| The superparamagnetic separation technology refers to the technique of adsorbing target pollutants through a customized adsorbent based on superparamagnetic nanoparticles as the core,and then simply and rapidly recovering these adsorbents from the solution by applying a magnetic field.Because of its advantages of simplicity,high efficiency,and rapidity technology has become an important research hotspot for heavy metal wastewater treatment in recent years.However,how to efficiently recover weak magnetic nanoparticles from a large volume of waste water solution is still a prominent problem faced by this technology.In order to solve this problem,it is proposed to couple the air flotation technology to the superparamagnetic separation technology and establish a continuous gas-assisted magnetic separation technology that can efficiently recover weak magnetic nanoparticles from large-volume wastewater solutions.The research content is mainly divided into the following three aspects:(1)Firstly,a continuous gas-assisted magnetic separation equipment was designed and constructed.The separation system was based on Fe3O4/PEG adsorption of Cu(?),Fe3O4/HA-Na adsorption of Pb(?)and Fe3O4/PPy adsorption of Cr(?)simulated wastewater.Based on the time required to reach the steady state of the continuous process under the flow rate of each raw material liquid,the effects of heavy metal loading,pH,gas flow rate,magnetic roller rotation speed and rotation mode on the efficiency of continuous gas assisted magnetic separation were investigated.Under optimized conditions:Separation criteria exceeded 95%recovery rate,and the particle size of 0.5 mg/mL Cu(?)-loaded Fe3O4/PEG and Cr(?)-loaded Fe3O4/PPy magnetic particles could reach 24 L/h.The scale of Fe3O4/HA-Na magnetic particles loaded with Pb(?)can reach 12 L/h.(2)The Fe3O4/HA-Na superparamagnetic nanoparticles were further used to adsorb Pb(II)in wastewater from a certain steel plant as the actual separation system,and the lead content,pH,ionic strength and turbidity in the actual wastewater were analyzed,and the appropriate amount was added.The nano-particles lead to the discharge of lead in wastewater.At this time,the initial concentration of magnetic particles was 1.15 mg/mL,and the effects of the main influencing factors on the efficiency of gas-assisted magnetic separation were investigated under intermittent conditions.The scale and performance of the treatment of magnetic nano-particles in the waste water at different gas rates.With a separation rate exceeding 95%,the treatment scale in the actual wastewater can reach 24 L/h.Under the same conditions,the treatment scale of the simulated wastewater with magnetic particle concentration higher than 0.5 mg/mL is 12 L/h.(3)The mechanism of the gas-assisted magnetic separation process was preliminarily explored.The effect of the contact angle of the magnetic particles loaded with heavy metals on the surface was studied.Mechanistic analysis was performed.The results show that the surface of the magnetic nanoparticles tends to be close to the hydrophilicity of the heavy metals themselves;the strong acid and strong base will reduce the hydrophobicity of the surface of the magnetic particles,which leads to the decrease of gas-assisted magnetic separation efficiency;and the ionic strength can be more prominent for the enhanced bubbles The hydrophobic force between the magnetic particles greatly accelerates the gas-assisted magnetic separation efficiency. |
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