铋基材料去除水中碘离子的性能及机理

Efficiency and mechanism of bismuth-based materials for iodide removal from water

原生高碘地下水是造成我国多地居民碘摄入量过高并导致甲状腺疾病的主要因素之一,为探究水体除碘技术,采用溶剂热法合成两种铋基吸附剂即(BiO)_(x)(OH)_(1)(NO_(3))_(m)(CO_(3))_(n)(BIN)和(BiO)_(2)CO_(3),探讨这两种铋基材料在复杂水体环境(不同p H值、共存阴离子和模拟地下水)中对碘离子的去除性能及吸附稳定性,运用BET、SEM、XRD、FTIR、Raman、XPS等表征手段分析铋基材料的微观结构和吸附机理。结果表明:BIN和(BiO)_(2)CO_(3)除碘速率很快,通过与碘离子发生化学反应,形成BiOI来完成除碘,反应过程符合伪二级动力学模型,吸附率分别为93.81%和95.11%;Langmuir模型能更好地描述二者的吸附等温线,最大吸附容量分别为129.37 mg/g和113.76mg/g;当p H值介于3~7时,BIN和(BiO)_(2)CO_(3)对I^(-)的吸附效果良好,pH>9时,吸附率明显下降;共存阴离子和离子强度试验结果表明,NO_(3)^(-)对两种铋基材料吸附碘离子几乎没有影响,CO_(3)^(2-)对吸附影响较大,离子竞争性遵循CO_(3)^(2-)>SO_(4)^(2-)>Cl^(-)>NO_(3)^(-);在CO_(3)^(2-)/SO_(4)^(2-)/Cl^(-)含量为0~10mol/L条件下,I^(-)吸附率均随离子强度的增加而受到一定程度的抑制;吸附产物解吸试验结果表明,吸附产物在纯水中的解吸率都低于0.76%,4种阴离子(10mol/L)条件下的解吸率也都低于50%。这表明所制备的两种铋基材料对阴离子以SO_(4)^(2-)、NO_(3)^(-)和Cl^(-)为主的高碘水体具有较好的除碘效果和应用前景,对保障供水安全具有重要的实际意义。

High iodine groundwater potentially causes high iodine intake and thyroid disorders in many areas of China.In order to remove iodide from groundwater,two bismuth-based materials,i.e.,(BiO)_(x)(OH)_(1)(NO_(3))_(m)(CO_(3))_(n)(BIN)and(BiO)_(2)CO_(3),were synthesized by the solvothermal method and further investigated to identify the removal efficiency and adsorption stability for iodide ions under complex aqueous environments(different pH,coexisting anions and simulated groundwater).The microstructure and adsorption mechanism of the bismuth-based materials were analyzed using BET,SEM,XRD,FTIR,Raman and XPS.The results are as follows:BIN and(BiO)_(2)CO_(3) have rapid rates of iodide removal,which are in accordance with the pseudo-second-order dynamics,and the rapid deiodination are completed by chemical reaction with iodide ions to form BiOI,with the adsorption rates of 93.81% and 95.11%,respectively;the Langmuir model can better describe the adsorption isotherms of both and the maximum adsorption capacities of BIN and(BiO)_(2)CO_(3) are 129.37 mg/g and 113.76 mg/g,respectively.Under the pH of 3 to 7,the adsorption rates of BIN and(BiO)_(2)CO_(3) on iodide are favorable,and decrease significantly when pH>9;the results of coexisting anion and ionic strength experiments show that NO_(3)^(-) has almost no effect on the adsorption of iodide by the two bismuth-based materials,while CO^(2-)_(3)has the greatest effect,and the ionic competition order is CO_(3)^(-2)>SO^(2-)_4>Cl^(-)>NO_(3)^(-).In the solution with 0~10 mol/L CO_(3)^(-2)/SO_(4)^(2-)/Cl^(-),the iodide adsorption rates are inhibited with increasing ionic strength;the results of desorption tests show that the desorption rates of the adsorption products in pure water are all less than 0.76%,and below 50% under four anions(10 mol/L).The two prepared bismuth-based materials have good iodine removal efficiencies and application prospects for the removal of iodine from water in specific water types whose anions are dominated by SO_(4)^(2-),NO_(3)^(-) and Cl^(-),which are of great practical importance for ensuring the safety of water supply.