Preparation Of Prussian Blue @ Porous Material For Efficient Removal Of Thallium(Ⅰ) From Wastewater

Thallium（Tl）is an extremely toxic and rare heavy metal element.In recent years,water pollution caused by heavy metals has become increasingly serious,and Tl pollution incidents have occurred frequently both domestically and internationally.Therefore,the removal of Tl has received considerable attention.Adsorption is one of the most promising methods for treating water contaminated with thallium,due to its advantages of simple operation,low sludge production,high selectivity for pollutants,and high efficiency.Prussian blue（PB,Fe₄[Fe（CN）₆]₃）and its analogues（PBA）have excellent selective adsorption capacity for Tl（I）due to their unique zeolite-like microporous inorganic solid structure and are often used as detoxifiers and Tl（I）adsorbents for animal and human thallium poisoning.However,PB powder is difficult to separate from water.When PB powder is used to treat Tl（I）-containing wastewater,it inevitably causes secondary pollution to the water.Membrane separation is one of the effective technologies to solve this problem.By fixing PB powder in the pores of membrane materials or porous materials,not only can the high efficiency performance of PB powder be maintained,but also the characteristics of different types of materials can be combined.Polytetrafluoroethylene（PTFE）membrane has a small pore size,high density,non-flammability,thermal stability,and chemical resistance,while melamine foam has good corrosion resistance and can be used stably in harsh environments such as acid,alkali,and oil for a long time.In this study,two new composite materials,Prussian blue-polytetrafluoroethylene（PB@PDA/PEI-M-1）and Prussian blue-melamine foam（PB@PDA/PEI-P-1）,were developed by co-deposition modification of polydopamine-polyethyleneimine（PDA/PEI）on PTFE membrane and melamine foam,respectively,to induce the in situ growth of PB on the materials.A series of characterization methods were used to analyze the physical and chemical properties of the two composite materials,including morphology,crystal phase composition,and surface functional groups.The efficiency and mechanism of the two composite materials for removing Tl（I）were systematically studied,and the treatment effect of the prepared materials on simulated thallium-contaminated Pearl River water was investigated,providing new ideas for the treatment of actual Tl-containing wastewater.The main results of this study are as follows:（1）The X-ray diffraction spectra and X-ray photoelectron spectroscopy analysis of PB@PDA/PEI-M-1 showed the same characteristic peaks as Prussian blue,indicating that PB@PDA/PEI-M-1 successfully loaded Prussian blue nanoparticles.SEM images showed that a large number of Prussian blue nanocubes with a length of less than 1μm uniformly grew in situ on the surface of PB@PDA/PEI-M-1.The X-ray diffraction spectra and X-ray photoelectron spectroscopy analysis of PB@PDA/PEI-P-1 also showed that Prussian blue nanocubes successfully grew in the prepared material.SEM images showed that a large number of Prussian blue nanocubes with a length of less than 3μm uniformly grew on PB@PDA/PEI-P-1.（2）PB@PDA/PEI-M-1 exhibits high efficacy in removing Tl（I）from synthetic wastewater with significantly higher dynamic adsorption rate and capacity than static adsorption.PB@PDA/PEI-M-1 and PB@PDA/PEI-P-1 are capable of working in a wide p H range and demonstrate strong anti-interference properties against many interfering ions(Na⁺,K⁺,Ca²⁺,and Mg²⁺).DFT calculations were used to study the adsorption behavior of Tl（I）on the materials,and the order of various ions’binding ability to Prussian blue was found to be Tl>Ca>Mg.The addition of humic acid（HA）enhances the Tl（I）adsorption capacity of PB@PDA/PEI-M-1 by forming Tl（I）-HA complexes on the material surface,significantly improving its adsorption effectiveness.Moreover,after 24 hours of continuous high-intensity tangential flow filtration,PB@PDA/PEI-M-1 maintains its surface morphology of Prussian blue intact,while PB@PDA/PEI-P-1 still exhibits stable Tl（I）adsorption after three cycles of adsorption/desorption experiments.（3）PB@PDA/PEI-M-1 and PB@PDA/PEI-P-1 can effectively reduce the concentration of Tl（I）in simulated Tl-contaminated water from the Pearl River;The presence of approximately 30 ppm COD in the Pearl River water may affect the removal efficiency of Tl（I）by the materials.Overall,the two newly developed composite materials,PB@PDA/PEI-M-1 and PB@PDA/PEI-P-1,show high efficiency,selectivity,and reusability in removing Tl（I）from water,providing a new approach for the treatment of Tl-containing wastewater without causing secondary pollution.