| Gold has extraordinary physical and chemical properties and plays an important role in high-tech fields such as electronics,telecommunications,aviation,chemistry and medical treatment.Therefore,the recovery of gold from industrial waste or wastewater has attracted great attention.In this paper,by modifying the zirconium-based metal organic framework material and preparing a new type of zirconium-based metal organic framework material,an adsorption material for the recovery of gold ions in wastewater was synthesized.Adsorption experiments were carried out in actual wastewater through the effects of pH,adsorption time,gold ion concentration,and the number of reuse times on adsorption performance.The adsorption mechanism was investigated by studying the adsorption kinetic model and isothermal adsorption model,which provided a theoretical basis for the recovery of gold in simulated wastewater.The main research work of this paper is summarized as follows:(1)This article first prepared three new types of adsorbent materials used to recover gold from waste liquid,which were 5-amino-2-mercapto-1,3,4-thiadiazole-modified zirconium-based metal organic framework materials UiO-66-NH2(UiO-66-MTD),lipoic acid modified zirconium-based metal organic framework material UiO-66-NH2(UiO-66-TA)and 2,2'-dithiodibenzoic acid as organic ligands synthesized new metalorganic framework material(DTDD-MOF),and characterized the adsorbent by field emission scanning electron microscope,infrared spectroscopy,thermogravimetry and Xray electron spectrometer;(2)The effects of pH,adsorption time,gold ion concentration,number of reuses and interfering ions were investigated.The results show that the maximum adsorpti on capacity of UiO-66-MTD at pH=6.0 and the adsorption time of 120 minutes is 301.5 mg/g;the optimal adsorption conditions for UiO-66-TA are pH=2.0 and the adsorption time 240 min,the maximum adsorption capacity is 372 mg/g;DTDD-MOF at pH = 2.0,the adsorption equilibrium time is 900 minutes,the maximum adsorption capacity is 1119 mg/g.After UiO-66-MTD,UiO-66-TA and DTDD-MOF were used 3 times,6 times and 5 times respectively,the adsorption capacity did not decrease significantly.UiO-66-MTD can selectively adsorb gold ions from a mixed simulated solution of gold,zinc,manganese,magnesium,cadmium,arsenic and cobalt,UiO-66-TA can choose from gold,lead,lithium,magnesium,chromium,iron and manganese,Cadmium,Copper,Zinc,Aluminum,Cobalt and Nickel can be selected to adsorb gold ions in the mixed simulated solution.UiO-66-MTD can be selected from the mixed simulated solutions of gold,chromium,magnesium,aluminum,nickel,iron,zinc and copper Adsorption of gold ions.Therefore,the three adsorbents prepared have good selectivity and repeatability;(3)The adsorption kinetic model and the isothermal adsorption model are studied.The results of the adsorption kinetic model show that the adsorption of gold by UiO-66-MTD,UiO-66-TA and DTDD-MOF conforms to the Pseudo-second-order model,so the kinetic limitation of the adsorption process is chemical adsorption.Isothermal adsorption simulation results show that the adsorption of gold ions by UiO-66-MTD,UiO-66-TA and DTDD-MOF conforms to the Langmuir model,so the adsorption process belongs to monolayer chemical adsorption;(4)The adsorption mechanism was experimentally studied.Zeta potential,XPS and DFT calculation results show that the adsorption mechanism of UiO-66-MTD,UiO-66-TA and DTDD-MOF to gold ions is chelation and ion exchange.According to the research,the adsorption of gold ions by these new gold adsorbents is based on chelation and ion exchange.They have high adsorption capacity,good selectivity and can be recycled.Therefore,these new adsorbents have broad application prospects in the application of gold ion recycling. |
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