Preparation Of Three-Dimensional Graphene-Based Composite Gel And Its Adsorption Performance Study Of Pollutants In Wastewater

In recent decades,humans have introduced various dangerous pollutants（such as dyes,antibiotics and other chemical substances）into the water system,seriously polluting water resources,and also causing damage to humans,wildlife and local ecosystems.Organic dye methylene blue are considered to be the main tapes of water pollutants and have a complex aromatic molecular structure.They are highly toxic and long-lasting compounds in our environment.Ciprofloxacin（CIP）is an important fluoroquinolone.These antibiotic substances are widely distributed in surface water due to their long conversion time and low degradation efficiency.Therefore,the effective removal of these antibiotics is of great practical significance.Many methods haved be used to remove these other organic/inorganic pollutants from wastewater samples in previous studies,for example biodegradation,adsorption,coagulation-flocculation,membrane treatment,p Hotocatalysis and so on.However,Adsorption is an effective,inexpensive and environmentally friendly method.Therefore,grap Hene oxide（GO）is used as a substrate to synthesize ZIF-8@GO_1:1 composite microgel and waste paper/GO_1:3 aerogels in this paper.Then their structures were characterized.At the same time,their adsorption performance was studied about their removal of methylene blue（MB）and ciprofloxacin（CIP）in wastewater.（1）ZIF-8 MOF material with dodecahedral structure is synthesized in methanol medium,and loaded on the GO to obtain ZIF-8@GO_1:1 composite powder.Lastly it was packaged with sodium alginate,cross-linked and freeze-dried to obtain ZIF-8@GO_1:1 composite microgel and characterize its structure.The research results show that:ZIF-8 with dodecahedral structure is successfully introduced into grap Hene oxide sheets,and the thermal stability of the ZIF-8@GO_1:1 composite microgel is increased.The surface area of ZIF-8@GO composite powder with a mass ratio of ZIF-8 to GO of1:1 is 1200.38 cm²/g,which is significantly higher than that of GO’s（133.91 cm²/g）and ZIF-8’s（1838.02 cm²/g）.The pore size of ZIF-8@GO_1:1 composite powder is 99.42nm,which is much larger than the sum of ZIF-8（66.24 nm）and GO（2.87 nm）.Through scanning electron microscopy,it can be found that the ZIF-8@GO_1:1 composite microgel has a large pore structure on the surface,which provides a channel for adsorbing contaminants.The composite microgel has a complete structure with a size of 1-2 cm.（2）The adsorption conditions of ZIF-8@GO_1:1 composite microgel for MB and CIP are optimized.Under optimized conditions,the maximum adsorption capacity of ZIF-8@GO_1:1 microgel for MB and CIP is 79 mg/g and 120 mg,respectively,all higher than pure GO.The adsorption process of MB and CIP conforms to the pseudo-second-order kinetic model,mainly chemical adsorption.The adsorption process of MB conforms to the Langmuir model,which is a single-layer homogeneous adsorption;and the adsorption of CIP is more in line with the Freundlich model;The adsorption process for MB and CIP are both self-discharging heat processes;and after four adsorption-desorption cycles,the removal rates of MB and CIP are 90%and 65%,respectively.（3）Using GO and waste paper（WP）as raw materials,and polyvinyl alcohol（PVA）as crosslinking agent,WP/GO_1:3 aerogel was synthesized by simple mixing and freeze-drying.The research results show that the WP/GO_1:3 porous aerogel with a three-dimensional network structure has been successfully prepared,and its pore size is 2-10nm mesopores.Compared with WP,the thermal stability of WP/GO_1:3 aerogel is improved.（4）The maximum adsorption capacity of WP/GO_1:3 aerogel for MB and CIP can reach 80 mg/g and 158 mg/g,respectively.Compared with ZIF-8@GO_1:1 composite microgel,the required adsorption equilibrium time is shortened.In other words,the adsorption rate is accelerated.The adsorption of MB and CIP fits well with the pseudo-second-order kinetic model.In terms of adsorption isotherms,the adsorption of MB is more in line with the Langmuir model,while the adsorption of CIP is more consistent with the the Freundlich model;The adsorption process of MB and CIP is an endothermic reaction,and high temperature is beneficial to adsorption.We also explore the adsorption of WP/GO_1:3 aerogel on the binary system of MB and CIP,and found that when CIP is present,it can promote MB a little,and when MB is present,it will inhibit CIP.Adsorption kinetic models are also in line with pseudo second-order kinetics.