Enhanced removal of high Mn(II) and minor heavy metals from acid mine drainage using tunnelled manganese oxides

Removal of Manganese(II) from Acid Mine Wastewater: A Review of the Challenges and Opportunities with Special Emphasis on Mn-Oxidizing Bacteria and Microalgae

“…Table 1 shows that the pH of manganese mine drainage ranges from 3.5 to 6.5, and the Mn ion content is high, especially in wastewater from electrolytic processing. In addition to Mn, high concentrations of other potentially harmful elements (mainly zinc (Zn), Cu, cadmium (Cd), Fe) are also found in the wastewater from Mn ore processing sites [15,30,31]. The oxidation state of Mn can significantly influence its distribution, transport, and accumulation in water.…”

“…Commonly used adsorbents for Mn removal include activated carbon [46], zeolites [47], kaolinite clay [48], nanoparticles [49,50], polymers [51,52], and a wide range of natural and artificial solids [53,54]. The search for low-cost adsorbents is a major focus of current research efforts, and a variety of natural minerals [15,55], agricultural and industrial wastes [56], and bio-sorbents [57] have been tested. Table 3 assembles the maximum adsorption capacities (Q max ) for Mn(II) by adsorbents reported in the literature , which are predominantly from the Langmuir isotherm modeling of experimental data.…”

“…However, the adsorption mechanism of Mn(II) ion by the pecan nutshell was found to be an interaction of active phenolic and carboxylic groups as the adsorbent of the metallic ion [56]. Three synthetic MnO 2 phases (pyrolusite, cryptomelane, and todorokite) exhibited different adsorption capacities, where todorokite was significantly more effective at removing Mn(II) than the other two phases, probably due to an ion-exchange mechanism involving tunneling, which intercalated Mg into todorokite [15]. Although the characteristics of adsorbents and their removal mechanisms play an important role in their removal ability to lower Mn(II), the comparison of Q max values should consider factors such as temperature, concentration range, and especially, the solution pH.…”

“…Manganese has been widely used in non-ferrous metallurgy, steel production, batteries, electrode materials, and catalyst production [12,13]. Most environmentally significant Mn contamination is directly related to the mining industry, where drainage waters have typically high concentrations of dissolved Mn [14,15] and Mn waste residues that can persistently release Mn into terrestrial and aquatic ecosystems [16]. South Africa, Russia, Australia, and China host the major Mn ore resources in the world [17].…”

Facile preparation of multiphosphonic acid functionalised multi‐walled carbon nanotubes for enhanced adsorption properties for heavy metal ions from wastewaters

“…Among these methods, adsorption is one of the most used techniques to treat heavy metal ions contaminated wastewaters, it is superior to other conventional methods because of its high‐level effectiveness in removing heavy metal ions from wastewaters, the ready availability of absorbents, the simple and amenable process, and the excellent recyclability [7–10]. For the above‐mentioned reason, there is a strong research interest in developing the adsorbents that have high efficiency and selectivity for heavy metal ions removal, efficient adsorbents have become the decisive factor in the removal process of heavy metal ions, and many different types of adsorbents have been developed and used for the removal of heavy metal ions to obtain good removal performances, including manganese oxides [11–13], functionalised silica gel [14–17], activated carbon [18, 19], zeolite [20–22], chitosan [23–25], granular biomass [26] etc. Among them, carbon nanotubes (CNTs) have emerged to be excellent heavy metal ions adsorbents because of their unique chemical and physical properties, such as high surface area, tunable surface chemistry, and non‐corrosive property [27–31].…”