| The treatment of urban sludge is a major problem in the current environmental field.Urban sludge contains a large number of metal elements,which play an important role in the process of phosphorus removal from adsorbent materials.This makes the town sludge have the potential to absorb phosphorus.Therefore,this study made a simple treatment of urban sludge into a lightweight filter material for the treatment of phosphorus-containing wastewater,providing new ideas for the development and improvement of phosphorus removal sorbents,and also for the sludge Resource utilization provides a new way.Firstly,the prepared sludge filter material was characterized by physicochemical properties and analyzed by SEM,XRD and FTIR to explore the material composition and structure of the sludge filter material.Secondly,in this paper,sludge adsorption was studied by static adsorption experiments to simulate the adsorption performance of phosphorus-containing wastewater for adsorption and removal of phosphorus from sludge filter media.The effects of factors such as the dosage of sludge filter and the solid-liquid ratio of wastewater containing phosphorus,the p H of the wastewater containing phosphorus,the adsorption time,the particle size of the sludge filter media,the initial phosphorus concentration of the wastewater containing phosphorus,the adsorption temperature and the competing ions were examined.Adsorption performance of phosphorus adsorption.The isothermal adsorption characteristics of phosphorus removal from sludge filter media were investigated,and the isotherm adsorption model was fitted.The adsorption kinetics of phosphorus removal from sludge filter media was investigated,and the kinetic model model was fitted.The thermodynamic characteristics of phosphorus removal from sludge filter media were investigated,and the thermodynamic state function was characterized.In addition,this article uses the sludge filter material to make the adsorption column to carry on the dynamic adsorption phosphorus removal experiment,and the measured penetration curve carries on the dynamic adsorption model fitting,studies the dynamic adsorption characteristic of the sludge filter material.Finally,the phosphorus in the saturated filter medium was extracted by fractional extraction to study the presence of adsorbed phosphorus on the surface of sludge filter media,and the mechanism of phosphorus removal by sludge filter was discussed.The results show that:(1)The surface of the sludge filter is porous and has a good crystal structure.Among them,the oxide structure of metal elements such as aluminum and calcium and the silicate structure formed of silicon,and manganese and magnesium in addition to aluminum and calcium.Metals such as iron and iron are also abundant.(2)The optimal dosing amount of phosphorus removal from sludge filter is 0.05,which is easier to absorb under weak acidic conditions.The optimum p H range is 5-7,and the adsorption equilibrium time is about 24 h.The initial phosphorus concentration is No filter material has a great influence on adsorption.The greater the concentration,the better the monthly adsorption.The decrease of the filter particle size can significantly increase the adsorption capacity and the adsorption rate.The increase in temperature also benefits the adsorption of the filter material.(3)Both the Freundlich model fitting and the Langmuir model fitting can get good fitting results.The fitting results show that the adsorption of phosphorus from sludge filter media at low concentration is monolayer adsorption,and at high concentration,the sludge filter The adsorption of phosphorus for the material is multi-layer adsorption.The Langmuir theory saturated adsorption capacity calculated from the segmented fitting results is 15.43 mg/g,which is closer to the measured maximum adsorption capacity than the results obtained by the full-range Langmuir fitting.The maximum measured adsorption capacity actually measured in the experiment.It is 16.21 mg/g.The pseudo-second-order kinetic model can accurately describe the kinetics of phosphorus removal from sludge filter media,and the adsorption process shows the characteristics of early and late rapid adsorption.The equilibrium adsorption amount and measured value predicted by the pseudo-second-order kinetics model are very small,and both are less than 7%.Through thermodynamic analysis,the phosphorus removal by sludge filter is a spontaneous and endothermic entropy increase reaction.The difference in thermodynamic characteristics between high and low phosphorus concentrations is more obvious.When the filter material absorbs low concentrations of phosphorus,the enthalpy change and the average adsorption energy are both large.The range of chemical adsorption,while the adsorption of high-concentration phosphorus when the enthalpy change and the average adsorption energy are small,belongs to the category of physical adsorption.(4)Under the condition of influent concentration of 10mg/L and flow rate of 0.3L/h,the concentration of 1mg/L of effluent was used as penetration concentration,and the penetration points of 10 cm,20cm,and 30 cm adsorption columns were 64 h,96h and 144 h,the exhaustion points were 624 h,708h,and 804 h,respectively.Adsorption capacities at the three adsorption column heights were 5.32 mg/g,3.68 mg/g,and 3.04 mg/g,respectively,and the total removal rates were 42.6%,52.1%,and 56.2%,respectively.Increasing the height of the adsorption column increases the total removal rate.,but the amount of filter material will decrease.From the results of model fitting,both the BDST model and the THOMAS model are able to better fit the breakthrough curve of the sludge filter,and the correlation coefficients all more than 0.96,and the predicted depletion adsorption amount and depletion point are both theoretical values.The error is small,both less than 15%.BDST model can accurately predict the exhaustion point of sludge filter adsorption column.THOMAS model can more accurately predict the dynamic adsorption capacity of sludge filter adsorption column.(5)The main forms of phosphorus adsorbed by sludge filter materials are Al-P and Ca-P,accounting for 52.5% and 23.8% of the total phosphorus,and the Fe-P forms account for a combination of 11.9%,aluminum and iron.The contribution of three kinds of metals to adsorption reached 88.2%.Therefore,phosphorus adsorption on sludge filter is chemical adsorption,mainly aluminum and calcium and phosphorus reaction,adsorption.The mechanism of phosphorus removal by the sludge filter is that the surface of the sludge filter material with iron,calcium,aluminum and other metal oxide structures are combined with coordinated water in the water,and a large amount of hydroxyl groups and hydration groups are generated on the surface of the solid and liquid to form a hydroxylated interface.These hydroxyl groups and hydrated groups undergo a complex exchange reaction with phosphate to form a stable structure,and the phosphate is adsorbed to the surface of the sludge filter material to remove phosphorus. |
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