Efficiency,mechanism and microbial community of Cd(II) removal by mixed bacteria enriched from heavy metals mine soil

Mixed bacteria were enriched from heavy metals mine soil for cadmium (Cd(II))-containing wastewater treatment. Batch adsorption experiment results showed that the optimal pH, temperature, initial Cd(II) concentration, and biomass dosage were 6.0, 30 °C, 20 mg/L, and 1 g/L, respectively. Living biomass exhibited better Cd(II) removal efficiency (91.97%) than autoclaved biomass (79.54%) under optimal conditions. The isotherms and kinetics of living biomass conformed to the Langmuir isotherm model and pseudo-first-order kinetic model, respectively. FTIR results implied that amine groups, hydroxyl groups and phosphoric acid play an important role in the Cd(II) adsorption process, while XRD results showed that crystalline Cd(OH)₂ and CdO were obtained. After Cd(II)-containing wastewater treatment exposure, the dominant bacteria genera included Comamonas (39.94%), unclassified_f__Enterobacteriaceae (34.96%), Ochrobactrum (14.07%), Alcaligenes (4.84%), Bordetella (2.07%), Serratia (1.04%), and Bacillus (1.01%). Function prediction showed that the abundance of metabolic genes changed significantly. This study proposes the potential application of mixed bacteria for Cd(II)-containing wastewater treatment.     

促植物生长内生细菌强化植物修复锌污染土壤

以超积累植物东南景天为材料,采用盆栽试验探讨了接种内生菌VI8L2、II8L4和VI8R2对土壤Zn有效性、植物生长和吸收积累锌的影响。结果表明,接种内生菌VI8L2、II8L4和VI8R2能够促进东南景天在Zn污染土壤中的生长,其根系和地上部的生物量分别比对照增加了80%~525%和11%~47%。在人工ZnCO3污染土壤中,接种菌株VI8L2、II8L4和VI8R2显著增加了东南景天根系和地上部的Zn含量;在人工Zn3(PO4)2污染土壤中,菌株VI8L2使东南景天地上部和根系的Zn含量分别比对照增加了44%和39%,但是菌株Ⅳ8R2显著降低了东南景天地上部的Zn含量;在长期被酸性废水污染水稻土壤中,接种菌株VI8L2、II8L4和VI8R2显著增加了东南景天根系的Zn含量,但降低了地上部的Zn含量。这表明金属抗性促生细菌可用于强化植物修复重金属污染土壤。     

Structure and magnetic properties of Cd doped copper ferrite

This report presents the synthesis of copper cadmium ferrite (Cu_1−xCd_xFe₂O_4,x = 0.3, 0.4, 0.5, 0.6 and 0.7) by citrate precursor method and its subsequent characterization by using X-ray diffraction (XRD), electron diffraction spectroscopy (EDS) and vibrating sample magnetometer (VSM) techniques. XRD results confirm the single cubic spinel phase formation with the particle size of 40 nm, which decreased up to 20 nm with increases in Cd content, while the lattice parameter increased with increase in Cd content. By using VSM technique, a significant change in the magnetic properties was observed in CuFe₂O₄ system with Cd doping. It is seen that magnetic field H_C and remnant magnetization M_R increases with increasing concentration up to x = 0.6 except for x = 0.4 and 0.7.     

Immobilization of Cd and Pb in soils by polymeric hydroxyl ferric phosphate

A polymeric hydroxyl ferric phosphate (PHFP) was prepared by using a byproduct of titanium dioxide containing ferrous sulfate and phosphates under alkaline condition. The PHFP was used to immobilize lead (Pb) and cadmium (Cd) in soils. Fourier transform infrared spectra, X-ray diffraction were applied to revealing the characteristics of PHFP, and the modified Tessier sequential extraction and column leaching experiment with simulated acid rain were used to assess the effectiveness of immobilization of Cd and Pb in soils by PHFP. The results showed that PHFP was indeed a polymer with complicated OH—Fe—P structure and consisted of Fe₆(OH)₅(H₂O)₄(PO₄)₄(H₂O)₂ and Fe₂₅(PO₄)₁₄(OH)₂₄. Moreover, the removal rates of DTPA-extractable Cd and Pb in soils reached up to 33% and 45%, and the water-soluble Cd and Pb decreased by 56% and 58%, respectively, when PHFP was added in soils at 4% dosage. In addition, the immobilization of Cd and Pb contributed to transforming water soluble, exchangeable and carbonate-bonded fractions to Fe and Mn oxides-bonded, organic-bonded and residual fractions. Under leaching with simulated acid rain, Cd and Pb release amount in PHFP amended soil declined by 53% and 52%, respectively, as compared with non-treated soil. The result implied that PHFP had a potential application for the remediation of Cd- and Pb-contaminated soils.     

改良剂对As、Cd、Pb污染土壤上芦竹生长及重金属吸收的影响(英文)

通过室内盆栽试验研究在As、Cd和Pb复合污染土壤中施用醋酸、柠檬酸、EDTA、海泡石和磷石膏5种改良剂对芦竹生长及重金属吸收的影响。结果表明,施加5.0mmol/kg柠檬酸或2.5mmol/kgEDTA时,芦竹地上部生物量较没添加的对照的分别增加了24.8%和15.0%,芦竹叶片中过氧化氢酶及过氧化歧化酶活性较对照的无显著变化。与对照相比,添加2.5mmol/kg醋酸、2.5mmol/kg柠檬酸、5.0mmol/kgEDTA及4.0g/kg海泡石时,地上部中As、Cd、Pb的浓度显著增加(P0.05)。改良剂能明显提高芦竹地上部重金属累积量,地上部中As、Cd的累积量在上述条件下均显著增加(P0.05),Pb累积量在添加4.0g/kg海泡石和8.0g/kg磷石膏时显著高于对照(P0.05)。醋酸、柠檬酸和海泡石可作为合适改良剂促进重金属污染土壤上芦竹对土壤中重金属的累积。     

Corrosion of electroplated CuCd alloys and its inhibition

The compounds o-, m- and p-phenylenediamine have been studied as possible inhibitors for use in the HNO₃ pickling of 94/6 and 80/20 CuCd electrodeposits on copper. Weight-loss and polarization data indicate that effective inhibition can be obtained for short periods of treatment and that effectiveness increases in the order p < m < o.     

Doping and annealing effects on ZnO:Cd thin films by sol-gel method

In this article, ZnO:Cd films were successfully deposited on glass substrates by a sol-gel technique. The influence of doping concentration and annealing temperature effects was carefully investigated. All films exhibited c-axis preferential orientation and optical transparency with visible transmittance >80%. The minimum room temperature resistivity of 0.0341 Ω cm was obtained with 10 at.% Cd doping under 600 °C annealing temperature. The optical band gap of ZnO:Cd film was reduced as Cd doping concentration increased, while the band gap increased with the increase of annealing temperature.     

Selective separation of Cu(II), Zn(II), and Cd(II) by solvent extraction

An experimental investigation was presented on the separation of Cu (II), Zn (II), and Cd (II) from a rich sulfate leachate of zinc slag by solvent extraction. The results of orthogonal experiments indicate that LIX 984N is highly selective and very efficient in the extraction of Cu (II), and the analysis of variance indicates that the sequence of parameters according to their influence on the separation efficiency is phase ratio>LIX 984N concentration>pH value>extraction time. The optimal condition for copper extraction is obtained as 25% of LIX 984N concentration, 7 min of extraction time, 3:2 of phase ratio O/A, and pH=1.7. The separation of Zn (II) and Cd (II) was performed after the copper extraction from the raffinate. Comparative analysis of the separation with di-2-ethylhexyl phosphoric acid (D2EHPA), D2EHPA-tributyl-phosophate (TBP) synergistic extracting system, and 2-ethylhexyl phosphonic acid mono 2-ethylhexyl ester (HEHEHP) was made at pH=2.0. It is demonstrated that the extraction efficiency with D2EHPA is improved after being saponified by sodium hydroxide, and D2EHPA-TBP synergistic extracting, as well as HEHEHP, has a superior selectivity to Zn (II) over Cd (II).     

Effects of Cd addition in welding wires on microstructure and mechanical property of wire and arc additively manufactured Al−Cu alloy

Wall structures were made by cold metal transfer-based wire and arc additive manufacturing using two kinds of ER2319 welding wires with and without Cd elements. T6 heat treatment was used to improve mechanical properties of these wall structures. Due to the higher vacancy binding energy of Cd, Cd-vacancy clusters are formed in the aging process and provide a large number of nucleation locations for θ′ phases. The higher diffusion coefficient of the Cd-vacancy cluster and the lower interfacial energy of θ′ phase lead to the formation of dense θ′ phases in the heat-treated α(Al). According to the strengthening model, after adding Cd in ER2319 welding wires, the yield strength increases by 43 MPa in the building direction of the heat-treated wall structures.     

Large magnetocaloric effect in a wide temperature range induced by two successive magnetic phase transitions in Ho2Cu2Cd compound

The magnetic and magnetocaloric properties of Ho₂Cu₂Cd compound have been studied. The compound reveals two successive magnetic phase transitions at 30 K and 15 K which are corresponding to the paramagnetic to ferromagnetic transition and a spin reorientation, respectively. Two successive magnetic transitions in Ho₂Cu₂Cd resulting two peaks in the temperature dependence of magnetic entropy change curves, −ΔS_M (T). Two peaks are partly overlapped and induced a large MCE in a wide temperature range, i. e., large refrigerant capacity (RC) and relative cooling power (RCP). For a magnetic field change of 0–7 T, the values of maximal −ΔS_M, RC and RCP are 25.1 J/kg K, 527 J/kg and 732 J/kg for Ho₂Cu₂Cd, respectively.     

Effects of Cd and Sn on double-peak age-hardening behaviors of Al-Si-Cu-Mg cast alloys

The effects of trace elements Cd and Sn on precipitation process of Al-Si-Cu-Mg cast alloys were investigated in the present research.It is shown that the addition of Cd and Sn not only increases remarkably the aging peak hardness and reduces the time to reach aging peak,but also eliminates the double-aging-peak phenomenon which appears in Al-Si-Cu-Mg alloys.In Al-Si-Cu-Mg alloys the first aging peak corresponds to GP zones(especially GPⅡ) ,and the second one is caused by metastable phases.The obvious time interval of transition from GPⅡ to metastable phases associates with the double-aging-peak phenomenon.The results of DSC and TEM show that Cd/Sn elements suppress the formation of GPⅠzone,stimulate the formation of θ",θ' and θ phases,and then shorten remarkably the temperature intervals of each exothermic peak.Because the transition interval between GPⅡzone and metastable phases is shortened by Cd/Sn in Al-Si-Cu-Mg cast alloys,θ' phase coexists with θ" phase in matrix of ageing peak condition,which causes effective hardening on the alloys,and at the same time,eliminates the double-aging-peak phenomenon.     

水域底泥中重金属Cd与Pb释放规律的数值模拟

采用实验研究与数值模拟相结合的方法,研究某水域底泥中典型重金属污染物Cd与Pb再释放过程和释放速率。结果表明,底泥中Cd和Pb的释放规律分为快速释放和动态平衡两个阶段,与准二级动力学方程具有较好的匹配度,相关系数R2大于0.99。随着河流流速的加快,底泥中重金属的释放速率增大。分析表明,该区域水质可以在3 h内超过地表水环境质量V类标准。数值模拟结果与实测值之间的相对偏差除一项外均在±10%以内。     

Comparison of corrosion-resistance and hydrogen permeation properties of Zn-Ni, Zn-Ni-Cd and Cd coatings on low-carbon steel

Zn-Ni-Cd alloy was electroplated from an alkaline sulfate bath under potentiostatic conditions. The corrosion and hydrogen permeation characteristics of Zn-Ni-Cd alloy coatings electrodeposited from alkaline bath were studied and compared with those of Cd and Zn-Ni coatings obtained using commercial baths. Zn-Ni-Cd alloy was electroplated from an alkaline sulfate bath under potentiostatic conditions. The corrosion potential of this Zn-Ni-Cd coating was −0.62 V vs. SCE, which is still negative potential compared to iron. The corrosion rate of Zn-Ni-Cd coated steel was 0.073 mm y⁻¹, which is estimated in a solution at a pH of 7. This value is much lower than the corrosion rate of Zn-Ni alloy (0.502 mm y⁻¹) and Cd (0.306 mm y⁻¹) coatings deposited from commercial baths. Zn-Ni-Cd alloys are also demonstrated to have superior hydrogen permeation inhibition properties compared to Cd and Zn-Ni coatings. Kinetic parameters of hydrogen permeation such as the transfer coefficient, α, the modified exchange current density, i₀^′, thickness dependent adsorption-absorption rate constant, k^″, recombination rate constant, k₃, surface hydrogen coverage, θ_s, were evaluated by applying a mathematical model to analyze experimental results.     

Precipitation Hardening of Cu-3Ti-1Cd Alloy

Precipitation strengthening of Cu-3Ti-1Cd alloy has been studied using hardness and tensile tests, electrical resistivity measurements, and transmission electron microscopy. The alloy exhibited a hardness of 117 Hv in solution-treated (ST) condition and attained a peak hardness of 288 Hv after aging at 450 °C for 72 h. Electrical conductivity increased from 7%IACS (International Annealed Copper Standard) in ST condition to 13%IACS on aging at 450 °C for 16 h. The alloy exhibited yield strength (YS) of 643 MPa and ultimate tensile strength (UTS) of 785 MPa in peak-aged (PA) condition. Strengthening in Cu-3Ti-1Cd alloy in PA condition is attributed to solid solution strengthening effect of cadmium (Cd) as well as fine scale precipitation of metastable and coherent β′-Cu₄Ti phase. On overaging at 450 or 500 °C, the alloy showed a decrease in hardness as a result of formation of equilibrium precipitate β-Cu₃Ti as continuous precipitation within the matrix and as discontinuous precipitation at the grain boundaries. While the tensile properties are better, the electrical conductivity of Cu-3Ti-1Cd alloy is less than that of binary Cu-2.7Ti alloy. The strengthening mechanism is the same in both binary and ternary alloys of Cu-Ti, i.e., precipitation of metastable and coherent β′-Cu₄Ti phase.     

Monotectic Al/Cd alloys with homogeneously dispersed Cd-droplets stabilized by strontium aluminide precipitates

Al-rich Al–Sr alloys contain dispersed Al₄Sr precipitates in the Al-matrix. When melted and emulsified together with a smaller volume of Cd, Cd-rich droplets are formed (being immiscible with the Al-rich liquid). The Al₄Sr precipitates prefer the Al/Cd interface, stabilizing the Cd droplets in the Al-matrix. The contact angle of the Cd-rich liquid on Al₄Sr intermetallic phase under the Al-rich liquid alloy is about 90°, being ideal for emulsion stabilization. In this way, Al/Cd monotectic alloys can be produced with homogeneously dispersed Cd particles. The key to the success of this process is the in-situ formation of strontium aluminide precipitates stabilizing the Cd droplets in the liquid Al/Cd emulsion.     

Removal of cadmium and zinc ions from aqueous solution by living Aspergillus niger

1 Introduction Heavy metals like copper, mercury, chromium, cadmium, lead, nickel and zinc cause serious threat to environment, animals and human for their extreme toxicity[1]. Many industries including metal plating, mining, battery, pigment, dyestuff a…     

Thermodynamic assessment of systems of actinide or rare earth with Cd

A pyrometallurgical process is being developed for recycling nuclear reactor fuels. Thermodynamic information on multicomponent systems of actinides and rare earths (REs) with liquid Cd is very useful in the design of a process in which a liquid Cd electrode is used for the selective recovery of Pu and U, and a reductive extraction process using a molten salt/liquid Cd system for the recovery of minor actinides, such as Np, Pu, etc. A key issue in the design of these processes is a variation in solubility or activity of actinides or REs in multielement systems. In the present study, phase diagrams of U-Cd, Pu-Cd, Np-Cd, Y-Cd, La-Cd, Ce-Cd, Pr-Nd, Nd-Cd, and Gd-Cd were optimized by the CALPHAD method. For these systems, thermodynamic data, such as the activity of solutes in liquid Cd and the Gibbs energies of formation of the intermetallic compounds as well as the phase diagram data were available for the optimization. For optimization, the calculated primary results were entered into a database. Then, some ternary systems were preliminarily assessed through the use of the optimized data for the binary systems. Two extreme conditions were assumed: one condition was complete miscibility between the compounds that have the same mole ratio between solutes and Cd; the other condition was no solid solubility between the compounds. The results indicated the tendencies toward solubility and activity of actinides and REs in multielement systems.     

Thermodynamic assessment of systems of actinide or rare earth with Cd

A pyrometallurgical process is being developed for recycling nuclear reactor fuels. Thermodynamic information on multicomponent systems of actinides and rare earths (REs) with liquid Cd is very useful in the design of a process in which a liquid Cd electrode is used for the selective recovery of Pu and U, and a reductive extraction process using a molten salt/liquid Cd system for the recovery of minor actinides, such as Np, Pu, etc. A key issue in the design of these processes is a variation in solubility or activity of actinides or REs in multielement systems. In the present study, phase diagrams of U-Cd, Pu-Cd, Np-Cd, Y-Cd, La-Cd, Ce-Cd, Pr-Nd, Nd-Cd, and Gd-Cd were optimized by the CALPHAD method. For these systems, thermodynamic data, such as the activity of solutes in liquid Cd and the Gibbs energies of formation of the intermetallic compounds as well as the phase diagram data were available for the optimization. For optimization, the calculated primary results were entered into a database. Then, some ternary systems were preliminarily assessed through the use of the optimized data for the binary systems. Two extreme conditions were assumed: one condition was complete miscibility between the compounds that have the same mole ratio between solutes and Cd; the other condition was no solid solubility between the compounds. The results indicated the tendencies toward solubility and activity of actinides and REs in multielement systems.     

Effect of arsenic on spatial pattern of radial oxygen loss and iron plaque formation in rice

The effects of different arsenic (As) treatments on spatial pattern of radial oxygen loss (ROL), iron (Fe) plaque formation and As accumulation in rice were investigated using three rice genotypes, planted under greenhouse conditions. Arsenic was applied to soil at 50 and 100 mg/kg, with untreated soil used as a control having an average As concentration of 8.5 mg/kg. It was demonstrated that the ratio of ROL in root tips to that at the root base slightly decreased with increasing As concentration, suggesting that the spatial ROL patterns in these groups may be shifted from the “tight” barrier towards the “partial” barrier form. Furthermore, increasing As concentration led to a increase in Fe plaque formation on root surfaces. In addition, root As concentrations of genotypes in 50 and 100 mg/kg As treatments were significantly higher than that of control treatment (P<0.05). Grain As concentration of genotype Nanyangzhan (with lower ROL) was significantly higher (P<0.05) than that of genotype CNT87059-3 with higher ROL.     

单晶体Cd1-xMnxTe中的法拉第旋转

室温下测量了本实验室生长的Cd0.8Mn0.2Te和Cd0.9Mn0.1Te单晶体的法拉第旋转谱.通过提高布里渊区中心L点的能隙值(E1)改进了法拉第旋转的多振子模型.用改进的模型拟合实验结果,得到Cd0.8Mn0.2Te和Cd0.9Mn0.1Te单晶体布里渊区中心F点的能隙值(E0)分别为1.804 eV和1.667 eV.该E0值比以往任何研究都更接近于计算值.