Removal of fluoride from aqueous solution by modified fly ash

Removal of fluoride from aqueous solution by modified fly ash was studied in batch model. The influences of the contact time, the initial F^- concentration, the dosage of fly ash, and the temperature on removal of F have been studied, respectively. It was found that fly ash modified with dilute HCl has the maximum adsorption of fluoride from aqueous solutions, and that the retention of fluoride ions by material was 85% or higher with initial 10 mg F^-/L. First-order kinetics was observed for the adsorption process, which follows the Langrnuir and Freundlich isotherms. The thermodynamic parameters such as ΔG0, ΔH0, ΔS0 were calculated from Langmuir constants. The positive value of ΔH0 （1.273 J/mol） confirms the endothermic nature of adsorption.     

Fractal-like adsorption kinetics of Pb^2＋ in rocks

The adsorption kinetics of Pb^2＋ in rocks has been studied using ion selective electrodes and atomic absorption spectrophotometer. The results showed that the adsorption process is a fractal-like reaction. The adsorption rate was relatively high before 30 minutes, and then dropped. The saturated adsorption capacity （a） of Pb^2＋ and kinetic parameters （b, a, D and k） increased with increasing initial concentrations of Pb^2＋. These parameters （except a） decreased while Na^＋ was present in the solution. Furthermore, the smaller the rocks were in grain size, the bigger these kinetic parameters would be, though the parameter a was almost constant.     

Heavy Metal Removal from Water by Adsorption Using Pillared Montmorillonite

Removal of Cu^2＋, Cr^3＋ and Cd^2＋ from aqueous solutions by adsorption on montmorillonite modified by sodium dodecylsulfate （SDS） and hydroxy-alumino-silicate （HAS） was investigated. Experiments were carried out as a function of solution pH, solute concentration, and time. The Langmuir model was adopted to describe the single-solute adsorption isotherm, in which the Langmuir parameters were directly taken from those obtained in single-solute systems. The kinetics of metal ions adsorption was examined and the pseudo-first-order rate constant was finally evaluated.     

Experimental research on adsorption/desorption for petroleum pollutants in the soil in Daqing oilfield

The Daqing oilfield is one of the biggest oilfields in the world. It has been exploited for several decades, which brings serious pollution to local natural environment. The crude oil on ground which is produced in the process of oil production contains various organic pollutants. The petroleum pollutants tend to adsorb, desorb, biodegrade and photolyze and so on in the soil, but adsorption/desorption is a pair of extremely important environment geochemistry behavior. In order to master the rule of petroleum pollutants migration and transformation in the soil environment, and provide scientific evidence for the prevent research project on petroleum pollution treatment in the Daqing oilfield, the chemozem was selected as the experimental sample, which is a kind of representative soil in the Daqing oilfield. The factors affecting adsorbent and desorption＇s characteristics were discussed, including pH of the soil, the concentrations of suspended particulates and temperature. The oscillation-equity was used in the experiment. The mechanism and dynamics process of the adsorption/desorption were researched. The results showed that adsorbing of the petroleum pollutants on the chemozem sediment is a kind of physical adsorption phenomenon. The adsorption function comes from the hydrophobic and sticky character of the petroleum its self. The velocity of adsorption and desorption is almost equivalent, both concentrations of water in the soil are close to the balance in two hours, thus they achieve homeostasis in three hours. The process of adsorption of the petroleum pollutants responses to Herry isothermal model, with increasing pH, concentration of suspended particulates and temperature, the quantity of adsorption show a descending trend. However, desorption is a contrary course of adsorption in the experiment. Due to various influenced phenomena reflect that the soil in the Daqing oilfield has factors, the quantity of desorption shows an ascending trend. These strong adsorption ability to petroleum pollutants.     

Removal of Lead,Copper, Zinc and Cadmium from Water Using Phosphate Rock

Removal of Pb^2＋, Cu^2＋, Zn^2＋ and Cd^2＋ from aqueous solutions by sorption on a natural phosphate rock （FAP） was investigated. The effects of the contact time and initial metal concentration were examined in the batch method. The percentage sorption of heavy metals from solution ranges generally between 50% and 99%. The amount of sorbed metal ions follows the order Cu〉Pb〉Cd〉Zn. Heavy metal immobilization was attributed to both surface complexation of metal ions on the surface of FAP grains and partial dissolution and precipitation of a heavy metal-containing phosphate. The very low desorption ratio of heavy metals further supports the effectiveness of FAP as an alternative and low-cost material to remove toxic Pb^2＋, Cu^2＋, Zn^2＋ and Cd^2＋ from polluted waters.     

Spectroscopic and macroscopic studies of the adsorption of arsenate and phosphate on polynuclear aluminum organomineral precipitates

Aluminum organic coprecipitates play important roles in the transport of oxyanions in soil environment.A new polynuclear aluminum organomineral precipitate(Al13-oxalate precipitate) was prepared to investigate the adsorption behavior of arsenate and phosphate on noncrystalline aluminum precipitates.Important thermodynamic parameters for adsorption reaction were evaluated using macroscopic adsorption data and equations.The result showed that,the adsorption reaction basically is a diffusion process.FTIR spectroscopic studies have provided evidence for the formation of two different types of complexes in substrate,protonated bidentate and deprotonated bidentate complexes at pH 4 and pH≥6,respectively.The classic competitive adsorption and XPS studies both indicated that phosphate has stronger chemical interaction with substrate than arsenate.The findings of XPS studies revealed that the precipitate substrate can act as Lewis acid when adsorbing oxyanions.     

Mutual effects of fluoride and phosphate on their adsorption and desorption in fluoride-contaminated softs

Phosphate is one of the important nutrients for plant growth. In acidic and highly weathered soils, phosphate is ready to adsorb on Al and Fe oxides and transform into sparsely soluble Fe-P and Al-P solid phases, greatly reducing phosphate bioavailability. Aluminum and iron oxides in soils are important sinks for both phosphate and fluoride. In acidic soils, fluoride adsorption can dramatically facilitate dissolution of Al- and Fe-containing phases, which may influence the distribution and migration of both pollutants and nutrients including phosphate. To date, little information is available on mutual effects of fluoride and phosphate in fluoride-contaminated acidic soils. The objective of this study is to evaluate mutual effects of fluoride and phosphate on their adsorption/desorption in red soil, collected fi＇om Yingtan, Jiangxi Province, China, using a batch equilibrium method. The following results and conclusions were obtained. In heavily fluoride-contaminated soils, the adsorption of both fluoride and phosphate decreases with an increase in solution pH. Phosphate adsorption decreases progressively with increasing concentration of fluoride, suggesting that fluoride competes with phosphate for adsorption sites.     

Removal of Arsenic(V) from Aqueous Solutions by Lanthanum-loaded Zeolite

A new adsorption process for the removal of As（V） ion from aqueous solutions is studied in this paper using lanthanum-loaded zeolite. The removal efficiency of different adsorbents, activated alumina and activated carbon are obtained in the study for comparison. The results show that lanthanum-loaded zeolite is an effective adsorbent for the removal of As（V） from aqueous solutions. Then, the pH effect and regeneration of modified zeolite on the As（V） removing efficiency are also assessed. It functions with a wide range of pH （2-8）. After adsorption, zeolite adsorbed with As（V） ions can be regenerated successfully with 1 M NaOH. Based on the data obtained, an adsorption mechanism and the possible complex structure are tentatively presented. Compare to other adsorbents, easy availability of this adsorbent, excellent adsorption capacity, wide optimum pH range, and regeneration are expected to be utilized in practical operations.     

Bromide removal and recovery with layered double hydroxides as an adsorbent

Grignard regents have been applied extensively in chemical industry, especially in pharmacy. A mass of bromide-containing wastewater was produced after reaction, and ozonation of these organic contaminants can produce bromate and other brominated pollutants. The US Environmental Protection Agency （EPA） has established a maximum contaminant level of 10 μg/L for bromate in finished water. Therefore, it is necessary and significant to remove the DBP （disinfection by-products） precursor - bromide. On the other hand, since the bromine is a valuable element, recovery of it from wastewater is significant. Bromide removal is important to control DBP （disinfection by-products） contaminant and an ion exchange process is one of several treatment processes for this purpose. Layered double hydroxides （LDHs） are useful as adsorbents for bromide removal because of theft ion exchange properties. In this study, the adsorption properties of LDHs for bromide and the method of regeneration of this material were examined. It has been found that the LDHs with Mg/Al molar ratio of 2 represented the highest capacity to remove bromide ion from aqueous solution at pH 6.0. The equilibrium isotherms of uptake of bromide by CLDH were well fitted by the Langmuir equation. Bromide adsorbed on the LDHs was effectively desorbed at 30% Na2CO3 solution and the LDHs were regenerated at the same time. The regenerated LDHs could be reused repeatedly for the bromide removal. Bromide in the exhausted desorption solution was recovered as bromine by oxidation using Cl2.     

非晶态金属-磷酸铝催化正庚醛和苯甲醛羟醛缩合制茉莉醛(英文)

Amorphous aluminophosphate(AlP) and metal-aluminophosphates(MAlPs, where M = 2.5 mol%Cu, Zn, Cr, Fe, Ce, or Zr) were prepared by coprecipitation method. Their surface properties and catalytic activity for the synthesis of jasminaldehyde through the aldol condensation of nheptanal and benzaldehyde were investigated. The nitrogen adsorption-desorption isotherms showed that the microporosity exhibited by the aluminophosphate was changed to a mesoporous and macroporous structure which depended on the metal incorporated, with a concomitant change in the surface area. Temperature-programmed desorption of NHand COrevealed that the materials possessed both acidic and basic sites. The acidic strength of the material was either increased or decreased depending on the nature of the metal. The basicity was increased compared to AlP. All the materials were X-ray amorphous and powder X-ray diffraction studies indicated the absence of metal oxide phases. The Fourier transform infrared analysis confirmed the presence of phosphate groups and also the absence of any M-O moieties in the materials. The selected organic reaction occurred only in the presence of the AlP and MAlPs. The selectivity for the jasminaldehyde product was up to 75% with a yield of 65%. The best conversion of nheptanal with a high selectivity to jasminaldehyde was obtained with FeAlP as the catalyst, and this material was characterized to have less weak acid sites and more basic sites.     

Seasonal variations of adsorption/desorption equilibrium concentrations of P at water-sediment interface in the Meiliang Bay, Taihu Lake, China

Seasonal variations of adsorption/desorption equilibrium were investigated by collecting overlying water and seasonal sediment from the Meiliang Bay, Taihu Lake, China. At the same time, seasonal variations of TP and P fractions＇ concentrations in the initial and end of adsorption experiment were also carried out. In addition, the effects of temperature on the P translocation process were also conducted and discussed. The following conclusions were obtained： The sequence of adsorption/desorption equilibrium concentrations of P at water-sediment interface was spring〈winter〈autumn. In sediment the concentrations of TP decline. Concentration P decreased with temperature.     

Removal of Lead, Copper, Zinc and Cadmium from Water Using Phosphate Rock

Removal of Pb2 ,Cu~(2 ),Zn~(2 )and Cd~(2 )from aqueous solutions by sorption on a natural phosphate rock(FAP)was investigated.The effects of the contact time and initial metal concentration were examined in the batch method.The percentage sorption of heavy metals from solution ranges generally between 50% and 99%.The amount of sorbed metal ions follows the order Cu>Pb>Cd>Zn. Heavy metal immobilization was attributed to both surface complexation of metal ions on the surface of FAP grains and partial dissolution and precipitation of a heavy metal-containing phosphate.The very low desorption ratio of heavy metals further supports the effectiveness of FAP as an alternative and low-cost material to remove toxic Pb~(2 ),Cu~(2 ),Zn~(2 )and Cd~(2 )from polluted waters.     

Microstructure and Photocatalytic Decomposition of Methylene Blue by TiO2-Mounted Halloysite, a Natural Tubular Mineral

On the basis of analysis of structure and properties, halloysite, a natural tubular mineral, was developed for an environmental treatment. TiO2 was mounted into halloysite by using hydrolysis of tetrabutyl titanate at room temperature. The adsorption and photocatalytic performance of halloysite and TiO2-mounted halloysite have been examined in methylene blue aqueous solution in the dark and under ultraviolet ray irradiation, respectively. Their performance of adsorption and photodecomposition was evaluated from the adsorbed and degraded amounts of methylene blue （MB）. Due to the mixture of adsorption and photodecomposition, the concentration of MB, organic pollution, in water decreased rapidly with TiO2-mounted halloysite powder, which is a faster reaction than that with halloysite-only adsorption. This new use of halloysite is leading to many interesting applications in the decomposition and elimination of various pollutants in air and water.     

Dechlorination of trichloroethylene in solution over supported nano zero valent Fe and Cu/Fe bimetal on exfoliated graphite

Degradation of organic halides by reductive dehalogenation promoted by zerovalent metals is a very active research area. The use of nano-sized particles of zero valent iron （ZVI） or bimetallic combinations of ZVI currently attracts the most attention due to their high surface areas and high reactive activity. The introduction of second catalytic metals, such as Pd, Pt, Cu, or Ni, results in an even higher dehalogenation rate. The supported zero-valent iron materials have higher activity and greater flexibility for environmental remediation applications than other forms of ZVI. Nano ZVI supported on micro-scale exfoliated graphite was prepared by using KBH4 as the reducing agent in the H2O/ethanol solution of Fe^2＋ in the laboratory. Then the ethanol solution of Cu^2＋ was added to the fleshly prepared wet supported nano ZVI. The Fe/Cu bimetallic particles supported on the graphite were obtained because of the reduction and deposition of Cu on the Fe surface. The TEM image showed that iron particles were highly dispersed on the surface of graphite. In this study, supported zero valent Cu/Fe bimetallic nanoparticles were used for the dehalogenation of trichloroethylene （TCE） in batch experiments. The dechlorination rate of supported zero valent Fe/Cu bimetallic nanoparticles was greater than the supported nano ZVI. Supported Cu/Fe bimetal with 4 wt% Cu had the fastest dehalogenation rate than that with different content of Cu. When the nana FeO dosage was 5 g/L in the dehalogention system, 8 mg/L of TCE was completely dechlorinated within 4 hours. Increasing or decreasing the FeO dosage, the dechlorination rate could be worse. When the concentration of Fe^2＋ was 0.05 mol/L during the preparation by KBH4 reduction, the nano Cu/Fe particles exhibited the spheral shape with 50-80 nm in size. When the concentration of Fe^2＋ was higher （0.2 mol/L）, the nano particles were the palpus structure and had the poor dehalogenation effect on the TCE.     

Desorption of zinc by kaolin from Suzhou, China

Heavy metals in soils may adversely affect environmental quality. This paper studied the influence of copper concentration, pH, temperature, and the ratio of solid to solution on the desorption of Zn in kaolin from Suzhou, China in a background solution of 0.01M CaC12 by batch extraction experiments. At 0, 5, 50, 100 mg/L Cu concentrations, for each 0.5, increase in pH between about 1.80 and 3.04 percent desorption decreasing by 3.80%, 13.87%, 9.97%, and 7.65%, respectively. The pH 50 （ pH at 50% Zn desorption） was found to follow the sequence of Cu （5mg/L, pH 50=2.60）.     

A Study of Chromium Adsorption on Natural Goethite Biomineralized with Iron Bacteria

Goethite, especially biogenic goethite, has high specific surface area and great capacity for the adsorption of many contaminants including metal ions and organic chelates. Chromium is a redox actively toxic metal ion that exists as either Cr^Ⅲ or Cr^Ⅵ in nature, and as such it is essential to understand its behavior of adsorption on natural goethite mineralized by iron bacteria, as Gallionella and Leptothrix in water body. The adsorption of Cr^3＋ and Cr^Ⅵ on naturally biomineralized goethite is studied in this paper. The results show that both Langmuir and Freundlich adsorption isothermal models are able to accurately describe the adsorption of these two ions. Investigation of SEM/EDS, TEM/EDS indicates that the two ions do not adsorb homogeneously on goethite owing to the different microstructures of goethite, and that the microspherical goethite has a greater adsorption capacity for chromium ions than the helical one. XPS data show that redox reaction of chromium on the surface of biomineralized goethite takes place in the adsorption of both Cr^3＋ and Cr^Ⅵ. The CrvI adsorbed on biogoethite is much easier to transform into CrIII than the oxidization of Cr^Ⅲ on the bio-goethite.     

Adsorption Kinetics of Methylene Blue from Aqueous Solutions onto Palygorskite

The adsorption kinetics of methylene blue from aqueous solutions on purified palygorskite was investigated. The kinetics data related to the adsorption of methylene blue from aqueous solutions are in good agreement with the pseudo-second order equation in ranges of initial concentration of 120-210 mg/L, oscillation speed of 100-200 r/min and temperature of 298-328K. The experimental results show that methylene blue is only adsorbed onto the external surface of purified palygorskite, and the apparent adsorption activation energy is 13.92 kJ/mol. The relatively low apparent adsorption activation energy suggests that the adsorption of methylene blue involves in not only a chemical, but also a physical adsorption process, and it is controlled by the combination of chemical adsorption and liquid-film diffusion.     

Removal of Cu（ Ⅱ） from Wastewater Using Acidified Sewage Sludge Ash

Sewage sludge ash (SSA), the waste generated in sewage sludge incineration, was obtained from Wuhan Sewage Treatment Plant and used as a low-cost sorbent for removing Cu (Ⅱ) from wastewaters. The sorbent was first modified with 5 % sulfuric acid to increase its sorption capacity. The specific surface area, porosity, cation-exchange capacity (CEC) and pHzzc of the sorbent were measured. Batch experiments were made to study the effect of contact time, solution pH value and temperature on sorption. Both Langmuir and Freundlich models well described the Cu (Ⅱ) sorption process,with correlation coefficient (R2 ) values of 0. 993 4 and 0.9899 respectively. And the sorption process follows the Lagergren first order kinetic model. The equilibrium sorption capacity of acidified SSA to Cu(Ⅱ) is estimated to be 7.78 mg/g under optimal conditions.     

Adsorption of Lead (II), Copper (II) on tourmaline from Altai mine in China's Sinkiang

Tourmaline from Altai mine in China's Sinkiang was used to remove lead (II), copper (II) from aqueous solution. The results demonstrate that tourmaline contains Na(Mg,V)3Al6(BO3)3Si6O18(OH)4, NaFe3Al6(BO3)3Si6O18(OH)4. The data show that Tourmaline from Altai mine in China's Sinkiang can be used natural adsorbent for lead (II), copper (II).It is observed that the adsorption data fitted to the Langmuir isotherm. Furthermore, both Pb (II) and Cu (II) absorbed by tourmaline and tourmaline were characterized by X-ray diffraction, Laser Raman Spectrum, Fourier transform infrared spectroscopy, X-ray energy dispersive spectrometer, Transmission electron microscopy and Zeta potential.     

An Experimental Study on the Conductivity Changes in Coal during Methane Adsorption-Desorption and their Influencing Factors

During the processes of methane adsorption and desorption, the internal structure of coal changes, accordingly leading to changes in electrical conductivity. In this paper, using low rank coal seams of the Yan’an Formation in the Dafosi field as the research subject, the relationship between coal resistivity, methane adsorption quantity, and equilibrium pressure is analyzed through proximate analysis, mercury injection tests, low temperature liquid nitrogen adsorption tests, and coal resistivity measurements during methane adsorption and desorption. The results show that during the process of pressure rise and methane adsorption, the conductivity of coal increases, resulting from heat release from methane adsorption, coal matrix swelling and adsorbed water molecules replaced by methane, but the resistivity reduction gradually decreases. The relationship between coal resistivity and methane adsorption quantity and equilibrium pressure can be described by a quadratic function. During the processes of depressurization and desorption, the resistivity of coal rebounds slightly, due to decalescence of methane desorption, coal matrix shrinkage and water-gas displacement, and the relationship coincides with a linear function. Methane adsorption leads to irreversible changes in coal internal structure and enhances the coal conductivity, and resistivity cannot be restored to the initial level even after methane desorption. The resistivity and reduction rate of durain are higher than those of vitrain, with relatively greater homogeneous pore throat structure and fewer charged particles in the double electric layer. In addition, moisture can enhance the conductivity of coal and makes it change more complexly during methane adsorption and desorption.