高效除砷分子筛新型材料制备及其吸附特性研究

为提高4A分子筛(MS)对水溶液中砷的吸附性能，以MS为载体，采用浸渍法制备载铁分子筛(FMS)和铁锰分子筛(FMMS)作为除砷吸附剂，利用扫描电镜(SEM)、傅里叶红外光谱(FT-IR)、比表面积测试法(BET)等手段对MS和FMS微观结构特点进行表征，并开展批次试验考察FMS和FMMS对水中五价砷(As5+)和三价砷(As3+)的吸附效果，对FMS吸附As5+过程进行吸附动力学、等温吸附试验和吸附热力学等拟合.结果表明:①铁盐浸渍改性能有效提高MS比表面积、改善其表面结构，改性后FMS是一种窄孔径、尺寸均匀的介孔材料，比表面积和孔体积分别从27.38 m2/g和0.068 cm3/g增至281.25 m2/g和0.16 cm3/g，平均孔径由9.93 nm减至2.21 nm；MS微观结构由密实粗糙颗粒转变为疏松多孔隙结构.②FT-IR表明，铁盐浸渍形成的铁氧化物主要与MS结构中O—H、Al—O和Si—O结合；批次试验设定ρ(As5+)为4 mg/L，与MS相比FMS对As5+的去除率约提高70%.③吸附动力学结果显示，FMS对As5+的吸附过程符合准二级动力学模型，相关系数(R2)达0.99，反应过程中化学吸附起主要作用.④等温吸附试验表明，FMS对As5+吸附过程与Freundlich等温吸附模型拟合程度较高，相关系数(R2)达0.98，计算最大吸附容量为9.9 mg/g.⑤热力学参数ΔG、ΔH和ΔS计算表明，温度升高有利于FMS吸附砷，反应过程中FMS表面固体与溶液的混乱度上升.⑥与FMS相比，FMMS对As3+吸附性能有效提高，ρ(As3+/As5+)(As3+与As5+共存条件下溶液质量浓度)分别为2.0、4.0、6.0 mg/L下，FMMS去除率分别约提高26.34%、28.06%和28.09%.研究显示，利用铁盐浸渍法对MS改性可有效提升其对As5+和As3+的吸附容量，发挥材料的实际运用价值. 

Preparation and Adsorption Characteristics of Novel Molecular Sieve for High Efficiency Arsenic Removal

In order to enhance the adsorption performance of 4A molecular sieve for arsenic in aqueous solution, using MS as a carrier, iron-loaded molecular sieves (FMS) and iron-manganese molecular sieves (FMMS) were prepared as adsorbents for arsenic removal by impregnation method. The MS and FMS were characterized by SEM, FT-IR and BET, and carried out batch experiments to investigate the adsorption and removal effects of FMS and FMMS for pentavalent arsenic (As5+) and trivalent arsenic (As3+). The adsorption kinetics, isothermal adsorption test and adsorption thermodynamics of the FMS adsorption process were performed. The results show that the specific surface area of FMS is significantly increased and the surface structure of the material is improved. The specific surface area and pore volume of the FMS increased from 27.38 m2/g and 0.068 cm3/g to 281.25 m2/g and 0.16 cm3/g, respectively. Meanwhile, the average pore size decreased from 9.93 nm to 2.21 nm. This could cause the dense coarse particles to become an adsorbent with loose porous microstructure. FT-IR analysis shows that iron oxide formed in the iron salt impregnation process is mainly combined with O-H, Al-O and Si-O in the molecular sieve structure. The results of batch experiments with 4 mg/L As5+ indicate that the removal rate increases by about 70% after the material modification. Moreover, the adsorption process is in accordance with the quasi second-order adsorption kinetics, and the correlation coefficient (R2) is 0.99, indicating that the chemical adsorption plays an important role in the adsorption process. The Freundlich isotherm adsorption model fits the adsorption data well with a correlation coefficient (R2) is 0.98, and the maximum adsorption capacity is calculated to be 9.9 mg/g. Furthermore, the calculation of thermodynamic parameters ΔG, ΔH and ΔS find that temperature increase is favorable for adsorption, and the disorder degree between solid and liquid on the surface of the material increases during the reaction. Compared with FMS, FMMS can effectively improve the removal performance of As3+. The initial concentrationof coexistence conditions were ρ(As3+/As5+)=2.0, 4.0, 6.0 mg/L, the removal rate of FMMS is increased by about 26.34%, 28.06% and 28.09%, respectively. The research shows that the use of iron salt impregnation method to modify MS can effectively increase the adsorption capacity of As5+ and As3+, and can give full play to the practical application value of the material.