Study On The Preparation Of Gangue-based Zeolite Modified Materials And Their Adsorption Properties On Cadmium In Water

Whether from the perspective of industry or environmental protection and human safety,the effective removal of heavy metal ions in sewage has become an urgent problem to be solved.At present,the commonly used adsorption materials have problems such as high cost,small adsorption capacity and slow adsorption speed,and how to prepare cheap and efficient adsorption materials has become the core problem in the development of adsorption technology.In view of the abundant coal gangue resources in Huainan mining area,this paper uses coal gangue as raw material to synthesize zeolite,and then uses dopamine and tannin acid two polyphenolic compounds to modify its surface to increase the number of functional groups on the surface of zeolite,to achieve the effect of"turning waste into treasure"and"treating waste with waste",which can effectively improve the adsorption efficiency of coal gangue.In this paper,three high-efficiency gangue-based adsorption materials（GZ）,polydopamine-modified zeolite（PDA@GZ）and tannin modified zeolite（TA@GZ）were synthesized from gangue,and the characteristics of the adsorption of heavy metal Cd（II）were discussed in depth,and the influence of adsorption conditions on its adsorption effect was studied.By combining adsorption kinetics,adsorption thermodynamics and characterization methods,the mechanism of GZ,PDA@GZ and TA@GZ improving the adsorption efficiency of heavy metals is understood as follows:（1）Gangue zeolite was synthesized with coal gangue as raw material.The influence of cations on the adsorption performance of gangue zeolite was studied by batch adsorption experiments,and the adsorption mechanism was analyzed by various characterization methods.The adsorption properties of zeolite prepared with gangue against Cd（II）were studied,and it was found that the adsorption effect was good when the initial p H was 7,the adsorption time was 1440 min,the initial concentration was 300mg/L,the temperature was 45°C,and the adsorbent dosage was 0.1 g/L.Through comparative analysis,we found that the reaction process conformed to the quasi-secondary kinetic model,and the Langmuir model had the best fitting effect in the adsorption isothermal model,and the theoretical maximum adsorption capacity of GZ was 66.49 mg/g.According to the in-particle diffusion model,the reaction process consists of two stages,one is surface diffusion,and the other is in-particle diffusion characterized by XRDFT-IR and XPS.The adsorption mechanism of GZ on Cd（II）includes ion exchange surface complexation and precipitation.According to the intraparticle diffusion model,the reaction process consists of two stages,one is surface diffusion and the other is intraparticle diffusion.XRD/FT-IR and XPS characterization showed that the adsorption mechanism of Cd（II）by GZ included ion exchange,surface complexation and precipitation.（2）Gangue-based zeolite was modified with dopamine hydrochloride to synthesize PDA@GZ,PDA@GZ was characterized by X-ray diffraction（XRD）,Fourier Transform Infrared Spectroscopy（FT-IR）,scanning electron microscopy（SEM）and thermogravimetry（TG）.Various characterization results showed that the structure of zeolite did not change after modification,the specific surface area doubled,and heavy metal ions were successfully adsorbed on the surface of the PDA@GZ.By batch adsorption,when the p H is 7,the adsorption time is 1440 min,the initial concentration is300 mg/L,the temperature is 318.15 K,and the adsorbent dosage is 0.1 g/L,the PDA@GZ has a large adsorption capacity for Cd（II）in water.Coexisting ions have an inhibitory effect on the PDA@GZ adsorption process,and the inhibition becomes more obvious with the increase of ion concentration.The quasi-secondary kinetic model and the Langmuir isothermal model are more suitable for describing the adsorption process of Cd（II）by PDA@GZ.Thermodynamic studies show that the adsorption process is a spontaneous endothermic process,and the degree of solid-liquid interface disorder of the material increases after adsorption.Based on the characterization results of XRD and XPS,we deduce that the adsorption mechanism of PDA@GZ is ion exchange,electrostatic attraction,precipitation/co-precipitation and complexation.（3）The TA@GZ was prepared and characterized using gangue-based zeolite and tannin as raw materials.Under the experimental conditions of the initial concentration of heavy metals of 50 mg/g,the adsorbent dosage of 0.01 g,the adsorption time and temperature of 4 h and 30°C,and the p H of 2-7,the adsorption capacity of Cd（II）TA@GZ was 76.6-179.1 mg,which was higher than that of GZ（13.8-63.2 mg）and PDA@GZ（66.4-111.2 mg）.In this paper,the kinetics,isotherm,and thermodynamic fitting studies of the TA@GZ adsorption experimental data were studied,and the fitting results showed that the adsorption isotherm data were more in line with the Langmuir model,and the saturated adsorption capacity was 215.52 mg/g.The adsorption process conforms to the quasi-secondary kinetic model,indicating that the adsorption process is chemosorption.When the dosage of TA@GZ is 0.6 g/L,the removal rate exceeds 97%.It can be seen from the thermodynamic parameters that the adsorption process of the TA@GZ to Cd is a spontaneous endothermic reaction.K⁺,Na⁺,Ca²⁺,Mg²⁺,NH₄⁺had a certain effect on the adsorption of Cd（II）,and the degree of influence was Ca²⁺>Mg²⁺>NH₄⁺>Na⁺>K⁺.Combined with the XRD,FT-IR,XPS and other characterization results of the adsorbed sample,the adsorption mechanism includes ion exchange,precipitation,surface complexation and electrostatic interaction.Figure[52]Table[17]Reference[141]...