Research On Treatment And Resource Recovery Of Waste Salt From Vanadium Extraction By Bipolar Membrane Electrodialysis

Vanadium is widely used in automobile,aerospace,electronics and medical industry etc as an alloying element in steels.And Vanadium is called as industrial monosodium glutamate.Its consumption in the iron and steel industry represents about85%of the vanadium-bearing products produced worldwide.At present,most of the vanadium leaching industries use the titanomagnetite steel slag as the raw material for vanadium extraction.The common production method of vanadium pentoxide is roasting–leaching.It produces a lot of high-salt and high-amino-nitrogen wastewater.Most of the wastewater treatments are converted into sodium sulfate waste salt by treatment steps such as deamination and four-effect evaporation in the domestic vanadium smelting industry.This kind of waste salt contains 0-5%ammonium salt,which cannot be removed and cannot meet the standard of industrial salt,so it can only pile up warehouses,causing serious waste of resources and land.Bipolar membrane electrodialysis technology,as an emerging technology with low cost,high economic efficiency and environmental friendliness,is widely used in chemical synthesis,food production,waste salt recycling and other fields.This paper proposes a resource-based process route for the treatment of waste vanadium sulfate and sodium sulfate to produce acid and alkali by using bipolar membrane electrodialysis.On the one hand,it can solve the long-standing sodium sulfate solid waste problem in the vanadium smelting industry;on the other hand,it can reuse the produced acid and alkali in the vanadium extraction process or industrial use,reducing production costs and improving production efficiency.Therefore,this paper uses bipolar membrane electrodialysis technology to process waste vanadium precipitation to produce acid and alkali,and optimizes experimental operating parameters,improves production efficiency,and reduces energy consumption.Meanwhile,in order to maximize the recycling of waste salt,obtain a higher concentration of industrial acid and alkali.At lab-scale conditions,the use of bipolar membrane electrodialysis acid-base production technology explored the limit of acid-base concentration obtained by this technology,and also discussed the role of osmotic pressure in the bipolar membrane electrodialysis system.The conclusions are as followings:(1)For the optimization experiment of bipolar membrane electrodialysis treatment of simulated waste salt acid and alkali production conditions.The current density is 30m A/cm~2,the salt concentration is 0.3 mol/L,the volume ratio is 1:2,and the flow rate is 500 cm~3/min as the optimal operating conditions.Its energy consumption is 1.32k Wh/kg and current efficiency is 60.2%.The concentration of H+and OH-ions in the acid-base compartment of the bipolar membrane electrodialysis for acid-base production can reach 1.04 mol/L and 1.03 mol/L respectively at optimized operating conditions.And the acid-base recovery rate can reach 90.1%and 98.6%respectively.(2)For the bipolar membrane electrodialysis technology to prepare high-concentration acid-base experiments.The highest concentration of H~+and OH~-ions can reach 4.74 mol/L and 5.26 mol/L respectively,when the extreme conditions of salt chamber concentration of 1.5 mol/L,current density of 50 m A/cm~2 and volume ratio of1:10.The acid-base concentration is close to the theoretically calculated maximum value.(3)Three sets of comparative experiments have verified the role of osmotic pressure in the bipolar membrane electrodialysis system.In the bipolar membrane electrodialysis system,the osmotic pressure will affect the leakage of hydrogen ions and hydroxide ions in the acid-base compartment and the permeation of the anion and cation membranes,thereby affecting the acid-base concentration and volume of the acid-base compartment.Through this research,the vanadium smelting industry has solved the long-stacked waste salt solid waste treatment and disposal problem,and provided it with a theoretical basis and parameter research.It is hoped that the waste salt in the vanadium industry will no longer be"waste"and can turn waste into treasure.Make more contributions to environmental protection.