载锰活性氧化铝除氟降铁效能研究

Fluorine and Iron Removal Efficiency of Manganese-loaded Activated Alumina

针对我国北方地区地下水型饮用水水源地铁氟超标问题,采用硫酸铝和硫酸锰改性制备载锰活性氧化铝对地下水进行同步除氟降铁,并通过静态试验和动态试验分析载锰活性氧化铝除氟降铁的影响因素、去除机理和再生效果。结果表明,活性氧化铝改性后表面呈现不规则凸起刺状颗粒结构,并出现锰的氧化物和氢氧化物特征峰,碱式氧化锰成功附着在氧化铝表面,改性后的除氟效果比改性前提高了70%,铁离子和氟离子去除率分别可以达到80. 5%和81%。BoxBehnken响应曲面试验模型得出,载锰活性氧化铝去除氟离子和铁离子的最优参数如下:吸附时间为8 h、pH值为4、温度为25℃,其中p H值对除氟降铁的影响最大。载锰活性氧化铝吸附氟离子的动力学过程符合准二级动力学方程,吸附等温线符合Freundlich模型,表明该吸附过程主要以多层化学吸附为主。动态试验结果表明,载锰活性氧化铝的出水氟超标时间由原来的11 h延长至27h,铁离子达标时间由原来的60 h缩短至5 h。改性后的载锰活性氧化铝的除氟降铁效果大大提高。经过3次再生后,载锰活性氧化铝滤柱的氟离子吸附量从0. 7 mg/g降低至0. 6 mg/g,再生后的载锰活性氧化铝吸附容量未出现明显衰减。

In order to solve the problem of excessive fluorine and iron in groundwater-type drinking water source in northern China,manganese-loaded activated alumina(MAA)was prepared by modification with aluminum sulfate and manganese sulfate to simultaneously remove fluorine and iron from groundwater.Influencing factors,removal mechanism and regeneration performance of MAA removing fluorine and iron were analyzed by static and dynamic tests.Surface of the modified activated alumina presented irregular convex thorn-like granular structure and had characteristic peaks of manganese oxides and hydroxides.Alkaline manganese oxide was successfully attached to the surface of the alumina,and its removal efficiency of fluorine was 70%higher than that before modification.The removal efficiencies of iron ions and fluorine ions in effluent reached 80.5%and 81%.The optimal parameters for removing fluoride and iron ions by manganese activated alumina adsorbent were obtained by Box-Behnken response surface test model,which were as follows:adsorption time of 8 h,pH value of 4 and temperature of 25℃.Among them,the pH value had the greatest influence on removal of fluorine and iron.Kinetics of fluoride ions adsorbed by MAA conformed to the pseudo-second-order kinetic equation.The adsorption isotherm conformed to the Freundlich model,indicating that the adsorption process was dominated by multi-layer chemical adsorption.The dynamic test results showed that penetration time of fluoride in the effluent treated by manganese activated alumina was extended from 11 h to 27 h,and the reaction time of iron ion was shortened from 60 h to 5 h.The removal efficiency of fluorine and iron by MAA was greatly improved.After three regenerations,fluoride ion adsorption capacity of the MAA filter column was reduced from 0.7 mg/g to 0.6 mg/g.The adsorption capacity of the regenerated MAA did not decrease significantly.