Study On Preparation Of Novel Layered Double Hydroxide Adsorbents And Their Electrocatalytic Oxidation Potential

Water pollution is becoming more and more serious under the condition of the rapid development of industrial society.Water purification technologies with high efficiency and low consumption are urgently needed as a hot research topic in the field of water supply and drainage.Adsorption and oxidation are important ways to remove pollutants from wastewater.If the pollutants can be further oxidized after being absorbed and the materials regenerate in situ,then the adsorption capacity of the adsorbents will be restored when they are saturated.This kind of way is the persistent pursuit of the water purification scholars.Supported by the National Natural Science Foundation of China?51878171?,a new adsorbent material was explored and developed and its oxidation potential was carried out preliminaryly to find a new way for water purification technology.Among many new adsorbents,the adsorption capacity and electrocatalytic oxidation potential of layered double hydroxide?LDH?have attracted much attention from water purification researchers due to their adjustable properties.In this paper,the preparation,microscopic morphology and structure of nano-scale and N-rich organic ligand-doped NiFe-LDH adsorbents were examined,and the adsorption capacity and electrocatalytic oxidation potential of LDH adsorbents in water purification were further discussed.It is believed that this will provide effective technical methods for the application of LDH materials in water purification in the future.The specific contents and conclusions of this work are as follows:?1?A series of LDH with different Ni/Fe molar ratio were synthesized by homogeneous coprecipitation process.The structure,composition and morphology of the materials were characterized by XRD,FTIR,ICP,TG,N₂ adsorption-desorption and SEM.The BET surface area of the typical mesoporous materials ranged from 276.589 m² g^-1 to 542.739 m²g^-1,which was higher than that reported in the general literature,and the average grain diameter of the materials was only about 20 nm.The great characteristics of the materials was attributed to the low crystallinity and high dispersion of LDH during the synthesis process.?2?The adsorption performance of LDH with different Ni/Fe molar ratio was investigated for the methyl orange?MO?as the target pollutant.The effect of Ni/Fe molar ratio on the adsorption performance was significant and Ni₂Fe-LDH showed the best.The maximum adsorption capacity calculated by Langmuir model was 343.64 mg g^-1.The adsorption process followed a pseudo-second order kinetic model and was dominated by chemisorption.The adsorption process could be divided into two stages including external surface adsorption and intraparticle diffusion.The adsorption mechanism could be considered as the synergetic action of electrostatic gravity and charge density of LDH laminates.Better adsorption performance of the carbonate intercalation NiFe-LDH was caused by multiple adsorption forces and inherent properties of the materials itself.?3?The performance for oxygen evolution reaction?OER?of LDH with different Ni/Fe molar ratio was revealed.The effect of Ni/Fe molar ratio on the OER performance was significant and Ni₃Fe-LDH was the best.In order to further improved the OER performance,Ni₃Fe-LDH was doped with organic ligand KBH?im?₃ containing nitrogen.The results showed that the OER performance of Ni₃Fe-LDH/KBH?im?₃-25 was the best.Only 258 mV overpotential was requird to achieve catalytic current density of 10 mA cm^-2 with a small Tafer slope of 44 mV dec^-1,and the potential at 10 mA cm^-2 increased only 43 mV after 20 h stability test in 0.1 M KOH solution.The smaller particle size and denser growth related to the exposure of more catalytic active sites and the electronic structure change of the materials were caused by a certain amount of KBH?im?₃ doping,which improved the OER performance of Ni₃Fe-LDH.