Study On Biochar-attapulgite Compound Lock Phosphorus Material And Its Phosphorus Control Effect

In recent years,with the continuous improvement of industry and quality of life,the problem of eutrophication of lakes in my country has become increasingly serious.According to the survey,my country’s phosphorus-controlled lakes account for the majority.Therefore,reducing phosphorus content is the key to controlling lake eutrophication.The existing phosphorus-locking materials in the world have the problems of low adsorption capacity and high cost.In this paper,the mineral-rich attapulgite and easy-to-produce biochar are used as the carrier to modify the metal solution to prepare the lanthanum-aluminum composite modified matrix material La/Al@TBA and biochar-attapulgite composite phosphorus-locking material La/Al@BA,and conducted batch experiments and long-term simulation experiments in the laboratory to study the adsorption capacity and actual phosphorus-fixing effect of phosphorus-locking materials.The main conclusions are as follows:（1）The proportion of lanthanum and aluminum in the biochar-attapulgite composite phosphorus-locking material is 5%and 2%respectively on the dry basis.Through the adsorption isotherm experiment,it is found that the Langmuir and Freundlich models are in line.The maximum adsorption capacity calculated by the Langmuir equation is 32.3 mg/g,and it is in line with the quasi-first and quasi-two kinetic models.Considering the two factors of mechanical strength and adsorption capacity,the lanthanum-aluminum composite modified La/Al@TBA type matrix material sintered at 500 degrees for 1 h was selected.Through the adsorption isotherm experiment,it is found that the Langmuir and Freundlich models are in line.The maximum adsorption capacity calculated by the Langmuir equation is 20.3 mg/g,and it is in line with the quasi-first and quasi-two kinetic models.The two phosphorus-locking materials can be used in a wide range of p H values.In the presence of different competing anions,the phosphorus removal effect of the material has almost no effect.（2）During the characterization and analysis of La@TBA and La/Al@TBA,it was found that after the metal solution modification,the content of lanthanum and aluminum in the material increased significantly;the calcium content in the matrix material after high temperature calcination decreased,and the high temperature calcination has Conducive to increase the specific surface area of the matrix material.Phosphorus exists in the form of HPO₄^2-and H₂PO₄^-on La/Al@TBA.The high resolution spectra of La 3d and Al 2p indicate that La-O-P and Al-O-P complexes may be formed.The dynamic experiment of the chromatographic column shows that the mass of adsorbent increases,the initial concentration of injection is small,and the water output gradually increases.When the initial concentration is 1 mg P/L and the adsorbent mass is 15 g,the water output reaches 118.9 BV.In the long-term adsorption column experiment,the 8 h HRT experimental group has a significantly better phosphate removal effect than the 4 h HRT experimental group.In the entire 60-day indoor simulation stage,the phosphorus removal rate reached more than 98.4%.（3）The results of long-term indoor culture experiments of columnar samples show that La/Al@BA is superior to ACLA and Phoslock（?）in controlling overlying water,interstitial water release and sediment phosphorus control in columnar samples under the same dosage.The La/Al@BA treatment group had 78.5%and 87.0%interstitial water phosphate removal rates at1X and 2X dosages,respectively,which could weaken more than 96.1%of the phosphate flux.The phosphorus grading study on the surface sediments after the material treatment found that La/Al@BA can reduce the Mobile-P content in the surface layer 0-2 cm and 2-4 cm sediments by 23.2%and 12.8%,respectively,and converted to For the more stable Ca-P component,the corresponding surface layer increased by 27.9%and 17.4%respectively.