Adsorption of Microamounts of Silver on Manganese Dioxide from Acid Solutions

Abstract

Adsorption of microamounts of silver on manganese dioxide from nitric and perchloric acid solutions has been studied and optimized with respect to shaking time, concentrations of electrolyte, adsorbent, and adsorbate. Maximum adsorp- tion (>99.5%) has been achieved from 0.01 mol/dm³ acid solution using 50 mg oxide at 10^?5 mol/dm³ silver concentration after 30 min shaking. The adsorption decreases with increasing concentration of acid and adsorbate from both the acids. The presence of a 10⁴-fold greater concentration of cyanide, thiocyanate, thiosulfate, and Pb(II) than silver reduces the adsorption drastically. The adsorption of silver follows the Freundlich adsorption isotherm over the entire concentration range investigated from 9.27 × 10^?6 to 2.92 × 10^?3 mol/dm³ with a value of A = 49 mmol/g and 1/n = 0.93. Moreover, the Langmuir adsorption isotherm is also valid except at the lowest and highest concentrations. The values of the limiting adsorption concentrtion (C_m ) have been found to be 1 mmol/g and of the equilibrium constant for adsorption 87 dm³/mol at 23 ± 2°C.     

Uptake of Traces of Selenite by Manganese Dioxide from Aqueous Solutions

Abstract

Sorption of selenite onto manganese dioxide has been investigated with respect to shaking time, concentration of sorbent and sorbate, nature of electrolyte, and influence of cations and anions. The sorption of other metal ions has been studied using optimal conditions selected for maximum sorption of selenite. The surface area, average pore diameter, porosity, and solid phase density of the sorbent have been measured. The sorption data followed only the Dubinin–Radushkevich (D–R) sorption isotherm among all the isotherms tested. The sorption capacity of 51.2 nmol·g^?1 and a constant β related to sorption energy have been estimated to be ?0.007521 mol²·kJ^?2. The sorption energy is found to be 8.15 kJ·mol^?1. The kinetics of the sorption follows the Lagergren equation in the initial stages. The first-order rate constant, k′, was evaluated to be 0.498 min^?1 and of intraparticle diffusion rate 3.06 × 10^?5 mol·g^?1·min^?2. Among all the anions and cations tested, only carbonate, Fe(III), and citrate reduced the sorption significantly. The sorption data for other metal ions showed that Te(IV) can be separated from ions showing higher degree of sorption; especially Se(IV), As(III), Sb(V), and Eu(III). It can be concluded that manganese dioxide may be used for the separation of certain metal ions, their preconcentration from very dilute solutions, and for decontamination and treatment of industrial effluents.     

Synthesis of Zirconium Dioxide Microfiber from Aqueous Solutions

A technology for producing filamentary crystals of zirconium dioxide for the production of high-strength ceramics is developed. Comparative characteristics of the methods of precipitation of zirconium oxychloride crystals by chilling a supersaturated solution and salting out using hydrochloric acid are provided. A method for producing filamentary crystals of zirconium dioxide from oxychloride without using high temperatures and pressure is analyzed.     

Adsorption of Europium on Manganese Dioxide from Binary Mixtures of Aqueous Sulfuric Acid and Methanol

Abstract

The adsorption of europium on manganese dioxide from a binary mixture of aqueous sulfuric acid and methanol has been studied in relation to the concentration of adsorbate. The influence of contact time, composition of binary mixture, and foreign ions was also investigated. Citrate, chromate, molybdate, EDTA, Cr(III), Fe(III), and Al(III) drastically reduce adsorption. Adsorption of other metal ions under the same conditions was also investigated. Based on the observed data, separation of europium from mercury can be achieved.     

A Kinetic and Thermodynamic Study of Silver Sorption onto Manganese Dioxide from Acid Solutions

Abstract

The batch kinetics of silver sorption at the tracer level onto manganese dioxide along with the thermodynamic parameters from dilute nitric and perchloric acid solutions are described. The values of ?H, ?S, and ?C found from both acid solutions are similar. The sorption equilibrium constant, K _c, has been calculated at different temperatures between 288 and 308 K. Tests of different isotherms have shown that the sorption data fit very well to the Freundlich and Dubinin-Radushkevich (D-R) models at different temperatures. The thermodynamic data indicate the endothermic nature of silver sorption onto the oxide. The sorption capacity in the 0.23–0.77 mmol/g range and a mean free energy of sorption of about 11.5–15.4 kJ/mol have been found by using the D-R approach. The values of B and the correlation factor (r) have been determined by using the D-R isotherm. These values are comparable with those reported earlier for other sorption systems.     

Studies on the Adsorption of Americium on Alumina from Aqueous Nitric Acid-Oxalic Acid Solutions

Abstract

This paper reports a study on the adsorption of Am(III) on alumina from oxalic acid-nitric acid solutions. Distribution coefficients for Am(III) on alumina at different oxalic acid-nitric acid concentrations have been determined and optimum conditions for loading and elution of Am from alumina columns have been established. Separation of Am from Pu and the effects of other ions, such as U(VI) and Fe(III), have also been studied. Am and Pu recoveries better than 99.5% were obtained.     

Adsorption of Uranium(VI) and Zirconium(IV) from Acid Solutions on Silica Gel

Abstract

Adsorption of uranium(VI) and zirconium(IV) from aqueous solutions on silica gel was investigated by the batch equilibration method. The influence of shaking time and concentrations of nitric acid (i.e., pH of solution) and metal ions in solution were studied. Adsorption of uranium(VI) and zirconium(IV) increases with an increase of pH (decrease of nitric acid concentration) and ion concentrations. The adsorption mechanism of uranium(VI) and zirconium(IV) from aqueous solutions on silica gel is proposed. It is shown that zirconium(IV) and uranium(VI) can be separated if the concentration of nitric acid in solution is higher than 0.01 mol/dm³.     

苯甲酸制备实验回收二氧化锰及含量测定

在有机化学实验苯甲酸的制备实验中,用甲苯作原料,用高锰酸钾作氧化剂,把苯甲酸氧化成苯甲酸钾,加入的高锰酸钾是过量的,需要用亚硫酸钠除去,减压过滤,得到苯甲酸钾溶液,再用盐酸酸化,制得白色苯甲酸固体.减压过滤后的滤渣是高锰酸钾和亚硫酸钠反应后生成的碱式氧化锰,煅烧碱式氧化锰可制得二氧化锰.用氧化还原滴定测得二氧化锰含量....     

The Stability of the Adsorption of Some Anions on Chemical Manganese Dioxide

The stability of the adsorption of three anions (nitrate, bromide, and chloride) on chemical manganese dioxide (CMD) was studied using a two‐variable, two level factorial design. The two variables were the concentration and pH of the solutions of the sodium salt of the anions. The concentration CMD was varied from 1 M–0.001 M and the pH from 3.5–2.5. 84, 67, and 54 % variations in the adsorption of Br^–, NO₃^–, and Cl^– on CMD, respectively, were obtained. Independently, the concentration and pH affected the electric surface charge. However, their combined influence has a negative and low effect. The surface response plots of the model equations, which did not show the optimum values for concentration and pH, reinforced this observation. The highest stability of the anions was observed when concentration and pH were at their minimum values of 0.001 M and 2.5, respectively.     

水合MnO_2强化FeCl_3共沉降去除水中微量Cd(Ⅱ)

采用烧杯混凝实验,分别以实验室配水和松花江水为本底,研究了水合二氧化锰强化三氯化铁共沉降去除水中微量镉的效能。详细探讨了影响水合二氧化锰强化三氯化铁共沉降去除水中微量镉的主要因素。结果表明:两种水质条件下,水合二氧化锰均可强化FeCl3混凝去除水中的微量镉,镉的去除率明显高于单纯FeCl3混凝。水体pH值、浊度、腐殖酸等水质参数对于水合二氧化锰强化三氯化铁共沉降去除水中微量镉的效能有不同程度的影响。其中水体pH值对水合二氧化锰强化三氯化铁共沉降去除水中微量镉的影响十分显著,Cd(Ⅱ)的去除效果随着水体pH增加显著升高。     

Equilibrium and Kinetic Studies for Fluoride Adsorption from Water on Zirconium Impregnated Coconut Shell Carbon

Abstract

The batch adsorptive fluoride removal from water by Zirconium ion impregnated coconut shell carbon (ZICSC) was investigated. ZICSC was found to have fluoride adsorption capacity, 25 to 30 times that of plain activated carbon. The effect of various parameters such as pH, agitation time, and adsorbent dosage on fluoride removal were studied. The fluoride adsorption by ZICSC was above 90% for the entire pH range of 2–9 and the adsorption rate was extremely rapid, with 91% of the adsorption being achieved within 10 min of ZICSC contact for an initial fluoride concentration of 10 mg/L. The experimental data have been analyzed by Langmuir, Freundlich, Redlich‐Peterson, and Temkin sorption isotherm models and the adsorption data for fluoride onto ZICSC were better correlated to the Langmuir isotherm. The batch adsorption kinetics have been tested by first order, pseudo‐first order, and pseudo‐second order kinetic models with the subsequent determination of the rate constants of adsorption. The comparison of ZICSC with other adsorbents suggests that ZICSC provides a cost‐effective working solution to the defluoridation problem in the developing countries by its great potential application in fluoride removal from water.     

高纯氯氧化锆和二氧化锆的制备

研究了工业氯氧化锆重结晶制备高纯氯氧化锆的过程，通过选择，确定氯氧化锆溶液浓度为160g/L，结晶酸度为5.5-6.0mol/L，煅烧过程中盛装高纯氯氧化锆匣钵为石英匣钵，从而得到产品纯度为99．9％的高纯二氧化锆。     

新生态MnO2的制备及其对2,4-二硝基苯酚吸附性能的影响

以KMnO₄和MnSO₄·H₂O为原料,在常温常压和水热条件下制备新生态MnO₂,借助XRD、TEM、低温N₂吸附-脱附等手段对材料进行表征,比较不同制备方法对产物结构和吸附性能的影响。结果表明,反应温度和压力对新生态MnO₂的形貌和吸附性能有较大影响,常温常压下合成产物均为短棒状,水热合成产物为介孔纤维,对2,4-二硝基苯酚的吸附效果优于常温常压合成产物。新生态MnO₂对2,4-二硝基苯酚的等温吸附和吸附动力学分别符合Langmuir等温式(R²>0.99)和准二级吸附动力学方程(R²>0.99),说明2,4-二硝基苯酚在新生态MnO₂上为单分子层吸附和化学吸附。溶液pH值能显著影响2,4-二硝基苯酚在新生态MnO₂上的吸附,在pH=7时最大吸附量为2.539 mg/g。     

Formation of Zircon from Zirconium Dioxide and Silicon Dioxide in the Presence of Vanadium Pentoxide

The high-temperature formation of zircon from zirconium dioxide and silicon dioxide in the presence of vanadium pentoxide was studied. A reaction between zirconium dioxide and vanadium pentoxide appeared to take place at about 730°C. That reaction product then reacted with silicon dioxide to form zircon. The experiments suggest that such zircon contains a few per cent of tetravalent vanadium in solid solution and has a light blue color. It appeared that the end product under equilibrium conditions would be pure zirconium silicate since vanadium pentoxide or tetroxide was liberated under prolonged heating. Zircon also formed from silicon dioxide and zirconium dioxide in the presence of niobium or tantalum pentoxide.     

二氧化锰氧化法合成酸性翠蓝AE

将N-乙基-N-苄基苯胺-3’-磺酸与苯甲醛邻磺酸钠缩合后，在磷酸的存在下用自制的新鲜二氧化锰作氧化剂进行氧化反应，然后在氨水的存在下，使Mn^ 以络合物的形式产生沉淀过滤除去Mn^ ，直接喷雾干燥得到酸性翠蓝AE(C．I．Acid Blue 9，42090)；产品中锰的含量为15ppm-50ppm,系统地测定了染料的染色性能和色牢度。     

闪锌矿-软锰矿湿法浸出制备MnO_2、ZnO

通过正交试验,研究了浸出时间、温度、矿比、酸用量对闪锌矿、软锰矿两矿浸出的影响。研究结果表明:温度是对两矿浸出率影响最主要因素,其次是酸用量。最佳工艺参数:温度为95℃、两矿比为1︰3.0、浸出时间为6h、20%酸用量80mL时,锰矿浸出率平均值达到91.69%,锌矿浸取率平均值为92.92%左右。     

Removal of Manganese and Iron from Drinking Water Using Hydrous Manganese Dioxide

ABSTRACT

This paper examines the use of synthetic manganese dioxide as a material for the removal of Mn⁺⁺ and Fe⁺⁺ from drinking water. Three different types of Mn02 were prepared. One involved the production of the dioxide from permanganate and hydrogen peroxide, the second involved the use of the permanganate and manganous ions and the third used a formulation the included all three reagents. Tests showed that the first type of dioxide was by far the best for both iron and manganese removal and that the mechanism for the process was by ion exchange. Other tests indicated that the dioxide exchanger could be regenerated partially by contact with chlorine gas or hypochlorite which is commonly available as a process chemical at water treatment works.     

多孔二氧化硅对酸性橙吸附性能的研究

以水玻璃和盐酸为原料,采用化学沉淀法制备出多孔、高比表面积的SiO2。改变灼烧温度,得到不同灼烧温度下SiO2对酸性橙的吸附曲线,找出了最佳灼烧温度。在此温度下制备出SiO2并对一定浓度的酸性橙溶液进行"吸附-灼烧-吸附"的反复吸收试验。实验结果表明400℃灼烧的SiO2的吸附性最好,并且随着循环次数的增多吸附能力慢慢下降。     

High-Strength Ceramics Based on Zirconium Dioxide Powder

The method of coprecipitation of components was used to obtain disperse powders of tetragonal zirconium dioxide stabilized by Y₂O₃, Yb₂O₃ and a combined additive (Y₂O₃ + CaO + MgO). The technological parameters of the processes of synthesis and preparation of initial ZrO₂ powders intended for ceramics with elevated strength parameters are proposed.     

Sorption of Zirconium from Nitrate and Sulfate Solutions

Theoretical Foundations of Chemical Engineering - The possibility of using sorption by sulfocationite in order to extract zirconium from nitrate and sulfuric acidic solutions has been shown. The...