Isotherm sorption of Cd2+, Co2+, and Ni2+ onto high-yield kraft fibers

The sorption capacity of high-yield kraft fibers for Cd2+, Co2+, and Ni2+ increased with pH and concentration of the cations in the liquid phase. Within the concentration range for the experiments, which was less than 2 mM, the experimental results fitted the Langmuir, Freundlich, and Sips models with regression coefficient greater than 0.97. Of the three cations investigated, Ni2+ had the highest sorption affinity, followed by Cd2+ and Co2+. The effect of the hydrated radius on the sorption affinity was discussed. Thermodynamically, the sorption was spontaneous and exothermic in the temperature range 283-308 K.     

Adsorption of tetracycline onto goethite in the presence of metal cations and humic substances

Adsorption of tetracycline, one of the most widely used antibiotics, onto goethite was studied as a function of pH, metal cations, and humic acid (HA) over a pH range 3-10. Five background electrolyte cations (Li(+), Na(+), K(+), Ca(2+), and Mg(2+)) with a concentration of 0.01 M showed little effect on the tetracycline adsorption at the studied pH range. While the divalent heavy metal cation, Cu(2+), could significantly enhance the adsorption and higher concentration of Cu(2+), stronger adsorption was found. The results indicated that different adsorption mechanisms might be involved for the two types of cations. Background electrolyte cations hardly interfere with the interaction between tetracycline and goethite surfaces because they only form weak outer-sphere surface complexes. On the contrary, Cu(2+) could enhance the adsorption via acting as a bridge ion to form goethite-Cu(2+)-tetracycline surface complex because Cu(2+) could form strong and specific inner-sphere surface complexes. HA showed different effect on the tetracycline sorption under different pH condition. The presence of HA increased tetracycline sorption dramatically under acidic condition. Results indicated that heavy metal cations and soil organic matters have great effects on the tetracycline mobility in the soil environment and eventually affect its exposure concentration and toxicity to organisms.     

Membrane filters for the concentration of trace elements in water: distribution of ion pairs between membrane filter and aqueous phases

The sorption of ion pairs on membrane filters (MFs) has been studied by taking the membrane filter as one of the homogeneous phases. The sorbability of some ionic species and the sorption abilities of different types of MF were evaluated in terms of the sorption constant defined by Ksor,CA = [(C+,A-)f]/[C+][A-], where C+, A- and (C+,A-) refer to the cation, anion and the ion pair, respectively, and f refers to the filter phase. The values of Ksor,CA were determined for many combinations of ionic complexes of cobalt(III) with pyridylazophenols, either as cations or anions, and oppositely charged organic ions having different alkyl chain lengths, with MFs made of different materials: nitrocellulose (NC; Toyo Advantec), acetylcellulose (AC; Fuji Film), regenerated cellulose (RC; Toyo Advantec) and polyethersulphone (PS; Toyo Advantec). For a given cobalt complex ion, the value of log Ksor,CA increased linearly with the increasing number of carbons in the counter ion. Membrane filters made of different materials showed different sorption abilities, the order being NC greater than PS greater than RC greater than AC. It was shown that the surface area of the MF is of greater significance than the volume of the matrix of the MF in determining the sorption constant.     

Ion equilibrium in lichen surrounding

In laboratory conditions, the ionic equilibriums between a solution and a cation-active layer of epiphytic lichens Hypogymnia physodes immersed in the solution were examined. It was found that such equilibriums, due to exchange of mobile cations: H, Na, K, Ca, and Mg, are established in natural conditions between a lichen and atmospheric water.     

Investigation of Lublin town environment contamination by radionuclides and heavy metals with application of Parmeliaceae lichens

Contamination of ground level air at Lublin town was studied by measurements of radioactive isotope and heavy metal contents in Parmeliaceae lichens exposed during six months on the area of the town. The concentration of the elements studied was compared with these ones measured in unexposed (blank) samples of lichens. The highest increase of radioactivity was noticed for ²³²Th, ²²⁶Ra and ⁴⁰K. The contamination by ¹³⁷Cs does not increased markedly, ranging from 2 to 107 Bq/kg of the dry lichen sample. Nearly half of the exposed samples do not reveal any increase of cesium radioactivity. Heavy metal concentrations in analyzed lichens were low. From the results obtained, one may conclude that concentration of these metals in ground air level does not reach appreciable values.     

The stimulatory effect of heavy metal cations on proliferation of aortic smooth muscle cells

Heavy metal cations Cd2+, Pb2+, and Hg2+ were added to substitute for Ca2+ in culture media to study their effect on the relationship between CaM and the proliferation of cultured rabbit aortic smooth muscle cells (ASMC). It was found that all the heavy metal cations studied stimulated the proliferation of ASMC in varying degrees, increased the CaM content in cells at late G1 stage and decreased the activity of cAMP PDE. These results suggest that the adverse effect of heavy metals may be related to the pathogenesis of atherosclerosis and hypertensive disease.     

Heavy metal immobilization in aqueous solution using calcium phosphate and calcium hydrogen phosphates

This study examines the possibilities for removing heavy metal cations from water with calcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate at 293 K. It was reported that immobilization of aqueous heavy metal cations, which is known to be one of the characteristic properties of calcium hydroxyapatite, proceeded favorably with these phosphates. Calcium phosphate, calcium hydrogen phosphate, and calcium dihydrogen phosphate could favorably remove Pb2+ from aqueous solution. Calcium hydrogen phosphate also removed aqueous Cu2+, Co2+, and Cd2+, whereas these cations were not immobilized by calcium phosphate and calcium dihydrogen phosphate. A contribution of the dissolution-precipitation mechanism to immobilization with these phosphates is suggested.     

Interlayer expansion and mechanisms of anion sorption of Na-montmorillonite modified by cetylpyridinium chloride: a Monte Carlo study

To study the change of interlayer structure of a Wyoming-type Na-montmorillonite as a result of the replacement of interlayer Na+ ions by cetylpyridinium (CP+) ions, a series of NPT Monte Carlo simulations of the clay mineral with different contents of CP+, Na+, Cl- ions and water in its interlayer space is carried out. In agreement with conclusions from experimental studies, the simulations show that the CP+ ions form monomolecular, bimolecular, and pseudotrimolecular layers with increasing interlayer contents. Calculated potential energies reveal that clay-organic interactions are stronger than organic-organic interactions in CP+-modified montmorillonite, which is in conformity with observations of earlier thermogravimetric experiments. The simulation results indicate that the pseudotrimolecular arrangement of CP+ ions is a prerequisite for the experimentally observed interlayer sorption of inorganic anions. Furthermore, in the interlayer space with a pseudotrimolecular layer, chloride ions favor the formation of pairs with inorganic rather than organic cations. On the basis of these findings and available experimental data, we propose that the interlayer sorption of inorganic anions from the pore space of an organically modified montmorillonite may occur not only in pairs with organic cations, as suggested earlier, but also in pairs with inorganic cations, which represents a so-far unconsidered and maybe more important mechanism of anion sorption on clay minerals.     

Quantitative EPR study on free radicals in the natural polyphenols interacting with metal ions and other environmental pollutants

Quantitative electron paramagnetic resonance (EPR) method was applied to characterise radicals stabilised in polyphenolic matrices of various biogenic materials: lichens, mosses, composts, soils, peats, brown coals and sewage sludge sediments. The investigations were carried out on raw materials and extracted fractions of humic acids (HA). General trends of g value and spin concentration changes were found. These parameters in lichens strongly depend on lichen species and air pollution. Determination of the g value and semiquinone spin concentration allows to assess degree of transformation of organic matter in compost, soil, peat and lignite. Application of gaseous ammonia as a base penetrating the organic matrices extends the possibilities and usefulness of the method. Interaction of metal ions with humic materials is illustrated by interaction of VO2+ ion with peat and lignite HA as well as demineralised (raw and carbonised) brown coal. Our investigations demonstrate that quantitative EPR is a rapid and effective monitoring method to study the influence of various environmental factors on substances containing polyphenolic matrices.     

Sorption of divalent metal ions on CrPO4

The divalent metal ion sorption (Cu(2+), Cd(2+), Ni(2+), and Pb(2+)) on chromium phosphate (CrPO(4)) was studied as a function of pH, temperature, and concentration of metal ions. The sorption of metal ions is observed to increase with the increase in pH, temperature, and concentration of metal ions in solution. The mechanism of sorption is found to be the exchange of the hydrolyzed metal cations with the protons from solid at high temperature. The sorption at low temperature is found to be accompanied by the precipitation of the corresponding metal phosphates such as Pb(3)(PO(4))(2).     

离子交换与离子排斥色谱柱串联体系中阳离子的多峰现象及其机理

研究了串联柱体系中阳离子的“多峰现象”。在阳离子交换柱后面接上阴离子分析用的离子排斥柱构成一个串联柱体系,当以酒石酸（ＴＡ）和吡啶二羧酸（ＰＤＣ）的混合溶液作淋洗液时,每一种阳离子同时出现３个色谱峰。这是因为从阳离子交换柱流出的阳离子与有络合作用的两种淋洗剂阴离子形成络合物,使流动相中淋洗剂阴离子浓度减少以及两种淋洗剂阴离子在离子排斥柱中被保留且保留值不同。     

Decationization and dealumination of clinoptilolite tuff and ammonium exchange on acid-modified tuff

The paper presents results of investigation of exchange of the clinoptilolite tuff cations with hydrogen ions from HCl solution of concentration 0.1 mmol cm(-3) and ammonium ions solutions of concentrations 0.0071 to 2.6 mmol cm(-3). Molal concentrations, x (mmol g(-1)) of cations exchanged in acid solution and in ammonium ions solutions were compared with molal concentrations of cations obtained by determination of the cation-exchange capacity of clinoptilolite tuff. The obtained results show that at ammonium ion concentrations lower than 0.1 mmol cm(-3), with regard to exchange capacity for particular ions, best exchanged are Na+ ions, followed by Mg2+ and Ca2+ ions, while exchange of K+ ions is the poorest (Na+ > Mg2+ > Ca2+ > K+). At ammonium concentrations from 0.2 to 1 mmol cm(-3) the order is Na+ > Ca2+ > Mg2+ > K+. At concentrations higher than 1 mmol cm(-3) the order is Na+ > Ca2+ > K+ > Mg2+. The results are a consequence of the uptake of hydrogen ions by zeolite samples in ammonium ions solutions at concentrations lower than 1 mmol cm(-3) and indicate the importance of Mg2+ (besides Na+ ions) for the exchange between clinoptilolite cations and H+ ions, in contrast to K+ ions, whose participation in the reaction with H+ ions is the lowest. During decationization of the clinoptilolite in acid solution, best exchanged are Na+, Mg2+, and Ca2+ ions, while exchange of K+ ions is the poorest. Due to poor exchange of K+ and H+ ions and good exchange of Na+, Mg2+, and Ca2+ ions, it is to be assumed that preservation of stability of the clinoptilolite structure is caused by K+ ions present in the channel C. Clinoptilolite is dissolved in the clinoptilolite A and B channels where Na+, Mg2+, and Ca2+ ions are present. On the acid-modified clinoptilolite samples, exchange of ammonium ions is poorer than on natural zeolite. The longer the contact time of the zeolite and acid solution, the worse ammonium ions exchange. It can be assumed that H+ ions exchanged with zeolite cations are consumed for solution of aluminum in the clinoptilolite structure; therefore the concentration of H+ ions as exchangeable cations decreases. In the ammonium ion solution at a concentration of 0.0065 mmol cm(-3), from the acid-modified zeolite samples, Al3+ ions are exchanged best, followed by Na+, Mg2+, Ca2+, and K+ ions. Further to the results, it is to be assumed that exchangeable Al3+ ions available from clinoptilolite dissolution are best exchanged with H+ ions in acid solution.     

Heavy water reactions with atomic transition-metal and main-group cations: gas phase room-temperature kinetics and periodicities in reactivity

Reactions of heavy water, D(2)O, have been measured with 46 atomic metal cations at room temperature in a helium bath gas at 0.35 Torr using an inductively coupled plasma/selected ion flow tube tandem mass spectrometer. The atomic cations were produced at ca. 5500 K in an ICP source and were allowed to decay radiatively and thermalize by collisions with Ar and He atoms prior to reaction. Rate coefficients and product distributions are reported for the reactions of fourth-row atomic cations from K+ to Se+, of fifth-row atomic cations from Rb+ to Te+ (excluding Tc+), and of sixth-row atomic cations from Cs+ to Bi+. Primary reaction channels were observed leading to O-atom transfer, OD transfer, and D2O addition. O-Atom transfer occurs almost exclusively (>or=90%) in the reactions with most early transition-metal cations (Sc+, Ti+, V+, Y+, Zr+, Nb+, Mo+, Hf+, Ta+, and W+) and to a minor extent (10%) with one main-group cation (As+). OD transfer is observed to occur only with three cations (Sr+, Ba+, and La+). Other cations, including most late transition and main-group cations, were observed to react with D2O exclusively and slowly by D2O addition or not at all. O-Atom transfer proceeds with rate coefficients in the range of 8.1 x 10(-13) (As+) to 9.5 x 10(-10) (Y+) cm3 molecule(-1)(s-1) and with efficiencies below 0.1 and even below 0.01 for the fourth-row atomic cations V+ (0.0032) and As+ (0.0036). These low efficiencies can be understood in terms of the change in spin required to proceed from the reactant to the product potential energy surfaces. Higher order reactions are also measured. The primary products, NbO+, TaO+, MoO+, and WO+, are observed to react further with D(2)O by O-atom transfer, and ZrO+ and HfO+ react further through OD group abstraction. Up to five D(2)O molecules were observed to add sequentially to selected M+ and MO+ as well as MO2+ cations and four to MO(2)D+. Equilibrium measurements for sequential D(2)O addition to M+ are also reported. The periodic variation in the efficiency (k/k(c)) of the first addition of D(2)O appears to be similar to the periodic variation in the standard free energy (DeltaG degrees) of hydration.     

Adsorption of cations onto the surfaces of silver nanoparticles

The effects of cations on the absorption spectra of silver sols have been investigated by the UV-vis spectrometry and TEM. Experiments showed that injection of certain amounts of transition metal cations into silver sols resulted not only in the aggregation of silver nanoparticles but also in the appearance of a new band centered near 510 nm in the absorption spectra of silver sols. However, the new band was not observed in the presence of alkaline earth metal cations or the Mv2+ cations. The peak position of the new band depends on the nature as well as the concentration of metal cations used. Comparing the peak positions of the new bands, it was found that the new band induced by the injection of Cr3+ was red-shifted with respect to those induced by Cu2+, Zn2+, or the Cd2+ cations. It is reasonable that this band near 510 nm should be attributed to the coeffects of the adsorption of metal cations onto the surfaces of silver nanoparticles and the aggregation of silver nanoparticles.     

Effective interaction potentials for alkali and alkaline earth metal ions in SPC/E water and prediction of mean ion activity coefficients

The potential of mean force (PMF) acting between two simple ions surrounded by SPC/E water have been determined by molecular dynamics (MD) simulations using a spherical cavity approach. Such effective ion-ion potentials were obtained for Me-Me, Me-Cl-, and Cl(-)-Cl- pairs, where Me is a Li+, Na+, K+, Mg2+, Ca2+, Sr2+, and Ba2+ cation. The ionic sizes estimated from the effective potentials are not pairwise additive, a feature in the frequently used primitive model for electrolytes. The effective potentials were used in Monte Carlo (MC) simulations with implicit water to calculate mean ion activity coefficients of LiCl, NaCl, KCl, MgCl2, CaCl2, SrCl2, and BaCl2. Predicted activities were compared with experimental ones in the electrolyte concentration range 0.1-1 M. A qualitative agreement for LiCl and a satisfactory agreement for NaCl were found, whereas the predictions for KCl by two K+ models were less coherent. In the case of alkaline earth metal ions, all experimental activities were successfully reproduced at c = 0.1 M. However, at higher concentrations, similar deviations occurred for all divalent cations, suggesting that the dependence of the permittivity on the salt concentration and the polarization deficiency arising from the ordering of water molecules in the ion hydration shells are important in such systems.     

Use of zwitterionic micelles in the eluent II: a new approach to ion chromatographic analysis of inorganic cations in biological fluids with direct sample injection

A new ion chromatographic (IC) technique has been developed for the determination of inorganic cations in biological fluids with direct sample injection. This involved the use of a mixed zwitterionic-micelle/electrolyte solution as an eluent. The proteins in the sample became bound to the zwitterionic micelles in the eluent and were thus eliminated from the column. The cations were separated by cation exchange. This method is ideal for the online, simultaneous determination of common inorganic cations (Na+, NH4+, K+, Mg2+, and Ca2+) in urine and serum samples. Such an application was demonstrated experimentally. Non-suppressed conductivity was used for analyte detection. The detection limits obtained using this IC system were 2.94, 5.22, 34.9, 32.6, and 56.7 microg/L for Na+, NH4+, K+, Mg2+, and Ca2+, respectively.     

二价金属离子对鲑鱼精DNA热稳定性的影响

二价金属离子与 DNA之间的作用在 DNA复制、转录以及新陈代谢过程中起到重要的作用 ,因此越来越受到关注 [1,2 ] .L uck等 [3 ]指出 ,碱土金属与 DNA分子的磷酸基团发生作用使 DNA的热稳定性升高 ,而二价过渡金属离子主要是与碱基作用而使 DNA热稳定性降低 . Eichhorn等 [4 ] 用变温紫外光谱法研究了在 DNA磷酸根离子的浓度较小 (0～ 4.0 )时 ,多种二价金属离子对小牛胸腺 DNA热稳定性的影响 ,发现 Mg2 + 及过渡金属离子 Mn2 + ,Co2 + 和 Ni2 + 都有利于 DNA的稳定 .最近 ,Duguid等 [5]用差示扫描量热法 (DSC)研究了在 c(M2 +…     

Application of multifunction group-containing ion exchange fibres for purification of waste water

The multifunction groups-containing ion exchange fibre is an amphoteric ion exchanger. It has high sorption capacities and good kinetic properties for the extraction of heavy metals. It might be an effective tool for removal and concentration of copper, cadmium, chromium, cobalt, nickel, lead, mercury, zinc and manganese.     

Influence of various monovalent cations and calcium ion on the colloidal fouling potential

The influence of various monovalent cations and of divalent calcium ions on colloidal fouling strength was investigated quantitatively on a bench-scale ultrafiltration device. A higher colloidal fouling potential (k) was consistently observed with lithium chloride compared to the same ionic strengths of chlorides of other monovalent cations (Na+, K+, and Cs+). This observation was attributed to the formation of an impervious layer around the colloidal particle by lithium ions that prevented the repulsive forces due to the interaction of the silica hairs formed on the particles in the presence of water. The impact of the divalent calcium ion on the fouling potential was more complex. The fouling potential first increased with calcium ion concentration and then decreased. The maximum value of fouling potential occurred at the ionic strength corresponding to the critical coagulation concentration, which decreased with increasing colloid concentration. The colloidal fouling potential was well correlated by a bilinear relationship with colloid concentration and ionic strength for all salts tested under the critical coagulation concentration.     

Ion-specific swelling of poly(styrene sulfonic acid) hydrogel

Poly(styrene sulfonic acid) (PSSA) hydrogel was prepared by radiation crosslinking using methyl N,N-bis-acrylamide as crosslinker. Effects of ion species and concentration on the swelling behavior of PSSA hydrogel were investigated in aqueous solution of selected anions (F-, Cl-, Br-, SCN-), cations (Li+, Na+, K+, Ca2+), and hydrophobic ions (tetramethylammonium cation TMA+, tetrabutylammonium cation TBA+, and dodecyltrimethylammonium cation TAB+). The deswelling extent of PSSA hydrogel follows anion Hofmeister series, i.e., SCN- < Br- < Cl- < F-, in solutions containing selected anions and K+ as counterion up to a concentration of 2 mol.L(-1). On the contrary, the deswelling extent of PSSA hydrogel in solutions containing selected cations and Cl- follows the sequence of Li+ < Na+ < K+ < Ca2+, which is the reverse of the Hofmeister series except Ca2+. We have discussed the effects of ions on the hydrogen bonding through SO3- and phenyl ring in salt solutions at low and high concentrations. Other interactions, such as the cation-pi and hydrophobic interactions, also contributed to the ion-specific swelling of PSSA hydrogel. The proposed mechanism was further elucidated by FTIR and NMR analysis. A very specific deswelling-reswelling phenomenon of PSSA hydrogel in KF solution has been observed and ascribed to the F- binding to phenyl ring through a specific interaction.