Research On Synthesis And Performance Of Water Purification Material For Dye Wastewater With Chlorine Ion

Printing and dyeing wastewater will pollute the environment without treatment because its organic matter content,chroma and cations is high.Layered double hydroxides?LDHs?have attracted more and more attention to the related research in the field in recent years,because of their unique crystal structure,high anion exchange capacities,flexible layered structure,specific surface area and the so-called memory effect.As adsorbent,LDHs have the advantages of large adsorption capacity,high temperature resistance,radiation resistance,aging resistance,high density,small size and so on.In addition,they have a certain light absorption properties,so that they can be used as catalyst or catalyst supports.In view of the characteristics above,this work primarily focuses on the study of synthesis and performance of water purification materials for dye wastewater with chlorine ion.At first,MgAl-layered double hydroxides with CO₃^2-as interlayer anion?denoted as Mg-Al-CO₃ LDHs?and calcined layered double hydroxides?denoted as Mg-Al-CLDHs?were prepared.Then dye in the wastewater was photocatalytic degraded using Mg-Al-CO₃ LDHs as catalyst.Next Cl^-in the wastewater were removed by Mg-Al-CLDHs as adsorbent.Finally,Mg-Al-CO₃ LDHs were retrieved after Cl^-were desorbed by Na₂CO₃ aqueous solution,which realizeed the purification of the wastewater and recycling of the materials.Mg-Al-CO₃ LDHs were prepared via ultrasonic irradiation method and chemical bath method with Mg?NO₃?₂·6H₂O,Al?NO₃?₃·9H₂O,NaOH and Na₂CO₃ as raw materials.Then roast in muffle furnace under a certain conditions to obtain Mg-Al-CLDHs.The size,microstructure,composition,thermal decomposition and light absorbing properties were investigated by SEM,XRD,FT-IR,TG-DTG and UV-vis.The results show that Mg-Al-CO₃LDHs possesse obvious layered structure and good crystallinity.However,Mg-Al-CLDHs are irregular particals because of roasting.They all have ultraviolet light absorptivity.The as-prepared Mg-Al-CO₃ LDHs were used as catalyst to degrade dye in the wastewater under ultraviolet visible light irradiation.The results show that Mg-Al-CO₃ LDHs obtained via chemical bath method and ultrasonic irradiation method and Mg-Al-CLDHs all had good photocatalytic performance,and the degradation rate of 40 m L,10 mg/L methylene blue solution after 60 min UV light irradiation was 96.7%,92.5%,90.0%,respectively,which was degraded by 1 g/L LDHs.Meanwhile,Mg-Al-CO₃ LDHs prepared via chemical bath method also had good effects to degrade methyl orange and rhodamine B,and the photocatalytic degradation rate after 60 min both reached 95.0%.In addition,Cl^-would have a certain inhibitory effect on photocatalytic performance and increased with the increase of Cl^-concentration.When the concentration of chloride ion 1000 mg/L,the methylene blue decolorization rate after 60 min decreased 4.3%.After photocatalytic treatment,the dye in the wastewater was degraded,but Cl^-still exist.Considering the so-called memory effect,adsprption performance of Mg-Al-CLDHs as adsorbent to remove chloride ion left were investgeted.Results show that the adsorption rate of 50 mL,100 mg/L chlorine ion solution is 72.0%at 3 h and 95.0%at 6 h,which was adsorped by 4 g/L Mg-Al-CLDHs at 20 ?.The studies of kinetics and adsorption isotherm indicate that the date fit to the pseudo second order kinetics and Langmuir isotherm model better.The studies of mechanism validate that the chloride ions enter the Mg-Al-CLDHs layer to restore the original layered structure.In addition,the adsorbents can be reused and its adsorption rate is 75.0%around after five cycles.Experiments show that the materials can be potential treatment agents to deal with wastwater contaminated by anion and dye.