A NEW MODEL FOR PHYSICAL ADSORPTION ON SOLID SURFACES

The principal assumptions about equivalence and energy distribution of the asdorption sites on solidsurfaces used by Langmuir for deriving the equation of monomolecular adsorption are generalized and anew physical adsorption model is proposed and tested with experimental data published in literature.Themodels of Langmuir,Freundlich,Temkin etc.are only the special cases.Assuming uniform density distributionof adsorption energy,the isotherm equation is given asn=K.1n[1+（bop）1/Mor n=K.1n[1+（boC）1/M]where n is the amount of adsorption per unit weight or area of solid p or C is tbe pressure of gas or the concen-tration of solution respectively.K,bo,M are constants with physical meanings as described in this paper.This equation can be used over wide range to quantitatively represent the five types of physical adsorptionclassified by Brunauer.

Chemisorption and Physical Adsorption Roles in Cadmium Biosorption by Chlamydomonas Reinhardtii

The aim of this study was to investigate the mechanism of cadmium (Cd) adsorbed by microalgae Chlamydomonas reinhardtii (C.reinhardtii). The kinetic and adsorption isotherm of the process could be well described by mathematical models. Chemical modification experiments and Fourier transform infrared spectra indicated that carboxyl and amine groups were the important functional groups for adsorption of Cd. The maximum contribution of physical adsorption in the overall adsorption process was evaluated as 5.5%. These results indicated that chemisorption was the dominating mechanism of Cd biosorption by C.reinhardtii.

Depressing behaviors and mechanism of disodium bis(carboxymethyl) trithiocarbonate on separation of chalcopyrite and molybdenite

This work focuses on the organic depressant,disodium bis(carboxymethyl)trithiocarbonate(DBT),as a selectivedepressant in copper?molybdenum sulfide flotation separation.Micro-flotation,Zeta potential,FTIR and XPS measurements werecarried out to investigate the selective depression mechanism of DBT on chalcopyrite.Zeta potential and FTIR measurementsrevealed that DBT had higher affinity for chalcopyrite than molybdenite and the XPS results of chalcopyrite before and aftertreatment with DBT further proved that DBT adsorbed on chalcopyrite surface.The investigation indicates that the mechanism ofDBT adsorbing on chalcopyrite is mainly physical adsorption.Locked circuit experiments were carried out and the results showedthat DBT could be considered as a cleaner option in commercial Cu?Mo flotation separation circuits.

Fabrication and characterization of Fe_3O_4@SiO_2@TiO_2@Ho nanostructures as a novel and highly efficient photocatalyst for degradation of organic pollution

In this work we synthesize a novel and highly efficient photocatalyst for degradation of methyl orange and rhodamine B. In addition, a new method for synthesis of FeO@SiO@TiO@Ho magnetic core-shell nanoparticles with spherical morphology is proposed. The crystal structures, morphology and chemical properties of the as-synthesized nanoparticles were characterized using Fourier transform infrared spectroscopy（FT-IR）, scanning electron microscopy（SEM）, transmission electron microscopy（TEM）, energy dispersive X-ray（EDS）, X-ray diffraction（XRD）, UV–vis diffuse reflectance spectroscopy（DRS） and vibrating sample magnetometer（VSM） techniques. The photocatalytic activity of FeO@SiO@TiO@Ho was investigated by degradation of methyl orange（MO） as cationic dye and rhodamine B（Rh B） as anionic dye in aqueous solution under UV/vis irradiation. The results indicate that about 92.1% of Rh B and78.4% of MO were degraded after 120 and 150 min, respectively. These degradation results show that FeO@SiO@TiO@Ho nanoparticles are better photocatalyst than Fe3O4@Si O2@TiO 2@Ho for degradation of MO and Rh B. As well as, the catalyst shows high recovery and stability even after several separation cycles.

Experimental Research on Flue Gas Desulfurization by Superfine Titanium Dioxied

The mechanism of all present adopted desulfurization technologies is chemical reaction. A new kind of desulfurization medium - TiO 2 particle having large fraction void and specific surface area which is made from TiO 2 with superfine size sintered at low temperature and processed with surface activation is tested and investigated. The mechanism of desulfurization is mainly physical adsorption instead of traditional chemical reaction. Four samples of such TiO 2 particles were characterized by advanced instruments and tested for adsorption dynamics at the temperature range of 90?℃ to 240?℃ in a fixed bed. The results show that its adsorption ability for SO 2in flue gas is dependent strongly on three factors: quality of TiO 2particles, adsorption temperature and SO 2 concentration in flue gas. Titanium dioxide has well desulfurization character and pretty good prospect in engineering application. Sintered at temperature range from 440?℃ to 540?℃, it has the best adsorption ability. In practical use the best adsorption temperature is around 120?℃.

Removal of aqueous Ni(Ⅱ) with carbonized leaf powder: Kinetics and equilibrium

Nickel is a heavy metal which has the potential threaten to human＇s health and attracts public concern recently. The carbonized leaf powder is expected as suitable adsorbent for Ni（II） removal became of the composition of some beneficial groups. In this work, carbonized leaf powder was evaluated for its adsorption performance towards Ni（II）. According to the results, adsorbent component, dosage, initial solute concentration, solution pH, temperature and contact time can significantly affect the efficiency of Ni（II） removal. Sips model fits the test results best, and the adsorption capacity towards Ni（II） is determined around 37.62 mg/g. The thermodynamic behaviors reveal the endothermic and spontaneous nature of the adsorption. The free adsorption energy （fluctuate around 8 kJ/mol） predicted by D-R model indicates that the adsorption capacity originated from both physical and chemical adsorption. Room temperature （15-25 ℃） is suitable for Ni（II） removal as well as low energy consumption for temperature enhancement. Further conclusions about the mechanism of chemical adsorption are obtained through analysis of the FT-IR test and XRD spectra, which indicates that the adsorption process occurs predominantly between amine, carbonate, phosphate and nickel ions.

Adsorbability of Mycobacterium phlei on hematite surface

The adsorption of microorganisms on the mineral surface is the base of microorganisms that are considered as mineral processing reagents. The principles of the use of a highly hydrophobic and negatively charged bacterium, Mycobacterium phlei, as a flocculating-flotating agent for finely divided hematite were investigated. The flocculating-floating recovery is strongly dependent on the pH and the dosage of the bacterium. Generally the pH should be controlled over the range of 5.5-7, and the dosage should be controlled about 16 mg/L. The infrared spectrometry analysis indicates that the six functional groups of M. phlei, substituted aromatic compound groups, -（CH2） n-groups, -CH2（-CH3） groups, carbonyl groups, aromatic hydrocarbon groups, and carboxyl groups, are on the hematite surface, among which the first five ones contribute physical adsorption and only the carboxyl groups provide chemisorption. Microscopic analysis reveals that the dimensions and tight aggregation degree of the flocs of hematite particles formed by M. phlei are also impacted by the pH and the content of M. phlei in flotation.

A Review of Hydrophobic Nanocellulose and Its Applications

Nanocellulose is of great interest in various areas nowadays as a natural nanostructured biomaterial.However,in many applications,the high hydrophilicity due to a large number of hydroxyl groups is not desired.The hydrophobic modification of nanocellulose can thus increase its application.This work reviewed recent developments of methods for nanocellulose hydrophobic modification,through physical adsorption and chemical grafting.The applications of hydrophobic nanocellulose were also reviewed.

DRIFT SPECTROSCOPIC STUDY OF THE MECHANISM OF SELECTIVE SHEAR-FLOCCULATION OF HEMATITE FROM KAOLINITE

The mechanism of separating hematite from kaolinite by shear-flocculation and the reason responsible for the selectivity of shear-flocculation was studied by using diffuse reflectance infrared Fourier transform (DRIFT) spec-troscopy, which was found to be effective for analysing adsorbed oleate species on the highly absorbing mineral hematite. The spectra suggest that chemisorption of oleate on hematite took place under shear-flocculation condition and that the chemisorbed species was bridged bidentate, corresponding to a peak at 1580 cm-1. Dimers of oleic acid, corresponding to a peak at 1710 cm-1, adsorbed via hydrocarbon chain association with the chemisorbed oleate. The coexistance of physically adsorbed oleic acid dimers and chemisorbed oleate ions made the surface of hematite hydrophobic, which would remain under the shear field. Under the same condition , the surface of kaolinite did not adsorb oleic acid or oleate and remained hydrophilic. The shear field of sufficient magnitude made the hydrophobic ultrafine particles of hematite to aggregate, whereas the hydrophilic ultrafine particles of kaolinite remained suspended in solution. This explains the mechanism of selective shear-flocculation of hematite from kaolinite.

Enzymatic Synthesis of Polycaprolactone:Effect of Immobilization Mechanism of CALB on Polycaprolactone Synthesis

Surface-modified rice husk ash was used as an inorganic support material for immobilization of Candida antarctica lipase B.(3-aminopropyl)trimethoxysilane was used for surface modification.Immobilization of CALB was performed via both physical adsorption and cross-linking.PCL synthesis was carried out by using these immobilized enzymes,free enzyme and Novozyme 435®.Molecular weight distribution of polymer samples was obtained by gel permeation chromatography(GPC)and chain structures of the polymer samples were observed by hydrogen nuclear magnetic resonance(1H-NMR).The highest monomer conversion is generally obtained by using cross-linked enzyme,around 90%.PDI values for all polymer samples were approximately 1.5 which can be considered as acceptable.In general cross-linked enzymes were better than physically adsorbed enzymes in terms of average molecular weights.It can be concluded that PCL can be synthesized with these immobilized enzymes with high molecular weight and low PDI values.

INTERACTION MECHANISM OF ORGANIC MATTER WITH GEL TYPE POLYSTYRENE STRONGLY BASIC ANION EXCHANGE RESIN AND REGENERATION OF THE ORGANISM FOULED RESIN Ⅰ.The interreaction mechanism between strongly basic anion exchange resin and organic matter

It was generally considered that contamination of the gel type polystyrenestrong basic anion exchange resin by organic matter in natural water is the result ofion exchange and Van der waal's adsorption on it. On the basis of laboratory and industrial experiments, this paper confirmed that the interreaction between organicmatter and resin polymer matrix is primarily controled by a Van der waal's adsorption.

Efficient quasi-stationary charge transfer from quantum dots to acceptors physically-adsorbed in the ligand monolayer

Alkanoate-coated CdSe/CdS core/shell quantum dots(QDs)with near-unity photoluminescence(PL)quantum yield and monoexponential PL decay dynamics are applied for studying quasi-stationary charge transfer from photo-excited QDs to quinone derivatives physically-adsorbed within the ligand monolayer of a QD.Though PL quenching efficiency due to electron transfer can be up to>80%,transient PL and transient absorption spectra reveal that the charge transfer rate ranges from single-digit nanoseconds to sub-nanoseconds,which is~3 orders of magnitude slower than that of static charge transfer and〜2 orders of magnitude faster than that of collisional charge transfer.The physically-adsorbed acceptors can slowly(500-1,000 min dependent on the size of the quinone derivatives)desorb from the ligand monolayer after removal of the free acceptors.Contrary to collisional charge transfer,the efficiency of quasi-stationary charge transfer increases as the ligand length increases by providing additional adsorption compartments in the elongated hydrocarbon chain region.Because ligand monolayer commonly exists for a typical colloidal nanocrystal,the quasi-stationary charge transfer uncovered here would likely play an important role when colloidal nanocrystals are involved in photocatalysis,photovoltaic devices,and other applications related to photo-excitation.

Study of the concentrations of Kr and Ar in high-purity nitrogen of JUNO

Purpose In the JUNO,the LS serves as the medium for detecting neutrinos.When purifying the LS using HPN,it is essential to ensure low background levels of radioactive krypton and argon in the HPN Methods Using the low-temperature physical adsorption properties of activated carbon to adsorb and separate radioactive gases such as radon,krypton,and argon from nitrogen in a liquid nitrogen environment.Results Our results indicated that the Kr concentration in the HPN purified by HP activated carbon is 6.84μBq/m,and the Ar concentration is 3.6μBq/m for overground HPN,while the Kr concentration is 31.4μBq/m for underground HPN.The^(85)Kr concentration in the nitrogen purified by coconut shell activated carbon is 0.46μBq/m.Conclusions After adsorption with activated carbon,the content of^(39)Kr and Ar in HPN is lower than the 50μBq/m required by JUNO.This work validates that the^(85)Kr and^(39)Ar concentrations in HPN is fit the JUNO requirement.

Single-Molecular Imaging of Anticoagulation Factor I from Snake Venom by Atomic Force Microscopy

Anticoagulation factor I (ACF I) from the venom of Agki^strodon acutus is a binding protein to activated coagulation factor X (FXa) and possesses marked anticoagulant activity. Single ACF I molecule has been successfully imaged in air by tapping mode atomic force microscopy (AFM) with high resolution using glutaraldehyde as a coupling agent. The physical adsorption and covalent binding of ACF I onto the mica show very different surface topographies. The former exhibits the characteristic strand like structure with much less reproducibility, the latter displays a elliptic granular structure with better reproducibility, which suggests that the stability of ACF I molecules on the mica is enhanced by covalent bonding in the presence of glutaraldehyde. A small scale AFM amplitude mode image clearly shows that the covalently bonded ACF I molecule by glutaraldehyde has olive shape structure with an average size of 7 4 nm×3 6 nm×3 1 nm, which is very similar to the size determined from the crystal structure of ACF I.