title: Modiﬁcation of waste coal gangue and its application in the removal of Mn(2+) from aqueous solution.
abstract: We developed a new calcination method to convert coal gangue (CG), a common waste generated from coal production process, into a modified form, which could be used as an adsorbent to remove Mn(2+) from aqueous solution. Sodium tetraborate (Na2B4O7·10H2O) was added into the CG calcination process as an additive, and the concentrations of Na2B4O7·10H2O were optimized along with the calcination temperature to obtain the best adsorbent capacity of modified coal gangue (MCG). We applied multiple analytical methods such as scanning electron microscopy, X-ray diffraction, Fourier transform infrared spectroscopy and Brunauer-Emmett-Teller analysis to characterize the MCG. The results showed it had a smaller particle size and a larger specific surface area and pore volume after modification. It also indicated that the phase of CG transformed from kaolinite to metakaolinite after calcination. Moreover, a new substance was generated with two new peaks at 1,632 cm(-1) and 799 cm(-1). The Mn(2+) absorption capacity of MCG was evaluated using a series of experiments with different adsorbent doses, pH values and initial Mn(2+) concentrations during the adsorption process. We found that Mn(2+) adsorbent capacity of MCG increased by more than seven-fold compared to that of CG. The Langmuir isotherm model and the pseudo-second-order kinetic model provided the best fit to the adsorption processes.
authors.affiliation: Institute of Resources & Environment Engineering, Shanxi University, State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources, Shanxi Innovation Hub of Resource Recycling and Ecological Engineering, Taiyuan 030006, China E-mail: qiurf@sxu.edu.cn; College of Environmental & Resource Sciences, Shanxi University, Taiyuan 030006, China.
authors.forename: Ruifang
authors.initials: R
authors.lastname: Qiu
authors.affiliation: Institute of Resources & Environment Engineering, Shanxi University, State Environmental Protection Key Laboratory of Efficient Utilization Technology of Coal Waste Resources, Shanxi Innovation Hub of Resource Recycling and Ecological Engineering, Taiyuan 030006, China E-mail: qiurf@sxu.edu.cn.
authors.forename: Fangqin
authors.initials: F
authors.lastname: Cheng
mesh_terms: D000327:Adsorption; D001881:Borates / Q000737:chemistry; D003031:Coal / Q000032:analysis; D006863:Hydrogen-Ion Concentration; D007220:Industrial Waste / Q000032:analysis*; D007700:Kinetics; D008345:Manganese / Q000737:chemistry*; D008906:Mining; D014865:Waste Disposal, Fluid / Q000379:methods*; D014874:Water Pollutants, Chemical / Q000737:chemistry*
chemical_list: D001881:Borates; D003031:Coal; D007220:Industrial Waste; D014874:Water Pollutants, Chemical; D008345:Manganese; C010634:sodium borate