Removal Of Manganese Ions By Conventional Water Purification Process And Titanium Dioxide Based Adsorption Materials

At present,most cities in China have taken surface water as the main source of urban water supply.Due to the frequent occurrence of seasonal and sudden manganese exceedances in surface water,this will undoubtedly have an impact on the current process of water purification plants and affect the operation condition of water purification plants.In response to the phenomenon of manganese exceedance in surface drinking water,this research group stayed in a water plant during the summer manganese exceedance period and carried out relevant research on the status of a water purification plant in Hefei to remove Mn²⁺.In understanding the operating parameters of each structure,water treatment chemicals dosing point and raw water quality during the period of manganese exceeded the standard,sampling and analyzing the inlet and outlet water of each unit of the water purification process and bottom sediment of the water plant to study the removal and migration transformation of manganese ions in the water purification process.According to the characteristics related to manganese pollution in water plants,the adsorption of Mn²⁺was investigated by preparing hydrated metal oxides with the hydroxyl-rich surface by different methods using titanium and aluminum salts as raw materials.The specific studies are as follows:（1）The water plant adopts a"high-load sedimentation tank and V-type filter"as the main body of the enhanced conventional treatment process.During the experimental period,the water quality of the drinking water source of the water purification plant was good,and the turbidity,ammonia nitrogen,COD_Mnand nitrite in the raw water met the quality requirements of the surface water quality standard for surface water of category III.The concentration of manganese in the water source is0.07～0.25mg/L and the concentration of Iron is 0.2～0.5mg/L.In order to cope with the phenomenon of manganese exceeding the standard,the water plant adopts the joint pre-oxidation coagulation process of potassium permanganate and sodium hypochlorite to stabilize the manganese content in the factory drinking water below0.025mg/L.（2）Water purification process for manganese ions is mainly removed in the two main processes of pre-oxidation coagulation and V-type filter manganese sand filtration.During the pre-oxidation period,the combined oxidative coagulation technology of potassium permanganate and sodium hypochlorite has a good effect on removing manganese,which can oxidize 63.8%of soluble manganese ions in raw water into suspended particles,and after coagulation and precipitation in the high-density pool and manganese sand filtration in V-type filter,the comprehensive removal effect of manganese ions reaches 95.2%.The V-type filter has a good dirt collection capacity,which can quickly retain and oxidize soluble manganese ions in water,and the manganese content in the filtered water is stable at 0.01mg/L.The manganese content in the production wastewater is high,and the water quality in the recovery pond fluctuates greatly,with turbidity ranging from 12.0～16.0 NTU and manganese ion concentration ranging from 0.2～0.8 mg/L.Due to the addition of potassium permanganate during the pre-oxidation period,the manganese element content in the bottom of each structure is high,and the manganese element content in the bottom of the discharge pond reaches 9450.8 mg/kg,with the exchangeable state accounting for 30%,which is unstable and easily released into the water body by the environment.The manganese element is unstable and can be easily released into the water body under the influence of the environment.（3）The hydrated titanium dioxide floc material（Ti）and titanium aluminum floc polymeric material（TA）was prepared by the alkaline method,and their structures before and after Mn²⁺adsorption were characterized by scanning electron microscopy（SEM）,X-ray photoelectron spectroscopy（XRD）,specific surface area（BET）,and Fourier transform infrared spectroscopy（FTIR）.The effects of kinetics,thermodynamics,adsorption isotherm,solution p H and aeration on the adsorption performance of Mn²⁺removal by adsorption were also studied.The results show that both materials have rough surfaces and are rich in folds and hydroxyl groups,among which the titanium-aluminum polymeric material is mesoporous with a specific surface area of 243.365 m~2/g,and the surface becomes smooth after adsorption of Mn²⁺.The aerated oxidation had a significant promotion effect on the removal of Mn²⁺by the homemade adsorption material,and the removal rate of Mn²⁺reached95.27%after aeration when the amount of titanium and aluminum substance ratio was7:3.The thermodynamic parametersΔG^?<0,ΔH^?>0,andΔS^?>0,indicate that the adsorption of Mn²⁺by both materials is a spontaneous heat absorption process,and the spontaneity of the reaction process increases with the increase of temperature.The adsorption process is in better agreement with the Langmuir and Temkin isothermal adsorption equation for unimolecular chemisorption.When the p H=7.0,the correlation coefficients R~2of the Langmuir isotherm equation were 0.9806 and 0.9984for the adsorption of the two materials,and the adsorption amounts Q_Maxwere 73.65and 177.32 mg/g,respectively.The two adsorption materials are influenced by the p H value,the adsorption capacity of titanium dioxide for manganese ions is very weak at p H=5,and the inhibiting effect of titanium-aluminum polymeric material on manganese ion adsorption is weakened.The actual test of manganese content of the reservoir raw water is 0.108mg/L,the remaining concentration of manganese ion in water is 0.026 and 0.015mg/L respectively,and the removal effect is 75.9%and86.1%respectively.Figure[37]table[12]reference[113]...