Adsorptive Removal Of Polysilicic Acid By Gallic Acid Type Resin And Its Dynamic Adsorption Performance

In many fields such as water cycle cooling,thermal power generation and reverse osmosis technology,water evaporation results in silicic acid being concentrated into polysilicic acid,and then deposited on the inner wall or membrane surface of equipment pipeline by forming silica scale,which reduces the service life of water utilization equipment and increases the cost of water treatment.Ion exchange method,coagulation method and reverse osmosis membrane are usually used to remove silicic acid from water.However,ion exchange resin has poor effect on polysilicic acid and the cost of reverse osmosis membrane is high.These disadvantages limit the development of silicic acid and polysilicic acid removal methods.In this study,gallic acid resin?GA resin?was used to adsorb polysilicic acid,and its adsorption performance and mechanism were studied.In order to combine the application of resin with practice,the dynamic adsorption of gallic acid resin on silicic acid was also studied,and the recycling efficiency of gallic acid resin in dynamic adsorption device was explored,which could provide reference for the design and operation of gallic acid resin adsorption column.The results show that GA resin can adsorb not only monosilicic acid but also polysilicic acid.The adsorption capacity of GA resin can reach13.48 mg/g,which is twice as much as that of monosilicic acid.In addition,the amount of polysilicic acid adsorbed during the adsorption process is proportional to the decrease of polysilicic acid with particle size less than 0.45?m in the solution,and the adsorption process is dominated by polysilicic acid with particle size less than 0.45?m.SEM-EDX analysis of GA resin adsorbed polysilicic acid showed that the polysilicic acid adsorbed on the resin surface was covered in the form of flakes or small particles aggregated into blocks.The results of ²⁹Si CP MAS NMR of GA resin adsorbed with polysilicic acid showed that the polysilicic acid adsorbed on the resin surface grew from small polymer?Q²?to two-dimensional flake?Q³?and three-dimensional network?Q⁴?,which were consistent with the results of SEM.In order to further study the practical application of GA resin,the dynamic adsorption of silicic acid on the resin was studied by changing the concentration of monosilicic acid,flow rate and resin dosage.The results show that when the initial concentration of silicic acid is 30 mg/L,the dosage of GA resin is 3.8777 g and the flow rate of the system is 0.95ml/min,the running time of the system is shorter,the utilization efficiency of resin is higher,and the dynamic adsorption efficiency can be maximized.BDST model and Thomas model were used to fit the dynamic adsorption of GA resin on silicic acid.It was found that BDST model can fully describe the relationship between resin thickness and penetration time in the adsorption column,and Thomas model can well describe the dynamic adsorption kinetics of resin on silicic acid.The results of dynamic adsorption-desorption-regeneration-reabsorption for four consecutive times show that the adsorption rate of GA resin decreases with the increase of the number of cycles,and the amount of water that can be treated decreases continuously,but the third adsorption capacity can still maintain the initial adsorption capacity of 76.1%.The results indicate that GA resin can be recycled at least three times and has practical application prospects.