7种改性水稻秸秆对溶液中Cd2+的吸附

为实现废弃水稻秸秆资源化利用及其治理水环境中Cd²⁺的污染问题，用KMnO₄、KOH、H₂O₂、KOH+H₂O₂、酒石酸、柠檬酸、TiO₂对水稻秸秆进行改性，制成不同的水稻秸秆吸附剂来吸附溶液中的Cd²⁺，利用扫描电子显微镜（SEM）、X射线衍射（XRD）、傅里叶红外光谱仪、比表面积及孔径分析仪和Zeta电位仪对改性前后的水稻秸秆进行表征分析，吸附过程采用准一级动力学方程、修正一级动力学方程、准二级动力学方程和颗粒内扩散模型进行拟合.结果表明：在Cd²⁺初始浓度100mg/L，pH7，水稻秸秆添加量为10g/L，25℃条件下，7种改性水稻秸秆吸附Cd²⁺的效果不同，其中经KMnO₄改性的水稻秸秆对Cd²⁺的吸附效果最好，吸附量达10.024mg/g，对Cd²⁺的去除率达到99.24%，比未改性水稻秸秆提高了99.44%，其次是KOH和KOH+H₂O₂改性处理的水稻秸秆，吸附量分别达到了9.302和9.189mg/g，对Cd²⁺的去除率分别达92.62%和90.82%，比未改性水稻秸秆分别提高了85.07%和82.83%.改性处理水稻秸秆吸附Cd²⁺的效果顺序为：KMnO₄ > KOH > KOH+H₂O₂ > TiO₂ > H₂O₂ > 柠檬酸 > 酒石酸.对于Cd²⁺的吸附过程，准一级速率方程只能较好地描述吸附初始阶段，准二级动力学方程则能很好地描述吸附的整个过程.经KMnO₄，KOH和KOH+H₂O₂改性的水稻秸秆是具有潜在利用价值的废水中Cd²⁺吸附剂.

The adsorption of Cd2+ in the aqueous solution by 7modified rice straws

Aiming at the reuse of discarded rice straw and its treatment of Cd²⁺ pollution in wastewater, rice straw was modified with KMnO₄,KOH, H₂O₂, KOH+H₂O₂, tartaric acid, citric acid, and TiO₂,and made as different types of rice straw sorbentsto adsorb Cd²⁺ in solution. These adsorbents were analyzed by scanning electron microscope (SEM), X-ray diffraction (XRD), FTIR spectrometer, specific surface area and aperture analyzer, and Zeta potentiometer. The adsorption kinetic data were fitted with pseudo-first-order, modified pseudo-first-order, pseudo-second-order and intra-particle diffusion models. The results showed that, under the condition of initial Cd²⁺ concentration of 100mg/L, pH 7, adsorbent dosage of 10g/Lrice straw and adsorption temperature of 25℃, rice straw modified with KMnO₄ had thebest Cd²⁺ adsorption in the aqueous solution, and the adsorption capacity was 10.024mg/g Cd²⁺. Its percentage of removal of Cd²⁺ reached 99.24% and had an increase of 99.44% compared with unmodified rice straw. Followed by rice straw was modified with KOH and KOH+H₂O₂,their adsorption capacity for Cd²⁺ were 9.302mg/g and 9.189mg/g, percentage of removal of Cd²⁺ reached 92.62% and 90.82%, respectively. Compared with unmodified rice straw treatment, Cd²⁺ removal of rice straw modified with KOH and KOH+H₂O₂ had increases of by 85.07% and 82.83%, respectively. The adsorption order of modified rice straw treatments was:KMnO₄ > KOH > KOH+H₂O₂ > TiO₂ > H₂O₂ > citric acid > tartaric acid. It was found that quasi first order rate equation only described the initial stage of Cd²⁺ adsorption suitably, however, apseudo-second order kinetic model was the proper approach for describling the whole process of adsorption. Sum up, the rice straw modified by KMnO₄, KOH and KOH+H₂O₂ could be the potentially valuable adsorbents for absorbing Cd²⁺ in the wastewater solution.