The Mechanism of Sol-Gel Synthesis of Normal Spinel LiMn_2O_4 with Chelation of Citric Acid

The sol-gel process of citric acid chelating with metal cations for the synthesis of normal spinel LiMn 2O 4 and the reaction mechanism were investigated by means of XRD,IR,TG-DTA, and SEM.The results show that at the beginning lithium citrate and chelate compound of citric acid with manganese ions formed,and then with heating the esterification and condensation reactions occured between them and glycol.The products obtained are polymers in which metal cations are distributed homogeneously on atomic scale that ensure high reactivity to cations of Li + and Mn 2+.Firing the gel prepared by this process,the lattice diffusions of solid reactant ions caused by non-homogeneity of reactants are eliminated and avoided.At 400℃ phase-pure LiMn 2O 4 with nanometer scale crystallization having precise stoichiometry and perfect crystallization can be obtained.The model of chelate coordinate of double-molecule between citric acid and Mn 2+ in the gel network is proposed.It is important for explaining the dispersion state of Mn 2+ and the formation process of gel by this model.

Synthesis of functional amino acids bearing 1,3-dithiane modification

Two protected single amino acid chelates,N~α-Fmoc-N~ε,N~ε-di((2,2-dimethyl-1,3-dithian-5-yl)methyl)-L-lysine(7) and N~α-Fmoc-N~ε-(2,2-dimethyl-1,3-dithian-5-yl)methyl,N~ε-Boc-L-lysine(9),were synthesized by modifying the side chain of lysine with 1,3-dithiane through direct reductive N-alkylation protocol.These amino acids have potential uses in peptide chemistry.

Flotation behavior and mechanism of rutile with nonyl hydroxamic acid

The flotation and surface interaction of rutile with nonyl hydroxamic acid were investigated in this work. The results show that the adsorption density and flotation recovery of rutile have similar tendency, especially the maximum recovery and adsorption occur at pH about 7.5. In terms of Fourier transform infrared（FTIR） spectroscopic analysis, chemical adsorption is identified on the surface of rutile, where a chelate of O,O-five-membered rings with Ti^4＋ on the surface of rutile may form. Adsorption measurements, Zeta potential test, IR spectrum analyses, and solution chemistry calculations illustrate that the adsorption on the rutile surface involves both physical and chemical adsorption, while chemical adsorption is dominant.

Fast removal of heavy metal ions and phytic acids from water using new modified chelating fiber

The graft copolymerization of acrylic acid（AA） onto polyethylene glycol terephthalate（PET） fiber initialed by benzoy peroxide （BPO） was carried out in heterogeneous media.Moreover,modification of the grafted PET fiber（PET-AA） was done by changing the carboxyl group into acylamino group through the reaction with dimethylamine.The modified chelating fiber（NDWJN1） was characterized using elementary analysis,SEM and FT-IR spectroscopy.Adsorption kinetic curves indicated that NDWJNl could fast remove heavy metal ions and phytic acids from water effectively.Furthermore,batch kinetic studies indicated that heavy metal ions adsorbed to NDWJNl could be filted well by both pseudo-first-order and pseudo-second-order adsorption equations,but the intra-particle diffusion played a dominant role in the adsorption of phytic acids.

Preparation and application of a novel orotic acid chelating resin for removal of Cu(Ⅱ) in aqueous solutions

A novel chelating resin OABA,capable of removing Cu（Ⅱ） from aqueous solution,was synthesized via the reaction of macroporous chloromethylated PS-DVB copolymer beads with orotic acid.The elemental analysis（EA）,Fourier transform infrared spectroscopy（FT-IR）,and scanning electron microscopy microscope-energy dispersive X-ray spectroscopy（SEM-EDS） were used in the characterization of the synthesized chelating resin.Multiple,static batch adsorption experiments were conducted at different initial concentrations and temperatures.OABA showed good adsorption capacity for Cu（Ⅱ） and the equilibrium data could be well matched with the Freundlich isotherm model.Coexisting sodium chloride and calcium chloride in solutions favored the Cu（Ⅱ） adsorption.Moreover,the desorption process of Cu（Ⅱ） was tested and over 90%regeneration efficiency for the spent OABA was achieved at ammonia concentrations ranging from 1.0%to 2.0%.The results suggested that OABA would be a potential alternative adsorbent for Cu（Ⅱ）,even with other heavy metal ion treatments of wastewater.

Influence of CaNa_2 EDTA on topical 5-aminolaevulinic acid photodynamic therapy

Background We asssessed whether the CaNa_2 EDTA could improve the accumulation of protoporphyrin Ⅸ (PpⅨ) and photosensitisation in HEp-2 cells as well as the depth of treatment of skin cancers on the topical 5-Aminolaevulinic acid (5-ALA) PDT.Methods HEp-2 cells were incubated with 5-ALA (0-1mmol/L) and CaNa_2EDTA (0-1mmol/L) for 4 hours,intracellular protoporphyrin Ⅸ content was quantified by extraction,and cell viability was assessed by use of the methyl-tetrazolium (MTT) assay four hours after exposure to light. In comparison with the pictures before and after treatment,depth of treatment could be determined using a Acuson Sequioa 512 phase-array system in paired experiments.Results PpⅨ accumulation increased with increasing extracellular concentrations of ALA (0-1mmol/L). Adding 1mmol/L of CaNa_2EDTA increased 30% PpⅨ accumulation over the same period of incubation in the concentration of 1mmol/L ALA. Significant difference was observed between the 5-ALA alone group and 5-ALA combined CaNa_2 EDTA group in the PpⅨ accumulation ( P <0.01). Cell viability after exposure to light decreased with adding CaNa_2 EDTA,a statistical difference in a same fluence above 1.2 J/cm 2 between two groups was demonstrated ( P <0.05,P <0.01 respectively). Depth of treatment of skin cancers were increased in CaNa_2 EDTA-treated group.conclusion CaNa_2 EDTA could improve the PpⅨ accumulation and photosensitisation in HEp-2 cells. Clinically,CaNa_2 EDTA could increase the depth of treatment in the cutaneous cancers.

Environmentally relevant concentrations of aminopolycarboxylate chelating agents mobilize Cd from humic acid

Although Cd is a pollutant of public health relevance,many dietary sources from which it can be absorbed into human tissues remain unknown.While it is well established that the biogeochemical cycle of Cd involves its complexation with environment-derived ligands（e.g.,humic acids,HAs） and anthropogenic ones（e.g.,chelating agents,CAs）,the interaction of Cd with both of these ligands is less well understood.To gain insight,a HA–Cd complex was injected on a size-exclusion chromatography（SEC） column coupled on-line with a flame atomic absorption spectrometer（FAAS） using 10 mmol/L Tris buffer（pH 8.0） as the mobile phase.This approach allowed us to observe the intact HA–Cd complex and the retention behavior of Cd as a function of 2–20 μmol/L concentrations of ethylenediaminetetraacetic acid（EDTA）,diethylenetriaminepentaacetic acid（DTPA） or methylglycinediacetic acid（MGDA） that were added to the mobile phase.An increase of the retention time of Cd was indicative of a partial or complete abstraction of Cd from HA.Our results revealed that all CAs abstracted Cd from the HA–Cd complex at concentrations of 5 μmol/L,while MGDA and DTPA were effective at 2 μmol/L.The bioavailability of some of the on-column formed CA–Cd complexes explains the previously reported increased accumulation of Cd in periphyton in the ecosystem downstream of wastewater treatment plants.In addition,our results imply that the use of effluents which contain CAs and Cd for the irrigation of food crops can introduce Cd into the food supply and compromise food safety.

Synthesis of functional amino acids bearing 1,3-dithiane modification

Two protected single amino acid chelates, NaFmoc-Nc, Ncdi（（2,2-dimethyl-1, 3-dithian-5-yl）methyl）-L-lysine （7） and NaFmoc-Nc-（2,2-dimethyl-l,3-dithian-5-yl）methyl, Nc-Boc-L-lysine （9）, were synthesized by modifying the side chain of lysine with 1,3-dithiane through direct reductive N-alkylation protocol. These amino acids have potential uses in peptide chemistry.