Study On Adsorption Of Typical Pollutants In Water By Modified Luffa

Heavy metal pollution,organic pollution and biological pollution in water are increasingly serious.The long-term accumulation of these substances in the environment will cause severe threats to human health,animal survival and ecological environment.Therefore,the removal of pollutants from water is the research direction of many researchers.Among the many pollutant removal methods,the adsorption method is widely used due to its simple operation,rapid adsorption rate,and simple requirements for adsorption conditions.The key point of adsorption method is to prepare excellent adsorbents.Luffa,as a natural plant fiber,has high mechanical strength and stiffness,and it is resistant to acid,alkali,salts solutions.The cellulose molecule contains a large number of hydroxyl groups,and the primary hydroxyl group at the C6 position of cellulose has high reactivity.And it is easy to modify,so the loofah(LG)is superior biomass adsorbent.In this paper,used loofah as the base material,used epichlorohydrin and iminodiacetic acid(IDA)modification to obtain iminodiacetic acid-modified loofah(IDA-LG),on this basis,zirconium and lanthanum were loaded onto IDA-LG in the form of complexation,and two new adsorbents,Zr-IDA-LG and La-IDA-LG,were obtained.Through the characterization of three modified adsorbents,fixed-bed and batch adsorption experiments of model pollutants,the effect factors and adsorption mechanism of the adsorption process were discussed.The characterization results showed that the surface morphology,specific surface area and internal functional groups of the adsorbent changed significantly after modification,and the isoelectric point moved to the acidic direction,indicating that the loofah was successfully modified.The effects of pH,salinity,temperature,and time on the adsorption were explored in the static adsorption experiments of Pb2+ and Zn2+by IDA-LG.The results showed that higher acidity and salinity had negative effects on adsorption.At 303 K,the maximum adsorption capacity of the adsorbent for Pb2+ and Zn2+was 82.5 mg·g-1 and 25.2 mg·g-1,respectively.The fitting of the Koble-Corrigan isotherm model(n is close to 1)and the kinetic model indicated that the adsorption experiment was dominated by the chemisorption of the monolayer,and accompanied by ion exchange.In the binary system,the affinity of IDA-LG for Pb2+ was higher than Zn2+and Cu2+.The Yan model could be used to describe the dynamic adsorption process,and the higher the column,the lower the flow rate,the better the adsorption.0.1 moL·L-1CaCl2+0.1 mol·L-1 HNO3 had good desorption and regeneration effect on the adsorbent under batch and fix bed conditions.Compared with the original loofah,the adsorption capacity of the modified loofah was significantly improved,and it showed good adsorption selectivity for Pb(Ⅱ).The results of adsorption research of Zr-IDA-LG for catechol and amoxicillin showed that the salinity was beneficial to the adsorption;The adsorption capacity of Zr-IDA-LG on catechol was increased gradually in the range of pH 2～6,and remained stable in the range of pH 6-8.The adsorption capacity of Zr-IDA-LG on amoxicillin was not affected by pH.Under the optimal adsorption conditions,the maximum theoretical adsorption capacity of Zr-IDA-LG for catechol was 39.7 mg·g-1,and the maximum theoretical adsorption capacity for amoxicillin was 29.3 mg·g-1.The adsorption isotherms and kinetic models of Zr-IDA-LG for catechol indicated that the adsorption process was dominated by chemical monolayer adsorption,while the adsorption isotherms and kinetic models of Zr-IDA-LG for amoxicillin indicated that the adsorption process was dominated by monolayer adsorption and there was hybrid adsorption,both accompanied by ion exchange.Thermodynamic studies of Zr-IDALG catechol and amoxicillin showed that the adsorption reaction was a spontaneous,endothermic and entropy-increasing reaction.In the fix bed adsorption experiment,the higher the column,the lower the flow rate,the better the adsorption,and the Yan model could be used to describe the adsorption process.Desorption and regeneration experiment showed that the new adsorption material was green,environmentally friendly and recyclable.The adsorption research results of La-IDA-LG for PO43-showed that the pH=4 was the most favorable for the adsorption,and the salinity was not conducive to the adsorption.Under the optimal adsorption condition of 303K,the maximum theoretical adsorption capacity of the adsorbent for PO43-was 11.3 mg·L-1(Calculated as total phosphorus).The static adsorption mechanism of PO43-by La-IDA-LG could be predicted by the isotherm models about Langmuir,Koble-Corrigan and RedlichPeterson as well as kinetic models about Pseudo-second-order,Double Constant equation and Elovich.Thermodynamic parameters indicated that the adsorption process was a spontaneous process with endothermic entropy increase.The Yan model could be used to describe the adsorption process of PO43-by La-IDA-LG.0.1 mol·L1NaOH could desorb and regenerate the adsorbed La-IDA-LG.The results of this paper lay a theoretical and experimental basis for the further development and utilization of loofah.