Adsorption Behavior Of Nitrophenol On Magnetic Ion Exchange Resin

Nitrophenol is a kind of organic compound widely used in many industries.In the meantime,nitrophenol pollution caused by the massive use of nitrophenol is also a problem that current scholars need to study and solve.Nitrophenolic pollutants are not easily degraded in the environment and are more harmful.Their long-term existence will cause continuous damage to the environmental ecosystem and threaten human health.The removal efficiency and mechanism of o-nitrophenol(ONP)and p-nitrophenol(PNP)by magnetic ion exchange resin(MIEX?)were studied systematically in this paper.This research consists of three parts.One is to investigate the influence of environmental factors on MIEX?’s removal of ONP and PNP,including static adsorption test speed,p H value,initial concentration of pollutants,MIEX?dosage,contact time,temperature,humus acid,etc.The second is to establish a response surface model for MIEX?to remove ONP and PNP based on a single factor,so as to predict and optimize the process of MIEX?to remove ONP and PNP.The third is the analysis and characterization of the mechanism of MIEX?removing ONP and PNP,including kinetics,adsorption equilibrium,thermodynamics,parameter calculations of the reaction,scanning electron microscopy before and after MIEX?removing ONP and PNP,Fourier analysis and the change of chloride ion before and after the solution reaction,systematically studied the adsorption process of ONP and PNP on MIEX?.The test results of environmental factors have shown that if MIEX?can be effectively contacted with nitrophenol,the rotation speed must be greater than 120 rpm,180 rpm is the best rotation speed for the experimental study;p H affects the adsorption effect by affecting the forms of nitrophenol and MIEX?.While the p H is greater than the isoelectric point of ONP and PNP,the ionization of nitrophenol will increase and the removal rate will increase.When the p H is 10,the maximum adsorption capacity is obtained.The greater the dosage of MIEX?,the better the removal effect can be obtained when the concentration of ONP and PNP is constant.The lower the initial ONP and PNP concentration,the higher the removal rate can be obtained when the dosage of MIEX?is constant.The adsorption of ONP and PNP by MIEX?can reach equilibrium in about 60 minutes.The increase in temperature will promote the adsorption of ONP and PNP on MIEX?.Humic acid will negatively affect the adsorption of ONP and PNP by MIEX?,but the inhibitory effect is weak.The second-order polynomial mathematical model of MIEX?adsorbing ONP and PNP established by the response surface method can well describe the adsorption of MIEX?to ONP and PNP.Variance significance analysis shows that the model is reliable,the error generated by the model can be ignored,and the normal distribution of residual proves the reasonable accuracy of the model.The independent factors of MIEX?dosage,initial concentration,initial p H value and adsorption time affect the removal of ONP and PNP by MIEX?:p H>MIEX?dosage>adsorption time>initial concentration.The interaction between p H value and MIEX?dosage and p H value and time has the most significant effect on MIEX?’s removal of ONP and PNP.The optimized conditions for ONP prediction are:the dosage of MIEX?is 1.59 m L/L,the initial ONP concentration is 6.88 mg/L,the p H is 9.71,the time is 97.60 min,the predicted removal rate is 82.15%,and the actual is 78.35%.The optimized conditions for PNP prediction are:the dosage of MIEX?is 1.32 m L/L,the initial PNP concentration is 6.18 mg/L,the p H is 8.55,the time is 93.76 min,the predicted removal rate is 81.72%,and the actual is 81.88%.MIEX?regeneration studies show that 5 g/L Na Cl solution has the best regeneration effect on MIEX?after adsorption of ONP and PNP.MIEX?still has better processing performance after several adsorption analyses.The kinetics showed that the adsorption of ONP and PNP by MIEX?can basically reach equilibrium within 40 minutes.The increase of temperature and concentration of ONP and PNP can accelerate the reaction rate and improve the adsorption performance of MIEX?.The adsorption kinetics of ONP and PNP by MIEX was in accordance with the pseudo-second-order model.The main step limiting the rate of adsorption reaction is liquid membrane diffusion.The Ea values of ONP and PNP on MIEX?are 29.1847KJ/mol and 53.4161 KJ/mol,respectively.It shows that the adsorption process is chemisorption.Langmuir model is more consistent with MIEX?adsorption isotherm for ONP and PNP,and the adsorption process is preferential adsorption.Under the isothermal conditions,Polanyi adsorption potential will decrease with the increase of concentration.When the concentration is constant,the increase of temperature can increase Polanyi potential,which is beneficial to the adsorption.△H~0,△S~0,△G~0variation indicate that the adsorption process is an endothermic reaction.This is a spontaneous reaction process,the entropy increases,and the increase in temperature can promote the spontaneity of the reaction process.The MIEX?surface changes,the pores and pore diameters are reduced,the vibration peak of the resin increases after adsorption,and new characteristic peaks appear,indicating the effective adsorption of ONP and PNP on MIEX?.The change of the amount of chloride ion in solution and the amount of adsorption of ONP and PNP by MIEX?confirm that the adsorption of ONP and PNP by MIEX?is through ion exchange.