中药通草渣对水中亚甲基蓝吸附效能与机理的研究

Study on adsorption efficiency and mechanism of methylene blue in water by Chinese medicine ricepaperplant pith residue

选择中药通草残渣作为生物吸附剂,对水中亚甲基蓝染料(MB)进行吸附,探究其吸附效能和吸附机理。采用响应面法中Box-Behnken Design,考察吸附剂投加量、pH、MB溶液初始质量浓度和吸附时间对通草残渣去除MB的影响,并对实验参数进行优化。在最优参数组合条件下,通过实验验证其预测值和实验值符合度一致。吸附等温线与动力学模型拟合结果显示:通草残渣对水中亚甲基蓝的吸附过程符合Langmuir模型(R^(2)=0.997)和准二级动力学模型(R^(2)=0.9998),其吸附量为115.72 mg/g,表明该吸附过程以均匀的单层吸附为主,对亚甲基蓝的吸附速率受膜扩散和颗粒内扩散共同控制。同时,该吸附过程存在Na^(+)、K^(+)、Ca^(2+)的交换情况,对Cl^(-)、SO_(4)^(2-)的影响不明显。表征结果显示,通草残渣吸附水溶液中的亚甲基蓝后,出现比表面积增大、孔容加深、孔径缩小、电荷强度变小、红外基团变化不大的特点,提示通草残渣对水中亚甲基蓝是以静电吸附作用为主的单层吸附类型。

The Chinese medicine ricepaperplant pith residue was selected as a biosorbent for the adsorption of methy⁃lene blue(MB)in water to investigate its adsorption efficacy and mechanism.The Box-Behnken Design of response surface methodology was used to investigate the effects of adsorbent dosing,pH,initial mass concentration of MB so⁃lution and adsorption time on the removal of MB,and the experimental parameters were optimized.The agreement be⁃tween the predicted and experimental values was verified experimentally under the conditions of optimal parameter combinations.The adsorption isotherm and kinetic model fitting results showed that the adsorption process of MB from water by ricepaperplant pith residue was consistent with the Langmuir model(R^(2)=0.997)and pseudo-second kinetic model(R^(2)=0.9998),and the adsorption amount was 115.72 mg/g,indicating that the adsorption process was domi⁃nated by homogeneous monolayer adsorption.The adsorption rate of MB was controlled by both membrane diffusion and intra particle diffusion.Meanwhile,the adsorption process had the exchange of Na^(+),K^(+)and Ca^(2+),and the effect on Cl^(-)and SO_(4)^(2-)was not obvious.The characterization results showed that the adsorption of MB in solution by ricepa⁃perplant pith residue showed an increase in specific surface area,deepening of pore volume,reduction in pore size,smaller charge intensity and little change in infrared groups,suggesting that the adsorption of MB in water by ricepa⁃perplant pith residue is a monolayer adsorption with mainly electrostatic adsorption effect.