treatment of domestic wastewater, the modified slag bed（35.5 kg） removed phosphate effectively and operated for 158 days until the effluent P rose above the limit concentration of 0.5 mg/L. The phosphate fractionation method, which is often applied in soil research, was used to analyze the phosphate adsorption behavior in the slag bed. The analysis revealed that the total contents of various Ca-P forms accounted for 81.4%-91.1%, i.e., Ca10-P 50.6%-65.1%, Ca8-P 17.8%-25.0%,and Ca2-P 4.66%-9.20%. The forms of Al-P, Fe-P, and O-P accounted for only 8.9%-18.6%. The formation of Ca10-P precipitates was considered to be the main mechanism of phosphate removal in the thermally modified slag bed.展开更多
Metal oxide/hydroxide-based nanocomposite adsorbents with porous supporting matrices have been recognized as efficient adsorbents for phosphorus recovery.Aiming at satisfying increasingly restrictive environmental req...Metal oxide/hydroxide-based nanocomposite adsorbents with porous supporting matrices have been recognized as efficient adsorbents for phosphorus recovery.Aiming at satisfying increasingly restrictive environmental requirements involving improving metal site utilization and lowering metal leakage risk,a glycol-solvothermal confined-space synthesis strategy was proposed for the fabrication of Fe OOH/anion exchanger nanocomposites(Fe/900s)with enhanced metal site utilization and reduced metal leakage risk.Compared to composites prepared using alkaline precipitation methods,Fe/900s performed comparably,with a high adsorption capacity of 19.05 mg-P/g with an initial concentration of 10 mg-P/L,a high adsorption selectivity of 8.2 mg-P/g in the presence of 500 mg-SO_(4)^(2-)/L,and high long-term resilience(with a capacity loss of~14%after five cycles),along with substantially lower Fe loading amount(4.11 wt.%)and Fe leakage percentage.Mechanistic investigation demonstrated that contribution of the specific Fe OOH sites to phosphate adsorption increased substantially(up to 50.97%under the optimal conditions),in which Fe(Ⅲ)-OH was the dominant efficient species.The side effects of an excessively long reaction time,which included quaternary ammonium decomposition,Fe OOH aggregation,and Fe(Ⅲ)reduction,were discussed as guidance for optimizing the synthesis strategy.The glycol-solvothermal strategy provides a facile solution to environmental problems through nanocrystal growth engineering in a confined space.展开更多
Fe_3O_4@SiO_2 magnetic nanoparticles functionalized with mesoporous cerium oxide（Fe_3O_4@SiO_2@mCeO_2） was fabricated as a novel adsorbent to remove phosphate from water. The prepared adsorbent was characterized by ...Fe_3O_4@SiO_2 magnetic nanoparticles functionalized with mesoporous cerium oxide（Fe_3O_4@SiO_2@mCeO_2） was fabricated as a novel adsorbent to remove phosphate from water. The prepared adsorbent was characterized by X-ray diffractometry（XRD）, transmission electron microscopy（TEM）, nitrogen adsorption-desorption and vibrating sample magnetometry（VSM）, and its phosphate removal performance was investigated through the batch adsorption studies. Characterization results confirmed that mesoporous cerium oxide was successfully assembled on the surface of Fe_3O_4@SiO_2 nanoparticles, and the synthesized adsorbent possessed a typical core-shell structure with a BET surface area of 195 m^2/g, accessible mesopores of 2.6 nm, and the saturation magnetization of 21.11 emu/g. The newly developed adsorbent had an excellent performance in adsorbing phosphate, and its maximum adsorption capacity calculated from the Langmuir model was 64.07 mg/g. The adsorption was fast, and the kinetic data could be best fitted with the pseudo-second-order kinetic model. The phosphate removal decreased with the increase of solution pH（2 to 10）, while the higher ionic strength slightly promoted the phosphate adsorption. The presence of Cl~– and SO^（2–）_4 could enhance the adsorption of phosphate whereas HCO~–_ 3 had interfering effect on the phosphate adsorption. The adsorption mechanism was studied by analyzing Zeta potential and FTIR spectroscopy, and the results indicated that the replacement of the surface hydroxyl groups by phosphate ions with the formation of inner-sphere complex played a key role in the phosphate adsorption. The spent adsorbent could be quickly separated from aqueous solution with the assistance of the external magnetic field, and the adsorbed phosphate could be effectively desorbed using a 1 mol/L NaOH solution.展开更多
Bimetallic oxides composites have received an increasing attention as promising adsorbents for aqueous phosphate (P) removal in recent years. In this study, a novel magnetic composite MZLCO was prepared by hybridizing...Bimetallic oxides composites have received an increasing attention as promising adsorbents for aqueous phosphate (P) removal in recent years. In this study, a novel magnetic composite MZLCO was prepared by hybridizing amorphous Zr-La (carbonate) oxides (ZLCO) with nano-FeOthrough a one-pot solvothermal method for efficient phosphate adsorption. Our optimum sample of MZLCO-45 exhibited a high Langmuir maximum adsorption capacity of 96.16 mg P/g and performed well even at low phosphate concentration. The phosphate adsorption kinetics by MZLCO-45 fitted well with the pseudo-second-order model, and the adsorption capacity could reach 79% of the ultimate value within the first 60 min. The phosphate adsorption process was highly p H-dependent, and MZLCO-45 performed well over a wide p H range of 2.0-8.0. Moreover, MZLCO-45 showed a strong selectivity to phosphate in the presence of competing ions (Cl^(-), NO_(3)^(-), SO_(4)^(2-), HCO_(3)^(-), Ca^(2+), and Mg^(2+)) and a good reusability using the eluent of Na OH/Na Cl mixture, then 64% adsorption capacity remained after ten recycles. The initial 2.0 mg P/L in municipal wastewater and surface water could be efficiently reduced to below 0.1mg P/L by 0.07 g/L MZLCO-45, and the phosphate removal efficiencies were 95.7% and 96.21%, respectively. Phosphate adsorption mechanisms by MZLCO-45 could be attributed to electrostatic attraction and the inner-sphere complexation via ligand exchange forming Zr/La-O-P, -OH and CO_(3)^(2-)groups on MZLCO-45 surface played important roles in the ligand exchange process. The existence of oxygen vacancies could accelerate the phosphate absorption rate of the MZLCO-45 composites.展开更多
基金Project (No. 49871043) supported by the National Natural Science Foundation of China.
文摘Surface charge, secondary adsorption- desorption and form distribution of Cu2+ and Zn2+ in Ultisols and Alfisols having adsorbed phosphate were studied by potentiometric titration, adsorption equilibrium and sequential extraction method, respectively. The soil surface negative charges increased whereas the amount of positive charges decreased with increase of P adsorbed. The soil secondary adsorption capacity for Cu2+ and Zn2+ was positively significantly correlated with the amount of P adsorbed by the soils, which could be described by the Langmuir equation. The amounts of Cu2+ and Zn2+ desorption from soils were decreased after P adsorption by the soils and the relationship between them was linear. After the soils adsorbed P, form distribution of Cu2+ and Zn2+ in soils changed remarforbly.
基金Supported by the National Natural Science Foundation of China(50978029,51008023)
文摘A group of Zn-Al layered double hydroxides (LDHs) were synthesized at different temperatures from 25-90 °C in order to investigate the influence of synthesis temperature on characteristics of the LDHs and their phosphate adsorption behaviour. The results reveal that an increase in the synthesis temperature generally improves the specific surface area of the sample and the phosphate adsorption capacity. The significantly enhanced crystallin- ity of the Zn-Al-30, synthesized at 30 °C, leads to a remarkable decrease in the specific surface area and consequently a poor phosphate adsorption capacity. It is suggested that the surface adsorption plays an important role in the phosphate uptake by the Zn-Al LDHs. Zn-Al-70 presents a relatively higher crystallinity and a lower specific surface area, compared with Zn-Al-60 and Zn-Al-80, but the highest phosphate adsorption capacity, indicating that surface adsorption is only one of the pathways for phosphate removal. The phosphate adsorption by the Zn-Al follows a pseudo-second-order kinetic equation. The adsorption isotherms fit Langmuir models, and the maximum a dsorption capacities of the Zn-Al-25, Zn-Al-50 and Zn-Al-70 are estimated to be 17.82, 21.01 and 27.10 mg·g-1 adsorbent, respectively.
文摘The phosphate adsorption and surface charge characteristics of the tropical and subtropical soils derived from different parent materials in China were determined, and their relations to soil mineralogy were analysed.The results showed that all soil phosphate adsorption curves were well fitted by Freundlich equation and Langmuir equation. The maximum buffering capacity of P ranged from 66 to 9880 mg kg-1, with an increasing order of purple soil, skeletal soil, red soil, lateritic red soil, yellow soil and latosol; and the highest value was 149 times the lowest value, which indicated great differences among these soils in phosphate adsorption and supplying characteristics. The pHo (zero point of charge) values obtained by salt titrationpotential titration varied from 3.03 to 5.49, and the highest value was found in the latosol derived from basalt whereas the lowest value was found in the purple soil. The correlation analysis indicated that the main minerals responsible for phosphate adsorption in the soils were gibbsite, amorphous iron oxide and kaolinite; and the pHo was mainly controlled by kaolinite, gibbsite and oxides.
基金supported by the National Major Research Plan for Water Pollution Control and Treatment of China (No.2008ZX07101-015)
文摘A series of lanthanum doped meosoporous MCM-41 （LaxM41, x is Si/La molar ratio） was prepared by sol-gel method. The surface structure of the materials was investigated with X-ray diffraction and N2 adsorption/desorption technique. The content of La in the materials was determined by ICE It was found that the La content of La25M41, La50M41 and La100M41 was 7.53%, 3.89% and 2.32%, respectively. The phosphate adsorption capacities increased with increasing amount of La incorporation. With 0.40 g La25M41 99.7% phosphate could be removed. The effects of Si/La molar ratio, LaxM41 dose, pH, initial concentration of phosphate solution, co-ions on phosphate adsorption were also evaluated. The phosphate adsorption kinetics of LaxM41 could be well-described by the pseudo second-order model, and Langmuir isotherm fit equilibrium data much better than the Freundlich isotherm.
文摘The study about the adsorption of phosphate on four variable charge soils and some minerals revealed that two stage adsorption appeared in the adsorption isotherms of phosphate on 4 soils and there was a maximum adsorption on Al-oxide-typed surfaces between pH 3.5 to pH 5.5 as suspension pH changed from 2 to 9, but the adsorption amount of phosphate decreased continually as pH rose on Fe-oxide typed surfaces. The adsorption amount of phosphate and the maximum phosphate adsorption pH decreased in the order of yellow-red soil > lateritic red soil > red soil > paddy soil, which was coincided with the content order of amorphous Al oxide. The removement of organic matter and Fe oxide made the maximum phosphate adsorption pH rise from 4.0 to 5.0 and 4.5, respectively. The desorption curves with pH of four soils showed that phosphate desorbed least at pH 5. Generally the desorption was contrary to the adsorption with pH changing. There was a good accordance between adsorption or desorption and the concentration of Al in the suspension. The possible mechanisms of phosphate adsorption are discussed.
基金supported by the National Natural Science Foundation of China(No.21007050)the Science and Technology Nova Program of Shaanxi(No.2014KJXX-66)
文摘Phosphate is one of the most predominant pollutants in natural waters. Laboratory experiments were conducted to investigate the phosphate adsorption performance of a（NFS） made from drinking water treatment residuals. The adsorption of phosphate on the NFS fitted well with the Freundlich isotherm and pseudo second-order kinetic models. At p H 7.0, the maximum adsorption capacity of 1.03 mg/g was achieved at 15°C corresponding to the wastewater temperature in cold months, and increased notably to 1.31 mg/g at 35°C.Under both acidic conditions（part of the adsorption sites was consumed） and basic conditions（negative charges formed on the surface of NFS, which led to a static repulsion of PO43-and HPO42-）, the adsorption of phosphate was slightly inhibited. Further study showed that part of the adsorption sites could be recovered by 0.25 mol/L Na OH. The activation energy was calculated to be above 8.0 k J/mol, indicating that the adsorption of phosphate on NFS was probably a chemical process. Considering the strong phosphate adsorption capacity and recoverability, NFS showed great promise on enhancing phosphate removal from the secondary treated wastewater in the filtration process.
文摘The types, contents and morphologies of crystalline Fe oxides and their relations to phosphate adsorptionon the clay fractions in soils with variable charge in southern China were investigated by means of XRD, TEM,EMA and chemical analysis methods.Results indicated that the types and contents of crystalline Fe oxidesvaried with the soils examined. The dominant crystalline Fe oxide was hematite in the latosols and goethitesin the red soils.In yellow-brown soils, the only crystalline Fe oxide was goethite.The difference between Aldand Alo came mainly from the Al substituting for Fe in the pe oxides. The crystal morphology of goethiteappeared mainly as subrounded flat or iso-dimensional rather than acicular particles. Hematites occurredin plates of various thickness. Their MCDa/MCDc ratios in the latosols and red soils were generally above1.5 and below 1.5, respectively. The MCD values of goethites and hematites were 15-25nm and 20-35nm,and their specific surface areas were 80-120m￣2/g and 35-75m￣2/g, respectively.The goethite crystals weregenerally smaller. Variations of the total amounts of crystalline Fe oxi es in clay fractions were not related tophosphate adsorption. The types, contents and morphologies of crystalline Fe oxides in the soils remarkablyaffected phosphate adsorption characteristics of the soils. The phosphate adsorption of goethite was muchgreater than that of hematite. The higher the MCD /MCDc rotio of hematite, the lower the phosphateadsorption.
文摘Chemical forms of the phosphate adsorbed on goethite surfaces and characteristics of the coordinategroups which exchange with P on goethite surfaces in solutions with different pll values were investigated.Results showed that the chemical forms of P on goethite surfaces changed from the dominance of monodentatecorrdination to that of bidentate one with increasing pH of the solution. By influencing types of phosphateions in solutions, pH affected the chemical forms of P on goethite surfaces. The amount of OH￣- displacedby phosphate on goethite surfaces was the most at pH 7.0, the second at pH 9.0, and the least at pH 4.5.
基金The authors would like to acknowledge the National Natural Science Foundation of China(No.52078189)the Key R&D Program of Jiangsu Province(China)(No.BE2020024)for supporting this research.
文摘The removal of phosphate from wastewater using traditional biological or precipitation methods is a huge challenge.The use of high-performance adsorbents has been shown to address this problem.In this study,a novel composite adsorbent,composed of dolomite-doped biochar and bentonite(DO/BB),was first synthesized via co-pyrolysis.The combination of initial phosphate concentration of 100 mg/L and 1.6 g/L of DO/BB exhibited a high phosphate-adsorption capacity of 62 mg/g with a removal efficiency of 99.8%.It was also stable in complex water environments with various levels of solution pH,coexisting anions,high salinity,and humic acid.With this new composite,the phosphate concentration of the actual domestic sewage decreased from 9 mg/L to less than 1 mg/L,and the total nitrogen and chemical oxygen demand also decreased effectively.Further,the cross-flow treatment using a PVC membrane loaded with DO/BB(PVC-DO/BB),decreased the phosphate concentration from 1 to 0.08 mg/L,suggesting outstanding separation of phosphate pollutants via a combination of adsorption and separation.In addition,the removal of phosphate by the PVC-DO/BB membrane using NaOH solution as an eluent was almost 90%after 5 cycles.The kinetic,isotherm and XPS analysis before and after adsorption suggested that adsorption via a combination of electrostatic interaction,complexation and precipitation contributed to the excellent separation by the as-obtained membranes.
基金This work was financially supported by the National Natural Science Foundation of China(Grant No.22208003)Natural Science Foundation of Anhui Province(No.1908085QB87)Major Science and Technology Projects in Anhui Province(No.202103a06020012).
文摘Herein,a Fe^(3+)-loaded aminated polypropylene fiber has been reported as an efficient phosphate adsorbent.The remarkable phosphate removal ability of the fiber is due to Fe^(3+)immobilization,and it demonstrates a maximum adsorption capacity of 33.94 mg·P·g^(–1).Adsorption experiments showed that the fiber is applicable over a wide pH range from 2 to 9.Furthermore,the adsorption kinetics and isotherm data were consistent with the pseudo-second-order and Langmuir adsorption models,respectively.The adsorption equilibrium of the fiber for phosphate was reached within 60 min,indicating an efficient monolayer chemisorption process.Moreover,the adsorbent maintained prominent phosphate removal in the presence of competitive ions such as NO_(3)^(–)and Cl^(–),exhibiting high selectivity.More importantly,the fiber demonstrated excellent reusability(5 times)and low adsorption limit below 0.02 mg·P·g^(–1).In addition,the phosphate removal efficiency of the fiber can exceed 99%under continuous flow conditions.The adsorption mechanism was studied by X-ray photoelectron spectroscopy,showing that the adsorption of phosphate on the fiber mainly depended on the chemical adsorption of the modified Fe^(3+).Overall,this study proves that the fiber possesses many advantages for phosphate removal,including high adsorption efficiency,lower treatment limit,good recyclability,and environmental friendliness.
基金This work was supported by the Beijing Municipal Science and Technology Project(No.Z181100005518007)the National Key Research and Development Program of China(No.2017YFC0505303)the National Natural Science Foundation of China(Nos.51978054 and 51678053).
文摘Cationic hydrogels have received great attention to control eutrophication and recycle phosphate.In this study,a type of La(OH)_(3) loaded magnetic MAPTAC-based cationic hydrogel(La(OH)_(3)@MMCH)was developed as a potential adsorbent for enhanced phosphate removal from aqueous environment.La(OH)_(3)@MMCH exhibited high adsorption capacity of 105.72±5.99 mg P/g,and reached equilibrium within 2 hr.La(OH)_(3)@MMCH could perform effectively in a wide pH range from 3.0 to 9.0 and in the presence of coexisting ions(including SO_(4)^(2-),Cl^(-),NO_(3)^(-),HCO_(3)^(-),SiO_(4)^(4-) and HA).The adsorption-desorption experiment indicated that La(OH)_(3)@MMCH could be easily regenerated by using NaOH-NaCl as the desorption agent,and 73.3%adsorption capacity remained after five cycles.Moreover,La(OH)_(3)@MMCH was employed to treat surface water with phosphate concentration of 1.90 mg/L and showed great removal efficiency of 95.21%.Actually,MMCH showed high surface charge density of 34.38-59.38 meq/kg in the pH range from 3.0 to 11.0 and great swelling ratio of 3014.57%within 24 h,indicating that MMCH could produce the enhanced Donnan membrane effect to pre-permeate phosphate.Furthermore,the bifunctional structure of La(OH)_(3)@MMCH enabled it to capture phosphate through electrostatic attraction and ligand exchange.All the results prove that La(OH)_(3)@MMCH is a promising adsorbent for eutrophication control and phosphate recovery.
基金supported by the Chinese National Special Science & Technology Project on Treatment and Control of Water Pollution (No.2008ZX07313-004)
文摘Zeolite （Na） modified by self-synthesized nano-Fe particles was used as infiltration media to adsorb phosphate in rainwater runoff. The adsorption capacities increased up to 75 times that of natural zeolite at a saturated equilibrium phosphate concentration of 0.42 mg/L. The correlation of capacity and material-specific surface area indicated that specific surface area was not the key factor contributing to the capacity improvement. SEM and XRD analysis showed that chemical reaction between Fe and P to form new products like cacoxenite is the main reason for the increased capacity, and that the method of adding metal ions or particles to improve the adsorption capacity for phosphate is feasible.
基金supported by the Mega-projects of Science Research for Water Environment Improvement of China (Nos. 2013ZX07209-001-003, 2012ZX07307-001-006)
文摘This study was performed to investigate the removal of phosphate from domestic wastewater using a modified steel slag as the adsorbent. The adsorption effects of alkalinity, salt, water,and thermal modification were investigated. The results showed that thermal activation at 800℃ for 1 hr was the optimum operation to improve the adsorption capacity. The adsorption process of the thermally modified slag was well described by the Elovich kinetic model and the Langmuir isotherm model. The maximum adsorption capacity calculated from the Langmuir model reached 13.62 mg/g. Scanning electron microscopy indicated that the surface of the modified slag was cracked and that the texture became loose after heating. The surface area and pore volume did not change after thermal modification. In the treatment of domestic wastewater, the modified slag bed（35.5 kg） removed phosphate effectively and operated for 158 days until the effluent P rose above the limit concentration of 0.5 mg/L. The phosphate fractionation method, which is often applied in soil research, was used to analyze the phosphate adsorption behavior in the slag bed. The analysis revealed that the total contents of various Ca-P forms accounted for 81.4%-91.1%, i.e., Ca10-P 50.6%-65.1%, Ca8-P 17.8%-25.0%,and Ca2-P 4.66%-9.20%. The forms of Al-P, Fe-P, and O-P accounted for only 8.9%-18.6%. The formation of Ca10-P precipitates was considered to be the main mechanism of phosphate removal in the thermally modified slag bed.
基金supported by the National Natural Science Foundation of China(Nos.52070100,51978341,52081330506,and 52011530433)the Natural Science Foundation of Jiangsu Province of China(No.BK20190087)+1 种基金the Foundation of Jiangsu Collaborative Innovation Center of Biomedical Functional Materialsa project funded by the Priority Academic Program Development of Jiangsu Higher Education Institutions。
文摘Metal oxide/hydroxide-based nanocomposite adsorbents with porous supporting matrices have been recognized as efficient adsorbents for phosphorus recovery.Aiming at satisfying increasingly restrictive environmental requirements involving improving metal site utilization and lowering metal leakage risk,a glycol-solvothermal confined-space synthesis strategy was proposed for the fabrication of Fe OOH/anion exchanger nanocomposites(Fe/900s)with enhanced metal site utilization and reduced metal leakage risk.Compared to composites prepared using alkaline precipitation methods,Fe/900s performed comparably,with a high adsorption capacity of 19.05 mg-P/g with an initial concentration of 10 mg-P/L,a high adsorption selectivity of 8.2 mg-P/g in the presence of 500 mg-SO_(4)^(2-)/L,and high long-term resilience(with a capacity loss of~14%after five cycles),along with substantially lower Fe loading amount(4.11 wt.%)and Fe leakage percentage.Mechanistic investigation demonstrated that contribution of the specific Fe OOH sites to phosphate adsorption increased substantially(up to 50.97%under the optimal conditions),in which Fe(Ⅲ)-OH was the dominant efficient species.The side effects of an excessively long reaction time,which included quaternary ammonium decomposition,Fe OOH aggregation,and Fe(Ⅲ)reduction,were discussed as guidance for optimizing the synthesis strategy.The glycol-solvothermal strategy provides a facile solution to environmental problems through nanocrystal growth engineering in a confined space.
基金supported by Natural Science Foundation of China(21706178)"utilization of low rank coal"Strategic Leading Special Fund,Strategic Leading Special Fund of CAS(XDA-07070800,XDA-07070400)the Opening Foundation of State Key Laboratory of Coal Conversion(J16-17-602)
文摘Fe_3O_4@SiO_2 magnetic nanoparticles functionalized with mesoporous cerium oxide（Fe_3O_4@SiO_2@mCeO_2） was fabricated as a novel adsorbent to remove phosphate from water. The prepared adsorbent was characterized by X-ray diffractometry（XRD）, transmission electron microscopy（TEM）, nitrogen adsorption-desorption and vibrating sample magnetometry（VSM）, and its phosphate removal performance was investigated through the batch adsorption studies. Characterization results confirmed that mesoporous cerium oxide was successfully assembled on the surface of Fe_3O_4@SiO_2 nanoparticles, and the synthesized adsorbent possessed a typical core-shell structure with a BET surface area of 195 m^2/g, accessible mesopores of 2.6 nm, and the saturation magnetization of 21.11 emu/g. The newly developed adsorbent had an excellent performance in adsorbing phosphate, and its maximum adsorption capacity calculated from the Langmuir model was 64.07 mg/g. The adsorption was fast, and the kinetic data could be best fitted with the pseudo-second-order kinetic model. The phosphate removal decreased with the increase of solution pH（2 to 10）, while the higher ionic strength slightly promoted the phosphate adsorption. The presence of Cl~– and SO^（2–）_4 could enhance the adsorption of phosphate whereas HCO~–_ 3 had interfering effect on the phosphate adsorption. The adsorption mechanism was studied by analyzing Zeta potential and FTIR spectroscopy, and the results indicated that the replacement of the surface hydroxyl groups by phosphate ions with the formation of inner-sphere complex played a key role in the phosphate adsorption. The spent adsorbent could be quickly separated from aqueous solution with the assistance of the external magnetic field, and the adsorbed phosphate could be effectively desorbed using a 1 mol/L NaOH solution.
基金supported by the Beijing Municipal Science and Technology Project (No. Z181100005518007)the National Key Research and Development Program of China (No. 2017YFC0505303)+1 种基金the National Natural Science Foundation of China (Nos. 51978054 and 51678053)Beijing Municipal Education Commission through the Innovative Transdisciplinary Program ‘Ecological Restoration Engineering’ (No. GJJXK210102)。
文摘Bimetallic oxides composites have received an increasing attention as promising adsorbents for aqueous phosphate (P) removal in recent years. In this study, a novel magnetic composite MZLCO was prepared by hybridizing amorphous Zr-La (carbonate) oxides (ZLCO) with nano-FeOthrough a one-pot solvothermal method for efficient phosphate adsorption. Our optimum sample of MZLCO-45 exhibited a high Langmuir maximum adsorption capacity of 96.16 mg P/g and performed well even at low phosphate concentration. The phosphate adsorption kinetics by MZLCO-45 fitted well with the pseudo-second-order model, and the adsorption capacity could reach 79% of the ultimate value within the first 60 min. The phosphate adsorption process was highly p H-dependent, and MZLCO-45 performed well over a wide p H range of 2.0-8.0. Moreover, MZLCO-45 showed a strong selectivity to phosphate in the presence of competing ions (Cl^(-), NO_(3)^(-), SO_(4)^(2-), HCO_(3)^(-), Ca^(2+), and Mg^(2+)) and a good reusability using the eluent of Na OH/Na Cl mixture, then 64% adsorption capacity remained after ten recycles. The initial 2.0 mg P/L in municipal wastewater and surface water could be efficiently reduced to below 0.1mg P/L by 0.07 g/L MZLCO-45, and the phosphate removal efficiencies were 95.7% and 96.21%, respectively. Phosphate adsorption mechanisms by MZLCO-45 could be attributed to electrostatic attraction and the inner-sphere complexation via ligand exchange forming Zr/La-O-P, -OH and CO_(3)^(2-)groups on MZLCO-45 surface played important roles in the ligand exchange process. The existence of oxygen vacancies could accelerate the phosphate absorption rate of the MZLCO-45 composites.
