Study On Preparation Of Municipal Sludge Ceramide And Adsorption Effect Of Cd²⁺

With the rapid development of urbanization and industrialization,a large amount of heavy metal wastewater produced by many industries is discharged into water bodies,causing pollution to water and soil environment,and even endangering human health.Among them,cadmium as Ⅰ kind of carcinogen,will cause serious damage to the environment and human health.Municipal sludge,as a kind of by-product produced in the operation process of municipal sewage treatment plant,has serious harm to the environment.Due to the toxicity and harmfulness of municipal sludge itself,harmless treatment is needed in the treatment or use of municipal sludge.Many scholars mix municipal sludge with other materials to make ceramide.The reduction and harmless treatment of municipal sludge can be achieved.At present,there have been many researches on the application of municipal sludge ceramide in the treatment of heavy metal wastewater,and the treatment effect is good.However,current researches mainly focus on the removal rate of heavy metals by municipal sludge ceramides,and the researches on adsorption mechanism are relatively weak.Through referring to the researches on the treatment of cadmium-containing wastewater by municipal sludge ceramides,it is found that the researches on the adsorption behavior and adsorption mechanism of Cd²⁺by municipal sludge ceramides are insufficient.In order to expand the harmless treatment and disposal approach of municipal sludge reclamation,this study takes municipal sludge,clay and bentonite as raw materials,and adopts pre-experiment,single factor experiment and orthogonal experiment,leaching toxicity experiment,simulated wastewater adsorption experiment and other methods.The optimum preparation conditions of municipal sludge ceramide,its fixation effect on heavy metals in municipal sludge and its adsorption properties on cadmium-containing wastewater were studied.Through adsorption kinetics,adsorption isothermal model and characterization analysis,the adsorption mechanism of ceramide on Cd²⁺was explored,providing scientific basis and technical support for municipal sludge resource utilization and treatment of Cd²⁺and pollutants.After experimental study,the optimal ratio of preparing municipal sludge ceramide is determined as follows:bentonite:municipal sludge:clay=5:2:3,and under the following conditions:The dried raw material balls were placed in a tubular furnace,preheated for 20 min at 400℃,and sintered for 15 min at 1100℃.The ceramic particles with a bulk density of 691.47 kg/m³,apparent density of 1.61g/m³,water absorption rate of 9%in 1 h and porosity of 57.05%were prepared successfully.The physical and chemical properties of the ceramide meet the requirements of"Light aggregate and its test methods Part 2:Test Methods for Light Aggregate"（GB/T17431-2010）and"Artificial ceramide filter Material for Water Treatment"（CJ/T299-2008）,and pass the toxic metal leaching test.It meets the requirements of Leaching Toxicity Identification of Hazardous Waste Identification Standard（GB 5085.3-2007）and will not cause secondary pollution to the environment.The scanning electron microscope test showed that the municipal sludge ceramide sintered after the internal pore structure is rich,honeycomb shape,pores cross and cross,with developed pore structure.The specific surface area of the ceramide is 0.912 m²/g,the pore volume is 0.002 cm³/g,and the average pore size is 9.786 nm.According to the International Union of Pure and Applied Chemistry（IUPAC）,it can be seen that the pore diameter of municipal sludge ceramide is within the mesoporous pore diameter:2-50 nm,which is the mesoporous pore diameter.The main mineral components are quartz,mullite,anorthite and hematite.The results show that the optimal adsorption conditions of municipal sludge ceramide are as follows:p H value 6.0（±0.1）,ceramide dosage 30 g/L,Cd²⁺concentration 120 min,adsorption time 25℃,and rotational speed 150 r/min.Under these conditions,the Cd²⁺removal efficiency of ceramide was the best,with a removal rate of 95.41%.Cd²⁺was removed by physical adsorption of municipal sludge ceramides.The adsorption process conforms to the quasi-first-order kinetic equation,and the correlation coefficient is above 0.96.At the same time,the adsorption of Cd²⁺by ceramides conforms to two Langmuir and Freundlich adsorption equations.There are a lot of closed pores inside municipal sludge ceramide,forming rich pore structure,so that ceramide has good adsorption property.The irregular shape of ceramide increases its specific surface area,which is more conducive to the adsorption of Cd²⁺.After adsorption of Cd²⁺,the inner pores of ceramides are filled,which has a good treatment effect on Cd²⁺in cadmium-containing wastewater.After adsorption of heavy metals,the mineral composition of municipal sludge ceramide remains unchanged,but generates oxidizing substances containing heavy metals,which proves that chemical adsorption is included in the adsorption process.In summary,the municipal sludge ceramides show good adsorption effect in the treatment of wastewater containing Cd²⁺.The adsorption process conforms to the quasi-first-order kinetic equation,and has the characteristics of single-layer and multilayer adsorption.The rich pore structure and large specific surface area of ceramides provide favorable conditions for its adsorption,which has a remarkable effect on the removal of Cd²⁺from wastewater containing cadmium.