Preparation of sodium molybdate from molybdenum concentrate by microwave roasting and alkali leaching

The preparation process of sodium molybdate has the disadvantages of high energy consumption,low thermal efficiency,and high raw material requirement of molybdenum trioxide,in order to realize the green and efficient development of molybdenum concentrate resources,this paper proposes a new process for efficient recovery of molybdenum from molybdenum concentrate and preparation of sodium molybdate by microwave-enhanced roasting and alkali leaching.Thermodynamic analysis indicated the feasibility of oxidation roasting of molybdenum concentrate.The effects of roasting temperature,holding time,and power-to-mass ratio on the oxidation product and leaching product sodium molybdate (Na_(2)MoO_(4)·2H_(2)O) were investigated.Under the optimal process conditions:roasting temperature of 700℃,holding time of 110 min,and power-to-mass ratio of 110 W/g,the molybdenum state of existence was converted from MoS_(2) to Mo O3.The process of preparing sodium molybdate by alkali leaching of molybdenum calcine was investigated,the optimal leaching conditions include a solution concentration of 2.5 mol/L,a liquid-to-solid ratio of 2 mL/g,a leaching temperature of 60℃,and leaching solution termination at pH 8.The optimum conditions result in a leaching rate of sodium molybdate of 96.24%.Meanwhile,the content of sodium molybdate reaches 94.08wt%after leaching and removing impurities.Iron and aluminum impurities can be effectively separated by adjusting the pH of the leaching solution with sodium carbonate solution.This research avoids the shortcomings of the traditional process and utilizes the advantages of microwave metallurgy to prepare high-quality sodium molybdate,which provides a new idea for the highvalue utilization of molybdenum concentrate.

Optimization of hydrogen networks with multiple impurities and impurity removal

To explore the effect of removing different impurities to hydrogen networks, an MINLP model is proposed with all matching possibilities and the trade-off between operation cost and capital cost is considered. Furthermore,the impurity remover, hydrogen distribution, compressor and pipe setting are included in the model. Based on this model, the impurity and source(s) that are in higher priority for impurity removal, the optimal targeted concentration, and the hydrogen network with the minimum annual cost can be identified. The efficiency of the proposed model is verified by a case study.

Preparation of high purity cadmium with micro-spherical architecture from zinc flue dust

This research has focused on the treatment of zinc flue dust by an acid leach process, combining an environmentally suitable impurity removal process to recover cadmium. Optimum conditions were found as follows： H2SO4 concentration 90 g/L, liquid/solid ratio 6：1, leaching temperature 60 ℃ and leaching time 1.0 h. Under these conditions, 95.8% cadmium was recovered. FeAsO4 and Fe（OH）3 precipitates with FeCI3 are found to be highly effective to obtain a high degree of separation of heavy metals and the oxyanions of arsenic from the leachate. The overall separation of arsenic and other heavy metals and precipitate settling rates are optimum at n（Fe）/n（As） ratio of 3：l and pH 6. The removal rates ofFe, Pb and Cu from the solution were greater than 98.9%, and As removal rate was 99.6%. A solvent extraction with P204 was used for the separation of zinc and cadmium. Optimum conditions are obtained as follows： 20% P204 （volume fraction） diluted with kerosene at room temperature, pH 3.0, and varying organic/aqueous （O/A） phase ratio 1：1. The extraction rate of zinc is 99.2% under these conditions. Spherical cadmium particles showing nearly uniform size were produced by hydrogen reduction at 310 ℃ and the crystal structure was cubic. In addition, the purity of the recovered cadmium powder is more than 99.99%.

Application of rare-earth element Y in refining impure copper

The effects of rare-earth element Y in refining impure copper were investigated in this paper. The composition, microstructures, and corrosion resistance properties of impure copper before and after refinement with Y were investigated using direct-reading spectrometry, inductively coupled plasma atomic emission spectrometry, optical microscopy, scanning electron microscopy, and potentiodynamic polariza- tion measurements. The results show that the concentrations of impurities S, As, Sb, Bi, A1, Cd, and Se are remarkably decreased. Adding an appropriate amount of Y refines the microstructure and enhances the corrosion resistance properties of impure copper in HC1 solution via a purification effect. The formation enthalpies of compounds formed between Y and various impurity elements were calculated on the basis of Miedema＇s theory. The thermodynamic mechanisms of the refinement of impure copper by Y were also discussed.

Unified Model of Purification Units in Hydrogen Networks

Purification processes are widely used in hydrogen networks of refineries to increase hydrogen reuse. In refineries, hydrogen purification techniques include hydrocarbon, hydrogen sulfide and CO removal units. In addition, light hydrocarbon recovery from the hydrogen source streams can also result in hydrogen purification. In order to simplify the superstructure and mathematical model of hydrogen network integration, the models of different purification processes are unified in this paper, including mass balance and the expressions for hydrogen recovery and impurity removal ratios, which are given for all the purification units in refineries. Based on the proposed unified model, a superstructure of hydrogen networks with purification processes is constructed.

Efficient Extraction and Isolation of Mangiferin from Mango Leaves by Ethyl Acetate Impurity Removal Method

[Objectives] To optimize the ethyl acetate impurity removal method for extracting and isolating mangiferin from mango leaves,and provide raw materials and technical support for development and use of mangiferin related products. [Methods]Five steps( material crushing→ ethyl acetate impurity removing → concentrated extract washing → extracting with methanol → crystallization and precipitation) were used.The single factor experiment and L9( 34) orthogonal experiment was carried out to optimize the process parameters including extraction time,ultrasonic power,extraction times,and extraction temperature.[Results] The optimum process of ethyl acetate impurity removal method for extracting and isolating mangiferin from mango leaves was as follows: the mango leaves were crushed and sieved; 3 m L/g of ethyl acetate was added,sealed and soaked for 4 h,ultrasonically shaken for 20 min( 50℃,350 W),filtered at room temperature,filtered with 100 mesh sieve,and extracted three times; added 100% methanol to the residue at 3 m L/g,extract by ultrasonic vibration for 20 min( 350 W,55℃)for four times,filtered with 100 mesh sieve when it was still hot; mixed the extract of each time,condensed by vacuum decompression to get the extract; added 100% methanol at 4 m L/g,mixed and washed for 5 min at room temperature,placed for 10 min,filtered with 100 mesh sieve,washed 3 times repeatedly,and dried the filter residue at 60℃ to obtain the crude mangiferin; added 100% methanol at 4 m L/g,mixed and washed at 50℃ for 5 min,placed at 6℃ for 8 h,dried the filter residue at 60℃,and repeatedly crystallized two times. According to the above process,crude and pure mangiferin products could be obtained,the purity of mangiferin of the crude product was higher than 64. 00%,the total recovery rate was 83. 90%,and the purity of mangiferin of the pure product was higher than 98. 00%,and the total recovery rate was about 66. 40%. [Conclusions] The optimized ethyl acetate impurity removal method is easy in operation,low in cost,and high in efficiency for extracting and isolating mangiferin,and can be applied for actual production of mangiferin.

Redistribution of Impurity and Visible Foreign Matter in Cotton during Carding

Impurity redistribution during cotton carding was investigated. The content and size of impurity in card sliver,takerin droppings,flat strips,and cylinder screen droppings (including droppings under cylinder screen and cylinder-doffer triangle section)at four taker-in speeds were tested by using USTER AFIS. Results show that both total impurities and visible foreign matter (VFM)weights are increased. Impurities in cotton lap are carded and redistributed in card sliver, taker-in droppings, flat strips and cylinder screen droppings. Impurity percentage in taker-in droppings are the highest,followed by that in card sliver,that in flat strips and that in cylinder screen droppings. Cylinder screen has better dust-removing efficiency than flats. The average sizes of impurities in card sliver and cylinder screen droppings are decreased,whereas those of flat strips are increased and those of taker-in droppings is almost the same,in comparison with cotton lap. The impurity contents of card sliver,taker-in droppings,flat strips and cylinder screen droppings have tendencies to decrease with the increase of taker-in speed.

Removal of impurities from scandium chloride solution using 732-type resin

The deep removal of Al, Fe（Ⅱ/Ⅲ）, Ca, Zr, Ti and Si from scandium chloride solution was carried out by using 732-type strong acid cation exchange resin. The effects of pH value, contact time and complexing agents（EDTA） on the purification process are investigated. The results indicate that the 732-type resin have a good scandium selectivity and the adsorption order is Sc 〉 Fe（Ⅲ）〉Al 〉 Ca 〉 Zr 〉 Ti 〉 Si in the pH range of 1-3. The separation of Sc and Zr, Si, Ti can be directly carried out because the resin have a good adsorption effect on Sc, AI and Fe（Ⅲ） but poor adsorption effect on Zr, Si and Ti under the condition of pH = 2.5 and contact time 180 min. The Fe（Ⅱ）, Ca and Al are selectively adsorbed on the resin by adding reducing agent ascorbic acid and EDTA into the solution for reducing Fe（Ⅲ） to Fe（Ⅱ） and complexing Sc.By using two-step ion exchange adsorption separation method, the removal rates of Fe（Ⅲ）, Ti, Al, Ca, Zr and Si are 95.5%,99.8%,100%,98.2%,98.6% and 100%,respectively.