Removal of Pb(II) from Acid Mine Drainage with Bentonite-Steel Slag Composite Particles

Abstract

Abandoned lead and zinc (Pb-Zn) mines around the world produce large amounts of acid mine drainage (AMD) containing Pb(II), which is toxic and accumulates in the environment and in living organisms. Bentonite-steel slag composite particles (BSC) are a new type of acid mine drainage (AMD) treatment material that can remove heavy metal ions and reduce acidity. To date, there have been no reports on the treatment of Pb(II)-containing AMD using BSC. Therefore, the effects of pH, reaction time, temperature, and Pb(II) concentration on the adsorption of Pb(II) onto BSC were studied. Moreover, the BSC before and after the reaction, as well as the precipitation after the reaction, were characterized by scanning electron microscopy and X-ray diffraction analyses. The effect of pH on the adsorption process is similar to that of the formation of soluble and insoluble hydrolysates of Pb(II) on pH. The adsorption mechanism includes ion exchange, complexation, precipitation, and synergistic adsorption–coagulation effect. Adsorption kinetics are best-fit with the pseudo-second order kinetics model ( R 2 > 0.98). Furthermore, the total adsorption rate is controlled by liquid film diffusion and in-particle diffusion, the liquid film diffusion rate being higher than the in-particle diffusion rate. The isothermal adsorption of Pb(II) onto BSC fit well with Langmuir and Brunauer Emmett Teller (BET) isotherms ( R 2 > 0.995), and both single layer adsorption and local multilayer adsorption were observed. Thermodynamic analysis revealed that the adsorption process is spontaneous and endothermic, and that the degree of freedom increases with time. In summary, this study provides a theoretical basis for the use of BSC in treating AMD containing Pb(II).

From Waste to Waste: Iron Blast Furnace Slag for Heavy Metal Ions Removal from Aqueous System

“…The BFS slag exhibited a strong ion exchange capacity, which was consistent with the sorption equilibrium. For divalent metal ions (M 2+ ) in solutions, the aforementioned equation may be expressed as (Zhan et al 2019):…”

Mechanism of Acid Mine Drainage Remediation with Steel Slag: A Review

“…Moreover, due to the limited pore structure of steel slag, the internal components are unavailable for utilization efficiently, resulting in a limited adsorption efficiency of steel slag. Several researchers have employed various activation technologies to improve the adsorbing performance of steel slag. ,, Duan et al tested the ability of the modified steel slag to remove Cd 2+ from AMD. It confirmed that the adsorption of Cd 2+ by modified steel slag is enhanced since the active site in the slag modified with aluminum hydroxide increased significantly, promoting the Cd 2+ to diffuse to the surface of the slag.…”

“…Owing to the relatively stable composition in steel slag, high-temperature treatment of steel slag would crack the dense surface of steel slag and release internal energy, making the surface area more loose and porous, increasing the specific surface area of steel slag, thereby improving the adsorption capacity. Zhan et al 39 employed bentonite-steel slag composite particles (BSC) as an adsorbent to treat AMD containing Pb 2+ . Due to the strong alkali release capacity of steel slag and the excellent adsorption potential of bentonite for heavy metal cations, the adsorbent can effectively neutralize acidic substances from AMD and achieve complete removal of heavy metal ions Pb 2+ .…”

Mine drainage: Remediation technology and resource recovery

“…Bentonite–steel slag composite particles (BSC) were examined for Pb adsorption in treating AMD rich in Pb and Zn (Zhan, Xiao, & Liang, 2019). Multiple adsorption mechanisms were involved for Pb removal.…”