Characteristics of Heavy Metal Ion Adsorption by Silty Mudstones in Coal Mine Goafs

Abstract

Coal mine goafs can be used to store and purify mine water; therefore, they are important for mitigating the environmental impact of mining on ecologically fragile areas in Western China. Coal gangue in goafs can reduce turbidity, suspended matter, total hardness, and chemical oxygen demand (COD) in mine wastewater. Because gangue in goaf areas is rich in clay minerals, they serve as ion exchange sites. We investigated the adsorption of heavy metal ions by silty mudstones in the Ulan Mulun mine. The adsorption kinetics and isothermal adsorption characteristics of four heavy metal ions, i.e., Pb(II), Cd(II), Cr(III), and Mn(II), were investigated using batch experiments. Under a pH of 6.75 and temperature of 20°C, the adsorption capacity of silty mudstone particles (<74 μm) was 6.3012 g, 1.5701, 1.2571, and 1.3729 mg/g for Pb(II), Cd(II), Cr(III), and Mn(II), respectively. Based on the experimental results, quantitative relationships between the adsorption quantity per unit of rock surface and the equilibrium concentration of heavy metals in solution were developed using Langmuir, Freundlich, and D–R equations. The relationships were used to obtain the equilibrium concentration of the solution. Finally, the ratio of the f value of the water-rock contact area in the goaf to the water volume was calculated and analyzed. The f value was inversely proportional to the average vertical opening of gaps between gangues in the goaf. The adsorption rate functions for Pb(II), Cd(II), Cr(III), and Mn(II) in the goaf were obtained, and the corresponding adsorption capacities were calculated. The adsorption capacities were controlled by the f value and adsorption properties of the gangue. These results can be used in future studies on mine wastewater treatment.

Adsorption of Vanadium(V) From Textile Industry Effluent Using Luffa cylindrica Activated Carbon

“…This was because, as the pH increased, the surface of LAC became less positively charged, which favoured electrostatic attraction between its surface and vanadium(V). 15 Fig. 7 indicates that the percentage removal of 97.83 % was obtained at an adsorbent dosage of 1.0 g, which was attributed to the increased adsorbent surface and the availability of more adsorption sites.…”

Biosorption of chromium (VI) from textile waste water using luffa cylindrica activated carbon

“…This is because as the pH increased, the surface of LAC becomes less positively charged which favors electrostatic attraction between its surface and Cr (VI). The Cr (VI) are most probably adsorbed at the surface of LAC via an ion exchange mechanism with the functional groups present at its surface (Adewuyi & Pereira, 2017; Okolo et al., 2019; Patel & Vashi, 2010; Yao et al., 2020).…”

“…The value of n is 3.968; hence, the adsorption process is favorable. It shows that the prepared adsorbents from LAC are extremely active in the removal of Cr (VI) ion from aqueous solutions (Okolo et al., 2019; Patel & Vashi, 2010; Ullah et al., 2020; Yao et al., 2020; Fox et al, 2012).…”

Analysis of the Control Effect and Parameter Optimisation of Urban Surface Deformation in Underground Coal Mining with Solid Backfilling

“…e control targets for solid backfilling in the rock are the key layer, the main roof, and the immediate roof, with the first being the most difficult target and the last being the most precise target. Guo et al [15][16][17], Cha et al [18,19], and Yao et al [20,21] proposed the use of the probability integral method to describe patterns of surface deformation, established a prediction model parameter system for surface subsidence with solid backfilling, and actually measured surface subsidence results using an electronic total station. Fei et al [22] and Niu et al [23] further analysed surface deformation characteristics using the analytic hierarchy process evaluation model and evaluation system.…”