| In recent years,with the development of industry and agriculture,the amount of solid waste and production sewage has been increasing.The development of aluminum industry in China is very rapid,and the amount of red mud produced in the production of aluminum by-products is also increasing.Improper treatment of red mud and random stacking will lead to environmental pollution.The development of animal husbandry has led to an increase in the amount of waste water discharged,and the free emission of high concentration of NH4+and PO43-in the wastewater will lead to the eutrophication of the water body.The highest water pollution in China's intensive livestock breeding industry allows the concentration of NH4+for daily average emission of 80mg/L,and the concentration of PO43-is 8mg/L.In order to solve the problem of industry and animal husbandry.This paper presents a method for the preparation of a magnesium modified calcium silicate from the recovered silica in the red mud to remove the nitrogen and phosphorus in the livestock wastewater.It can not only solve the problem of waste treatment,but also remove the pollutants in the waste water.The contents of the study are as follows:?1?Firstly,the silica was extracted by two acid leaching from red mud,and then reacted with CaO under high pressure.The experimental results show that the optimum ratio is n?Ca/Si?1:1.8 and the solid-liquid ratio is 1:30.The samples were heated at220?for 16 hours and dried at 120?for 8 hours.By means of characterization,it can be seen that calcium silicate hydrate is xonotlite.?2?Calcium silicate hydrate?CSH?was prepared,and CSH was improved by acid.The best experimental conditions:solid liquid ratio is 1:10.The stability of pH is about3.The ability of CSH@SiO2 to release Ca2+in water for one hour was controlled by54.90%,and the effect of Ca2+on NH4+and PO43-removal by MgO was also solved.The water of pH control during 8.510.?3?MgO doped on CSH@SiO2,the best ratio in the molar ratio of n?H2O?:n?Mg?NO3?2·6H2O?:n?citric acid?:n?ethanol?=100:9:9:2.1 and 0.6g CSH@SiO2 mixed.Stirring in water bath for 6 hours,calcination temperature of 700?for 1 hour.The experimental results show that different calcination temperatures have different effects for using MgO in process.The removal rate of NH4+and PO43-can reach 83.88%and93.87%at the calcination temperature of 700?.The pH stability of the solution is about8.5.?4?In order to further improve the composite material,the original removal rate is maintained.The phosphorus removal by CSH can also be fully applied.CSH@MgO core-shell material?CMCS?was prepared to solve this problem.The best experiment ratio is:0.6g of CSH and 40mL glucose?5mol?are heated in water,reaction at 180?for 9 hours,and drying at 50?.The brown samples were deposited in an inert gas with a flow rate of 25mL/s and carbonized at 500?for 4 hours to obtain the CSH coated with carbon layer.By characterization,the carbon layer is perfectly wrapped around CSH to form a rounded sphere.?5?According to the best ratio of the previous experiments,the molar ratio of n?H2O?:n?Mg?NO3?2·6H2O?:n?citric acid?:n?ethanol?=100:9:9:2.1 and 0.6g wrapped carbon layer of CSH is mixed.The composite silicate material?CMCS?of MgO was calcined at 700?for 1 hour.CMCS was used to test the performance of NH4+and PO43-.The removal rates of NH4+and PO43-were 76.63%and 87.18%respectively.The removal rate of two kinds of materials is similar.If the removal rate of CMCS PO43-increases with the increase of time,the removal rate of PO43-will be increased.Its advantages will also be reflected.?6?After removal of NH4+and PO43-from these two materials,the two materials were regenerated and regenerated by chemical reaction.The hydrochloric acid?1mol?and the after reaction of two materials.The solid liquid ratio 1:5 was regenerated for 5minutes,and the number of regeneration was 5 times.Under the two regeneration modes,the efficiency of NH4+and PO43-removal could reach 73.51%and 80.86%at the same time.The desorption rates of NH4+and PO43-in the solid after reaction were 88%and 80%.This two materials may be recycled?7?The morphology and composition of CSH@SiO2@MgO and CMCS were analyzed by various characterization methods and the mechanism of simultaneous removal of NH4+and PO43-in water was studied.The results show that both CSH@SiO2@MgO and CMCS can be removed by chemical precipitation,and the suitable reaction conditions can be self adjusted in the process of removal. |
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