Leaching characteristics of coal gangue in a new dynamic cyclic leaching device
ZHAO Hong-yu1, LI Yu-huan2, SONG Qiang1, SHU Yuan-feng1, LÜ Jun-xin1, SHU Xin-qian1
1. School of Chemical and Environmental Engineering, China University of Mining &Technology Beijing, Beijing 100083, China;
2. College of Energy and Power Engineering, Inner Mongolia University of Technology, Hohhot 010051, China
The leaching rule of heavy metals in coal gangue was studied by 240 h sequential cyclic leaching experiments which were carried out in a new dynamic cyclic radial flow leaching device. CPAM was added to the leaching solution to investigate the sedimentation characteristics of the solid particles. Results showed that, Na in coal gangue was dissolved in the water and formed alkaline solution when the time of leaching reaction extended, leading to a higher pH at the beginning of the reaction. The concentration of As and Zn ions was increasing during the first 24h of leaching but decreased from the 24th to 72nd hours. The concentration of Cr, Pb and Ba was all increasing during the first 120h. The leaching rate of Cr irons increased by the alkalinity of the leaching solution from the 120th hour to the 240th, but the concentration decreased as the times of sample test increased. Pb ions were oxidized into smaller solubility of precipitation in the process of leaching, which decreased the migration ability of Pb ions to the leaching solution. The concentration of Ba irons in the leaching solution decreased as the solution diluted and sediments of Ba irons formed. During the period from the 120th hour to the 240th, the organics in the solution were decomposed by microorganism, and water was added. Therefore, the concentration of COD and BOD was diluted. In the first 24h, the values of TON and NH3-N had a wave type change, both of which increased after 24h. The sedimentation rate of the solid particles in the leaching solution slowed down as the leaching time extended, and prolonged the sedimentation duration. Some nitrogen compounds in coal gangue were dissolved in water, and ionization of ammonium ions in the leaching solution formed the alkaline environment.
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ZHAO Hong-yu, LI Yu-huan, SONG Qiang, SHU Yuan-feng, LÜ Jun-xin, SHU Xin-qian. Leaching characteristics of coal gangue in a new dynamic cyclic leaching device. CHINA ENVIRONMENTAL SCIENCECE, 2016, 36(7): 2090-2098.
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