Modification of waste coal gangue and its application in the removal of Mn2+ 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.

Study on the Effectiveness of Sulfate-Reducing Bacteria Combined with Coal Gangue in Repairing Acid Mine Drainage Containing Fe and Mn

“…According to Figure 11a, FTIR peaks of Coal Gangue 1-4 were basically the same before and after AMD treatment, indicating that the same coal gangue had the same functional group. The absorption peaks at 1034, 1010, 799 and 466 cm −1 indicated the possible presence of quartz, and 3698, 3650, 1097, 1034, 1010, 799, 687, 533 and 466 cm −1 indicated the possible presence of kaolinite [23]. The absorption peaks at 2920, 2860 and 750-700 cm −1 indicated the presence of organic substances in coal gangue [57].…”

“…It is found that coal gangue modified by physical or chemical methods can improve its adsorption and can be used for the pre-treatment of industrial wastewater [22]. Ruifang Qiu [23] modified the microstructure of coal gangue by a new calcination method, making coal gangue a low-cost adsorbent that can remove Mn 2+ from industrial wastewater. Preliminary test results show that the spontaneous combustion coal gangue of Gaode coal mine in Fuxin has a certain adsorption effect on Fe and Mn in AMD, and the removal effect is as follows: SRB combined with spontaneous combustion coal gangue > NaOH modified spontaneous combustion coal gangue > unmodified spontaneous combustion coal gangue [24].…”

Novel design of microsphere adsorbent for efficient heavy metals adsorption

“…23 A low-cost adsorbent for Mn 2+ removal was prepared by adding Na 2 B 4 O 7 •10H 2 O into coal gangue during calcination, and the adsorption capacity went up from 3.2 to 23.9 mg/g. 24 Raw coal gangue powders modified with NaCl, NaOH, and HCl were used to treat Fe 2+ and Mn 2+ in acid wastewater and the coal gangue modified by NaOH showed the best adsorption capacity, that is, 0.811 and 0.321 mg/g for Fe 2+ and Mn 2+ . 25 Although some studies about the adsorption properties of coal gangue have been reported, there still exit a few questions: (a) the coal gangue treated with simple methods is usually grinded by manual operation in small numbers with uneven properties and poor adsorption capacity, (b) chemical modification for coal gangue or using coal gangue as starting material to synthesis zeolite is complicated and costly, which limits its practical application in industrial production.…”

“…Coal gangue was combined with biomass to prepare biochar for phosphate removal; the adsorption capacity of the prepared biochar could reach to 3.196 mg/g 23 . A low‐cost adsorbent for Mn 2+ removal was prepared by adding Na 2 B 4 O 7 ·10H 2 O into coal gangue during calcination, and the adsorption capacity went up from 3.2 to 23.9 mg/g 24 . Raw coal gangue powders modified with NaCl, NaOH, and HCl were used to treat Fe 2+ and Mn 2+ in acid wastewater and the coal gangue modified by NaOH showed the best adsorption capacity, that is, 0.811 and 0.321 mg/g for Fe 2+ and Mn 2+ 25 .…”

Synthesis of low-cost porous ceramic microspheres from waste gangue for dye adsorption

“…Moreover, many investigations have focused on its promising adsorption property in polluted water, especially for heavy ions and organic dyes [21][22][23][24]. Qiu and Cheng [21] modified the coal gangue with sodium tetraborate (Na 2 B 4 O 7 ·10H 2 O) during calcination process to improve its removal efficiency of Mn 2+ , which was due to the increase of pore volume (from 0.021 to 0.067 cm 3 /g) and specific surface area (from 9.29 to 20.05 m 2 /g) for raw coal gangue. The decomposition of carbonate minerals and dehydration of coal gangue particles by addition of sodium tetraborate during calcination were originated from the generation of porous structure and large specific surface area.…”