Adsorption kinetics of the interaction between Pt, Pd and Rh (defined here as platinum group elements, PGEs) ions and macromolecular organic compounds (MOCs, >10 kDa), including humic acid, carrageenan and bovine serum albumin, and different cutoff fractions of natural organic matter (>1 kDa and >3 kDa) obtained from seawater using centrifugal ultrafiltration devices were investigated. For a given element, all the adsorption kinetics did not reach equilibrium except the interaction between Pt and >1 kDa cutoff, and between Pd and humic acid. For all the tested MOCs, the adsorption kinetics could be divided into two stages, a rapid adsorption process in the first 8 h and the desorption stage after the first 8 h until the equilibrium. The change trend of partition coefficient (log₁₀K_d) values with experiment time was consistent with that of the kinetic curves. However, in the interaction between PGE ions and natural dissolved organic matter (NDOM), an obvious difference in the change trends of log₁₀K_d and kinetic curves was observed. It indicated that the partition behavior of PGE ions interacting with NDOM in seawater was a combined effect of different organic constituents. The adsorption and log₁₀K_d of PGEs in the >1 kDa NDOM fraction were higher and more stable than those in the >3 kDa NDOM fraction. The results also indicated that the 1–3 kDa NDOM may dominate the interaction between PGEs ions and NDOM. Moreover, no kinetic model could perfectly simulate the adsorption process. It indicated that the colloidal struction and morphology of MOCs or NDOM in seawater might be inhomogeneous. Hence, the interaction between PGE ions and organic matter in seawater was a complicated process and needs further research.

The mechanism of uranium adsorption from seawater by polyacrylamidoxime resin is investigated by means of the experiments of adsorption isotherm and adsorption rate.The uranium uptake increases with the adsorption temperature and varies with the pH of seawater.Thermochemical and kinetic calculation show that the enthalpy change (△H) and the activation energy (E) of the uranium adsorption are 42.4 42.4 kJ mol^-1 and 41.2 kJ mol^-1 respectively, indicating that the uranium adsorption on the resin proceeds via a certain complex chemical reaction in which the amidoxime group in the resin chelates uranyl ions.

A number of data on the organic adsorbent applied to extract from sea water have reported^[1-3], In this paper, we introduce a new organic adsorbent which has high extracting uranium capacity.The syntheses and the experimental uranium adsorption as well as its mechanism arediscribed.

Through introducing amidoxime and carboxyl groups into polyacrylonitrile fiber, a fibrous adsorbent with high capacity and fast adsorption rate was obtained, which could adsorb 4.6 mg uranium/g in 10 days from natural seawater. The influence of the functional group content on equilibrium adsorption capacity X_m and adsorption rate constant K of the adsorbent was studied, thus indicating that the contents of amidoxime and carboxyl groups correlated with X_m and K respectively. It is concluded that the amidoxime group is of reactive adsorption, while the carboxyl group is of promotion in the adsorption of uranium. In this paper, the mechanism of uranium adsorption on the fibrous adsorbent is deduced and the chelating structure of adsorption species is discussed with molecule orbit theory.

An account is given of the thermodynamical characteristics of the adsorption of uranyl complex ions on hydrous titanium oxide (HTO) in NaCl-NaHCO₃ solution and in seawater.Determined are the adsorption isotherms and the adsorption density in various pH.The contribution of each component to the adsorption density,the adsorption free energy ΔG_ads,t,the coulostatic energy ΔG_coul,t,and the cqemisorption potential energy G_chem,t are estimated.The average free energy ΔG_ads enthalpy change,ΔH_ads,and entropy change,ΔS_ads,of the adsorption in this system are -7.33 kcal/mol,6.30 kcal/mol and 45.7 cal/mol K respectively.It is hereof concluded that the complex chemisorption process is spontaneous and thermonegativc.

1.The adsorption action of basic zinc carbonate adsorbent on uranium in natural seawater can be expressed with the following formula of adsorption isotherm:
C=k (U^*)n=8.51×10^-1 (U^*)0.49,
where C is the concentration of uranium on adsorbent; U^* is content of uranium in natural seawater employed.
2.when the quantity of basic zinc carbonate adsorbent (T) is constant, with the increase of natural seawater quantity through the adsorption column (G), also increased are the adsorption content of uranium of the adsorbent (U), the concentration of uranium on the adsorbent (C) and the concentration of residual uranium (C₀^*) in natural seawater after adsorbing uranium, while the rate of recovery of uranium (R) is decreased.With the increase of (G) the coefficient of distribution (K_d) decreases to a certain value and then a little rises again.

The process of adsorption of Cu²⁺, Cd²⁺ by immobilized marine algae was investigated.It can be noted from the results that, the process for biosorption of heavy metals (copper, cadmium) by immobilized Laminaria japonica can be described by the Banerm model.According to the model, the adsorption rate constant calculated was 0.107 8 and 0.030 28 min^-1 for Cu²⁺ and Cd²⁺ respectively.The experimental biosorption equilibrium data for Cu²⁺ and Cd²⁺ were in good agreement with those calculated by the Langmuir model.The maximum uptake capacity calculated was 83.3 and 112.4 mg/g for Cu²⁺ and Cd²⁺ according to the Langmuir model, respectively.The appetency of Laminaria japonica to Cu²⁺was better than Cd²⁺.

The adsorption kinetics of Pb, Cu and Cd on hydrous ferrk oxide (HFO) has been approached in tthe simulated environmental conditions of the Changjiang Estuary.The forward adsorption rate constants of different systems under different temperatures have been determined, and the activation energies of the adsorption for Pb and Cu evaluated (Pb=7 kcal/mol, Cu=11 kcal/mol).The results show that Pb and Cu are strongly adsorbed by HFO; the order of their adsorption rate is found to be Pb ≥ Cu ≥ Cd, which follows thte order of their theonody-namic equilibrium constants.It has been demonstrated that the surface exchange-adsorption is the determining step of the solid-liquid interface process.The field investigation results are theoretically explained by the kinetic mechanism.

This paper first presents the molecule design and synthesis of crown-link type alkyd resin,and its enrichment behaviour for potassium ion in low concentration solution and sea water.On the basis of some theory concepts of Host-Guest chemistry developed in recent years,we have designed and synthesized a new polymer enrichment agent of crow-link resin for potassiumion,i.e.,polymacrocyclic ether bislactone of diethylene glycolpyromyllitic acid(briefly called crown-link type alkyd resin or PBL resin).The yield was about 97.4%,almost quantitatively.

The i.r.spectra of Na₄[UO₂(CO₃)₃], Na[UO₂(OH)₃] and the surface species of uranium on HTO underthe condition of flowing natural seawater and concentrated seawater (NaCl-NaHCO₃-U) were recorded, with the bands of uranyl of surface species obtained and the finding that iigands of surface species besides HTO are mainly water and OH, and there are some CO₃^2- groups under the condition of natural seawater.Some relations between the complex properties and the j.r.spectroscopic characters for uranyl complexes were studied, and the transferred change quantity of surface complex was calculated.
Structure models for surface species of adsorption are herein presented and the mechanism for uranium adsorption is deduced.