Dynamaic Adsorption Perdoemance Of Boric Acid And Silicic Acid By Tiron Type Resin And Its Application

Excessive intake of boron poses a serious threat to the survival and reproduction of animals and plants.However,the content of boron in untreated seawater and domestic sewage is much higher than the relevant discharge standards,so proper treatment is needed.Compared with the traditional water treatment technologies,the modified resin adsorption technology is widely used in boron pollution control due to its high efficiency,low cost and reusability.However,silicon has made an impact on the removal efficiency of boron in the adsorption process,which is ubiquitous in water and has similar chemical properties to boron.In addition,silicon is easy to form silica scale in water treatment and regeneration system to block pipes or membranes and reduce water treatment efficiency.Therefore,in this study,tiron was used to grafted on resin to form a new adsorbent,adsorbing toxic element boron and inhibiting the formation of silica scale based on the formation of stable complexes with boric acid and silicic acid.This paper simulates the dynamic adsorption process of the actual water treatment,exploring the adsorption performance and recycling efficiency of the tiron type resins for boron and silicon,revealing the adsorption mechanism.In order to provide the theoretical support for the practical promotion and application,the simulated water and the salt lake water were absorbed.The main conclusions are as follows:（1）In the process of dynamic adsorption,when the boric acid concentration is 5mg/L,the column height is 1.5 cm and the system flow rate is 6.0 m L/min,the resin has high adsorption efficiency on boric acid,short operation time and good utilization rate,which is the optimal dynamic adsorption condition in the study.（2）The adsorption process of boric acid on the resin can be well described by BDST model,Thomas model and Yoon Nelson model.BDST model can predict the breakthrough time after changing the adsorption conditions;Thomas model shows that neither internal nor external diffusion can limit the adsorption process,and the theoretical adsorption capacity can reach 5.97 mg/g;Yoon Nelson model can predict the theoretical adsorption capacity of the resin and breakthrough time.（3）The results of dynamic adsorption showed that the tiron resin can be recycled,and after three cycles adsorption on boric acid,the adsorption capacity can still maintain the initial adsorption capacity 53.05%;Besides,the column bed can ensure that boric acid would be not reach the breakthrough value of 0.5 mg/L at the time is zero after 7 cycles for boron removal.It was predicted that the column bed would be completely exhausted after 7.8 cycles.（4）The resin has good ability to adsorb silicic acid and boric acid at the same time,and it can be recycled well.After three cycles adsorption on boric acid and silicic acid,the adsorption capacity can still maintain the initial adsorption capacity60.95%,and it was predicted that the column bed would be completely exhausted after 15.2 cycles.In the treatment of simulated water and actual salt lake water with tiron resin,the adsorption capacity was obviously improved by adding anion and cation exchange column,which can reduce the influence of cations and anions effectively.The adsorption capacity can reach 2.63 mg/g and 2.38 mg/g for simulated water and actual salt lake water,respectively.（5）When the tiron resins adsorb the boric acid alone,boron is fixed on the resin through the formation of triangular complex of[LB（OH）,1:1]and tetrahedral complexes[LB（OH）₂,1:2]and[BL₂,1:1].When the mixed solution of silicon and boron is adsorbed,boron is adsorbed on the resin in the above forms due to the adsorption speed of boron is faster than silicon on the resin.Among them,the triangular complex[LB（OH）]and tetrahedral complex[LB（OH）₂]combine with the silicic acid（or boric acid）in the solution to form B-O-Si（B-O-B）bond,which are adsorbed on the resin surface in the main forms of complexes.In addition to monosilicic acid,silicon on the surface of the resin will polymerize to form a small amount of binary,linear and flaky polysilicic acid,and continue to combine with boron and its complexes.Therefore,the existing forms of silicon and boron on the resin surface are complex and diverse,it can not only form complexes with tiron alone,but also adsorbed on the resin surface through Si-B,Si-Si or B-B bonding.