The Preparation Of Compound Modified Bentonite And Its Adsorption Performance For Cr⁶⁺ And Phenol In Water

With the rapid development of science and technology,there are industrial wastewater,agricultural wastewater and domestic wastewater discharge also increased accordingly.Heavy metal ions and organic wastewater are particularly serious emissions into the environment,Which is need to select the appropriate wastewater treatment methods for multi-component wastewater treatment.There are so many methods of treating pollutants were studied,such as membrane separation,photocatalysis,adsorption and so on.The membrane separation method has the disadvantages of poor selectivity and low stability.The photocatalytic method has the disadvantages of low utilization rate of sunlight and difficulty in solid-liquid separation.Adsorption method has the advantages of simple operation process,no introduction of secondary pollution and high adsorption efficiency,Which has become a popular wastewater treatment method.Bentonite is a kind of silicate clay mineral,which is rich in our country and has the advantages of large specific surface area,good adsorption performance and cation exchange performance.It can be used as an adsorbent material to replace expensive activated carbon adsorbent with difficulty in solid-liquid separation.In order to improve the capacity of bentonite adsorbed pollutants and to improve the poor performance of bentonite adsorbed organic pollutants,two kinds of modification methods were used to modify the bentonite,which was applied to the treatment of the coexistence of heavy metal ions and organic matter.The main research contents are as follows:(1)The preparation of influencing factors of La/Fe-CTMAB modified bentonite by the adsorption of Cr6+ and phenol was studied,and its characterization was carried out.The results showed that the perfect preparation conditions of La/Fe-CTMAB modified soil were as follows:the molar ratio of La3+and Fe3+was 0.5,the preparation temperature of polyhydroxy iron columnifier was 40℃,the reaction temperature of column was 40℃,the mass ratio of total molar of La3+and Fe3+to soil was 12 mmol/g and the dosage of CTMAB was 1.0CEC.Inorganic La3+,Fe3+and organic molecules CTMAB enter into the bentonite internal structure,the bentonite layer spacing from the original bentonite 1.32 nm increased to La/Fe-CTMAB modified bentonite 1.89 nm,The hydrophobicity of La/Fe-CTMAB modified bentonite is enhanced,La/Fe-CTMAB modified bentonite surface layer structure stripping significantly and modified bentonite surface area decreases,pore size increases.(2)The adsorption performance and adsorption mechanism of La/Fe-CTMAB modified bentonite on Cr6+and phenol were investigated.The results showed that when the shock time was 60 min,the pH was 5.37,the temperature was 25℃,the concentration of mixed wastewater was 50 mg/L and the dosage of modified bentonite was 15 g/L,the removal rates of Cr6+and phenol by La/Fe-CTMAB modified bentonite were 99.99%and 69.77%,respectively.Under the same conditions,the removal rate of Cr6+and phenol by raw bentonite was 32.32%and 12.04%,respectively.La/Fe-CTMAB modified soil is consistent with the quasi-second-order kinetic model for the adsorption process of Cr6+and phenol.The inner diffusion model is not the only step of rate control.Both Langmuir model and Freundlich model can describe the adsorption of Cr6+and phenol by the La/Fe-CTMAB modified soil.The adsorption of Cr6+and phenol was an endothermic reaction and the adsorption of Cr6+is spontaneous,the adsorption of phenol is non-spontaneous.For the whole adsorption system,the adsorption process entropy is added.(3)The preparation,characterization,adsorption and adsorption kinetics of CTMAB-CTS modified bentonite were studied.The results showed that when the dosage of CTS was 0.15 g,the shock time was 80 min,the pH was 6.30,the temperature was 25℃ and the dosage was 20 g/L,the removal rates of Cr6+and phenol by CTMAB-CTS modified bentonite were 100%and 92.3%,respectively.Under the same conditions,the removal rate of Cr6+and phenol by raw bentonite was 26.8%and 13.57%,respectively.Layer spacing from the original bentonite 1.32 nm to CTMAB-CTS modified bentonite 1.91 nm.The CTMAB molecules enter into the internal structure of bentonite,while the CTS molecules are supported on the surface of bentonite.The adsorption of Cr6+and phenol by CTMAB-CTS modified bentonite is in accordance with the quasi-second order kinetic equation.