Adsorption Properties Of Modified Pinecone Activated Carbon For Nitrate Nitrogen And Total Nitrogen Studies

High water-soluble nitrate nitrogen is one of the pollution sources of drinking water.When the concentration of nitrate nitrogen deposited in drinking water exceeds its limit,it will pose a serious threat to human health.And the total nitrogen in the surface water and shallow groundwater is 60%～90%.Therefore,in order to reduce the threat to human beings,biological organisms and reduce environmental pollution,it is urgent to remove nitrate nitrogen form water.In this study,modified pine cone activated carbon（CWPAC-Fe）was prepared from waste pine cone powder by microwave+trichloride iron activation+chemical loading method,and nitrate nitrogen and total nitrogen were removed from water by CWPAC-Fe.The main research results are as follows:（1）By optimizing the preparation process of pine cone activated carbon through activation of microwave+chemical combination and load modification agent,the results showed that the modified pine cone activated carbon（CWPAC-Fe）has the best adsorption performance,and the removal rate of nitrate nitrogen is as high as 92.19%,with Fe Cl₃as an activator,under the optimal preparation conditions of microwave activation power of567W,activation time of 7min,Fe Cl₃concentration of 1 mol/l,impregnation ratio of 1:2,microwave activated carbonization power of700W and time of 8min,loaded with 1%chitosan.（2）SEM,EDS,XRD,FTIR,BET,Zeta potential were used to characterize the physicochemical properties of pine cone and modified pine cone activated carbon.The results showed that the structure of pine cone powder fiber was complete and compact,showing amorphous type and no obvious pore structure,which was mainly composed of C and O elements.The main constituent element of CWPAC-Fe is C,O,Fe,Cl,and N elements,with stable structure,forming abundant micropore structure,specific surface area and pore volume are about 495 times and 204 times that of raw materials respectively,and CWPAC-Fe surface was attached a large amount of Fe Cl₃and chitosan,which is conducive to the adsorption of nitrate nitrogen by CWPAC-Fe。The zero point charge of CWPAC-Fe is p H_ZPC=2.9,the The surface of CWPAC-Fe is positively charged when p H is less than 2.9,which is conducive to remove nitrate nitrogen.（3）The static adsorption experiment of CWPAC-Fe was carried out,which explore the effects of adsorption time,CWPAC-Fe dosage,p H value and initial concentration of pollutants on the adsorption effect of CWPAC-Fe.The results showed that the adsorption time was 12h,p H=2,the dosage of CWPAC-Fe was 2g,the initial concentration of nitrate nitrogen was 30mg/L,which is the optimal adsorption condition of nitrate nitrogen,and the removal rate of nitrate nitrogen by CWPAC-Fe was97.07%.It is the optimal adsorption condition of total nitrogen that the adsorption time was 16h,p H=3,the dosage of CWPAC-Fe was 2g and the initial concentration of total nitrogen was 40mg/L.The removal rate of total nitrogen by CWPAC-Fe was 97.5%.（4）The adsorption mechanism of CWPAC-Fe on nitrate nitrogen and total nitrogen was explored by adsorption kinetics model,adsorption isotherm model and adsorption thermodynamics fitting.It was found that the adsorption of nitrate nitrogen and total nitrogen by CWPAC-Fe was consistent with Langmuir adsorption isotherm model and Freundlich adsorption isotherm model（R²was greater than 0.99）and the description of quasi-second-order kinetics model has the best effect（R²was 0.99939 and0.99807 respectively）.The results show that the adsorption of nitrate and total nitrogen by CWPAC-Fe is dominated by monolayer chemisorption and supplemented by physical adsorption,the adsorption rate is mainly controlled by the force of chemical adsorption,liquid membrane diffusion and energy-heterogeneous surface diffusion,and the adsorption of nitrate and total nitrogen by CWPAC-Fe is an endothermic reaction with spontaneous and entropy increase.（5）The effects of filling height of CWPAC-Fe in adsorption column and influent flow rate of pollutant wastewater on dynamic adsorption breakthrough curves were investigated by dynamic adsorption experiments.The results showed that the removal rates of nitrate nitrogen and total nitrogen were 95.002%and 95.021%respectively when the influent flow rate was 4m L/min and the filling height of CWPAC-Fe was 30cm and 20cm,and the adsorption breakthrough time was 378min and 490min respectively.Through the fitting of Thomas model,BDST model and Yoon-Nelson model,it can be seen that the dynamic adsorption of nitrate and total nitrogen by CWPAC-Fe conforms to Thomas model（R²is greater than 0.896）,which indicates that the adsorption rate is not controlled by external diffusion or internal diffusion.The fitting effect of BDST model（R²is greater than 0.93）shows that BDST dynamic model has high accuracy in predicting the breakthrough time and depletion time of CWPAC-Fe adsorption of nitrate nitrogen and total nitrogen at low influent flow rate.Yoon-Nelson model can describe the dynamic adsorption behavior of total nitrogen by CWPAC-Fe,most of R²is above 0.9,which indicates that the probability of total nitrogen wastewater breakthrough CWPAC-Fe is proportional to the adsorption rate.（6）When coexisting Cl^-、HCO₃^-and SO₄^2-present in the solution,the inhibitory effect on nitrate nitrogen and total nitrogen is Cl^->HCO₃^->SO₄^2-、SO₄²>Cl^->HCO₃^-,respectively.（7）From the perspective of economic and environmental protection,the Na Cl solution with better regeneration effect was selected as regeneration desorption solution of CWPAC-Fe.And regenerated three times,CWPAC-Fe had a better adsorption effect on nitrate nitrogen and total nitrogen.（8）After the actual wastewater was treated by CWPAC-Fe adsorption,the removal rate of nitrate nitrogen and total nitrogen was 91.77%and88.32%,and the average concentration of nitrate nitrogen and total nitrogen in the effluent was about 0.7 mg/L and 1.66 mg/L,which was far lower than the sanitation standard limit of drinking water.