Removal Of Organic Contaminants In Water And Its Mechanism By 3D Flower-like LDH

Nowdays the wastewater containing organic pollution,especially dyestuff wastewater,is one of the major causes of environmental pollution and gives rise to certain hazards and environmental problems with the development of modern industry.Recently,the removal of pollutants from aqueous solutions via adsorption has attracted much attention due to its easy to operate,wide adaptability and renewable advantages.Three-dimensional flower-like LDH evolved from two-dimensional LDH materials,which is a new type of environment-friendly adsorption materials developed rapidly in recent years.Three-dimensional flower-like LDH?3D-MgAl-LDH?microspheres were successfully synthesized via coprecipitation-hydrothermal method.The sodium dodecylsulfate was used as soft template.The crystallinity,composition and morphology of 3D-MgAl-LDH were investigated by XRD,FT-IR,SEM,TEM,TG-DTA and Zeta analyze.Static batch adsorption experiments were used to remove organic pollutants from water to provide experimental theoretical basis for 3D-MgAl-LDH industrial application,the results were as follows:?1?3D-MgAl-LDH was successfully prepared by coprecipitation-hydrothermal method.The results show that the 3D-MgAl-LDH microsperes with high crystallinity,regular flower-like morphology and thickness,more than 40%of the total mass of organic components,and negative surface electricity in aqueous solution.?2?The removal of anionic methyl orange?MO?by 3D-Mg-Al LDH showed that3D-MgAl-LDH was particularly effective to remove MO,the maximum adsorption capacity was about 370 mg·g^-1.The effective dosage was about 1g·L^-1,the adsorption reached equilibrium within 6 h.The removal reaction was endothermic reaction.Temperature rise was beneficial to the removal of MO.?3?The equilibrium isotherm showed that the adsorption was consistent with Langmuir equation,which is monolayer adsorption.After the adsorption reaction,the characteristic peak of MO appeared in the XRD pattern of the product,and the interlayer spacing changed from 2.73 nm to 2.45 nm.XPS result showed that the content of DS^-decreased from 71.11%to 42.35%.Combined with XRD and XPS data analysis,some MOs were adsorbed on the surface of the material,and some MOs replaced DS^-into the LDH layer.Therefore,the removal mechanism of 3D-MgAl-LDH to MO was the interaction of interlayer anion exchange and surface adsorption.?4?The removal of cationic rhodamine B?RhB?by 3D-Mg-Al LDH showed that the maximum adsorption capacity of 3D-MgAl-LDH to RhB was about 47 mg·g^-1.The effective dosage was about 2.5 g·L^-1,the adsorption reached equilibrium within 4 h.The removal reaction was endothermic reaction.Temperature rise was beneficial to the removal of RhB.?5?The adsorption of RhB by 3D-MgAl-LDH conformed to the Langmuir adsorption isotherm equation,and the adsorbate and the adsorbent are combined in a monolayer.Rhodamine B is a cationic organic dye.The surface of the 3D-MgAl-LDH combined with this subject is negatively charged,so 3D-MgAl-LDH and RhB can be combined by electrostatic action.In addition,the FTIR spectrum of the product after solid phase reaction showed that the characteristic peaks of RhB such as C=O and NH showed different degrees of shift.When the concentration of rhodamine B was 200mg·L^-1,the shift was more obvious.Shift was confirmed to be related to the generation of hydrogen bonds.Therefore,the removal mechanism of RhB by 3D-MgAl-LDH involved electrostatic interaction and hydrogen bonding.?6?The removal of nonionic organic naphthalene by 3D-Mg-Al LDH showed that the maximum adsorption capacity was about 31 mg·g^-1,the adsorption reached equilibrium within 3h.The removal reaction was endothermic reaction.Temperature rise was beneficial to the removal of naphthalene.The isotherm of 3D-MgAl-LDH for removal of naphthalene is linear,R² was greater than 0.97,and the partition coefficient Kp of 3D-Mg-Al-LDH for naphthalene was 0.9064,which was close to 1,so the removal mechanism of naphthalene by 3D-MgAl-LDH was distributed.effect.