勃姆石对稀土离子的吸附性研究

稀土元素在铝(氢)氧化物矿物表面的吸附过程对铝土矿中稀土元素的富集和以吸附态存在的稀土元素的提取回收均具有重要影响。本文选择勃姆石作为研究对象,La和Y分别作为轻稀土和重稀土元素的代表,以批实验的方法,探究吸附时间、溶液pH值和背景电解质对勃姆石吸附稀土离子的影响。研究发现:勃姆石吸附稀土离子在72 h内能够接近平衡,对La^(3+)和Y^(3+)的吸附率分别约为45%和35%;在所选pH值范围内吸附率随pH值增加而升高;同时,吸附率随背景电解质浓度增加而升高。由于质子化效应,在弱酸性条件下,勃姆石表面携带正电荷,与稀土离子之间存在静电斥力,稀土离子与勃姆石之间可能形成内圈络合物。通过对比轻稀土和重稀土的吸附行为发现,勃姆石对轻稀土有更强的吸附能力。此外,通过热力学和动力学模型拟合分析发现,勃姆石对稀土离子的吸附更符合Langmuir单层吸附模型和准二级动力学模型。

Corrosion of in-situ grown Mg Al-LDH coating on aluminum alloy

Mg Al-layered double hydroxides（LDH） coatings were fabricated by the in-situ hydrothermal treatment method on the AA5005 aluminum alloy.The characteristics of the coatings were investigated by XRD,FT-IR,SEM and EDS.The effect of the p H value of the solution on the formation of the LDH coatings was studied.The optimum p H value of the solution was 10.0.The corrosion resistance of the LDH coatings was studied using potentiodynamic polarization tests and electrochemical impedance spectrum（EIS）.The results demonstrate that the LDH coatings,characterized by platelets vertically to the substrate surface possess excellent corrosion resistance.The influence of the hydrothermal crystallization time on the corrosion resistance was evaluated.Prolonging the crystallization time can increase the corrosion resistance of the obtained LDH coatings.The anticorrosion mechanism of the LDH coatings was discussed.

Comparative Study on Characteristics of P Fixation by Mn, Fe and Al

An experiment was conducted to examine the role of Mn in P fixation through comparing with Al and Fe. Hydroxides and oxides of Al, Fe and Mn were prepared in lab under opened and closed conditions to react with phosphate. The newly formed Mn hydroxide showed the strongest P-fixing abilityl even several times higher than Fe hydroxide, but became the lowest rapidly due to ageing when exposed to air. Mn oxide showed the lowest p-fixing ability. Therefore, a sound consideration on P fixation should be based on both quantities and p-fixing abilities of the compounds of Fe, Al and Mn. The importance of Mn on P availability should receive more attention especially under oxidation-reduction dynamic conditions.

Fabrication of cobalt aluminum-layered double hydroxide nanosheets/carbon spheres composite as novel electrode material for supercapacitors

A new design route was presented to fabricate cobalt aluminum-layered double hydroxide(CoAl-LDH)thin layers whichgrow on carbon spheres(CSs)through a growth method.The CoAl-LDH thin layers consist of nanoflakes with a thickness of20nm.The galvanostatic charge-discharge test of the CoAl-LDH/CSs composite shows a great specific capacitance of1198F/g at1A/g(based on the mass of the CoAl-LDH/CSs composite)in6mol/L KOH solution,and the composite displays an impressive specificcapacitance of920F/g even at a high current density of10A/g.Moreover,the composite remains a specific capacitance of928F/gafter1000cycles at2A/g,and the specific capacitance retention is84%,indicating that the composite has high specific capacitance,excellent rate capability and good cycling stability in comparison to pristine CoAl-LDH.

Effects of Current on Microcosmic Properties of Catalyst and Reforming of Bio-oil

Highly effective production of hydrogen from bio-oil was achieved by using a low-temperature electrochemical catalytic reforming approach over the conventional Ni-based reforming catalyst （NiO-Al2O3）, where an AC electronic current passed through the catalyst bed. The promoting effects of current on the bio-oil reforming were studied. It was found that the performance of the bio-oil reforming was remarkably enhanced by the current which passed through the catalyst. The effects of currents on the microcosmic properties of the catalyst, including the Brunauer-Emmett-Teller （BET） surface area, pore diameter, pore volume, the size of the crystallites and the reduction level of NiO into Ni, were carefully characterized by BET, X-ray diffraction, X-ray photoelectron spectroscopy, and scanning electron microscope. The desorption of the thermal electrons from the electrified catalyst was directly observed by the TOF （time of flight） measurements. The mechanism of the electrochemical catalytic reforming of bio-oil is discussed based on the above investigation.

Effect of interlayer anions on chromium removal using Mg–Al layered double hydroxides:Kinetic,equilibrium and thermodynamic studies

The influence of interlayer anions such as NO3-, 5042- and Cl- on Mg-AI hydrotalcites for Cr（Vl） removal from aqueous solution was studied. The structure of the prepared LDHs was characterized by XRD, SEM, FTIR, TGA, BET surface area and pHzpc. The sorbent ability and sorption mechanisms were also investigated. The LDHs exhibit high removal for Cr（VI）, and the sorbed amount depends on the nature of interlayer anion, which decreased in the following order： NO3- 〉 Cl 〉 SO42-, Nitrate-containing LDH reached a Cr（VI） sorption equilibrium within only 30 min. The effects of operating conditions, including initial concentration, solution pH, agitation time and sorbent amount have been studied in batch mode. The optimum conditions were observed at an initial concen- tration of 100 mg. L- 1, pH = 6, agitation time of 60 min and a sorbent dose of 2 g.L- 1. The equilibrium data were fitted to the Langmuir, Freundlich and Dubinin-Radushkevich isotherm models. The Langmuir model was found to sufficiently describe the sorption process, offering a maximum sorption capacity of 71.91 mg-g 1. The sorp- tion kinetic follows pseudo-second-order reaction with high accuracy. Thermodynamic parameters suggested that the sorption process is spontaneous and endothermic in nature.

Adsorption of Cd（II） on Zn-AI LDHs （Layered Double Hydroxides） Intercalated with Chelating Agents EDTA

The hydrotalcite-like compound [Zn2AI（OH）6]NO3-mH20 （shorted as ZnAI-NO3） was intercalated with the chelating agent EDTA （ethylene diamine tetraacetic acid） by anion exchange to uptake cadmium ion from aqueous solutions. The materials synthesized in this work were characterized by chemical analysis, FT-IR （fourier transform infrared spectroscopy）, XRD （X-ray powder diffraction） to confirm their properties. In order to investigate the optimum conditions for Cd（II） adsorption, the amount of Cd（ll） adsorbed by Zn-AI LDHs intercalated with EDTA （ZnAI-EDTA） under different conditions （i.e., adsorbent dosage, temperature and contact time） were determined by ICP-AES （inductively coupled plasma-atomic emission spectrometry）. Adsorption isotherms of Cd（II） onto ZnA1-EDTA were measured at varying initial Cd concentrations （0.05 mg/L to 1 mg/L） under optimized conditions. The data were applied to Langmuir and Freundlich isotherms model, and well fitted by the Freundlich isotherms model. The pseudo-second-order kinetic model was more adequate to describe the kinetic in this case.

3种表面修饰活性炭对水体中磷的吸附

为克服活性炭磷吸附能力有限的问题,使用ZnCl_2、十六烷基三甲基氯化铵(CTAC)和Fe/Al(氢)氧化物纳米颗粒分别研究了物理结构法、表面活性剂法和载体法3种表面修饰方法对活性炭磷吸附能力的影响。实验发现,载体法为3种方法中最好的修饰方法。对载体法制备吸附剂的材料用量的比较发现,在Fe(Ⅲ)和Al(Ⅲ)摩尔比为9:1的条件下,把1.5 g活性炭加入到总浓度为1 mol·L^(-1)的200 m L Fe(Ⅲ)和Al(Ⅲ)混合溶液中,形成的纳米Fe/Al(氢)氧化物能够较好地利用活性炭表面,该复合材料1.5AC-Fe/Al在磷平衡浓度约为50 mg·L^(-1)时吸附量达到29.3 mg·g^(-1)。该材料表征结果表明,纳米Fe/Al(氢)氧化物颗粒被成功负载在活性炭表面。在酸性条件下,复合材料表面的—H^+和—OH_2^+所引起的静电吸附和配位交换是促进吸附带负电磷酸根离子的原因。

Influence of pH on the thixotropy of magnesium aluminum hydroxide-kaolinite suspension

The influence of pH on the thixotropy of pure kaolinite suspension and magnesium aluminum hydroxide (Mg-Al-MMH)-kaolinite suspension was studied. The results show that the thixotropic type of pure kaolinite suspension was not affected by pH studied in the range of 3.60– 12.00. The thixotropic type of Mg-Al-MMH-kaolinite suspension with mass ratio (R) value of MMH to kaolinite 0.029 transformed from complex thixotropy into positive thixotropy with increasing of pH in the range of pH 3.83–12.00, and the type of thixotropy of Mg-Al-MMH-kaolinite suspension withR = 0.129 transformed from positive thixotropy into complex thixotropy with increasing of pH in the range of pH 3.70–11.96.