| In recent years,the harmless disposal and resource utilization of solid waste such as sludge and coal gangue has become a hot issue in research.Using sludge and coal gangue to prepare ceramsite and applying them to the advanced treatment of tailing water in sewage plants can not only effectively solve the secondary pollution problem of solid waste,but also reduce the burden of a large amount of tailing water discharge to the surface water environment.In this paper,a new type of composite ceramsite was prepared by using sludge and coal gangue as main raw materials and adding appropriate amount of clay as auxiliary materials.The effects of different factors on the adsorption capacity of nitrogen and phosphorus were investigated by static adsorption experiments and the reaction mechanism of adsorption process was analyzed.The effect of ceramsite on tailing water purification under dynamic conditions was investigated by using a self-made small experimental device,and the feasibility of advanced treatment of nitrogen and phosphorus in tailing water of sewage treatment plant was further demonstrated.In this paper,the feasibility of preparing ceramsite with sludge and coal gangue as main raw materials was determined by analyzing the properties of raw materials.Taking the bulk density,compressive strength and water absorption of ceramsite as evaluation indexes,the optimal raw material ratio was determined as sludge: coal gangue: clay=35% : 50% : 15%,preheating system was 300℃,30 min,roasting system was 1125℃,20 min through optimization experiment and orthogonal experiment.The physical properties of the ceramsite prepared under the optimal technological conditions can meet the requirements of Artificial ceramide Filter Material for Water Treatment(CJ/T 299-2008).The ceramsite has a variety of mineral components and developed pore structure,and the concentration of heavy metal leaching solution is much lower than the limit value of Identification Standards for Hazardous Wastes-Identification for Extraction Toxicity(GB5085.3-2007).Static adsorption experiment results showed that the removal rate of nitrogen and phosphorus from ceramsite increased with increasing dosage.The optimal dosage was 10 g/L for ammonia nitrogen solution with initial concentration of 5mg/L,and 8 g/L for phosphate solution with initial concentration of 0.5 mg/L;When p H is neutral or weakly basic,the adsorption effect of nitrogen and phosphorus is the best.The optimum p H for adsorption of ammonia nitrogen and phosphate was 8 and7 respectively;The quasi-second-order kinetic model can better fit the adsorption process of nitrogen and phosphorus by ceramsite,and the adsorption reaction is mainly controlled by chemical adsorption.The Langmuir isothermal adsorption model has the best fitting degree for the nitrogen and phosphorus adsorption process of ceramite,and the adsorption process is homogeneous adsorption on the surface of monolayer.The dynamic adsorption column experiment showed that the reactor had a good removal effect on nitrogen and phosphorus in the tail water of simulated sewage treatment plant.Under the operating conditions of hydraulic retention time of 8 h and filter layer height of 30 cm,the ammonia nitrogen removal rate reached 76.52%,the effluent ammonia nitrogen concentration was 1.88 mg/L,the total phosphorus removal rate was 71.57%,and the effluent total phosphorus concentration was 0.28mg/L.In this study,the composite ceramsite was prepared with sludge and coal gangue as the main raw materials,and the optimal raw material ratio and technological conditions were determined,which provided a theoretical basis for the resource utilization of solid waste.At the same time,the adsorption effect of optimal ceramsite on nitrogen and phosphorus in the tail water of simulated sewage treatment plant was investigated,which provided a new way to improve the water environment. |
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