Preparation Of Red Mud Based Porous Ceramic And Study On Phosphorus Adsorption Performance

Red mud is the by-product of alumina industry.The disposal of red mud not only wastes a lot of soil but also pollutes the environment.For the purpose of treating waste with waste,in this paper,firstly,Bayer red mud was modified to produce phosphorus removal agent and the performance of its phosphate adsorption was studied.Then,red mud was used as the main raw material to produce red mud-based porous ceramic adsorption material,and the performance of its phosphate adsorption was studied.The main results are as follows:(1)The results of red mud modification test show that thermal modification,acid modification and lanthanum modification can improve the phosphorus adsorption performance of red mud;In the joint modification test,acid+lanthanum modified red mud has the best phosphorus adsorption performance.Under the conditions of dosage of 5 g/L,p H 7,initial concentration of phosphorus of 80 mg/L and adsorption at room temperature of 25?for 4 h,the removal rate of phosphorus was 96.99%,it can be reused after regeneration.(2)The phosphorus adsorption conditions of acid+lanthanum modified red mud were further optimized by Design-Expert response surface methodology,with adsorption time,dosage,p H and initial concentration as variables and phosphorus removal rate as response value,the regression quadratic model was obtained by experiment data from RSM.According to the results of ANOVA,the p-value(Prob>F)of the model was less than 0.0001,the coefficient of determination R²was 0.9785,the adjust coefficient of determination R²_Adjwas 0.9570,and the Adeq Precision value was 22.18,the residuals were normally distributed,which all means the predictability of the model was excellent.Using this prediction model,the optimal experimental conditions for phosphorus adsorption by acid+lanthanum modified red mud were determined:1.91 h of the adsorption time,6 g/L of the dosage,p H of 4.78,80mg/L of the initial concentration.In these experiment conditions,the predicted removal rate of phosphate was 100%,and the actual removal rate was 99.47%.The relative error was0.53%.(3)The red mud-based porous ceramic filter ball was prepared by adding pore-forming agent,and the best preparation conditions of red mud-based porous ceramic filter ball were determined as follows:The mass ratios of acid+lanthanum modified red mud,polystyrene,portland cement and sodium carboxymethyl cellulose were 69%,12%,10%and 9%,The roasting temperature was 600?and the roasting time was 30 min.The volume density of ceramic filter balls was 816.80 kg/m³,and the water absorption rate was 53.92%.Under the conditions of dosage of 40 g/L,p H of 3,initial concentration of phosphorus of 50 mg/L and adsorption at room temperature of 25?for 4 h,the removal rate of phosphorus was 99.52%,it can be reused after regeneration.(4)The red mud-based porous ceramic sponge was prepared by the organic foam impregnation method,and the optimal red mud-based porous ceramic sponge preparation conditions were determined as follows:The mass ratios of red mud,calcium carbonate and sodium silicate were 76%,5%and 19%,respectively.With polyurethane sponge as the organic template,The baking temperature was 800?and the baking time was 50 min.The volume density of the ceramic sponge was 531.65kg/m³,and the water absorption rate was 70.52%.Under the conditions of dosage of40 g/L,p H value of 3,initial concentration of phosphorus of 50 mg/L and adsorption at room temperature of 25?for 4 h,the removal rate of phosphorus was 98.80%,it can be reused after regeneration.