Study On Adsorption Performance Of Zirconium-Based Metal Organic Framework For Dyes In Water

With increasing population,industrialization and urbanization,water pollution has become a serious problem that needs to be addressed.Organic dyes are widely used in the textile,paper,leather and printing industries,and they raise the chromaticity of water bodies when discharged.Due to their toxicity,potential mutagenicity and carcinogenicity,they can damage the environment at only very low concentrations and pose a serious threat to human health.Currently,many methods,such as oxidation,adsorption,photodegradation,electrocatalytic degradation,and biological treatment membrane filtration,have been used to remove those organic dyes from wastewater.Among them,adsorption method is favored by researchers because of its low cost,high efficiency,easy operation and easy regeneration of adsorbent.In this paper,four zirconium-based metal organic framework materials-UiO-66,UiO-66-NH₂,UiO-66-SO₃H and MIP-202-were synthesized based on zirconium metal centers,and the adsorption influencing factors and adsorption mechanisms were investigated.recycling and practical application by recycling adsorption test and simulated textile wastewater adsorption test.The details are as follows:（1）UiO-66 and UiO-66-NH₂ were successfully synthesized by solvothermal method using ZrCl₄ as the metal source,BDC and H₂BDC as ligands,and acetic acid as a regulator for the removal of anionic dye methyl orange.The results showed that the equilibrium time for UiO-66 to adsorb methyl orange was 100 minutes,while the equilibrium time for UiO-66-NH₂ to adsorb methyl orange was 90 minutes.The adsorption process of methyl orange on both materials followed pseudo-second kinetics.The adsorption performance of UiO-66-NH₂ for methyl orange is superior to that of UiO-66,due to the corrected potential of UiO-66-NH₂,which is beneficial for enhancing the adsorption performance of methyl orange through electrostatic attraction.The Langmuir adsorption isotherm equation is more suitable for the adsorption of methyl orange by UiO-66 and UiO-66-NH₂,with maximum adsorption capacities of 207.39,184.81,159.18 mg/g and 243.16,236.64,236.41 mg/g at temperatures of 303.15 K,313.15 K,and 323.15 K.The adsorption process of methyl orange by both materials belongs to exothermic reaction,and the adsorption of methyl orange by UiO-66-NH₂ is less affected by temperature.After 5 cycles of utilization,UiO-66 and UiO-66-NH₂ still have 85.20%and 91.60%of the initial adsorption capacity for methyl orange,indicating good recycling performance.The adsorption test of simulated textile wastewater shows that the adsorption capacity of UiO-66 and UiO-66-NH₂ for methyl orange solution in simulated textile wastewater is 80.47%and 86.08%of that of methyl orange solution prepared with ultrapure water.It had some potential for practical application.（2）UiO-66-SO₃H was successfully synthesized using Zr Cl₄ as the metal source by introducing sulfonic acid groups and solvothermal method.Through adsorption experiments on two cationic dyes methylene blue and crystal violet,it was proven that UiO-66-SO₃H has excellent adsorption effects on both cationic dyes,and the reason why UiO-66-SO₃H has better adsorption effect on methylene blue than crystal violet is explained from the perspective of size effect.The equilibrium time for the adsorption of methylene blue and crystal violet by UiO-66-SO₃H is 90 minutes,and both follow pseudo-second kinetics.The Langmuir adsorption isotherm equation is more suitable for the process of UiO-66-SO₃H adsorption of methylene blue and crystal violet.At temperatures of 298.15 K,308.15 K,and 318.15 K,the maximum adsorption capacity for methylene blue is227.27,213.39 and 183.25 mg/g,respectively,and the maximum adsorption capacity for crystal violet is 170.03,171.24,175.43 mg/g.In addition,the process of adsorption of methylene blue by UiO-66-SO₃H belongs to exothermic reaction,which is greatly affected by temperature;The adsorption process of crystal violet is a endothermic reaction,which is less affected by temperature.The recycling test and simulated textile wastewater adsorption test show that UiO-66-SO₃H has good recycling performance and it has some potential for practical application.（3）The green Zr-based adsorbent MIP-202 was synthesized with LA as ligand and water as solvent,and the irregular spherical structure and large specific surface area were obtained by SEM and BET.The adsorption capacity of MIP-202 for methylene blue and crystal violet increased with increasing p H,which was highly correlated with its surface charge and revealed its nature of adsorption by electrostatic interaction.The equilibrium time for methylene blue and crystal violet adsorption was 8.5 h and 8 h,respectively,and the optimal adsorbent dosage was 20 mg and the optimal initial mass concentration of dye was 100 mg/L.The adsorption was more effective at low temperatures and less affected by coexisting ions.The maximum adsorption capacities were 192.31mg/g,178.57 mg/g and 163.93 mg/g for methylene blue and 196.08 mg/g,189.76 mg/g and 182.43mg/g for crystal violet at 303.15 K,313.15 K and 323.15 K,respectively.The adsorption capacities of methylene blue and crystal violet were still 85.10%and 88.56%of the initial adsorption capacities after 5 times of recycling,which had good recycling performance;the adsorption capacities of methylene blue and crystal violet solutions in simulated textile wastewater were 89.04%and 92.14%of the adsorption capacities of methylene blue and crystal violet solutions prepared from ultrapure water,which indicated that it had some potential for practical application.