煤基腐植酸对Cd^(2+)的吸附—解吸特性研究

Characteristics of Cd^(2+) adsorption and desorption of coal humic acid

环境pH对腐植酸-重金属的结合稳定性有显著影响,采用不同pH解吸液对吸附Cd^(2+)后的腐植酸(腐植酸-Cd^(2+))进行解吸规律研究。结果表明,煤基腐植酸(HA1和HA2)的官能团、腐殖化与芳构化程度是影响腐植酸-Cd^(2+)稳定性的主要结构特征。HA1较HA2含氧官能团更多,Cd^(2+)吸附量更高,HA1和HA2对Cd^(2+)吸附量在Cd^(2+)初始浓度100mg/L时分别为905mg/g和582mg/g;HA1-Cd^(2+)和HA2-Cd^(2+)在纯水解吸的保留率总体大于80%;pH=3解吸液中Cd^(2+)保留率降低明显,HA2对Cd^(2+)的保留作用更强;pH=5、7解吸液中随Cd^(2+)初始浓度的增大HA1-Cd^(2+)和HA2-Cd^(2+)解吸规律一致,Cd^(2+)初始浓度越高,三次解吸后保留率越大,均在60%左右;ζ电位分析表明,HA-Cd^(2+)中Cd^(2+)解离存在自发解离和离子交换两种途径,H、Na及醋酸根配体的共同作用导致结合不稳定的Cd^(2+)再次释放。

Environmental pH has a significant effect on the binding stability of humic acid-HMs. Desorption characteristics of humic acid after adsorption of Cd^(2+)(humic acid-Cd^(2+)) was studied using different pH desorption solution. The results show that the functional group, humification and aromatization degree of coal humic acid are the main structural features that affect the stability of HA-Cd^(2+). HA1 has more active oxygen-containing functional groups than HA2, so adsorption capacity of Cd^(2+) is higher than HA2. At the initial concentration of Cd^(2+) is 100 mg/L, Cd^(2+) adsorption capacity of HA1 and HA2 could reach 905 mg/g and 582 mg/g. The retention rate of HA1-Cd^(2+) and HA2-Cd^(2+) in pure water desorption is more than 80%. The retention rate of Cd^(2+) in the desorption solution with pH=3 decreases obviously, and HA2 has stronger retention effect on Cd^(2+). The desorption regularity of HA1-Cd^(2+) and HA2-Cd^(2+) is consistent with the increase of initial concentration of Cd^(2+) in desorption solution with the pH of 5 and 7. When the concentration of Cd^(2+) is higher, the retention rate after three desorption is higher, which is about 60%. Zeta potential analysis shows that there are two pathways of Cd^(2+) dissociation including spontaneous dissociation and ion exchange. The co-action of H, Naand acetate ligand leads to the re-release of unstable Cd^(2+).