The generation and accumulation of discarded coal gangue (CG) have severe environmental impacts. CG can adsorb other pollutants in the aquatic environment. However, previous studies have not assessed whether CG can adsorb the emerging contaminant tetracycline hydrochloride (TC). Here, discarded CG taken from a mine was pretreated by crushing, cleaning, and sieving and subsequently applied to the adsorption of TC. The adsorption studies were carried out by batch equilibrium adsorption experiments. Our findings indicated that the adsorption behavior could be accurately described using the quasi-first order kinetic and Langmuir adsorption isotherm models, indicating that monolayer adsorption was the main mechanism mediating the interaction between CG and TC. The adsorption process was classified as a thermodynamic endothermic and spontaneous reaction, which was controlled by chemical and physical adsorption, including electrostatic interaction and cation exchange. The pH of the solution had a great influence on the TC adsorption capacity of GC, with higher adsorption occurring in acidic environments compared to alkaline environments. This was attributed to the changes in CG Zeta potential and TC pKa at different pH conditions. Collectively, our findings demonstrated the potential applicability of discarded CG for the adsorption of TC and provided insights into the adsorption mechanisms.Keywords:natural coal gangue;spent coal-associated waste;removal;tetracycline hydrochloride;antibiotics pollutant;water environment
Yumeng Chen,Dian Zhang,Junguo Li,Changning Wu,Ke Liu
Waste coal is a major environmental hazard produced in the traditional coal preparation unit operations. In this paper, a case study is presented for further scavenging the combustible matter in waste coal using flotation with a self-designed collector (Ksw) consisted of kerosene (K), span (S) and water. The said collector took advantage of both the emulsification and pre-dispersion technique so that the waste coal processability could be improved to a greater extent. Our flotation tests have shown comparable combustible matter recovery when using Ksw and emulsified kerosene (Ks), and both collectors significantly outperformed that of K. At 4 kg/t collector dosage, combustible matter recovery was at 54.9%, 64.9% and 65.3% for K, Ks and Ksw respectively. However, Ksw represented an economically superior option due to its specific composition features. The zeta potential measurements and interaction energy calculations have suggested that although there existed an electrostatic repulsion between the selected oil droplets and coal particles, flotation of waste coal was still feasible because of the hydrophobic force dominating the interaction process. Further, it was found that the interaction energy calculation results could not sufficiently account for the superior flotation performance of using Ksw as collector. Dynamic light scattering (DLS) measurement has shown that the other key instruments at play were the diameter and number of the oil droplets. At 400 mg/L collector suspensions, emulsification reduced the effective diameters of K from 4.23 to 1.62 μm (Ks), and further decreasing to 1.12 μm (Ksw) when dispersion was imposed. The outcomes of this work have suggested Ksw as an economically and technically superior reagent over the conventional hydrocarbon oil collectors for waste coal reprocessing.
危险品化学品经营许可证（带存储）