| With the increasing demand for scientific and technological development,more and more mining of mineral resources has produced a large amount of mining wastewater,which seriously affects people’s lives.Copper is a common heavy metal ion in mining wastewater,which directly threatens people’s health through the accumulation and transfer of biological chains in the water environment and the non-degradable characteristics of heavy metals.At present,chemical precipitation method,redox method,ion exchange method,electrochemical method,adsorption method and other technologies have been applied to the treatment of copper pollution in water at home and abroad,among which the adsorption method has been widely concerned due to its advantages of simple operation,low cost and small energy consumption.As a new type of nanomaterial,graphene oxide is a water treatment adsorption material with great potential due to its good hydrophilicity,large specific surface area and large number of oxygen-containing functional groups in the structure.However,powdered graphene oxide is not easy to recover after water treatment,resulting in secondary pollution.Therefore,a structurecontrollable graphene oxide macrosomal adsorbent was prepared by 3D printing,which changed the composition ratio of the graphene oxide precursor ink to regulate the printability,mechanical properties and adsorption properties of the macroscopic body.By testing the chemical composition and micromorphology of graphene oxide macromaterials,the relationship between their macroscopic properties and microstructure was clarified,and the adsorption mechanism of macroscopic bulk materials was discussed,including the following:(1)Structured graphene oxide macrobodies(3DG)were prepared by 3D printing and used as an adsorbent to remove Cu ions.The stability,printability and printability of the precursor ink were investigated,and the mechanical properties and adsorption capacity of the macrobody of printed graphene oxide were tested.The factors that affect the successful preparation and use performance of macroscopic adsorbents are investigated.Mechanical tests showed that the optimal ratio of graphene oxide:sodium alginate was 1.5:2.0 and the compressive strength was 6.23 MPa.The adsorption experiment showed that the material had good adsorption performance,and the adsorption capacity of Cu2+ was 43.1 mg/g at pH=5 and temperature of 303.15 K,and the adsorption mechanism of Cu2+ was mainly a chemically dominant process,involving the oxygen functional groups contained in graphene oxide and sodium alginate.The results of the desorption and regeneration test showed that the adsorption capacity of 3DG still had 74.6%of the initial adsorption capacity after 5 cycles of experiment.Solid printing graphene oxide macrobody adsorbent has both convenient recovery and excellent adsorption capacity.(2)Using polyvinyl alcohol as the secondary crosslinking agent,a double network structure was introduced into the macroscopic body of 3D printing,which simultaneously improved the adsorption and mechanical properties of the material.In this paper,the printability,microstructure and surface properties of graphene oxide macrobody(DGSP)prepared with different proportions of inks are studied,and the relationship between the double network structure and the improvement of DGSP mechanical properties and adsorption capacity is explored.The adsorption experiment showed that Cu2+adsorption was an endothermic reaction,and the maximum adsorption capacity calculated by the Langmuir model at pH=5.0 and temperature of 303.15 K was 208.0 mg/g,because PVA and SA formed a blending modification of GO,and the addition of PVA increased the dispersion performance of graphene oxide.Kinetics,FTIR and XPS analysis also showed that the Cu2+adsorption mechanism was dominated by oxygen functional groups contained in GO,PVA and SA.Mechanical tests show that DGSP-1 can withstand a pressure of 95.95 MPa and the structural holes remain intact after extrusion,because the soft physical bonds formed by PVA crosslinking and SA-CA2+ form a better double network mechanical structure.In summary,the introduction of PVA greatly improves the potential of materials.(3)In order to further improve the adsorption performance of the material,2,3-dimercaptosuccinic acid(DMSA)was used as a modifier to modify graphene oxide.Not only the surface of graphene oxide is grafted with-SH and N-H bonds,but also the bonding properties of DMSA are used to make the graphene oxide sheet layer present a porous superposition three-dimensional structure.The modified graphene oxide was dispersed in cellulose solution,and sodium alginate was added to adjust the viscosity to prepare a graphene oxide-based composite ink that could be 3D printed.The printed graphene oxide macrobody(DMSA-GO/CE)not only has a porous three-dimensional surface modified by DMSA,but also has an internal support structure of cellulose.It greatly increases the transport of Cu2+inside the macrobody,greatly improves the adsorption efficiency,and enables DMSA-GO/CE to reach 80%of the total adsorption capacity after 60 minutes of adsorption.Through the Langmuir model,the theoretical maximum adsorption capacity of 250.0 mg/g was calculated at pH=5.0 and temperature of 303.15 K,and the initial adsorption capacity was still 80%after 5 adsorption-desorption cycles.In the dynamic adsorption column experimental test,when the influent concentration was 40 mg/L,the adsorbent layer height was 20cm,and the influent flow rate was 10 ml/min,the adsorption saturation time was 3240 minutes,indicating that DMSA-GO/CE has great practical potential. |
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