High-affinity fluoride ions absorbent from TiO2-based ionic liquid pyridinium propylsulfonate

Abstract

The development of materials for high efficiency removal of fluoride ions (F-) from sewage water remains a significant challenge. Unfortunately, traditional metal oxide adsorbents remove F-, but suffer from poor adsorption capacity and generate secondary pollution due to byproducts. To solve this problem, a highly-efficient and recyclable F- adsorbent with rich pore structure (BET specific surface area of 172.15 m2·g−1) was developed by multi-element doping strategy. The F- adsorbent was composed of TiO2 as substrate and ionic liquid pyridinium propylsulfonate as doping. This absorbent displayed good F- adsorption capacity (qmax = 224.11 mg∙g−1, 298 K), which operated through single molecule complex adsorption mechanism, outperformed many commercial adsorbents, and it also exhibited satisfactory adsorption kinetics for improving the efficiency of water treatment. Interestingly, the porous adsorbent had excellent regeneration potential (maintaining more than 70 % F- removal efficiency after 5 cycles of adsorption and desorption) and practical ability in complex water environments of tap water, lake and river. More importantly, a fixed-bed for F- adsorption was designed to simulate the equipment of sewage treatment plant. The breakthrough time and saturation time obtained by fixed-bed experiments proved the practical application value of this novel adsorbent. Most strikingly, the cost estimate showed that the economic feasibility and practical promotion potential of the renewable, continuous and efficient F- wastewater purification system using the novel absorbent were remarkable. This innovative approach showcases a viable solution for addressing F- removal and water treatment.