NaOH预处理对香菇废弃物镉吸附性能的影响

Effect of sodium hydroxide pretreatment of Lentinus edodes residue on cadmium adsorption

为得到一种高效、廉价的生物吸附剂,采用NaOH对香菇废弃物进行预处理。研究了吸附时间、pH和镉初始浓度对香菇废弃物NaOH处理前后镉吸附性能的影响。结果表明,香菇粉NaOH处理前后对镉吸附的最适宜pH值范围不变均为6~7,平衡吸附时间均为1 h。当镉初始浓度从10 mg/L增加到60 mg/L,两种香菇对镉的吸附量线性增加,继续增加镉浓度(60~100 mg/L),未处理香菇对镉的吸附量不再增加(2.82 mg/g),NaOH处理香菇则继续增加至12.50 mg/g,但未达到饱和;伪二级动力学模型拟合香菇废弃物NaOH处理前后吸附镉的动力学过程结果良好,相关系数R^2分别为0.999 8和0.999 9;Langmuir模型和Freundlich模型均能较好的拟合两种香菇对镉的等温吸附热力学过程;NaOH处理香菇粉对镉的理论最大吸附量q_m13.78 mg/g,是未处理前q_m(2.832 mg/g)的约4.4倍。红外光谱分析表明,香菇吸附镉的过程中,香菇细胞壁上的N—H、C—H及O—H官能团发挥了作用,而NaOH处理活化了这些官能团,提高了对镉的吸附容量。

To investigate a cheap and high efficiency absorbing material,Lentinus edodes residue was modified by sodium hydroxide for Cd2＋ removal in wastewater. The biosorption of Cd2＋ was examined on the effect of time,initial Cd2＋ concentrations and p H values. The results showed that the modified L. edodes residue had a same operation time（ 1 h） as the L. edodes residue blank did. The modified L. edodes residue and the L. edodes residue blank had the same suitable adsorption p H range was 6 7. With the initial concentration of Cd2＋ increasing from 10 mg/L to 60 mg/L,the biosorption quantities of Cd2＋ by the two kinds gained linearly. The initial concentration of Cd2＋ further increased from 60 mg/L to 100 mg/L,the Cd2＋ adsorption quantities by the blank one kept at 2. 82 mg/g,while that by the pretreated one continued to increase to 12. 50 mg/g,and hadn’t saturated. Pseudo-second-order model well fitted Cd2＋ biosorption kinetics of the modified L. edodes and the L. edodes blank. The biosorption equilibrium data for both L. edodes residue blank and modified L. edodes fitted the Freundlich model and Langmuir model well,the correlation coefficient was R2= 0. 999 8 and R2= 0. 999 9,and the theoretical adsorption capacity of Cd2＋ on modified L. edoded（ 13. 78 mg/g） was far higher than that on the L. edodes blank（ 2. 832 mg/g）. The infrared spectrum analysis revealed that such functional groups as O—H,C—H,N—H on L. edodes played an important role on Cd2＋ biosorption,while sodium hydroxide actived these functional groups and improved its adsorption quantity.