Protective efficacy of an H5/H7 trivalent inactivated vaccine(H5-Re13,H5-Re14, and H7-Re4 strains) in chickens, ducks, and geese against newly detected H5N1, H5N6, H5N8, and H7N9 viruses

Some H5 viruses isolated in poultry or wild birds between 2020 and 2021 were found to be antigenically different from the vaccine strains(H5-Re11 and H5-Re12) used in China. In this study, we generated three new recombinant vaccine seed viruses by using reverse genetics and used them for vaccine production. The vaccine strain H5-Re13 contains the hemagglutinin(HA) and neuraminidase(NA) genes of an H5 N6 virus that bears the clade 2.3.4.4 h HA gene, H5-Re14 contains the HA and NA genes of an H5 N8 virus that bears the clade 2.3.4.4 b HA gene, and H7-Re4 contains the HA and NA genes of H7 N9 virus detected in 2021. We evaluated the protective efficacy of the novel H5/H7 trivalent inactivated vaccine in chickens, ducks, and geese. The inactivated vaccine was immunogenic and induced substantial antibody responses in the birds tested. Three weeks after vaccination, chickens were challenged with five different viruses detected in 2020 and 2021: three viruses(an H5 N1 virus, an H5 N6 virus, and an H5 N8 virus) bearing the clade 2.3.4.4 b HA gene, an H5 N6 virus bearing the clade 2.3.4.4 h HA gene, and an H7 N9 virus. All of the control birds shed high titers of virus and died within 4 days post-challenge, whereas the vaccinated chickens were completely protected from these viruses. Similar protective efficacy against H5 viruses bearing the clade 2.3.4.4 h or 2.3.4.4 b HA gene was observed in ducks and geese. Our study indicates that the newly updated H5/H7 vaccine can provide solid protection against the H5 and H7 N9 viruses that are currently circulating in nature.

Protective efficacy of an H5/H7 trivalent inactivated vaccine produced from Re-11, Re-12, and H7-Re2 strains against challenge with different H5 and H7 viruses in chickens

We developed an H5/H7 trivalent inactivated vaccine by using Re-11, Re-12, and H7-Re2 vaccine seed viruses, which were generated by reverse genetics and derived their HA genes from A/duck/Guizhou/S4184/2017(H5N6) (DK/GZ/S4184/17) (a clade 2.3.4.4d virus), A/chicken/Liaoning/SD007/2017(H5N1) (CK/LN/SD007/17) (a clade 2.3.2.1d virus), and A/chicken/ Guangxi/SD098/2017(H7N9) (CK/GX/SD098/17), respectively. The protective efficacy of this novel vaccine and that of the recently used H5/H7 bivalent inactivated vaccine against different H5 and H7N9 viruses was evaluated in chickens. We found that the H5/H7 bivalent vaccine provided solid protection against the H7N9 virus CK/GX/SD098/17, but only 50–60% protection against different H5 viruses. In contrast, the novel H5/H7 trivalent vaccine provided complete protection against the H5 and H7 viruses tested. Our study underscores the importance of timely updating of vaccines for avian influenza control.

Improvement of stability of trivalent chromium electroplating of Ti based IrO_2+Ta_2O_5 coating anodes

The preparation process and properties of the thermally prepared Ti anodes coated with IrO2+Ta2O5 was studied. The structure and morphologies of the IrO2+Ta2O5 coatings were determined by XRD and SEM. Their electrochemical properties were studied by polarization curve and cyclic voltammetry. Trivalent chromium electroplating using Ti/IrO2+Ta2O5 anodes is carried out and the results were analyzed. Results show that this anode exhibits excellent electrochemical activity and stability in sulfate electrolysis. The electrocatalytic activity is determined not only by the content of IrO2 but also the structure and morphology of the anode coatings. The electroplating results indicats that Ti/IrO2+Ta2O5 anodes have excellent capabilities and merits in improving the stability of trivalent chromium electroplating in sulfate system.

Influence of glycine additive on corrosion and wear performance of electroplated trivalent chromium coating

The aim of this study is to evaluate the effect of various molar ratios of glycine to chromium salt(Gly:Cr)and different current densities on the corrosion and wear behaviors of Cr(III)electroplated coatings.The morphology and thickness of the coatings were investigated by scanning electron microscopy.The wear properties of the coatings were studied using pin on disk and hardness tests,while corrosion behavior of the coatings was identified using linear polarization,small amplitude cyclic voltammetry,and electrochemical impedance spectroscopy methods.By increasing the glycine concentration,a structure with low crack density was obtained.In all molar ratios,maximum thickness and current efficiency was observed at a current density of 150 mA·cm?2.All the electrochemical methods had a consistent result,and maximum corrosion resistance of approximately 16000Ω·cm2 was obtained in the case of Gly:Cr=3:1 and current density of 200 mA·cm?2.

The Hardness and Corrosion Properties of Trivalent Chromium Hard Chromium

The formulation of hard chromium plating from trivalent chromium electrolyte and its related process have been intensively studied in this work. Through optimized conditions, the coating hardness can achieve more than HV0.1900 without any treatment and HV0.11700 after heat treatment for five minutes at 300°C, and the thickness of hard chromium coating was about 100 μm. The hard chromium coatings show good adhesion on the carbon steel and low alloy structural steel. The corrosion resistance of hard chromium coatings was enhanced by the adding nanometer materials into trivalent chromium plating coatings. More than 120 hours salt spray corrosion resistance can be achieved with 40 to 50 microns thickness of trivalent chromium plating coatings.

Preparation and Properties of Lanthanum Trivalent Ion Doped TiO_2 Nanopowders by Liquid Plasma Spray

The lanthanum trivalent ion doped TiO2 nanopowders were prepared by liquid plasma spray with solution of titanium tetra-tert-butoxide and alcohol as feedstock and La(NO3)3·6H2O as doping component. The photocatalytic activity of samples at different doping concentrations in photocatalytic degradation of methyl orange was discussed. The powders were characterized by Transmission Electron Microscopy (TEM) and X-Ray Diffraction (XRD), and the effect of doped ion on the pattern, phase composition and crystallite sizes were analyzed. The results indicated that lanthanum trivalent ion doped TiO2 nanopowders could be prepared by liquid plasma spray. Lanthanum trivalent ion doping increased the photocatalytic activity of TiO2 greatly, the optimal doping concentration was 0.5%. The doped powders were the mixture of anatase phase and rutile phase. The contents of anatase phase decreased firstly and then increased with an increase in the contents of lanthanum trivalent ion. Doping lanthanum trivalent ion could make the TiO2 nanopowders uniform and reduced its particle size.

Supercritical Fluid Chromatography—Mass Spectrometry (SFC-MS) and MALDI-TOF-MS of Heterocyclic Compounds with Trivalent and Pentavalent Nitrogen in Cough Relief Medical Forms Tuxi and Cosylan

Alkaloids are natural, semisynthetic or synthetic organic compounds, normally polar with basic chemical properties and containing at least one nitrogen atom in a heterocyclic ring. Some synthetic or semisynthetic substances resemble the alkaloid architecture. Trivalent nitrogen in these substances is normal;however, some natural and semisynthetic alkaloids have pentavalent nitrogen. The drug pholcodine is a derivative of morphine. Pholcodine has very little addiction- developing effect. It is a semisynthetic alkaloid that was first synthesized in 1950 by Chabrier et al. Pholcodine possesses antitussive (cough relief) properties similar to codeine, morphine and ethylmorphine. The drug was used in liquid formulations as Tuxi and Tuxi Forte, and it is in present use in Tuxidrin as liquid mixture and in tablet form. Pholcodine is an Active Pharmacological Ingredient (API) in tablets and liquid mixtures. Leiras International and Weifa in Norway manufacture medical forms with pholcodine. Several impurities in pholcodine were described by J. Roe in 1997 and by Denk et al. in 2000 and 2002. In addition, several degradation products may be formed in liquid formulations under storage. Some of these products are related not to the original production of pholcodine but rather to its oxidation under storage. The appearance of degradation products strongly depends on the storage temperature and pH of the liquid phase. Pholcodine-N-oxide and pholcodine-N,N’-dioxide are among the degradation (oxidation) products;pholcodine can also degrade to morphine. There is little information about the toxicity of the N-oxide and no information on the N,N’-di- oxide of pholcodine. In this study, the fact that morphine is generated during the storage of formulations containing pholcodine is presented. Another antitussive mixture under the name Cosylan was analyzed to examine the oxidation of ethylmorphine to ethylmorphine-N-oxide. Ethylmorphine is the API in Cosylan.

Hydrothermal Synthesis, Crystal Structure, and Characterization of a Novel Terbium(Ⅲ) Coordination Polymer Bridged by 5-Sulfoisophthalate Trivalent Anions

Hydrothermal reaction of terbium（ Ⅲ） chloride with 5-sulfoisophthalic acid monosodium salt and 1,10-phenanthroline（phen） at 415 K resulted in the formation of a novel coordination polymer, [ Tb （sip） （phen） （H2O） ],（sip =5-sulfoisophthalate trivalent anion） with a three-dimensional network structure. Each centrosymmetrically related pair of terbium ions axe linked by two sip anions, forming a binuclear unit, and each binuclear unit links to four adjacent tetranuclear units, extending a two-dimensional hybrid layer at crystallographic bc plane. On the other hand, every three-terbium ion is connected by three sip anions, generating a trinuclear ring, and the trinuclear ring connects six neighboring trinuclear rings to produce another two-dimensional layer at crystallographic ab plane. Moreover, each sip anion acts as a pontadentate bridge, interconnecting two different types of layers to yield a novel three-dimensional framework.

Hydrothermal Synthesis and Crystal Structure of Binuclear Copper(Ⅱ) Complex Bridged by 1,2,4,5- Benzenetetracarboxylato Trivalent Anion

The title complex [(phen) 2Cu(Htcb)Cu(phen) 2]H 3tcb(tcb=1,2,4,5-benzenetetracarboxylato tetravalent anion; phen=1,10-phenanthroline) was synthesized by the hydrothermal synthesis method. The crystal structure was determined by single-crystal X-ray diffraction analysis. It crystallizes in the triclinic system with space group P1, a=1.04174(8) nm, b=1.07119(8) nm, c=1.26360(10) nm, α=98.169(2)°, β=99.679(10)°, γ=93.658(10)°, V=1.37031(18) nm3, Z=1. The two copper(Ⅱ) cations are bridged by Htcb in the monodentate fashion, and have the same five-coordinated environment completed by the four N atoms from the two phen molecules and one O atom from the carboxylic group of Htcb respectively, which can be best described as distorted trigonal-bipyramid geometry. Moreover, the three dimensional network is formed by H-bonding interactions [O…O distance from 0.2506(10) nm to 0.3176(11) nm] and π-π stacking interactions between the phen rings of adjacent binuclear entities with a face-to-face separation of ca. 0.354 nm.

Impact of Corrosive Liquid on Trivalent Chromium over Aluminium Alloys

Considering aviation and space sectors, aluminium alloys are commonly used due to its excellent mechanical and physical properties. Though satellite hard-ware is confined to controlled environment, it requires anticorrosive treatment over metal substrate followed by a systematic coating scheme. The trivalent chromium coating was deposited over three aluminium alloys namely AA6063, AA7075 and AA6082. The variation in corrosion resistance property of trivalent chromium over each aluminium alloy has been studied in detail. The Neutral Salt Spray (NSS) test result shows that trivalent chromium coating over AA7075 alloy is affected by pitting corrosion compared to other two alloys. In addition to that, NSS test also proves that thickness of the layer does not have any influence corrosion resistance property of trivalent chromium coating. Furthermore, ions in trivalent chromium coating was identified using Secondary Neutral Mass Spectroscopy (SNMS) and degradation of coating in a corrosive liquid studied using Inductively Coupled Plasma Optical Emission Spectroscopy (ICP-OES) instrument to understand mechanism of corrosion. The results indicated that both coating and substrate is involved in corrosion process. The number of elements dissolved in to salt solution reveals the weak ionic bonding of coating towards substrates. In comparison, AA7075 alloy has weaker bonding than AA6082 and AA6063 series. The alloying elements such as zinc and copper are removed from substrate by corrosive solution.

Trivalent Chromium Promotes Healing of Experimental Colitis in Mice by Suppression of Inflammation and Oxidative Stress

Ulcerative colitis (UC) has reactive oxygen species (ROS) and immunologic pathways implicated in its pathogenesis. The search for new therapeutic protocols in managing UC is tailored in suppressing or preventing these pathways. The influence of trivalent chromium (Cr3+), an essential mineral on experimental colitis was investigated. Mice were grouped into 3;group 1 (control) received clean drinking water while groups 2 and 3 received 10 and 100 ppm Cr3+ respectively for 12 weeks through drinking water. After Cr3+ administration, 5 animals per group were sacrificed on day 0. Thereafter, experimental colitis was induced intra-rectally using acetic acid (4%, 0.3mL) and 5 mice per group were subsequently sacrificed on days 3, 7 and 14. Blood and colonic tissues were obtained and processed appropriately. Blood Cr3+ level, haematological variables, gross and microscopic colitis scores, colonic myeloperoxidase (MPO), Superoxide Dismutase (SOD) and malondialdehyde (MDA) levels were determined using standard methods. Colon cytokine mRNA genes were quantified using real-time PCR. There was a significant decrease in colon gross and histology scores on days 3 and 7 in chromium treated compared with control. The MPO and MDA in chromium groups reduced significantly compared with control while SOD activities increased significantly in Cr3+ groups compared with control. Total RNA increased in chromium groups compared with control on day 3 post-colitis. There was up-regulation of IL-10, down-regulation of TNF-α and IFN-λ in chromium administered groups compared with control. Chromium enhanced healing of colitis by suppression of ROS, inflammation and promotion of antioxidant activities.

Mass Spectrometric Structure Elucidation of the Trivalent and Pentavalent Nitrogen Contaminants of Pholcodine in the Cough Relief Medical Form Tuxidrin

In the paper “Supercritical Fluid Chromatography-Mass Spectrometry (SFC-MS) and MALDI-TOF-MS of Heterocyclic Compounds with Trivalent and Pentavalent Nitrogen in Cough Relief Medical Forms Tuxi and Cosylan” [1], the presence of morphine and other degradation products of pholcodine in cough relief medical forms of Tuxi are discussed. Tuxiis recalled from the Norwegian market by Weifa pharmaceutical company, and hence it no longer presents problems to users and health authorities there;however, the medical form Tuxidrin, which contains a significant amount of pholcodine as the active pharmacological ingredient, is still marketed. In the present paper, Tuxidrin is analyzed to determine the presence of degradation products of pholcodine. The degradation of pholcodine to morphine has been discussed previously as a factor in the development of addiction to narcotics in young persons. The structures of the contaminants in Tuxidrin, such as oxides of pholcodine, are elucidated in the present paper. The toxicity and pharmacology of oxides of alkaloids have generally not been well studied, and very little is known about the toxicity and pharmacology of the degradation (oxidation) products of pholcodine: the N-oxide and the N, N'-dioxide of pholcodine. According to Brondz and Brondz[1], the N-oxide and possibly also the N, N'-dioxide are less toxic than the original alkaloids and possess greater pharmacological activity, and hence they may be a source of useful new semisynthetic drugs. The question of possible addiction to pholcodine oxides has not been studied, and the potential of these substances to provoke allergies is unclear. The recall of Tuxi from the Norwegian marketis mainly based on the fact that pholcodine causes significantly increased levels of IgE antibodies in sensitized patients. Tuxidrin contains pholcodine and has the same negative effect as Tuxi, namely provoking allergies or even anaphylactic shock. From this point of view, Tuxidrin has no advantage over Tuxi. These two medical forms only differ in one respect: Tuxidrin requires a prescription (prescription duty medicine), but Tuxi doesnot (prescription free medicine). This aspect is also discussed in the present paper.

Synthesis, characterization and photophysical properties of quinolin-8-olato chelated osmium(II) organometallics bearing a pendant imine-phenol motif and electrogeneration of trivalent analogue

The reaction of Os(RL1)(PPh3)2(CO)Br, 1b, with qui-nolin-8-ol (HQ), 2, has furnished complexes of the type [Os(RL2)(PPh3)2(CO)(Q)], 3, in excellent yield (RL1 is C6H2O-2-CHNHC6H4R(p)-3-Me-5, RL2 is C6H2OH-2-CHNC6H4R(p)-3-Me-5 and R is Me, OMe, Cl). In this process, quinolin-8-olato (Q) undergoes five-membered chelation, the iminium-phenolato function tautomerizing to the imine-phenol function. The trans geometry of the Os(PPh3)2 fragment is consistent with the occurrence of a single 31P resonance near –6.0 ppm in 3. In dichloromethane solution, 3 displays a quasireversible 3+/3 couple near 0.40 V vs. SCE (3+ is the osmium (III) analogue of 3). Coulometrically generated solutions of 3+ displays a strong absorption near 340 nm, 415 nm and 500 nm and are one-electron paramagnetic (low-spin d5, S = 1/2) and show rhombic EPR spectra in 1:1 dichloromethanetoluene solution at 77 K with g values near 2.44, 2.20, 1.83. Distortion parameters using the observed g values have been computed. Solutions of 3 absorb near 420 nm and emit near 510 nm at 298 K and 580 nm at 77 K. The fluorescence is believed to originate from the 3MLCT state.

A Comparative Study on the Hemato-Biochemical and Immunological Effects of the Hexavalent FMD Vaccine Alone or in Combination with Trivalent FMD Vaccine in Cattle

Foot and mouth disease is the most contagious disease of mammals and has a great potential for causing severe economic loss in susceptible cloven-hoofed animals. Routine prophylactic vaccination in Egypt from 2012 till now has been conducted with Trivalent and/or hexavalent vaccine of MERIAL, against virus strains (O manisa + O-3039 + A Iran 05 + A Saudi 95 + Asia 1 + Sat2). This study aimed to evaluate the hemato-biochemical and immunological changes associated with the use of hexavalent vaccine alone or in combination with trivalent FMD vaccine. This study was carried out on 24 cattle divided into three groups eight cattle each. Group I served as control. Group II were selected from farms vaccinated with hexavalent FMD vaccine. Group III were selected from farms vaccinated with a combination of trivalent and hexavalent FMD vaccine. The results showed that both vaccinated groups showed a significant increase in total leukocytic count. Sera from hexavalent-trivalent vaccinated cattle demonstrated a significant increase in serum cortisol concentrations. Significant increase in serum activity of aspartate aminotransferase was recorded in animals vaccinated with a combination of hexavalent and trivalent vaccine. In addition, both regimes resulted in a significant increase in serum blood urea nitrogen compared to control. Both regimes induced a significant increase in serum levels of ceruloplasmin while phagocytic activity of neutrophils and phagocytic index was enhanced only by the hexavalent vaccine. Both vaccinated groups had significantly increased serum values of gamma globulins. These results suggested that hexavalent vaccine produced higher levels of safety and protective effects against FMD in cattle as compared to those produced by a combination of hexavalent and trivalent vaccines. It is also advisable to include the hexavalent vaccine within the program of obligatory and imperative vaccination against FMD.

Full-profile pharmacokinetics, anticancer activity and toxicity of an extended release trivalent PEGylated irinotecan prodrug

Irinotecan is an anticancer topoisomerase I inhibitor that acts as a prodrug of the active metabolite,SN-38.Unfortunately,the limited utility of irinotecan is attributed to its pH-dependent stability,short half-life and dose-limiting toxicity.To address this problem,a novel trivalent PEGylated prodrug(PEG-[Irinotecan]3)has been synthesized and its full-profile pharmacokinetics,antitumor activity and toxicity compared with those of irinotecan.The results show that after intravenous administration to rats,PEG-[Irinotecan]3 undergoes stepwise loss of irinotecan to form PEG-[Irinotecan]3-x(x=1,2)and PEG-[linker]during which time the released irinotecan undergoes conversion to SN-38.As compared with conventional irinotecan,PEG-[Irinotecan]3 displays extended release of irinotecan and efficient formation of SN-38 with significantly improved AUC and half-life.In a colorectal cancer-bearing model in nude mice,the tumor concentrations of irinotecan and SN-38 produced by PEG-[Irinotecan]3 were respectively 86.2 and 2293 times higher at 48 h than produced by irinotecan.In summary,PEG-[Irinotecan]3 displays superior pharmacokinetic characteristics and antitumor activity with lower toxicity than irinotecan.This supports the view that PEG-[Irinotecan]3 is a superior anticancer drug to irinotecan and it has entered the phaseⅡtrial stage.

晶体电场对离子自旋─轨道耦合参数的影响

晶体电场对三价稀土离子自旋─轨道耦合参数有影响，是人们长期怀疑但尚无人作过定量分析与计算的问题．本文从相对论Ｄｉｒａｃ方程式给出的电子自族─轨道耦合参数表达式出发，以稀土氯化物为例，首次详细计算了晶体电场对稀土离子（Ｃｅ３＋、Ｐｒ３＋、Ｎｄ３＋、Ｓｍ３＋、Ｅｕ３＋、Ｇｄ３＋、Ｄｙ３＋、Ｅｒ３＋、Ｙｂ３＋）４ｆ自旋─轨道耦合参数贡献的相对大小．计算结果表明：晶体电场对电子自旋─轨道耦合参数的贡献至多占稀土离子核库仑场贡献的万分之一，因此可以忽略不计．寻找电子自旋─轨道耦合参数实验值与理论值差别的途径，应该从离子的电子结构本身着手来研究．

Structure, Chemical State and Luminescent Properties of Ce,Gd：YAG Transparent Ceramic for Flip-chip White LED Application

Ce,Gd：YAG transparent ceramic was prepared by tape casting and solid state reaction method. Meanwhile, its crystal structure, chemical state and luminous properties were discussed. The prepared samples are identified as pure garnet structure by the XRD results. The valence states of tetravalent and trivalent Ce ions were identified distinctly by X-ray photoelectron spectroscopy. A strong broad band yellow emission was found in photoluminescence（PL） spectra. The quantum yield reached 90.2% at room temperature. When collaborated with a 1.0 mm × 1.0 mm flip-chip, a luminous efficiency（LE） as high as 116.5 lm/W with a correlated color temperature（CCT） of 6627 K at a power dissipation of 1.13 W at 350 m A was demonstrated, indicating that Ce,Gd：YAG transparent ceramics had a promising potential for high power white light-emitting diodes.

Novel Cr^(3+)-activated far-red emitting phosphors withβ-Ca_(3)(PO_(4))_(2)-type structure for indoor plant cultivation

Cr^(3+)-activated far-red and near-infrared phosphors have drawn considerable attention owing to their adjustable emission wavelengths and wide applications.Herein,we reported a series of Cr^(3+)-doped phosphors withβ-Ca_(3)(PO_(4))_(2)-type structure,of which Ca_(9)Ga(PO_(4))_(7):Cr^(3+) possessed the highest far-red emission intensity.At an excitation of 440 nm,the Ca_(9)Ga(PO_(4))_(7):Cr^(3+) phosphors exhibited a broad emission band ranging from 650 to 850 nm and peaking at 735 nm,and the broadband superimposed two sharp lines centering at 690 and 698 nm.The optimal sample Ca_(9)Ga_(0.97)(PO_(4))_(7):0.03 Cr^(3+) had an internal quantum efficiency of 55.7%.The luminescence intensity of the Ca_(9)Ga_(0.97)(PO_(4))_(7):0.03 Cr^(3+) phosphor obtained at 423 K could maintain 68.5%of that at room temperature,demonstrating its outstanding luminescence thermal stability.A phosphor-conversion light-emitting diode was fabricated,indicating that the Ca_(9)Ga(PO_(4))_(7):Cr^(3+) phosphor has potential applications in indoor plant cultivation.

Electroplating process of amorphous Fe-Ni-Cr alloy

A novel process of electroplating amorphous Fe Cr Ni alloy in chloride aqueous solution with Fe(Ⅱ), Ni(Ⅱ) and Cr(Ⅲ) was reported. Couple plasma atomic emission spectrometry (ICP AES), X ray diffractometry(XRD), scanning electronic microscopy(SEM), microhardness test and rapid heating cooling method were adopted to detect the properties of the amorphous Fe Ni Cr deposit, such as composition, crystalline structure, micrograph, hardness, and adherence between deposit and substrate. The effects of the operating parameters on the electrodeposit of the amorphous Fe Ni Cr alloy were discussed in detail. The results show that a 8.7?μm thick mirror like amorphous Fe Ni Cr alloy deposit, with Vicker’s hardness of 530 and composition of 45%～55% Fe, 33%～37% Ni, 9%～23% Cr was obtained by electroplating for 20?min at room temperature(10～30?℃), cathode current 10～16?A/dm 2, pH=1.0～3.0. The XRD patterns show that there only appears a broad hump around 2 θ of 41?°～47?°for the amorphous Fe Ni Cr alloy deposit, while the SEM micrographs show that the deposit contains only a few fine cracks but no pinholes.

An improved implementable process for the synthesis of zeolite 4A from bauxite tailings and its Cr^(3+) removal capacity

A simple and practical method for the synthesis of zeolite 4A from bauxite tailings is presented in this paper. Systematic investigations were carried out regarding the capacity of zeolite 4A to remove Cr（III） from aqueous solutions with relatively low initial concentrations of Cr（III）（5–100 mg·L^（-1））. It is found that the new method is extremely cost-effective and can significantly contribute in decreasing environmental pollution caused by the dumping of bauxite tailings. The Cr（III） removal capacity highly depends on the initial p H value and concentration of Cr（III） in the solution. The maximum removal capacity of Cr（III） was evaluated to be 85.1 mg×g^（-1） for zeolite 4A, measured at an initial p H value of 4 and an initial Cr（III） concentration of 5 mg·L^（-1）. This approach enables a higher removal capacity at lower concentrations of Cr（III）, which is a clear advantage over the chemical precipitation method. The removal mechanism of Cr（III） by zeolite 4A was examined. The results suggest that both ion exchange and the surface adsorption-crystallization reaction are critical steps. These two steps collectively resulted in the high removal capacity of zeolite 4A to remove Cr（III）.