Study On Adsorption Of Phosphorus In Water Using Waterworks Sludge And The Synthesized Sludge Ceramsite

Based on the current status of phosphorus removal in water and utilization of water-supplied sludge,the waterworks iron-containing sludge was acid-activated,the waterworks aluminum-containing sludge was heat-activated,and then the adsorbent was used for the static adsorption experiment of phosphorus.Since the powdered adsorbent is difficult to filter in practice,a novel process for preparing ceramsite was established with the waterworks sludge as the main material.In this study,the optimal raw material ratio and sintering range of ceramsite were determined by different experimental methods.The effects of different raw material ratios and sintering conditions on ceramsite properties were analyzed,and the ceramsite with certain mechanical strength and high phosphorus adsorption capacity was prepared.The static adsorption experiment and dynamic adsorption experiment of phosphorus on waterworks sludge ceramsite were carried out to investigate the adsorption performance of ceramsite on phosphorus.The research conclusions are as follows:（1）The waterworks iron-containing sludge was activated by sulfuric acid.Among them,0.5 mol/L and 1 mol/L sulfuric acid activated sludge powders（A-0.5 and A-1）had good adsorption effects on phosphorus,and the adsorption amounts were 3.72 mg/g and 3.79 mg/g.For economic reasons,A-0.5 was used as an adsorbent to study the adsorption performance of phosphorus in water.The experimental results show that the acidic conditions are more favorable for the adsorption of phosphorus.The addition of NaCl,ZnSO₄ and Na₂SO₄ as impurity ions has little effect on the adsorption of phosphorus.The adsorption capacity of A-0.5 increases with the extension of the reaction time,increasing the temperature favors the adsorption of phosphorus.The adsorption process of phosphorus by A-0.5 accords with the quasi-second-order kinetic equation.The adsorption process of A-0.5 were described by Langmuir model.The adsorption of phosphorus by A-0.5 is a process of spontaneous,endothermic and entropy increase.（2）The waterworks aluminum-containing sludge was heat-activated.Among them,the sludge powder（H-900）treated at 900°C high temperature had the best adsorption effect on phosphorus,and the adsorption amount was 6.22 mg/g.H-900 was used as an adsorbent to study the adsorption performance of phosphorus in water.The experimental results show that the alkaline conditions are not conducive to the adsorption of phosphorus by H-900.The addition of NaCl does not have a significant effect on the adsorption effect.Na₂SO₄ inhibits the adsorption of phosphate on the sludge,and the adsorption of phosphate on the sludge increases after the addition of ZnSO₄.The adsorption capacity of H-900 increases with the extension of the reaction time,increasing the temperature favors the adsorption of phosphorus.The adsorption process of phosphorus by H-900 accords with the quasi-second-order kinetic equation.The adsorption process of phosphorus by H-900 accords with the quasi-second-order kinetic equation.The reaction system is a process of spontaneous,endothermic and entropic increase.（3）The best ratio for preparing ceramsite raw materials is:waterworks aluminum-containing sludge∶calcium carbonate=96∶4.The firing conditions were as follows:the raw ball was naturally cured for 24 hours,oven dried at 100℃for 20 minutes,the preheating temperature was 600℃,the preheating time was 30 minutes,the sintering temperature was1124℃,and the sintering time was 10 minutes.The ceramsite has a particle size distribution of 1 to 2 mm,a specific surface area of 30.02 m²/g,a pore diameter of 4.256 nm,and a density of 1 g/m³.The ceramsite has many mesopores and macropores.（4）Study on the adsorption performance of phosphorus in water by using the prepared ceramsite.The experimental results show that the adsorption of phosphorus on ceramsite is best at pH=4,and the adsorption capacity is 3.6mg/g.As the initial pH of the solution increases,the amount of adsorption and removal rate decrease.The amount of phosphorus adsorbed by ceramsite increases with the reaction time,increasing the temperature favors the adsorption of phosphorus.The adsorption process of phosphorus in the granules of the waterworks sludge accords with the quasi-secondary kinetic model.The Freundlich model better describes the adsorption process of phosphorus in the granules of the waterworks sludge.Thermodynamic analysis shows that the adsorption reaction is a process of spontaneous,endothermic and increased degree of freedom of the system.（5）Filling the adsorption column with the prepared ceramsite for the phosphorus adsorption dynamic experiment.when the influent flow rate is 5mL/min and 15mL/min,the depletion time corresponding to the adsorption end point is 1935 minutes and 940 minutes respectively.Both the Thomas model and the Yoon-Nelson model can accurately describe the dynamic adsorption process of phosphorus in the waterworks sludge ceramsite.The waterworks sludge ceramsite is feasible as a water treatment filler.According to the characteristics of China’s water-supplied sludge,This paper selects two representative waterworks waterworks iron-containing sludge and waterworks aluminum-containing sludge as raw materials.The sludge was treated by acid activation,heat activation and preparation of ceramsite.Theoretical guidance is provided for the preparation of the granules and the resource utilization of the sludge.At the same time,the adsorption performance of the treated adsorbent on phosphorus in water was investigated,which provided a reference for the water phosphorus removal technology.