Research On Wastewater Treatment By Attapulgite Composite Adsorbent

Due to the development of the agricultural and industrial production,water pollution has become a serious environmental problem,mainly because the wastewater produced by these industries includes various pollutants such as metals and dyes.If the concentration of pollutants exceeds the allowable range,such pollutants will produce toxicity and adversely affect organisms.Therefore,it is very important to remove these pollutants from wastewater.Adsorption is widely used due to its high flexibility,low cost,superior performance and high efficiency.Attapulgite（ATP）has a unique porous layered chain structure and is an excellent environmentally friendly decolorizing agent.However,its high viscosity makes it difficult to separate.Therefore,the work in this paper is mainly to prepare recyclable attapulgite composite materials to adsorb pollutants in wastewater.1.Efficient adsorption of Cu（II）,Pb（II）and Ni（II）from waste water by PANI@APTS-magnetic attapulgite compositesPANI@APTS-Fe₃O₄/ATP adsorption material was prepared by introducing polyaniline（PANI）into the Fe₃O₄/ATP system through aminopropyltriethoxysilane（APTS）,and use it for Cu（II）,Pb（II）and Ni（II）adsorption.Firstly,Fe₃O₄/ATP was prepared by co-precipitation method,then aniline was connected by APTS,and finally PANI@APTS-Fe₃O₄/ATP was generated by oxidative polymerization.The maximum adsorption capacity of PANI@APTS-Fe₃O₄/ATP for Cu（II）,Pb（II）and Ni（II）is 189.03,270.27 and 142.86 mg g^-1,respectively.The adsorbent is a homogeneous monolayer adsorption,which is in line with Langmuir model.The adsorption equilibrium time of PANI@APTS-Fe₃O₄/ATP is only 15 min,which conforms to the pseudo-second-order reaction kinetics,and chemical adsorption is a rate-controlling step.In the meantime,it has magnetism for magnetic separation and recovery and good stability,so it is very likely to be used in practice.2.Preparation of EDTA-modified magnetic attapulgite chitosan gel bead adsorbent for the removal of Cu（II）,Pb（II）,and Ni（II）Firstly,ATP was combined with magnetic Fe₃O₄nanoparticles to obtain Fe₃O₄-ATP that is easy to recycle and reuse.Then,Fe₃O₄-ATP nanoparticles were embedded in chitosan（CS）gel beads,and glutaraldehyde was used for cross-linking and curing.Lastly,ethylenediaminetetraacetic acid（EDTA）was successfully connected to Fe₃O₄-ATP/CS gel beads through amidation reaction,which further increased the capability of the adsorbent to adsorb heavy metal ions.The prepared magnetic composite adsorbent is a sphere with a rough surface and porous structure.The maximum adsorption capacity of the prepared Fe₃O₄-ATP/EDTA/CS adsorbent for Pb（II）,Cu（II）,and Ni（II）is 368.32,267.94 and 220.31 mg g^-1,respectively.After5 times of repeated use,Fe₃O₄-ATP/EDTA/CS still showed good adsorption capacity for Cu（II）,Pb（II）,and Ni（II）.Fe₃O₄-ATP/EDTA/CS has a large adsorption capacity for heavy metal ions,a wide p H applicability,good reuse,and rapid magnetic separation.This study prepared a new type of adsorbent with good adsorption performance and provided a promising method for the treatment of heavy metal ions in wastewater.3.Preparation and performance study of MOF@CS modified by attapulgite composite materialMetal organic frameworks（MOFs）material has become a new adsorption material due to its large specific surface area and ultra-high porosity.Adding CS and compounding with CS can solve the problems of powder morphology which are not easy to recover and instability.At the same time,ATP has large specific surface area,excellent mechanical properties and adsorption properties,and is further compounded with MOF@CS material to enhance the service performance of the composite material.The organic dye methylene blue（MB）was selected as the research object,and the adsorption properties of the prepared MOF@ATP-CS beads were explored.In the end,Zr-MOF@ATP-CS composite beads performed better in terms of adsorption efficiency,reaching adsorption equilibrium within 30 min,and the maximum adsorption capacity could reach 442.86 mg g^-1.The composite beads are small balls with a diameter of about 2 mm,which are convenient for recycling.