Adsorption characteristics of Pb(Ⅱ)ions on sulfidized hemimorphite surface under ammonium sulfate system

In this work,the effect of ammonium sulfate on the adsorption characteristics of low-concentration Pb(Ⅱ)ions on the sulfidized hemimorphite surface was comprehensively investigated.The results showed that ammonium sulfate could increase the maximum recovery of hemimorphite from 69.42%to 88.24%under a low concentration of Pb(Ⅱ)ions.On the hemimorphite surface pretreated with ammonium sulfate,the adsorption of Pb(Ⅱ)ions was enhanced and the main species of Pb adsorbed was changed from Pb―O/OH to PbS.This was due to the larger amount of ZnS providing more effective adsorption sites for Pb components to generate Pb S.Meanwhile,the intensity of ZnS decreased with the formation of PbS,demonstrating that ZnS was covered by PbS which formed later on the mineral surface.It was beneficial for the adsorption of butyl xanthate on the hemimorphite surface to form more hydrophobic substances.As a result,ammonium sulfate played a crucial role in realizing the efficient recovery of hemimorphite.

STUDY ON THE PROPERTIES OF DIFFERENT ACTIVATED CARBON FIBERS AND THEIR ADSORPTION CHARACTERISTICS FOR FORMALDEHYDE

Porous structure and surface chemistry of activated carbon fibers obtained by differ-ent precursors and activation methods were investigated. Adsorption isotherms werecharacterized by nitrogen adsorption at 77K over a relative pressure range from 10 6to 1. The regularization method according to Density Functional Theory (DFT) wasemployed to calculate the pore size distribution in the samples. Their specific surfaceareas were calculated by BET method, micropore volume and microporous specificsurface area calculated by t-plot method and MPD by Horvath-Kawazoe equation. Mi-cropore volume of rayon-based ACF was higher than that of other samples. The staticand dynamic adsorption capacity for formaldehyde on different ACFs was determined.The results show that steam activated Rayon-based A CFs had higher adsorption capac-ity than that of steam and KOH activated PAN-A CFs. Breakthrough curves illustratedthat Rayon-ACFs had longer breakthrough time, thus they possessed higher adsorp-tion capacity for formaldehyde than that of PAN-ACFs. The entire sample had smalladsorption capacity and short breakthrough time for water. Rayon-A CFs had exccl-lent adsorption selectivity for formaldehyde than PAN-ACFs. And the samples withhigh surface areas had relatively high adsorption capacity for formaldehyde. Elementaicontent of different A CFs were performed. Rayon-based A CFs contained more oxygenthan PAN-ACFs, which may be attributed to their excellent adsorption capacity forformaldehyde.

Adsorption,in vitro digestion and human gut microbiota regulation characteristics of three Poria cocos polysaccharides

Poria cocos(PC)is a famous traditional Chinese medicine(TCM)and a widely used healthcare ingredient,which has antiobesity,enhancing immunity and improving sleep effects.Traditionally,only water-soluble poria polysaccharide(WSP)is extracted and applied for clinical application,while insoluble polysaccharide(alkali-soluble poria polysaccharide,ASP)is discarded as herb residue.However,the whole PC has also been historically utilized as functional herbal food.Considering the beneficial role of dietary fiber and the traditional use of PC,ASP may also contribute substantially to the therapy function of PC.Compared to WSP,little attention has been paid to ASP and ASP modified product carboxymethyl poria polysaccharide(CMP)which has been used as an antitumor adjuvant drug.In this study,the oil,cholesterol,metal ions and polyphenols adsorption ability,in vitro simulated digestive and the gut microbiota fermentation characteristics of WSP,ASP and CMP were studied to evaluate the functional values of three P.cocos polysaccharides(PCPs).The results showed that all three PCPs had good adsorption capacity on cholesterol,polyphenols and metal ions(Cd^(2+)/Zn^(2+)/Mg^(2+)),among which ASP showed the highest capacity than WSP and CMP.The adsorption capacity of all three PCPs on heavy metal ions(Cd^(2+)/Zn^(2+))was stronger than that of non-heavy metal ions(Mg^(2+));The in vitro digestibility of all three PCPs was very low,but WSP was slightly higher than ASP and CMP;Moreover,the indigestible residue of all three PCPs could improve the richness and diversity of gut microbiota,among which ASP had the greatest influence.In general,ASP and CMP could significantly promote the proliferation of some probiotics and inhibit the growth of some harmful bacteria.The gut microbiota diversity of CMP was reduced,but the richness of probiotics,especially Parabacteroides distasonis was significantly enhanced compared with the ASP group,and the growth of harmful bacteria Klebsiella pneumoniae was inhibited after CMP treatment.The short-chain fatty acids(SCFAs)analysis results showed that all three PCPs could significantly promote the production of acetic acid,propionic acid and the total acid content compared with blank control group,and SCFAs producing activity was positively correlated with the proliferative capacity of probiotics.Taken together,the good adsorption characteristics and gut microbiota regulatory activity of ASP may lay foundation for its lipid-lowering and immune-improving function.Additionally,the probiotic effect of CMP and ASP indicated that except for only use the water extract of PC in clinic,CMP and ASP also can be used in healthcare to take full advantage of this valuable medicine.

Comparative experimental study on porosity, mechanical and CO_(2) adsorption characteristics of coal and shale

To compare the pore structure, mechanical and CO_(2) adsorption properties of coal and shale, a series of experiments were carried out using nuclear magnetic resonance (NMR), uniaxial compression, Brazilian splitting, and high-pressure CO_(2) adsorption. The results show that the total porosity of coal is 7.51 times that of shale, and shale is dominated by adsorption pores, while adsorption pores and seepage pores in coal are equally important. Moreover, it is found that the micropores in shale are more advantageous, while meso-macropore in coal are more significant. The adsorption pore surface of coal is rougher than that of shale, and the seepage pore structure of shale is more complex. The uniaxial compressive strength, elastic modulus and absorption energy of shale are 2.01 times, 2.85 times, and 1.27 times that of coal, respectively, indicating that shale has higher compressive capacity and resistance to elastic deformation than coal. The average tensile strength, Brazilian splitting modulus, absorbed energy and brittleness index of shale are 7.92 times, 6.68 times, 10.78 times, and 4.37 times that of coal, respectively, indicating that shale has higher tensile strength and brittleness, but lower ductility, compared with coal. The performed analyses show that under the same conditions, the CO_(2) adsorption capacity of coal is greater than that of shale. The present article can provide a theoretical basis to implement CO_(2)-enhanced coalbed methane (CBM)/shale gas extraction.

Adsorption characteristics of droplets applied on non-smooth leaf surface of typical crops

To further understand the adsorption characteristics of different-type leaf surfaces adsorbing pesticide droplets and reveal the adsorption mechanism of pesticide droplets on non-smooth leaves,non-smooth leaves of 12 kinds of typical target plants were investigated in this study.The parameters of surface morphological characteristics were measured,which include contact angle between leaves and water droplets,water holding capacity surface tension,polar component,dispersion component and other quantitative range of indicators and variation by modern means.The relationships between the indicators and water holding capacity were investigated respectively.The experimental results show that the number of trichomes,epidermal wax,morphology and distribution characteristics have influences on adsorption characteristics of the water droplets.There is a negative correlation between free energy of obverse side and the water holding capacity(R=−0.447)while the free energy of reverse side and the water holding capacity show a positive correlation(R=0.212).Also,there is a negative correlation between polar component of obverse side and the water holding capacity(R=−0.357)while the polar component of reverse side and the water holding capacity in plant leaves show a positive correlation(R=0.149).The research can provide a scientific theory for reasonable spraying of pesticide in the agricultural production,and can be a reference for the development of pesticide adjuvants and bionic pesticides.

Characteristics of isothermal adsorption and desorption of aluminum ion to/from humic acids

The adsorption and desorption characteristics of Al^3＋ to/from humic acids at different pH, ionic strength, and temperature were studied by the C-25 glucosan-gel chromatography method. The results showed that the maximum adsorption amount （Qmax） and adsorption constant （k） increased, whereas, the absolute value of standard thermodynamic molar free energy change （ΔGm^0） decreased with the increase of pH at constant ionic strength and temperature. With ionic strength increasing from 0 to 0.15 mol/L, Qmax, and k increased and the absolute value of ΔGm^0 decreased at constant pH and temperature. High temperature was unfavorable for the adsorption reaction, as indicated by the dramatic decrease of Qmax and the absolute value of ΔGm^0 with an increase in temperature. The standard thermodynamic molar free energy change （ΔGm^0） and the standard thermodynamic enthalpy change （ΔHm^0） of the adsorption reaction were both negative, suggesting that adsorption reaction was spontaneous and exothermic. The desorption rate of HA-Al^3＋ complex accelerated with the decrease of pH, and a significant linear relationship could be obtained between pH and the desorption rates of Al^3＋ from humic acids. These results demonstrated that the Al^3＋ adsorption reaction was a ＂biphase＂ reaction, and adsorption occurred at both the interior and exterior adsorption sites of humic acids.

Adsorption Regularity and Characteristics of sp^3-Hybridized Gas Molecules on Anatase TiO_2(101) Surface

We report the anatase titanium dioxide （101） surface adsorption of sp3-hybridized gas molecules, including NH3, 1-12 0 and CH4, using first-principles plane-wave ultrasoft pseudopotential based on the density functional theory. The results show that it is much easier for a surface with oxygen vacancies to adsorb gas molecules than it is for a surface without oxygen vacancies. The main factor affecting adsorption stability and energy is the polarizability of molecules, and adsorption is induced by surface oxygen vacancies of the negatively charged center. The analyses of state densities and charge population show that charge transfer occurs at the molecule surface upon adsorption and that the number of transferred charge reduces in the order of N, 0 and C. Moreover, the adsorption method is chemical adsorption, and adsorption stability decreases in the order of NH3, tt2 0 and CH4. Analyses of absorption and reflectance spectra reveal that after absorbed CH4 and H2 O, compared with the surface with oxygen vacancy, the optical properties of materials surface, including its absorption coefficients and reflectivity index, have slight changes, however, absorption coefficient and reflectivity would greatly increase after NH3 adsorption. These findings illustrate that anatase titanium dioxide （101） surface is extremely sensitive to NH3.

Adsorption of Ag on M-doped graphene:First principle calculations

Graphene is an ideal reinforcing phase for a high-performance composite filler,which is of great theoretical and practical significance for improving the wettability and reliability of the filler.However,the poor adsorption characteristics between graphene and the silver base filler significantly affect the application of graphene filler in the brazing field.It is a great challenge to improve the adsorption characteristics between a graphene and silver base filler.To solve this issue,the adsorption characteristic between graphene and silver was studied with first principle calculation.The effects of Ga,Mo,and W on the adsorption properties of graphene were explored.There are three possible adsorbed sites,the hollow site(H),the bridge site(B),and the top site(T).Based on this research,the top site is the most preferentially adsorbed site for Ag atoms,and there is a strong interaction between graphene and Ag atoms.Metal element doping enhances local hybridization between C or metal atoms and Ag.Furthermore,compared with other doped structures(Ga and Mo),W atom doping is the most stable adsorption structure and can also improve effective adsorption characteristic performance between graphene and Ag.

Phosphorus removal by adsorbent based on poly-aluminum chloride sludge

Phosphorus adsorption tests were carried out using poly-aluminum chloride sludge(PACS),which was collected from a water treatment plant in Nanjing.The amount of phosphorus adsorbed by PACS increased quickly within the first hour and reached equilibrium after about 48 h.The adsorption behavior of PACS for phosphorus is consistent with the Langmuir adsorption isotherm equation(R2>0.99)and parallel first-order kinetic equation(R2>0.98).With the increase of the PACS concentration,the adsorption capacity of PACS for phosphorus decreased,and the removal rate increased.The results of batch tests showed that the adsorption capacities of PACS for phosphorus ranged from 1.64 to 1.13 mg/g when the pH value varied from 4 to 10.However,the adsorption capacity of PACS was not evidently influenced by temperature.In comparison with the ion exchange resin,the adsorption capacity of PACS was barely inhibited by competitive ions,such as SO2
4,NO
3,and Cl
.The PACS surface after adsorption became smooth,and the vibration peaks of AleO and AleOH shifted.Both HCl and NaOH have a strong desorption effect on PACS after adsorption saturation,and with higher concentrations of HCl and NaOH,the desorption effect was stronger.Results of column adsorption experiments showed that with lower phosphorus and hydraulic loads,the adsorption column took longer to reach saturation.This indicated that PACS could be used as an efficient material for removal of phosphorus from water.This study provides a new treatment method with PACS.

Adsorption of rare earth elements on organic matter in coal

The occurrence modes of rare earth elements(lanthanide and yttrium,abbreviated as REY) in coal are impo rtant both for coal geochemistry studies and the application potential of REY as a by-product of coalbased resources.In this study,the adsorption behaviors of REY on organic matter in coal were investigated by leaching tests using REY solution and ultra-low ash coal samples.On this basis,the adsorption mechanism of REY on organic matter in coal was also studied by molecular simulation calculations.The leaching tests show that the organic matter in coal has a relatively strong adsorption capacity for REY,and that the average adsorption rate or the net adsorption amount of heavy rare earth elements(HREY:Gd,Tb,Y,Dy,Ho,Er,Tm,Yb and Lu) is always higher than that of the light rare earth elements(LREY:La,Ce,Pr,Nd,Sm and Eu).A molecular model of humic acid(HA) was constructed and the adsorption amount between REY and HA was calculated.The results show that the theoretical adsorption rate of HREY(84.88%) is higher than that of the LREY(84.00%).The analysis of the adsorption distances between REY atoms and various functional groups on HA molecules shows that the minimum adsorption distance of LREY is 0.372 nm on average,which is larger than that of HREY(0.368 nm),indicating that the adsorption capacity of the latter is stronger.In addition,a coal molecule(C_(18)H_(22)O) was also constructed to investigate the adsorption characteristics of various REY atoms on the molecule.As a result,it is found that the average binding ene rgy and bond length between the hydroxyl functional group and LREY atoms are 0.12469 Ha(Hartree,the unit of energy in the atomic unit system) and 0.1407 nm,respectively,while for HREY,0.12883 Ha and 0.1121 nm,respectively.This confirms that HREY is more stable than LREY in binding on organic matter in coal.To conclude,both leaching tests and molecular simulation calculations reveal that REY has a strong adsorption affinity for organic matter in coal,and in particular,HREY shows a stronger organic adsorption preference in coal than LREY,which is probably due to stronger chemical bonding between the former and the functional groups on the coal molecule.

Coagulation efficiency and flocs characteristics of recycling sludge during treatment of low temperature and micro-polluted water

Drinking water treatment sludge,characterized as accumulated suspended solids and organic and inorganic matter,is produced in large quantities during the coagulation process.The proper disposal,regeneration or reuse of sludge is,therefore,a significant environmental issue.Reused sludge at low temperatures is an alternative method to enhance traditional coagulation efficiency.In the present study,the recycling mass of mixed sludge and properties of raw water （such as pH and turbidity） were systematically investigated to optimize coagulation efficiency.We determined that the appropriate dosage of mixed sludge was 60 mL/L,effective initial turbidity ranges were below 45.0 NTU,and optimal pH for DOMs and turbidity removal was 6.5-7.0 and 8.0,respectively.Furthermore,by comparing the flocs characteristics with and without recycling sludge,we found that floc structures with sludge were more irregular with average size growth to 64.7 μm from 48.1 μm.Recycling sludge was a feasible and successful method for enhancing pollutants removal,and the more irregular flocs structure after recycling might be caused by breakage of reused flocs and incorporation of powdered activated carbon into larger flocs structure.Applied during the coagulation process,recycling sludge could be significant for the treatment of low temperature and micro-polluted source water.

Adsorption ability of rare earth elements on clay minerals and its practical performance

The adsorption behaviors of rare earth elements on clay minerals would have great influence on the mineralization process and the leaching process of the ion-adsorption type rare earths ore.In this work,the adsorption thermodynamics of REEs on kaolin were investigated thoroughly and systematically.The experimental results showed that the adsorption characteristics of La,Nd,Y on kaolin did fit well with the Langmuir isotherm model and their saturated adsorption capacities were 1.731,1.587 and 0.971 mg/g,respectively.The free energy change（ΔG）values were –16.91 kJ/mol（La）,–16.05 kJ/mol（Nd）and –15.58 kJ/mol（Y）,respectively.The negative values of ΔG demonstrated that the adsorption of rare earth on kaolin was a spontaneously physisorption process.The deposit characteristic of the volcanic ion-adsorption type rare earths ore and the behavior of the rare earth in the column leaching process were also developed here.With the increase of the ore body depth,the distribution of the LREEs decreased and the HREEs increased.And the slight differences in the adsorption ability of REEs on clay minerals led to the fractionation effect in the column leaching process.These developed more evidences and better understanding of metallogenic regularity,and provided a theoretical basis and scientific approach to separation of the HREEs and LREEs in the leaching process.

A STUDY ABOUT SOIL WATER CHARACTERISTIC,CONDUCTIVITY OF WATER AND EQUILIBRIUM ADSORPTION OF CUPRIC ION IN SOIL——A UTILITY EQUIPMENT USED IN SOIL SCIENCE AND ITS ILLUSTRATION OF USE

A utility equipment used in soil science is designed and installed.The equipment can be used in research pro- grams of soil water and solute transport.Pressure in pressure chamber of the equipment in which a tested soil sam- ple is laid can be adjusted exactly so that we can determine the water content of soil sample.With the equipment we can not only study the problems related water movement in soil but also measure some solute,such as cadmi- um,plumbum and so on,adsorption on surface of soil in saturated and unsaturated state.As an illustration of the use of the equipment,we give the isothermal of cupric ion adsorption in soil.This equipment can be used in the re- search work and application of soil science.