Mesoporous hollow silicon spheres modified with manganese ion sieve: Preparation and its application for adsorption of lithium and rubidium ions

In this work, mesoporous hollow silicon spheres modified with 3‐aminopropyl‐ triethoxysilane (APTES) of loaded hydrogen manganese oxide lithium ion sieve (APTES/HMO‐ HS) was prepared. The structure and morphology of as‐prepared APTES/HMO‐HS were characterized by Fourier transform infrared spectroscopy, scanning electron microscopy, X‐ray photoelectron spectroscopy, transmission electron microscopy and nitrogen adsorption‐desorption measurements. The Brunner‐Emmet‐Teller (BET) surface areas, pore diameters and pore volumes of APTES/HMO‐HS decreased gradually, while the Li:Mn:Si molar ratios range from 1:1:50 to 1:1:10. The obtained hierarchical porous APTES/50HMO‐HS has a high specific surface area (557.1694 m² g^‐1). The lithium and rubidium ions solutions were used to measure the adsorption performance of the APTES/HMO‐HS adsorbent. The pseudo‐first‐order and pseudo‐second‐order kinetics, Langmuir and Freundlich isotherms of APTES/HMO‐HS were investigated; suggesting that the adsorption kinetics can be described by the pseudo‐second‐order kinetic model and the adsorption isotherms well fits the Langmuir isotherm equation. The obtained results show that the prepared APTES/HMO‐HS exhibits excellent abilities to simultaneously and selectively recover Li⁺ and Rb⁺ (11.22 mg·g^‐1 and 8.31 mg·g^‐1) and have a promising application in the simultaneous adsorption of lithium and rubidium ions.     

Analytical investigation of the chemical reactivity and stability of aminopropyl-grafted silica in aqueous medium

Various samples of aminopropyl-functionalized silica (APS) have been prepared by grafting an organosilane precursor 3-aminopropyl-triethoxysilane (APTES) onto the surface of silica gel. The amine group content of the materials has been adjusted by varying the amount of APTES in the reaction medium (toluene). The grafted APS solids have been characterized with using several analytical techniques (N₂ adsorption, X-ray photoelectron spectroscopy, infrared spectrometry) to determine their physico-chemical properties. Their reactivity in aqueous solutions was studied by acid-base titration, via protonation of the amine groups, and by way of complexation of these groups by Hg^II species. APS stability in aqueous medium was investigated at various pH and as a function of time, by the quantitative analysis of soluble Si- or amine-containing species that have been leached in solution upon degradation of APS. The chemical stability was found to increase when decreasing pH below the pK_a value corresponding to the RNH₃⁺/RNH₂ couple, but very low pH values were necessary to get long-term stability because of the high local concentration of the amine groups in the APS materials. Adsorption of mercury(II) ions on APS was also performed to confirm the long-term stability of the grafted solid in acidic medium. Relationship between solution pH and APS stability was discussed. For sake of comparison, the stability of APS in ethanol and that of mercaptopropyl-grafted silica (MPS) in water have been briefly considered and discussed with respect to practical applications of silica-based organic–inorganic hybrids, e.g., in separation science or in the field of electrochemical sensors.     

具有双亲特性的水相哑铃型SiO2纳米粒子的制备

以纳米SiO2水溶胶为原料,3?氨丙基三乙氧基硅烷(APTES)和3?氯丙基三乙氧基硅烷(CPTES)为改性剂,在水基环境下分别对SiO2纳米粒子进行改性,得到了具有亲水特性的APTES改性SiO2粒子和具有亲油特性的CPTES改性SiO2粒子水溶胶。2种粒子按不同比例混合,利用接枝在SiO2粒子表面氨基和氯丙基的取代反应,使得2种具有亲水/亲油特性的改性SiO2纳米粒子偶联,制备了粒径为40~50 nm的哑铃型SiO2纳米粒子。并通过透射电镜(TEM)、傅里叶变换红外光谱(FT?IR)、X射线光电子能谱(XPS)以及动态光散射(DLS)等方法对其进行了系统表征。结果表明,2种粒子成功偶联形成了具有哑铃型结构的水相SiO2纳米粒子,该粒子两面具有不同的亲水性,粒径近似等于APTES改性SiO2粒子和CPTES改性SiO2粒子的粒径之和。     

Adsorption of methyl orange on nanoparticles of a synthetic zeolite NaA/CuO

CuO supported on an NaA zeolite (CuO/NaA) was prepared with an NaA zeolite through the ion-exchange (CuO/NaA) method. The morphology and the physicochemical properties of the prepared samples were investigated by XRD, MEB, and EDS. The various parameters, such as contact time, catalyst dose, initial dye concentration, initial pH, and temperature, influencing the adsorption of methyl orange (MO) were optimized. The MO adsorption equilibrium was reached after 240 min of contact time. Removal of MO is better at neutral pH than in acidic and alkaline solutions. Among the tested models, the equilibrium adsorption data are well fitted by the Langmuir isotherm. The adsorption kinetics is best described by the pseudo-second-order model. The evaluation of the thermodynamic parameters, i.e. ΔG^o, ΔH^o, and ΔS^o, revealed that MO adsorption was spontaneous, while the activation energy (20.98 kJ/mol) indicates a physical adsorption. The photodegradation of MO decreased from 100 mg/L down to 2 mg/L when the solution is exposed to visible light.     

Surface properties of submicrometer silica spheres modified with aminopropyltriethoxysilane and phenyltriethoxysilane

The surface of submicrometer silica spheres are modified with aminopropyl and phenyl groups through a one-step process. Various experimental techniques, i.e., scanning electron microscopy (SEM), quasi-elastic light scattering (QELS), differential scanning calorimetry (DSC), thermogravimetry (TG), zeta potential measurement, nitrogen sorption, and water vapor and organic dye adsorption are used to comprehensively characterize the pure (TEOS particles) and modified silica particles. The SEM micrographs of the particles demonstrate that the modified particles are spherical with uniform size and shape. The particles modified with aminopropyl groups (APTES particles) show the highest isoelectric point (IEP) and the highest weight loss at 780 degrees C because of the basic nature of aminopropyl groups and the higher reactivity of aminopropyltriethoxysilane. The particles modified with the phenyl groups (PhTES particles) show the lowest water vapor adsorption because their surface is more hydrophobic than that of TEOS and APTES particles. The organic dye (brilliant blue FCF or BBF) adsorption experiments demonstrate that the adsorption capacity of the particles increases greatly after acidification. This is caused by the protonation of silanol groups and amine groups on the particle surface, which presents an enhanced electrostatic attraction with BBF anions. The APTES particles exhibit the highest dye adsorption due to the hydrophobic attractions and the enhanced electrostatic attractions from aminopropyl groups.     

Characterization of cyclotrimethylenetrinitramine (RDX) by pyrolysis H2O/D2O atmospheric-pressure chemical ionization tandem mass spectrometry

The oxidative pyrolysis-atmospheric-pressure chemical ionization tandem mass Spectrometry (Py-APCI MS/MS) of Cyclotrimethylenetrinitramine (RDX) was investigated under various sample introduction conditions. Subambient (0.97 atm) as opposed to ambient (0.98 atm) pressure (1 atm = 101325 kPa) facilitated the appearance of new pyrolysis mass spectral ions, including m/z 44. Deuterated decomposition products from [²H]RDX contained amide groups and, depending on the ion source pressure, significant differences in the degree of proton-deuterium exchange occurred on the amide groups. The D₂O Py-APCI MS/MS method also confirmed and extended the analogous H₂O APCI information from RDX, [²H]RDX and pure standards. The m/z 44 decompositon species was identified as protonated dimethylimine, [H₃CN?CH₂]⁺ as opposed to its primary amine isomer, [H₃CC(H)?NH]H⁺, which contains an acidic proton. It was determined that m/z 60 is due to protonated N-methylformamide and acetaldoxime, [H₃CC(H)?NOH]H⁺.     

Adsorption and protection of plasmid DNA on mesoporous silica nanoparticles modified with various amounts of organosilane

Ordered MCM-41-type mesoporous silica nanoparticles (MSNs) with pore size of 2.6 nm were synthesized and were further modified with various amounts of 3-aminopropyltriethoxysilane (APTES), respectively, by a direct co-condensation method. These amine functionalized mesoporous silica nanoparticles (Am-MSNs) were employed to complex with plasmid DNA (pDNA) to study their adsorption and protection capacities. The results demonstrate the MSNs functionalized with aminopropyl groups present advanced adsorption capacities for pDNA immobilization. And Am-MSNs with high APTES amount lead to high amount of pDNA adsorption. Further investigation of pDNA protection shows that Am-MSNs with moderate APTES amount could completely protect pDNA from enzymatic degradation, while those with smaller and/or higher amount of APTES could partially provide protection of pDNA.     

Electrochemiluminescence Detection of TNT by Resonance Energy Transfer through the Formation of a TNT–Amine Complex

2,4,6‐Trinitrotoluene (TNT) is a widely used nitroaromatic explosive with significant detrimental effects on the environment and human health. Its detection is of great importance. In this study, both electrochemiluminescence (ECL)‐based detection of TNT through the formation of a TNT–amine complex and the detection of TNT through electrochemiluminescence resonance energy transfer (ECRET) are developed for the first time. 3‐Aminopropyltriethoxysilane (APTES)‐modified [Ru(phen)₃]²⁺ (phen=1,10‐phenanthroline)‐doped silica nanoparticles (RuSiNPs) with uniform sizes of (73±3) nm were synthesized. TNT can interact with APTES‐modified RuSiNPs through charge transfer from electron‐rich amines in the RuSiNPs to the electron‐deficient aromatic ring of TNT to form a red TNT–amine complex. The absorption spectrum of this complex overlaps with the ECL spectrum of the APTES‐modified RuSiNPs/triethylamine system. As a result, ECL signals of the APTES‐modified RuSiNPs/triethylamine system are turned off in the presence of TNT owing to resonance energy transfer from electrochemically excited RuSiNPs to the TNT–amine complex. This ECRET method has been successfully applied for the sensitive determination of TNT with a linear range from 1×10^?9 to 1×10^?6 M with a fast response time within 1 min. The limit of detection is 0.3 nM . The method exhibits good selectivity towards 2,4‐dinitrotoluene, p‐nitrotoluene, nitrobenzene, phenol, p‐quinone, 8‐hydroxyquinoline, p‐phenylenediamine, K₃[Fe(CN)₆], Fe³⁺, NO₃^?, NO₂^?, Cr³⁺, Fe²⁺, Pb²⁺, SO₃^2?, formaldehyde, oxalate, proline, and glycine.     

Why Are B ions stable species in peptide spectra?

Protonated amino acids and derivatives RCH(NH₂)C(+O)X · H⁺ (X = OH, NH₂, OCH₃) do not form stable acylium ions on loss of HX, but rather the acylium ion eliminates CO to form the immonium ion RCH = NH ₂ ⁺ . By contrast, protonated dipeptide derivatives H₂NCH(R)C(+O)NHCH(R′)C(+O)X · H⁺ [X = OH, OCH₃, NH₂, NHCH(R″)COOH] form stable B₂ ions by elimination of HX. These B₂ ions fragment on the metastable ion time scale by elimination of CO with substantial kinetic energy release (T _1/2 = 0.3–0.5 eV). Similarly, protonated N-acetyl amino acid derivatives CH₃C(+O)NHCH(R′)C(+O)X · H⁺ [X = OH, OCH₃, NH₂, NHCH(R″)COOH] form stable B ions by loss of HX. These B ions also fragment unimolecularly by loss of CO with T _1/2 values of ～ 0.5 eV. These large kinetic energy releases indicate that a stable configuration of the B ions fragments by way of activation to a reacting configuration that is higher in energy than the products, and some of the fragmentation exothermicity of the final step is partitioned into kinetic energy of the separating fragments. We conclude that the stable configuration is a protonated oxazolone, which is formed by interaction of the developing charge (as HX is lost) with the N-terminus carbonyl group and that the reacting configuration is the acyclic acylium ion. This conclusion is supported by the similar fragmentation behavior of protonated 2-phenyl-5-oxazolone and the B ion derived by loss of H-Gly-OH from protonated C₆H₅C(+O)-Gly-Gly-OH. In addition, ab initio calculations on the simplest B ion, nominally HC(+O)NHCH₂CO⁺, show that the lowest energy structure is the protonated oxazolone. The acyclic acylium isomer is 1.49 eV higher in energy than the protonated oxazolone and 0.88 eV higher in energy than the fragmentation products, HC(+O)N⁺H = CH₂ + CO, which is consistent with the kinetic energy releases measured.     

Polyamine chitosan adsorbent for the enhanced adsorption of anionic dyes from water

A simple synthesis route for amine protected-introduced-released chitosan (APIR-CS) was investigated to improve the adsorption of anionic dyes. The C₂ amine groups of the chitosan (CS) were initially protected via a Schiff-base reaction by benzaldehyde. They were then synthesized by the introduction of ethylenediamine into C₆ hydroxyl groups on CS via epichlorohydrin. The final product was obtained after removal of the Schiff base with dilute hydrochloride solution. Amine-introduced chitosan (AI-CS) was directly synthesized at the C₂ amine groups. The adsorbents were characterized by FTIR, X-ray diffraction (XRD), and X-ray photoelectron spectroscopy (XPS). For Congo red (CR) and methyl orange (MO), most of the amine groups in CS were converted to–N?CH₂ groups after the benzaldehyde treatment. Hydrochloric acid treatment after the cross-linking reaction released protected nitrogen atoms into the form of the primary amine again. APIR-CS had significantly greater adsorption capacities than AI-CS. The increased adsorption performance was attributed to the large number of primary amine groups on the surfaces. The adsorption mechanism was based on electrostatic interaction, while the adsorption process was mainly physisorption.     

Adsorption of Li by a lithium ion-sieve using a buffer system and application for the recovery of Li from a spent lithium-ion battery

A lithium ion-sieve manganese oxide (MO) derived from Li-enriched MO was prepared by the glycolic acid complexation method. The Li adsorption performance in a LiCl–NH₃·H₂O–NH₄Cl buffer solution, simulated a spent lithium-ion battery (LIB) processing solution, and actual spent LIB processing solution were studied. An adsorption capacity of 27.4 mg/g was observed in the LiCl–NH₃·H₂O–NH₄Cl buffer solution (Li concentration of 0.2 mol/L, pH?=?9), and the adsorption behavior conformed to the Langmuir adsorption isotherm equation with a linear correlation coefficient (R²) of 0.9996. An adsorption capacity of 19 mg/g was observed in the simulated buffer spent battery solution (Li concentration of 0.15 mol/L, pH?=?7), and an adsorption capacity of 17.8 mg/g was observed in the actual spent battery solution (Li concentration of 0.15 mol/L, pH?=?7). X-ray diffraction, scanning electron microscope, and infrared spectrum results revealed that the structure and morphology of MO are stable before and after adsorption, and the adsorption of MO in all of the abovementioned buffer systems conforms to the Li⁺–H⁺ ion-exchange reaction mechanism. The lithium ion-sieve MO demonstrates promise for the recovery of lithium from spent LIBs.     

Determination of molar ratio of primary secondary and tertiary amines in polymers by applying derivatization and NMR spectroscopy

A trifluoroacetic acid derivatization combined with ¹H NMR spectroscopy method for determining the molar ratio of primary, secondary, and tertiary amines in small molecules and polymers was discussed. Amines reacted with trifluoroacetic acid to form their salts RNH₃⁺, R₂NH₂⁺, and R₃NH⁺. The ¹H NMR signals of these protonated amines (NH₃⁺, NH₂⁺, and NH⁺) were separated well in the spectra. Based on the integration of these protonated amine signals, the molar ratio of primary, secondary, and tertiary amines can be calculated.     

Comparative electrochemistry of technetium(V) and rhenium(V) dioxo complexes

The heavy use of^99mTc in nuclear medicine and the recent development of¹⁸⁸Re radiopharmaceuticals have encouraged the comparative study of Tc and Re coordination compounds. In this work, the electrochemistry of [M^VO₂ (amine)₂]⁺ (M=Tc, Re; amine = ethylenediamine, 1,3-diaminopropane, diethylenetriamine, triethylenetetramine) complexes is studied by cyclic voltammetry and the results are compared. The voltammograms of these compounds, obtained at different pH values, show that [ReO₂(amine)₂]⁺ cations are thermodynamically stable even when protonated. On the other hand, analogous Tc compounds are not so stable and easily decompose if existing as [TcO(OH) (amine)₂]²⁺.     

Molecular‐Level Insights into the Oxidative Degradation of Grafted Amines

The oxidative degradation of CO₂ adsorbents consisting of amine‐grafted pore‐expanded mesoporous MCM‐41 silica was investigated. The adsorbents were treated under flowing air at various temperatures, and the degree of deactivation was evaluated through the measurement of their CO₂ adsorption capacity prior and subsequent to exposure to air. To decipher the chemical structure of surface species upon air‐deactivation of grafted amines, a solvent extraction procedure was developed using a deuterated basic solution. The obtained solutions were analyzed by a variety of 1D and 2D NMR spectroscopy techniques, such as ²⁹Si, ¹³C, ¹H, [¹H,¹⁵N] HMBC, [¹H,¹³C] HMQC, COSY and DOSY. The surface species generated by oxidative degradation of amine‐grafted silica were found to contain functional groups such as imine, amide and carboxylic groups. Several structural units were conclusively demonstrated.     

Electrode processes in the oxidation of tetrahydroisoquinoline derivatives

The electrochemical oxidation of the alkaloid laudanosine (Ia) to O-methylflavinantine (II) has been studied in acetonitrile solvent. Using cyclic voltammetry, rotating disc voltammetry and preparative electrolyses on several alkaloids, simple aliphatic amines and aromatic compounds, some aspects of the mechanism of this coupling reaction are elucidated. The first anodic wave for laudanosine at platinum has E_p=0.55 V vs. Ag/Ag⁺. The electrode rapidly becomes partially passivated at potentials above 0.5 V. This is due to a film which “dissolves” below 0.5 V, at a rate independent of the potential. It is shown that the reaction (Ia)→(II) proceeds at 0.5 V by initial oxidation of the amine moiety. If acids such as sodium bicarbonate are added to the anolyte the amine is protonated causing the first wave to disappear. Oxidation at 1.1 V under these acidic conditions produces the same product, but more rapidly and in significantly higher yield because electrode filming and side reactions resulting from the amine oxidation are abrogated.     

The effects of pH and ionic strength on fulvic acid uptake by chitosan hydrogel beads

The objective of this work is to investigate the effects of pH and ionic strength on the adsorption capacity for fulvic acid (FA) by chitosan hydrogel beads. The results indicated that the sorption amount increased with decreasing pH and increasing ionic strength concentration. The sorption isotherms were well described by using non-linear Langmuir, Freundlich and Redliche–Peterson equation. The adsorption kinetics of FA onto chitosan hydrogel beads could be described by pseudo-second-order rate model. The extent of FA removal in the presence of other ions decreases in the order Ca²⁺ > Mg²⁺ > Na⁺ ≈ K⁺ and Cl⁻ > NO₃⁻ > CO₃²⁻. FTIR along with XPS analyses revealed the amine groups on the beads were involved in the sorption of FA and the organic complex between the protonated amino groups and FA was formed after FA uptake. Sorption mechanisms including electrostatic interaction and surface complexation were found to be involved in the complex sorption of FA on the chitosan hydrogel beads.     

螯合树脂研究——Ⅺ.一类新的氨基二硫代甲酸型螯合树脂的合成及吸附性能

 本文报道了以多乙烯多胺为主链的巯基胺树脂与二硫化碳反应,合成了四种新型的氨基二硫代甲酸型螯合树脂,这类树脂对贵金属具有高的吸附容量和优良的吸附选择性。并通过红外光谱和X光电子能谱研究树脂及其金属螫合物。     

Cationic Aluminium Complexes as Catalysts for Imine Hydrogenation

Strongly Lewis acidic cationic aluminium complexes, stabilized by β–diketiminate (BDI) ligands and free of Lewis bases, have been prepared as their B(C₆F₅)₄⁻ salts and were investigated for catalytic activity in imine hydrogenation. The backbone (R1) and N (R2) substituents on the ^R1,R2BDI ligand (^R1,R2BDI=HC[C(R1)N(R2)]₂) influence sterics and Lewis acidity. Ligand bulk increases along the row ^Me,DIPPBDI<^Me,DIPePBDI≈^tBu,DIPPBDI<^tBu,DIPePBDI; DIPP=2,6-C(H)Me₂-phenyl, DIPeP=2,6-C(H)Et₂-phenyl. The Gutmann-Beckett test showed acceptor numbers of: (^tBu,DIPPBDI)AlMe⁺ 85.6, (^tBu,DIPePBDI)AlMe⁺ 85.9, (^Me,DIPPBDI)AlMe⁺ 89.7, (^Me,DIPePBDI)AlMe⁺ 90.8, (^Me,DIPPBDI)AlH⁺ 95.3. Steric and electronic factors need to be balanced for catalytic activity in imine hydrogenation. Open, highly Lewis acidic, cations strongly coordinate imine rendering it inactive as a Frustrated Lewis Pair (FLP). The bulkiest cations do not coordinate imine but its combination is also not an active catalyst. The cation (^tBu,DIPPBDI)AlMe⁺ shows the best catalytic activity for various imines and is also an active catalyst for the Tishchenko reaction of benzaldehyde to benzylbenzoate. DFT calculations on the mechanism of imine hydrogenation catalysed by cationic Al complexes reveal two interconnected catalytic cycles operating in concert. Hydrogen is activated either by FLP reactivity of an Al⋅⋅⋅imine couple or, after formation of significant quantities of amine, by reaction with an Al⋅⋅⋅amine couple. The latter autocatalytic Al⋅⋅⋅amine cycle is energetically favoured.     

Mass Spectrometric Identification of Multihydroxy Phenolic Compounds in Tibetan Herbal Medicines

A highly selective and accurate method based on derivatization with dansyl chloride coupled with liquid chromatography–mass spectrometry has been developed for identification of natural pharmacologically active phenolic compounds in extracts of Lomatogonium rotatum plants (Tibetan herbal medicine) obtained by solid-phase extraction. The number of hydroxyl groups on the dansylated phenols was estimated by LC–MS–MS analysis in positive-ion mode. Dansyl derivatization of the compounds introduced basic secondary nitrogen into the phenolic core structures and this was readily ionized when acidic HPLC mobile phases were used. MS fragmentation of the derivatives generated intense protonated molecular ions of m/z [MH]⁺ (phenol aglycones were transformed into the corresponding free phenols by cleavage of an aglycone bond). Collision-induced dissociation of the protonated molecule generated characteristic product ions of m/z 234 and 171 corresponding to the protonated 5-(dimethylamino)naphthalene sulfoxide and 5-(dimethylamino)naphthalene moieties, respectively. Selected reaction monitoring based on the m/z [MH]⁺ to 234 and 171 transitions was highly specific for these phenolic compounds. Characteristic ions with m/z values of [MH – 234]⁺, [MH – 2 × 234]⁺, and [MH – 3 × 234]⁺ were of great importance for estimation of the presence of multihydroxyl groups on the phenolic backbone.     

刷状结构的阳离子性接枝微粒QPDMAEMA/SiO2对牛血清白蛋白的吸附特性

以微米级硅胶微粒为基质, 通过接枝聚合和大分子反应, 制备了具有刷状结构的阳离子性接枝微粒, 深入研究了其对牛血清白蛋白(BSA)的强吸附能力、吸附机理和吸附热力学. 首先使含叔胺基团的单体甲基丙烯酸二甲基氨基乙酯(DMAEMA)在硅胶微粒表面发生接枝聚合, 制得接枝微粒PDMAEMA/SiO₂, 然后以氯乙胺为试剂, 使接枝大分子PDMAEMA链中的叔胺基团发生季铵化反应, 获得了具有刷状结构的阳离子聚电解质的功能接枝微粒QPDMAEMA/SiO₂. 测定了微粒QPDMAEMA/SiO₂的zeta 电位, 实施了对BSA的等温吸附实验, 考察了介质pH值、离子强度及温度对吸附作用的影响, 研究了吸附热力学. 研究结果表明, 功能接枝微粒QPDMAEMA/SiO₂ 比接枝微粒PDMAEMA/SiO₂ 具有更高的zeta 电位, 在静电相互作用驱动下, 微粒QPDMAEMA/SiO₂对BSA具有很强的吸附能力. 吸附容量随介质pH值的增大呈现先增大后减小的变化趋势,当pH值等于BSA的等电点(pI=4.7)时, 具有最高的吸附容量(高达112 mg·g^-1). 以等电点为界, 离子强度对吸附容量会产生完全相反的影响作用: 当介质pH值小于BSA的等电点时, 电解质浓度增大, 吸附容量增高; 当介质pH值等于BSA的等电点时, 吸附容量几乎不随电解质的浓度发生变化. 吸附过程熵值减小而且放出热量,是一个焓驱动的吸附过程.