Facile copolymerization synthesis of vinylimidazole/dibromodecane/vinylpyridine polymer with high capacity for selective adsorption of nitrate from water

Abstract

In this study, a novel polymer 1-vinylimidazole/1,10-dibromodecane/4-vinylpyridine polymer (VDV) with high nitrate adsorption capacity and selectivity was synthesized using a facile copolymerization method. The maximum nitrate adsorption capacity of VDV reached 52.6 mg N/g, which was 54.17 % and 52.42 % higher than those of 1-vinylimidazole/1,10-dibromodecane and 4-vinylpyridine/1,10-dibromodecane, respectively. For the co-existing anions interference, dibromodecane improved the hydrophobicity of VDV; thereby, reducing the sulfate interference on nitrate adsorption that the nitrate adsorption capacity in sulfate (250 mg/L)/nitrate (56.4 mg N/L) binary solution still reached 77.2 % of the control group (56.4 mg N/L of nitrate alone). When sulfate concentration increased from 150 to 350 mg/L in sulfate/nitrate (56.4 mg N/L) binary solution, nitrate adsorption capacity dropped from 88 % to 55.2 % of the control group. Meanwhile, the adsorption selectivity (Ke/c) for nitrate was higher than 1 (Ke/c = 1.3–2.6), indicating that VDV still has adsorption affinity to nitrate in companion with a high concentration of sulfate. For chloride and bicarbonate (150–350 mg/L), they almost had no interference with nitrate adsorption. Besides, the adsorption process is preferably fitted with the pseudo-second-order kinetics (R2 = 0.992) and the Freundlich model (R2 > 0.99), indicating that the process is multilayer chemisorption. After five times recycle, nitrate adsorption capacity maintained above 91 % of that of the first cycle, indicating the stable reusability of VDV, and it exhibited excellent nitrate adsorption from real wastewaters. Therefore, with a conspicuous enhancement of adsorption capacity and selectivity for nitrate, VDV is promising in nitrate removal from waters.