| Phosphorus is the most important nutrient for water eutrophication.With the increasingly stringent requirements for phosphorus emission standards,people pay more and more attention to phosphorus pollution.The phosphorus produced by domestic sewage is one of the main sources of phosphorus,which is characterized by complicated composition and difficult discharge of phosphorus.There are many methods for phosphorus removal,in which adsorption method has the advantages of simple operation and no two pollution.Montmorillonite is a non-metallic mineral with montmorillonite as the main mineral component.It is widely distributed in the world and mainly based on sodium bentonite(SB)as a common industrial product.It also has good adsorption performance and low price.However,the hydrophilicity of bentonite is very strong,which causes its poor adsorption to pollutants in wastewater.Therefore,it is of great significance to improve its adsorption performance of bentonite by modified.In order to prepare environmental phosphorus adsorption materials with good performance and stability,explore the adsorption law of simplifying the preparation process and shorten the preparation method and the phosphorus cycle,ferric sulfate modified sodium bentonite(Fe-MSB)and aluminum sulfate modified sodium bentonite(Al-MSB)were prepared using sodium bentonite with Fe2(SO4)3 and Al2(SO4)3 as modifiers by efficient microwave irradiation method and water bath oscillation respectively.The optimum preparation conditions were explored with the removal rate of phosphorus as the verification result by single factor experiment.By comparing the preparation cycle of the adsorbent,the removal of phosphorus and a series of characterization,the modified mechanism and adsorption performance were analyzed,and the best adsorbent Fe-MSB was screened out.The optimum adsorption conditions of Fe-MSB for simulated phosphorus wastewater and domestic wastewater were investigated by single factor experiments.The adsorption process was analyzed by adsorption kinetics and thermodynamics.The conclusions are as follows:(1)The best preparation conditions of Fe-MSB prepared by efficient microwaveradiation are: ferric sulfate dosage of 0.8g/10 gSB,microwave power of 199 W and microwave time of 6min;The best preparation conditions of Al-MSB prepared by efficient microwave radiation are: aluminum sulfate dosage of 1.0g/10 gSB,microwave power of 280 W and microwave time of 7min.The optimum preparation conditions of Fe-MSB1 prepared by water bath oscillation are: ferric sulfate dosage of0.8g/10 gSB,the oscillation rate of 120r/min,the reaction time of 3.0h,water bath temperature of 298K;The optimum preparation conditions of Al-MSB1 prepared by water bath oscillation are: aluminum sulfate dosage of 1.0g/10 gSB,the oscillation rate of 120r/min,the reaction time of 3.0h,water bath temperature of 298 K.The preparation cycle is 12 h with the preparation method of high efficiency microwave irradiation,and the preparation cycle is 16 h with the preparation method of water bath oscillation.The efficiency of the adsorbent prepared by efficient microwave irradiation is higher than that by water bath oscillation method.(2)The phosphorus removal rates were 4%,98.82% and 99.92% respectively with SB0,Al-MSB and Fe-MSB,respectively,which were prepared by efficient microwave radiation,however,The phosphorus removal rate respectively were 3.27%,98.71% and 99.13% with SB1,Al-MSB1 and Fe-MSB1 which were prepared by water bath oscillation.The preparation efficiency and and the phosphorus removal rate of the adsorbent prepared by the efficient microwave irradiation method are better than that of the water bath oscillation method.The best preparation method was selected as efficient microwave radiation method.The XRD,SEM,IR and surface area analysis of Al-MSB,Fe-MSB and unmodified SB show that Al-MSB and Fe-MSB compared with the unmodified SB,adsorbent layer spacingincreases,pore and pore structure is improved,and the interlayer elements changed,the bond strength of-OH increased and the peak position offset,the specific surface area increased.The adsorption capacity of Fe-MSB is higher than Al-MSB.The best adsorbent is Fe-MSB.(3)The optimum conditions for the adsorption of phosphorus in simulated wastewater with phosphorus content of 25mg/L by Fe-MSB were as follows: Fe-MSB dosage of 20g/L,initial pH of 6,the oscillation rate of 120r/min,the oscillation time of 120 min and the temperature of 303 K.Under the optimum adsorption conditions,the phosphorus removal rate was 98.67%,and the residue concentration of phosphorus in water was 0.33mg/L.(4)The optimum conditions for the treatment of P and COD in domestic sewage with P content of 10mg/L and COD content of 180mg/L by Fe-MSB were as follows:Fe-MSB dosage of 40g/L,initial pH of 6,the oscillation rate of 120r/min,the reaction time of 30 min and the temperature of 303 K.Under the optimal conditions,the P and COD removal rates were 100% and 74.09% respectively in domestic sewage,and the residue concentration of P and COD in water were 0 and 46.64mg/L,respectively.(5)Fe-MSB adsorption phosphorus was fitted by using the kinetic equation and the adsorption isotherm.The results show that the adsorption of phosphorus on Fe-MSB comforms to the pseudo two order kinetic equation,and the Fe-MSB adsorption process is a spontaneous,endothermic and irreversible process. |
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