Preparation Of Modified Mulberry Rod Activated Carbon And Its Study On Adsorption Of Phosphorus And Chromium

With the development and progress of society,more and more human activities have destroyed the phosphorus cycle in nature.Phosphorus is a nutrient that is easily absorbed by plants,so the concentration of phosphorus in natural waters is low.Excess phosphorus in water is mainly derived from agricultural wastewater,industrial wastewater,and urban domestic wastewater.At present,the treatment of wastewater containing heavy metals is a hot topic in the field of environmental engineering.After the heavy metal material enters the environment,it is enriched and amplified in the organism through the cycle of the food chain,which poses a serious threat to the normal metabolism of the organism.In addition,the heavy metals that enter the environment and the organic matter in the environment undergo physical and chemical interactions and are fixed and enriched,thereby affecting the migration and transformation of heavy metals in the environment.?1?In this study,a rich source of mulberry rods was used as raw material,and modified mulberry rod activated carbon was prepared by combined modification of mulberry rod activated carbon with potassium permanganate,ferrous chloride,triethylenetetramine,and epichlorohydrin.The Zata point of the modified mulberry rod activated carbon is 4.52.The modified activated carbon structure remained well and the pores did not collapse or break.?2?The pH value of the solution has a significant effect on the removal of phosphorus.Under different solution pH conditions,the amount of phosphorus adsorbed on the adsorbent decreases gradually as the pH value of the solution increases.When pH=2,the adsorption effect was the best;different concentrations of NO₃^-,CO₃^2-,and SO₄^2-had different effects on the effect of phosphorus removal,and the inhibitory effect on the adsorption process was:CO₃^2->SO₄^2->NO₃^-As the ionic strength increases,the removal rate of phosphorus by the adsorbent gradually decreases.The results of kinetic fitting show that the removal behavior of phosphorus by modified mulberry rods is more consistent with the second-order kinetic equation.The results showed that the removal behavior of phosphorus by the modified mulberry rod activated carbon was in line with the Langmuir model.The maximum adsorption capacities at 25?,35? and 45? were 23.09mg/g,25.32mg/g and 26.34mg/g,respectively.In addition,the increase in temperature is conducive to promoting the adsorption effect.In the investigation of the stability of the material,when the initial pH>2,the dissolution of iron was not detected and the adsorbent had a good stability in the adsorption process.?3?The pH value of the solution had a significant effect on the removal of Cr?VI?.Under different pH values,the adsorption of Cr?VI?by the adsorbent gradually decreased as the pH value of the solution increased.When pH=2,the best adsorption effect.Different concentrations of NO₃^-,CO₃^2-,and SO₄^2-have different influences on the effect of phosphorus removal,and the order of inhibitory effect on the adsorption process is:SO₄^2->CO₃^2->NO₃^-.The fitting of kinetic equations to experimental data shows that the adsorption behavior of adsorbent for Cr?VI?is more consistent with the second-order kinetic equation.The correlation coefficients R² fitted by Langmuir isotherm adsorption model were 0.999,0.998,and 0.999,respectively,and the maximum adsorption capacities at 25?,35?,and 45? were 28.31 mg/g,31.02 mg/g,and 37.14 mg/g,respectively.Langmuir can be used to better express the adsorption process.When the temperature increases from 25? to 45?,the adsorption capacity of the adsorbent also increases by a certain extent,indicating that the elevated temperature has a promoting effect on the adsorption effect.In the investigation of the stability of the material,a small amount of iron was eluted at the initial pH=2,and when the initial pH was>2,the dissolution of iron was not detected and the adsorbent had a good stability during the adsorption process.?4?Phosphorus before and after the sorbent characterization analysis.FTIR analysis showed that there was a clear new peak around 1058 cm^-1,which was the characteristic absorption peak of P vibration.Surface hydroxyl and phenolic hydroxyl groups participated in the adsorption reaction.XPS analysis showed that the iron and manganese oxides in the adsorbent participated in the adsorption reaction.After P was adsorbed,the P2p spectra showed obvious peaks of P2p orbital at the binding energy corresponding to the phosphate group at 132.87 eV,which further indicated that the phosphates had been chemically adsorbed on the surface of the adsorbent and was consistent with the FTIR results.?5?Characterization and analysis of adsorbents before and after phosphorus adsorption.FTIR analysis showed that there was a clear new peak near 540 cm^-1,which was generated by adsorption between Cr?VI?and the adsorbent.The absorption peak at 540 cm^-1 conformed to the vibrational characteristics of the metal oxide,indicating Cr?VI?Formation of surface complexes with metal oxides,surface hydroxyl groups and phenolic hydroxyl groups are involved in the adsorption reaction;XPS analysis shows that the iron and manganese oxides in the adsorbent participate in the adsorption reaction;after adsorbing Cr?VI?,The Cr2p spectrum has a characteristic peak of Cr2p orbital where the binding energy corresponding to Cr?VI?is at 576.32eV,which further indicates that Cr?VI?has been chemically adsorbed on the surface of the adsorbent and is consistent with the FTIR results.