Zhang Qixiu

Separation of molybdenum from tungstate solution by a combination of moving packed bed and fluid bed ion-exchange techniques

A new ion-exchange method to separate molybdenum from tungstate solution is presented. It employs a moving packed bed to adsorb thiomolybdate from the sulfurized tungstate solution and a fluid bed to desorb molybdenum and thereby regenerate the resin. Under appropriate flow rate the Mo-removal is better than 99% and a tungsten loss below 0.65%. It is moreover combined with good resin reusability and less consumption of desorption reagent.

A study on separation of molybdenum from tungsten by an adsorption process using activated carbon

In this paper a new process for separation of molybdenum from tungsten is described. When sodium tungstate solution containing molybdenum is treated with alkali sulfide in the proper condition, the molybdenum is transformed into the thiomolybdate and the tungsten is present as tungstate. When the solution is brought into contact with activated carbon, the molybdenum contained in the solution can be adsorbed quantitatively and the tungsten remaining in the raffinate can be recovered. The new process has advantages such as good results in removing molybdenum, little loss of tungsten and easy operation.

Study on the Removal of MIBK from Aqueous Solution by Vacuum Membrane Distillation

Methyl isobutyl ketone(MIBK) is widely used as extraction agent in hydrometallurgy. As it has a definite solubility in water, so when using MIBK as extraction agent, there will be MIBK in stripping solutions inevitably, which not only pollutes working conditions, but also affects the quality of ultimate product. In order to remove MIBK from aqueous solutions, the means of flat vacuum membrane distillation(VMD) is studied in the paper. The area of the membrane used in the study is 0.02 m2, the initial volume of feed is 2 L, each experiment was conducted over a time period of 60–120 min. The influences of the factors such as temperature(34.8–55.0 °C); pressure in the permeate side(10.67–14.67 kPa) and feed flow rate(27.8–69.4 mL/s) were experimentally studied. Increasing the temperature or reducing the pressure in the permeate side results in a faster removal of MIBK; however there is a decrease in removal factor β, increasing the feed flow rate results in a faster removal of MIBK and an increase of removal factor β, especially in the range of lower flow rate. The study indicates that the aim of MIBK removal and recycle from dilute aqueous solutions can be achieved by VMD.

Preparation and properties of metal-PVA composite hydrophilic ultrafiltration membranes

Metal-polyvinyl alcohol (PVA) composite ultrafiltration membranes were prepared by coating a certain concentration of PVA solution on metallic fiber sintered membranes. The effects of preparation conditions, such as the coating solution concentration, sequence and times of coating, and heat-treatment on the properties of the composite membranes were studied. The results show that the hole diameter of the composite membrane decreases with the increases of the concentration of PVA, the hole diameter of composite membrane is different when the sequence of coating is different. When the higher concentration of PVA solution is used to coat the metallic membrane for the first time and the other smaller one for the second time, the hole diameter of the composite membrane is relatively small, compared with that of the composite membrane made by the smaller concentration of PVA solution for the first time and the other higher one for the second time. The holes of the composite membrane contract and the stability of the membrane is improved by heat treatment. When metal-PVA composite hydrophilic membranes are used to treat the oil/water emulsion with the concentration of 1000 mg·L−1, the retention is from 80% to 90%, and the permeate flux is from 15 L·m−2·h−1 to 40 L·m−2·h−1 at pressure of 0.2 to 0.3 MPa.

Electrodeposition of copper by IMPC method

In order to develop an energy-saving electrodeposition process of copper, the electrodeposition of copper in copper sulfate solution by the ion-exchange membrane primary cell (IMPC) method has been studied. The experiments were carried out in an ion-exchange membrane primary cell with dimensions of 200 mm in length, 52 mm in width and 90 mm in height. The influences of temperature (294–323 K), interval between the anode and cathode (1.5–3.5 cm), mass concentrations of Cu2+ (6–40 g/L), H2SO4 (0–120 g/L) and Fe3+ (3–9 g/L) in catholyte and solution flow rate (0–8 cm/s) on current density and current efficiency were investigated experimentally. The current density increases with the increase of temperature and concentrations of Cu2+ and H2SO4 in catholyte. Cathode current efficiency decreases with the increase of concentration of Fe3+ in catholyte and anode current efficiency decreases with the increase of temperature. The high-quality cathodic copper can be obtained and the current density of membrane can be higher than 150 A/m2 and the current density of cathode can be higher than 300 A/m2. The experiment results show that IMPC method is effective for electrodeposition of copper.

Production of pure ammonium tungstate by one-step removal of P, As, Si, Mo through ion-exchange

Abstract A new method for the removal of P, As, Si and Mo to obtain the purified solution of ammonium tungstate in one step by ion-exchange adsorption has been investigated. Adjusting the pH of raw sodium tungstate and converting the MoO 4 2− to MoS 4 2− fully at first, an ‘acid conditioning without harmful anions’ process for pH adjustment in solution is adopted. The solution is then adjusted to have the correct concentration of tungsten and pH-value. When the solution passes through the ion-exchange column, tungsten and molybdenum (in the form of arsenic) are adsorbed in resins together preferentially, the ions of P being unwanted. (As) · Si goes into the raffinate. Then, tungsten is desorbed preferentially from resin, by a mixed solution containing ammonium to separate molybdebum from tungsten. Lastly, we use alkaline sodium hypochlorite solution to oxidize and desorb molybdenum (arsenic) to regenerate resins.

Removal of organic matter from H2TaF7 solution by adsorption

The removal of organic matter from H2TaF7 solution by adsorption was investigated in order to reduce the carbon content in the K2TaF7 crystal. Three kinds of adsorbent, LSA-5 resin, LSA-20 resin and active carbon were applied in the fixed bed respectively. Experimental results indicate that LAS-5 resin, LAS-20 resin, the mixture of LAS-5 resin and LAS-20 resin (with volume ratio of 1:1), and the active carbon can all reduce chemical oxygen demand (COD) value of the H2TaF7 solution, and reduce consequently carbon content of K2TaF7 crystal to 0.0010%–0.0015% from 0.0025%–0.0030%. Comparing with the others, the active carbon is an approved adsorbent whose bed volumes of effluent reaches 70. In addition, there is a linear relationship between the COD value of H2TaF7 solution and the carbon content in K2TaF7 crystal, and the carbon content in K2TaF7 crystal decreases with the decreasing of COD value of H2TaF7 solution. When the COD value of H2TaF7 solution is lower than 7 mg/L, the carbon content in K2TaF7 crystal would decrease to less than 0.0015%.

Treatment of low-concentration lye of red mud mound

Based on the systematic experiment of treating low-concentration lye in the red-mud mound, several key problems in the selection of technological process for industrial trial, such as aluminum precipitation in the process of electrodilalysis, dealuminum with carbon dioxide at low temperature, the selection of the technology for electrodialysis and estimation of benefit of the trial production line, are studied in the paper. For a production line with the handling capacity of 50 m3/h, its annual direct economic benefit can reach RMB 4 million yuan, calculated by 300 working days a year.

Electrode selection of electrolysis with membrane for sodium tungstate solution

AbstracBy measuring the electrode polarization curves of many kinds of materials and life spans of electrodes through intensifying electrolysis in the process, the appropriate electrode materials for different stages of electrolysis of sodium tungstate solution with membrane have been selected The effects of the electrodes with different shapes on electrolysis have been investigated. The result shows that network electrode is more suitable to electrolysis of sodium tungstate solution.