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Extraction behaviours of titanium and other impurities in the decomposition process of ilmenite by highly concentrated KOH solution

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International Journal of Minerals,Metallurgy and Materials 2012年第1期19卷 9-14页

作者： Yu-min Liu Hua Lv Tao Qi Yi Zhang College of Chemistry and Environmental Science Henan Normal University Xinxiang 453007 China Institute of Process Engineering Chinese Academy of Sciences Beijing 100080 China

To effectively utilize ilmenite and recycle KOH solution, the extraction behaviours of titanium and other associated impurities in the decomposition process of ilmenite by highly concentrated KOH solution were studied. Experiments on the extraction behaviours of tita- nium as well as other associated impurities of ilmenite such as iron, silicon, calcium, and aluminium were carried out. The effects of various parameters, including reaction temperature, KOH concentration, reaction time, alkali-to-ore mass ratio, and particle size on the extraction rate of titanium and other impurities were examined. When the finely ground ore （58-75 ~tm） reacted with KOH solution （80wt%） in an al- kali-to-ore mass ratio of 7：1 at 260~C for 60 min, almost complete extraction of titanium was achieved, while the extraction rate of aluminium was 78% and that of other impurities was less than 22%. Moreover, high purity （98.2wt%） TiO2 with the anatase structure could be gained in the purification process.

关键词： ilmenite titanium dioxide potassium hydroxide leaching

Removal of iron from ilmenite by KOH leaching-oxalate leaching method

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Rare Metals 2010年第1期29卷 9-15页

作者： WANG Yuanbo QI Tao CHU Jinglong ZHAO Wei Graduate School of Chinese Academy of Sciences Beijing 100039 China Key laboratory of Green Process and Engineering Institute of Process Engineering Chinese Academy of Sciences Beijing 100080 China

Oxalic acid was used for the removal of iron from the intermediates of ilmenite leached by KOH liquor. Various parameters, such as pH, temperature, initial oxalate concentration, and illumination were investigated. Meanwhile, it was found that orthorhombic crystal Ti2O2（OH）2（C2O4）-H2O formed as the leaching proceeded. Scanning electronic microscope （SEM） images implied that the formation of Ti2O2（OH）2（C2O4）.H2O with good crystallinity proceeded through three stages. Calcining Ti2O2（OH）2（C2O4）·H2O, anatase （350℃） or mtile （550℃） type TiO2 was obtained, respectively. Element analysis found that the calcined product contained 94.9% TiO2 and 2.5% iron oxide, but only about 1600 ppm dissolvable iron oxide was left, which indicates that oxalic acid was comparatively effective on iron oxide removal from the intermediates. Finally, an improved route was proposed for the upgrading of ilmenite into mtile.

关键词： ilmenite iron removal titanium oxide oxalate potassium hydroxide KOH leaching

Synthesis of kalsilite from microcline powder by an alkali-hydrothermal process

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International Journal of Minerals,Metallurgy and Materials 2014年第8期21卷 826-831页

作者： Shuang-qing Su Hong-wen Ma Jing Yang Pan Zhang Zheng Luo National Laboratory of Mineral Materials China University of Geosciences Blue Sky Technology Corporation

The properties of aluminosilicate kalsilite have attracted the interest of researchers in chemical synthesis, ceramic industry, biofuels, etc. In this study, kalsilite was hydrothermally synthesized from microcline powder in a KOH solution. The microcline powder, rich in potassium, aluminum, and silicon, was collected from Mountain Changling in Northwestem China. The effects of temperature, time, and KOH concentration on the decomposition of microcline were investigated. The kalsilite and intermediate products were characterized by means of wet chemistry analysis, X-ray Diffraction （XRD）, infi＇ared spectrometry （IR）, 29Si magic angle spinning nuclear magnetic resonance （29Si MAS NMR）, 27A1 MAS NMR, and scanning electron microscope （SEM）. With increasing temperature, the microcline powder transforms into a metastable KAlSiO4 polymorph before transforming further into pure kalsilite. A mixture of both kalsilite and metastable KAlSiO4 polymorph is obtained when the hydrothermal reaction is carried out within 2 h; but after 2 h, kalsilite is the predominant product. The concentration of KOH, which needs to be larger than 4.3 M, is an important parameter influencing the synthesis ofkalsilite.

关键词： kalsilite microcline potassium hydroxide hydrothermal synthesis

Multimode Interference 3-dB Coupler in Silicon-on-Insulator Based on Silicon Rib Waveguides with Trapezoidal Cross Section

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Chinese Physics Letters 2004年第1期21卷 104-106页

作者：夏金松余金中樊中朝王章涛陈少武 StateKeyLaboratoryonIntegratedOptoelectronics InstituteofSemiconductorsChineseAcademyofSciencesBeijing100083

A 3-dB multimode interference optical coupler based on rib waveguides with trapezoidal cross section was designed and fabricated on silicon-on-insulator wafer. potassium hydroxide (KOH) anisotropic chemical etching of silicon was used to fabricate the waveguides to obtain smooth interface. A modified finite-difference beam propagation method was used to simulate the multimode rib waveguide with slope interfaces. The rms roughness of etching interface is as small as 1.49nm. The propagation loss of the waveguide is 1.3dB/cm at wavelength of 1.55μm. The fabricated 3-dB coupler has a good uniformity of 0.2dB.

关键词： potassium hydroxide

Density and viscosity of aqueous solution of K_2CrO_4/KOH mixed electrolytes

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Transactions of Nonferrous Metals Society of China 2010年第S1期20卷 32-36页

作者：郭雅杰徐红彬郭奋郑诗礼张懿 Research Center of the Ministry of Education for High Gravity Engineering and Technology Beijing University of Chemical Technology National Engineering Laboratory for Hydrometallurgical Cleaner Production Technology Institute of Process Engineering Chinese Ac ademy of Sciences

The physicochemical properties are very important in theoretical investigation of aqueous electrolyte solution and industrial design of hydrometallurgical processes. In the green hydrometallurgical process of chromite ore with sub-molten salt medium of KOH, the ternary system of KOH+K2CrO4+H2O is essential to process control and industrial operation. In order to satisfy the needs of both fundamental research and industrial application, the dynamic viscosity (η) and density (ρ) of mixed aqueous electrolyte solution of KOH and K2CrO4 were measured over a temperature range from 15 to 60 ℃ by using Ubbelohde-type capillary viscometers and a series of densimeters, respectively. The temperature is controlled to an accuracy of ±0.01 ℃ throughout the experiment with thermostat. The dynamic viscosity and density of the ternary systems are performed as functions of chromate and hydroxide concentration and temperature. The regression equations for viscosity and density are obtained with a least-square method and the calculated values are consistent well with the experimental data. The semi-empirical equation obtained will be helpful and instructive to industrial application.

关键词： viscosity density potassium chromate potassium hydroxide mixed electrolytes

Eco-friendly preparation of chitooligosaccharides with different degrees of deacetylation from shrimp shell waste and their effects on the germination of wheat seeds

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Marine Life Science & Technology 2019年第1期1卷 95-103页

作者： Xiaodan Fu Lin Zhu Li Li Tan Zhang Meng Li Haijin Mou College of Food Science and Engineering Ocean University of ChinaNo.5 Yushan RoadQingdao 266003China

Production of chitosan and its derivatives by traditional methods involves the excessive use of a reaction solution comprisedof sodium hydroxide and hydrochloric acid. Waste water resulting from this process has lim让ed the application of chitosanas a fertilizer as the process causes serious environmental pollution. Specifically, the resulting waste water contains highlevels of dissolved nitrogen and minerals from shrimp shells. In this study, an eco-friendly method was established to produce chitooligosaccharides (COS) with different degrees of deacetylation (DDAs) from shrimp shell waste. At a solid-tosolventratio of 1:6, the degree of demineralization was above 90% with the treatment of 30 g-L_1 H3PO4, and the degree ofdeproteinization was above 80% when treated with 30 g-L_1 KOH at 70 °C. Chitosans with different DDAs were obtainedby microwave-assisted KOH metathesis and the COS with Mw approximately 1500 Da were then prepared by oxidativedegradation. In summary, 33.73 kg H3PO4,12.77 kg, and 241.31 kg KOH were supplied during the processes of demineralization,deproteinization, and deacetylation of 100 kg shrimp shell waste, respectively. The process water was totally recycled,demonstrating that the shrimp shell could be wholly transformed into fertilize The entire process created a product withthe fractions of N:P2O5:K2O:COS = 7.94:24.44:10.72:1 &27. The test on the germination promotion of wheat seeds revealedthat the COS with 72」2% DDA significantly promoted germination. This work demonstrated the use of an eco-friendlypreparation method of COS with a specific degree of deacetylation that can be applied as a fertilizer.

关键词： Chitooligosaccharide Deacetylation degree Phosphoric acid potassium hydroxide Germination promotion

Dissolution kinetics of molybdite in KOH media at different temperatures

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Transactions of Nonferrous Metals Society of China 2018年第1期28卷 177-185页

作者： A.ARACENA A.SANINO O.JEREZ Escuela de Ingeniería Química Pontificia Universidad Católica de Valparaíso Instituto de Geología Económica Aplicada (GEA) Universidad de Concepción

The dissolution kinetics of synthetic molybdite(MoO3)in a potassium hydroxide(KOH)medium was studied by varying the system temperature,KOH concentration,and particle ***,the effects of the stirring rate and different reagents such as barium hydroxide(Ba(OH)2),calcium hydroxide(Ca(OH)2),and sodium hydroxide(NaOH)were also *** experiments were performed in a reactor with controlled temperature and *** results indicated that the dissolution reaction mechanism of molybdite generates potassium molybdate(K2MoO4)without intermediate ***(6-80°C),KOH concentration(0.0005-0.025mol/L),and particle size(5-40μm)positively affected the dissolution of *** maximum Mo recovery was67.5%in0.25h for80°C and0.01mol/L *** the lowest temperature(6°C),which is near the freezing point of water(0°C),a substantial amount of Mo was recovered(17.8%in45min).The kinetics equation describing the molybdite dissolution in a KOH environment indicated that diffusion occurs through the porous *** activation energy was calculated to be47.81kJ/mol.A reaction order of1.0with respect to KOH concentration was obtained and was found to be inversely proportional to the squared particle *** kinetics equation was *** dissolution of molybdite resulting from the oxidation of a molybdenite concentrate(MoS2)led to a low molybdenum recovery,which was primarily caused by the consumption of KOH by impurities such as CaCO3and Cr(MO4)3.

关键词： molybdite dissolution kinetics potassium hydroxide

Preparation and Characterization of Activated Carbons from Asparagus Palm (Laccosperma robustum) Bark by Chemical Activation with H₃PO₄ and KOH

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American Journal of Analytical Chemistry 2023年第2期14卷 55-71页

作者： Phil Lewis Mpampoungou Langama Jean Jacques Anguile Crislain Bissielou Adam Bouraïma Albert Novy Messi Me Ndong Daouda Kouotou Joseph Ketcha Mbadcam Laboratoire de Chimie des Matériaux Inorganiques Département de Chimie Faculté des Sciences Université des Sciences et Techniques de Masuku Franceville Gabon Physical and Theoretical Chemistry Laboratory Department of Inorganic Chemistry Faculty of Science University of Yaoundé 1 Yaoundé Cameroon

The present work deals with the preparation and characterization of activated carbons from the bark of the asparagus palm (Laccosperma robustum) by chemical activation with phosphoric acid and potassium hydroxide. The process was optimized on the basis of the analysis of the iodine number, methylene blue number and activated carbons yield as a function of the preparation parameters (concentration of the activating agents and the pyrolysis temperature). It emerges that the pyrolysis temperature and the concentration of activating agents influence the activated carbons preparation process. Their values were 500°C and 20% respectively for activated carbon with H3PO4 (ACP) and 700°C and 1.5% for activated carbon with KOH (ACK). The iodine numbers obtained were 850.26 mg/g for ACP and 865.49 mg/g for ACK. The methylene blue numbers obtained were 149.35 mg/g for ACP and 149.25 mg/g for ACK. The activated carbons yields obtained were 25% for ACP and 5.9% for ACK. The activated carbons prepared under optimal conditions have shown the pH of zero-point charge (pHzpc) of 4.4 and 7.0 for ACP for ACK respectively. The determination of the surface functions revealed that ACP had a strong acidic character while ACK had neutral character. The Fourier transformed infrared spectroscopy also showed the presence of different functional groups on the surface of the precursor and activated carbons.

关键词： Activated Carbons Asparagus Palm Bark Chemical Activation Phosphoric Acid potassium hydroxide

Compressive Strength of Metakaolin-Based Geopolymers: Influence of KOH Concentration, Temperature, Time and Relative Humidity

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Materials Sciences and Applications 2016年第11期7卷 772-791页

作者： Tania Ariadna Garcí a-Mejí a Ma. de Lourdes Chávez-Garcí a Facultad de Quí mica UNAM Universidad Nacional Aut&oacute noma de Mé xico Ciudad de M&eacute xico M&eacute xico

The influence of KOH concentration (8 and 12 M) and curing conditions as temperature (40℃ and 60℃), time (7 and 28 days) and relative humidity (85% and 95% RH), on compressive strength of metakaolin-based geopolymers (MK-based GP) was evaluated. Derived from the experimental design technique, and using a factorial design 2K with two replications in the center point, eighteen experiments were conducted. The results reveal that the best performance conditions of geopolymerization to develop a higher compressive strength of 20 MPa are 12 M KOH to 60℃ and 85% RH at 28 curing days. With these conditions, the value of relative humidity of 85%, promotes high strength compact samples, and a maximum of 42 MPa at 90 days. The results of significant, compressive design of GP showed that KOH concentration and curing relative humidity were the most important factors, followed by curing time and temperature. The GP were characterized by XRD, and their evolution on compression strength was followed by SEM.

关键词： Geopolymers Metakaolin Relative Humidity potassium hydroxide Design of Experiments