Study On The Preparation Of Ceramsite Based On Composite Waste And Its Adsorption Characteristics For Phosphorus In Water

In the process of sewage treatment and urbanization,a large number of wastes such as sludge,building bricks and fly ash are generated,resulting in a large number of environmental problems.At the same time,the non-point source pollution is becoming more and more serious,which aggravates the eutrophication of water,causing red tide and water bloom.In this study,a kind of mixed ceramsite was prepared,and an appropriate modification method was selected to investigate the adsorption effect of phosphorus removal.Its main conclusions are as follows:（1）The best mixed ceramsite was prepared under the conditions of drying time of 120min,drying temperature of 105℃,preheating temperature of 350℃,preheating time of10 min,sintering temperature of 1150℃,sintering time of 10 min,and the distribution ratio of ceramsite to each group was 60 g of fly ash,30 g of sludge,20 g of cement block and 10 g of clay.（2）The modification methods of ceramsite were as follows:the concentration of FeCl₃and Al NO₃are 0.75 mol/L,modified at normal temperature,solid-liquid ratio 1:3,modified time 180 min.The results of phosphorus adsorption showed that the optimal dosage of unmodified ceramsite was 100 g/L,and that of Fe and Al modified ceramsite was 40 g/L.Adsorption equilibrium time is 20 h;The increase of temperature can promote the adsorption.The initial concentration has a positive correlation to adsorption.The adsorption effect of acid condition is better than other conditions;Anions have an influence on adsorption,and the order of influence is:F^->CO₃^2->SO₄^2->Cl^-.（3）Langmuir and Freundlich isothermal equation simulated the adsorption process properly,and the theoretical maximum adsorption capacity is deduced to be:76.085 mg/kg（unmodified ceramsite）,458.26 mg/kg（Fe modified ceramsite）,and 669.1 mg/kg（Al modified ceramsite）.The fitting parameters of the first order kinetic model and the second order kinetic model of the three kinds of ceramsite were above 0.95,the fitting degree of the second order kinetic model was better,and the correlation coefficient was above 0.97.The correlation coefficient of the three models of internal diffusion of ceramsite was low,and the correlation coefficient of Elovich equation and double constant model were all above0.93,and the fitting was suitable.The desorption test of three kinds of ceramsite showed that the desorption effect was the best under alkaline condition and the desorption amount reached the maximum at 48 h.Among the four desorption agents Na AC,Na₂CO₃,Na₃PO₄and Na OH,Na OH had the best desorption effect on ceramsite with desorption rate of about70%.The desorption rate was positively correlated with the concentration of the desorption agent Na OH.（4）In the practical application test using Al modified ceramsite as the filler of small device,it was found that the best phosphorus removal effect for rainwater was found when the flood zone height was 5 cm and the packing height was 15 cm,both of which were lower than the surface type I water eutrophication standard.It was found that the device had a good phosphorus removal effect at different flow rates and was almost unaffected by the drought interval.