Study on the Structures and Properties of Copper Removal Adsorbent Prepared from Sinter-free Pulverized Oyster Shell Materials

A hollow tubular copper removal adsorbent was prepared with oyster shell and cement as the main raw materials. The effects of different formulas, different initial copper concentrations and different pH values of samples on the copper removal efficiency were investigated to determine the optimal conditions for copper removal. The content of copper in the wastewater is determined by Atomic Absorption Spectrophotometer. The microstructure and elemental composition of the samples were characterized by scanning electron microscopy(SEM) and EDS. As a result, the formula with the content of cement to be 8 wt% and the oyster shell powder of 92 wt% is optimal. Under the condition of 30 ℃, when the pH value was 9.0, the Cu2+ adsorption capacity of the sample could reach 0.59 mg/g at 48 h. SEM analysis revealed that there are abundant pores in the sample, which is beneficial for Cu2+ absorption on the adsorbent.     

Researches on the Removal of Pb（Ⅱ） by Hydrothermally Modified Oyster Shells

A novel wastewater purification material was prepared by a hydrothermal method. It was mainly made from oyster shells with the merits of long service time, large surface area, high lead removal efficiency and excellent recyclable properties. The technological conditions were decided respectively based on the lead removal efficiencies. At pH = 5 and 30 ℃, for the wastewater with the initial concentration of Pb2+ to be 5 mg/L, adsorption time 24 h, and 1 mg to 40 mL of mass ratio between adsorbent and Pb2+, the maximum adsorption capacity can reach 0.19 mg/g. The lead removal material prepared by hydrothermal method has excellent recycle performance. The equilibrium adsorption capacity can get to 9.71 mg/g and the average Pb2+ removal rate is as high as 66.39%. After reusing for 60 times, the SEM observation shows that the hydrates of reticular formation is formed after hydrothermal modification, which provides a good attachment position for Pb2+, indicating the physical adsorption is dominant.     

Preliminary Research on Cd^2＋ Removal from Wastewater by Sphaerotilus Natans

Influencing factors, such as the biomass concentration, pH value, temperature and time of adsorption on the removal of Cd^2＋ were investigated when Sphaerotilus natans was used as a biosorbent. The results show that Sphaerotilus natans has a significant effect on the adsorption of Cd^2＋. The process of adsorption will reach the equilibrium in 20 min. Temperature has no significant effect on the adsorption. The removal rate of Cd^2＋. can approach to 90% under the conditions of pH 5.5, the biomass mass concentration O. 6 g/L and the initial mass concentration of cadmium ≤20 mg/L. The maximum specific uptake is 1.9 mmol/g dry biomass . The adsorption was fitted with the Freundlich isotherm adsorption equation when the concentration of Cd^2＋ is in a range of 0--100 mg/L. HCl and EDTA can desorb Cd^2＋ from biomass effectively.     

STUDY ON THE ADSORPTION OF PHENOL BY CHITOSAN FROM AQUEOUS SOLUTION

The effects of pH, initial concentration and temperature on the adsorption of phenol by chitosan were investigated in this paper. The isothermal data was applied to Langmuir linear and the Freundlich linear isotherm equation, and the thermodynamic parameters （AH, AG, AS） were calculated according to the values of binding Langmuir constant, KL. Results indicated that the adsorption between chitosan and phenol was significantly physical in nature, the negative ΔH constant at lower temperature confirmed that more phenol was adsorbed by chitosan at lower temperature. The kinetics of the sorption process of phenol on chitosan was investigated using the pseudo-first order and pseudo-second order kinetics, and results showed that the second order equation model provided the best correlation with the experimental results.     

Fabrication of carboxymethyl chitosan–hemicellulose resin for adsorptive removal of heavy metals from wastewater

Carboxymethyl chitosan–hemicellulose resin(CMCH) was synthesized by thermal cross-linking process and characterized by FTIR, TGA, and SEM. Subsequently, the adsorption properties of CMCH toward Ni(Ⅱ),Cd(Ⅱ), Cu(Ⅱ), Hg(Ⅱ), Mn(Ⅶ) and Cr(Ⅵ) were evaluated. Various factors affecting the uptake behavior such as pH, temperature, contact time and the initial concentration of the metal ions were investigated.The results showed that all adsorption processes fit the pseudo-second-order model and Langmuir isotherm equation. Significantly, the regeneration experiments showed CMCH can be used as a potentially recyclable and effective adsorbent for the removal and recovery of metal ions from wastewater.     

Characterization,Adsorption Properties and Mechanism of Modified Sophora Japonica Leaves to Benzene

The biosorbent has been prepared with the sophora japonica leaves from the agricultural residue as the raw material by the alkaline blanching method, and characterized by BET, SEM, EDS and FTIR analysis methods. The modified sophora japonica leaves possessed more adsorption sites and had more strongly adsorbed chemical groups, which were beneficial to the adsorption. We have further investigated the adsorption performance of the indoor benzene. The secondary regression orthogonal rotation was employed to optimize the preparation process for the optimal processing conditions and regression model. The effects of single factors such as particle size, temperature, and adsorbent dosage of the sophora japonica leaves were analyzed, and adsorption isotherms and adsorption kinetics were studied. The results show that the optimal adsorption conditions were as follows: sodium hydroxide concentration with 0.1 mol/L, water bath time for 70 min, water bath temperature at 60 ℃ and Ymax = 21.38%. The best single factors included particle size with 30 mesh, temperature at 25 oC, 3 g dosage, which are consistent with the Freundlich model, and the adsorption state was more inclined to multilayer active site adsorption with 25 mg/g of saturated adsorption amount; furthermore, the adsorption kinetics followed the quasi-secondary kinetic model(R2 = 0.9731) and the adsorption process was a physicochemical mixed adsorption process controlled by chemisorption; Compared with the adsorption effect, the removal rate to the benzene of modified sophora japonica leaves was significantly superior to other materials at the level 1%, namely, modified sophora japonica leaves diatomite bamboo charcoal activated carbon macroporous resin, and the modified biosorbent had a good cycle regeneration ability.     

Adsorption of Pb~(2+) and Cu~(2+) with Unburned Desulphurization Slag Modified Nickel Slag

Desulphurization slag modified nickel slag adsorbent was prepared by unburned forming technology. The structure of the sample was characterized by BET,XRD,IR,SEM and EDAX. The adsorption performance of Pb~(2+) and Cu~(2+) onto the resultant adsorbent from aqueous solution was studied. Results indicated that the adsorbent possesses a network pore structure formed by the AFt and C–S–H through cross lapping; the adsorbent contains a large number of Si–OH and Al–OH functional groups. The presence of functional groups not only provides abundant adsorption sites for Pb~(2+) and Cu~(2+),but also improves the adsorption performance of Pb~(2+) and Cu~(2+) from waste water through the complexation of heavy metal ions. The result of specific surface area analysis showed that the adsorbent sample possesses mesoporous structure and the BET specific surface area is 27.15 m~2/g. The solution p H values for the adsorption of Pb~(2+) and Cu~(2+) were optimized to be 6 and 5.5,respectively. The adsorption capacities of Pb~(2+) and Cu~(2+) gradually increase,whereas the removal rates of the two metal ions decrease with increasing the initial concentration of simulated solution. The resultant adsorbent gives a higher adsorption capacity for Cu~(2+) than for Pb~(2+) in the single ion solution. However,it shows preferential adsorption of Pb~(2+) rather than that of Cu~(2+). Meanwhile,results of recyclability indicate the remarkable regeneration capacity,re-adsorption ability and reusability performance of the adsorbent sample.     

Synthesis of new superabsorbent poly(NIPAAm/AA/N-allylisatin)nanohydrogel for effective removal of As(Ⅴ) and Cd(Ⅱ) toxic metal ions

The present studies highlight the effective removal of As（V） and Cd（II） from aqueous solutions by superabsorbent poly （NIPAAm/AA/N-allylisatin） nanohydrogel. Batch removal studies were performed as a function of treatment time, initial metal ion concentration, pH, and adsorbent dose. TEM micrographs confirm the particle size distribution in the range between 5 nm and 10 rim. The simple and metal ions adsorbed nanohydrogels were characterized by FF-IR, TGA, and EDX analysis. Finally, the equilibrium removal efficiency of the nanohydrogel was analyzed according to the Langmuir and Freundlich adsorption isotherm models which showed the removal of As（V） and Cd（II） metal ions fitted to Freundlich and Langmuir isotherms, respectively. Removal efficiency order of the metal ions is As（V） 〉 Cd（II）.     

Mesoporous V-doped TiO2 Nanoparticles as New Adsorbents for the Removal of Methylene Blue from Color Textile Wastewater

V-doped TiO2 nanoparticles(NPs) as dye adsorbents are synthesized by the co-precipitation method and characterized by X-ray powder diffraction, transmission electron microscope, N2 adsorption at 77 K, and X-ray photoelectron spectroscopy. The adsorption of methylene blue(MB) on the V-doped TiO2 NPs is studied in detail by varying the calcination temperature and V doping amount of the adsorbent, adsorbate concentration, adsorbent dosage, agitation rate, reaction temperature, and p H. The comparison of dye adsorption on V-doped TiO2 and parent TiO2 demonstrates that the adsorptive activity of TiO2 can be improved by V doping. The enhanced adsorptive performance can be attributed to the tremendous changes in texture, structure, and surface morphology of adsorbent. The adsorption kinetic analysis shows that the adsorption follows the pseudo-second order kinetics. The apparent activation energy for adsorption is calculated by Arrhenius formula to be 37.6 k J·mol-1, indicating that the adsorption is controlled by both of the diffusion and interfacial adsorption steps. The adsorption data are analyzed using Langmuir and Freundlich isotherms and the results indicate that the Langmuir model provides better correlation of the experimental data. The results conclusively show that the adsorption of MB is a spontaneous behavior and endothermic reaction with the ΔH value of 17.60 k J·mol-1.     

Carbon Dioxide/Methane Separation by Adsorption on Sepiolite

In this work,the use of sepiolite for the removal of carbon dioxide from a carbon diox- ide/methane mixture by a pressure swing adsorption(PSA)process has been researched.Adsorption equilibrium and kinetics have been measured in a fixed-bed,and the adsorption equilibrium parameters of carbon dioxide and methane on sepiolite have been obtained.A model based on the LDF approxima- tion has been employed to simulate the fixed-bed kinetics,using the Langmuir equation to describe the adsorption equilibrium isotherm.The functioning of a PSA cycle for separating carbon dioxide/methane mixtures using sepiolite as adsorbent has also been studied.The experimental results were compared with the ones predicted by the model adapted to a PSA system.Methane with purity higher than 97% can be obtained from feeds containing carbon dioxide with concentrations ranging from 34% to 56% with the proposed PSA cycle.These results suggest that sepiolite is an adsorbent with good properties for its employment in a PSA cycle for carbon dioxide removal from landfill gases.     

Mechanism and kinetics of 2-chlorophenol decomposition using coupled ultrasound and electrocatalysis

A coupled ultrasound/electrocatalysis(US/EC) process was used to enhance the decomposition effi-ciency of organics.The synergetic kinetics and the mechanism of 2-chlorophenol(2-CP) decomposi-tion with coupled US/EC were studied.It was found that in a US/EC process 2-CP is attacked by active radicals(such as hydroxyl radicals) to form 2-chloro-p-benzoquinone,and the latter is oxidized to simple organic acids when the ring is opened.The enhancement factor expressed by the apparent rate constant of 2-CP decomposition with coupled US/EC is 1.324 at a current density of 20 mA·cm-2,an ultrasonic frequency of 20 kHz,an ultrasonic intensity of 0.27 W·cm-2,and a 2-CP initial concentration of 200 mg·L-1,which means that a synergetic effect exists.A model derived from Langmuir adsorption theory of solid surface and reaction kinetics equations can describe exactly the decomposition of 2-CP with coupled US/EC.The numerical values are in good agreement with the experimental data.The model parameters are associated with reaction conditions.     

Application of Modified Nickel Slag Adsorbent on the Removal of Pb~(2+) and Cu~(2+) from Aqueous Solution

Al(OH)_3 modified nickel slag adsorbent was prepared by sintering technology. The structure of the sample was characterized by BET, XRD, IR, SEM and EDAX. The sample's adsorption performance of Pb~(2+) and Cu~(2+) from aqueous solution was studied. Results indicated that the adsorbent is a loose and porous mesoporous material. Its surface had mass aluminosilicate, high-activity γ-Al_2O_3 and its p H ranges from 4 to 12 that all have negative charges. The BET surface of the adsorbent is 23.90 m~2/g. Furthermore, its surface contains rich oxygenic functional groups, which could not only provide abundant adsorption sites for Pb~(2+) and Cu~(2+), but also improve the adsorption performance of Pb~(2+) and Cu~(2+) from waste water through the complexation of heavy metal ions. The best p H values selected in the adsorption of Pb~(2+) and Cu~(2+) are 6 and 5, respectively. With the increase of the initial concentration of simulated solution, the adsorption capacities of Pb~(2+) and Cu~(2+) gradually increased but the removal rates showed a downward trend. The competitive adsorption results of Pb~(2+) and Cu~(2+) showed that Pb~(2+) has better preferential adsorption than Cu~(2+).     

Effects of Experimental Conditions and Kinetics of Photodegradation of Methylene Blue over TiO2

The authors investigated the catalytic activity of TiO2 for methylene blue（MB） degradation under solar light.The reaction parameters such as reaction time,TiO2 content,temperature,pH,MB concentration and light irradiation were in attention.Then,the experimental data was analyzed to investigate the adsorption order and adsorption model.The results indicate that the optimum conditions for the removal of MB are a TiO2 content of 0.5 g/L,0.50 mg/L MB solution,a temperature of 30 ℃ and reaction time of 60 min.It was found that the amount of MB removal was decreased when the pH and temperature increased.This suggests that the removal process is exothermic.However,the solar light irradiation plays a vital role in enhancing the removal amount of MB.In the dark reaction,the ability of TiO2 to remove MB was increased when the pH increased.The kinetics studies confirm that the adsorption of MB is the Pseudo-second-order.And the adsorption model was fitted with the Freundlich isotherm.     

Removal of Cd(Ⅱ) from Aqueous Solutions by Natural Freshwater Surface Coatings

Natural freshwater surface coatings(biofilms and associated minerals), which were developed in the Nanhu Lake, Changchun, P. R. China, were used as an efficient biosorbent for the removal of Cd(Ⅱ) from aqueous solutions. The batch experiments were carried out to determine the adsorption properties of Cd(Ⅱ) onto the natural surface coatings. The classical Langmuir adsorption isotherm was applied to estimating the equilibrium coefficients of Cd(Ⅱ) adsorbed on the surface coatings. The results show that the maximum adsorption capacity of the surface coatings is 434.78 μmol Cd/m2(being equal to 0.17 mmol Cd/g of surface coatings or 10.38 mmol Cd/g Fe) and the Cd(Ⅱ) removal from solution media by the natural surface coatings was shown to be strongly affected by solution pH and ion strength. The resulted information also indicates that the maximum Cd removal efficiency(CRE) was determined to be approximately 90% at initial Cd mass concentration of 0.1 mg/L(the concentration limit of Cd (Ⅱ) in wastewaters for discharge in aquatic media in Chinese legislation), and the kinetic adsorption of Cd(Ⅱ) onto the surface coatings is fast with around 70% of the total adsorption-taking place in 150 min in solution under the controlled laboratory conditions (mineral salts solution with defined speciation, ionic strength 0.05 mol/L, and 25 ℃). With the advantage of high Cd adsorption capacity, the natural surface coatings appear to be a potentially effective biosorbent for the removal and recovery of Cd (Ⅱ) from polluted water.     

Removal of Cd（ Ⅱ ） from Aqueous Solutions by Natural Freshwater Surface Coatings

Natural freshwater surface coatings (biofilms and associated minerals), which were developed in the Nanhu Lake, Changchun, P. R. China, were used as an efficient biosorbent for the removal of Cd(Ⅱ) from aqueous solutions. The batch experiments were carried out to determine the adsorption properties of Cd(Ⅱ) onto the natural surface coatings. The classical Langmuir adsorption isotherm was applied to estimating the equilibrium coefficients of Cd(Ⅱ) adsorbed on the surface coatings. The results show that the maximum adsorption capacity of the surface coatings is 434. 78μmol Cd/m^2 (being equal to 0. 17mmol Cd/g of surface coatings or 10. 38mmol Cd/g Fe) and the Cd(Ⅱ) remnoval from solution media by the natural surface coatings was shown to be strongly affected by solution pH and ion strength. The resulted information also indicates that the maximum Cd removal efficiency(CRE) was determined to be approximately 90% at initial Cd mass concentration of 0. 1mg/L (the concentration limit of Cd (Ⅱ) in wastewaters for discharge in aquatic media in Chinese legislation), and the kinetic adsorption of Cd (Ⅱ) onto the surface coatings is fast with around 70% of the total adsorption-taking place in 150min in solution under the controlied laboratory conditions (mineral salts solution with defined speciation, ionic strength 0. 05mol/L, and 25℃). With the advantage of high Cd adsorption capacity, the natural surface coatings appear to be a potentially effective biosorbent for the removal and recovery of Cd(Ⅱ) from polluted water.     

PREPARATION OF SURFACE ION-IMPRINTED ATTAPULGITE-SUPPORTED POLYMER AND ITS ADSORPTION BEHAVIORS OF Sr（II）

The surface ion-imprinting concept and chitosan incorporated sol-gel process were applied to the preparation of a new attapulgite-supported organic-inorganic hybrid polymer for selective separation of Sr（II） from aqueous solution. The prepared polymer was characterized with SEM, IR and XRD. The results showed that as a sorbent, it had good configuration and binding sites. Its adsorption behaviors for Sr（II） was investigated by FAAS and ICP-AES. The effects on adsorption capacities, including pH, quiescent time, and adsorbent amount were discussed, and the adsorption isothermal curve was obtained. Then the Kd a parameter estimating relative adsorbability, was conducted to study the selectivity towards Sr（II） of the prepared polymer. Under the optimum conditions, the ion-imprinted polymer offered a fast kinetics for the adsorption of Sr（II） and the maximum capacity was 12.9mg/g. The Kd and K parameters estimating relative adsorbability towards target ion, suggested that selective recognition of the ion-imprinted polymer towards Sr（II） was much higher than that of the non-imprinted polymer and attapulgite. Furthermore, the ion-imprinted polymer is of great regeneration capacity. The prepared functional polymer was shown to be promising for selective preseparation and enrichment of trace Sr（II） in environmental samples.     

A new fast swelling poly[DAPB-co-DMAAm-co-AASS] superabsorbent hydrogel for removal of anionic dyes from water

The objective of this research is to utilize a new poly[N,N-diallyl pyrrolidinium bromide-co-N,Ndimethyl acrylamide-co-acrylic acid sodium salt]superabsorbent hydrogel（SAH）for the removal of two anionic dyes,e.g.,Reactive Red 5B（RR5B）and Reactive Orange M2R（ROM2R）,from water.The SAH was characterized by swelling in water,FTIR,TGA and SEM.The SAH DDA6showed good swelling property and thermal stability.We have also investigated the parameters affecting dye adsorption such as pH,adsorbent dose,adsorption rate and initial dye concentration.The experimental data were also analyzed by applying the well known Langmuir and Freundlich isotherm models.     

Kinetic simulation of oxidative coupling of methane over perovskite catalyst by genetic algorithm： Mechanistic aspects

The reaction kinetics of oxidative coupling of methane catalyzed by perovskite was studied in a fixed bed flow reactor. At atmospheric pressure, the reactions were carried out at 725, 750 and 775 ℃, inlet methane to oxygen ratios of 2 to 4.5 and gas hourly space velocity (GHSV) of 100 min-1. Correlation of the kinetic data has been performed with the proposed mechanisms. The selected equations have been regressed with experimental data accompanied by genetic algorithm (GA) in order to obtain optimized parameters. After investigation the Langmuir-Hinshelwood mechanism was selected as the best mechanism, and Arrhenius and adsorption parameters of this model were obtained by linear regression. In this research the Marquardt algorithm was also used and its results were compared with those of genetic algorithm. It should be noted that the Marquardt algorithm is sensitive to the selection of initial values and there is possibility to trap in a local minimum.     

Preparation, Properties and Mechanism of Inhomogeneous Calcium Alginate Ion Cross-linking Gel Microspheres

Inhomogeneous calcium alginate ion cross-linking gel microspheres,a novel ion absorbent,were prepared by dropping a sodium alginate solution to a calcium chloride solutioin via an electronic droplet generator.Calcium alginate microspheres have uniform particle sizes.a smooth surface and a microporous structure.The electrode probe reveals the inhomogeneous distribution of calcium ions with the highest concentration on the surface,and the lowest concentration in the cores of the spheres.As a novel ion adsorbent,calcium alginate gel microspheres have a lower limiting adsorption mass concentration,a higher enrichment capacity and a higher adsorption capacity for Pb^2 than usual ion exchange resins.The highest percentage of the adsorption is 99.79%.The limiting adsorption mass concentration is 0.0426mg/L.The adsorption capacity for Pb^2 is 644mg/g,Calcium alginate gel microspheres have a much faster ion exchange velocity than D418 chelating resin and D113 polyacrylate resin.The moving boundary model was employed to interpret the ion exchange kinetics process,which indicates that the ion exchange process is controlled by intraparticle diffusion of adsorbable ions.So the formation of inhomogeneous gel microspheres reduces the diffusion distance of adsorbable ions within the spheres and enhances the ion exchange velocity.Alginate has a higher selectivity for pb^2 than for Ca^2 and the selectivity coefficient KCa^Pb is 316. As an ion cross-linking gel,calcium alginate inhomogeneous microspheres can effectively adsorb heavy metal Pb^2 at a higher selectivity and a higher adsorption velocity.It is a novel and good ion adsorbent.     

Aluminum Lon Removal from Monoaluminum Ovotransferrin by Pyrophosphate

The rates at which aluminum was removed from the N- and C-terminal monoaluminum ovotransferrins by pyrophosphate were evaluated by UV difference spectra in 0.01 mol/L Hepes, pH=7.4 and at 37℃. Pesudo first-order rate constants as a function of pyrophosphate concentration were measured. The results indicate that the pathways of aluminum removal are different. For the N-terminal binding site, aluminum removal follows simple saturation kinetics, while the removal of aluminum from the C-terminal binding site reverts to the combination of saturation and first-order kinetics. The saturation component is consistent with a rate-limiting conformational change in the protein as has been reported. We propose that the first-order kinetics mechanism is attributed to a pre-equilibrium process. The rate constants of saturation kinetics are accelerated from both terminals with the addition of 0.1 mol/L chloride to the monoaluminum ovotransferrin solutions, whereas the rates of the first-order kinetics are decreased for the C-terminal binding site. The effect of chloride ionic strength causes a continuing increase on kobs for the N- and C-terminal binding sites. Moreover, the kinetics behavior of the N-terminal is more easily affected by chloride than that of the C-terminal. In the experiment presumably the N-terminal site is apparently kinetically more labile than the C-terminal site.