Azetomycin II

The phenoxy-amino ligands 2-(((2-(diethylamino)ethyl)amino)methyl)phenol (L1) and 2-(((2-mercaptoethyl)amino)methyl)-phenol (L2) were studied as model chelating agents for liquid-liquid extraction of copper(II), zinc(II), cadmium(II), and lead(II) cations from water using dichloromethane-water biphasic system. The relative affinities of these chelating ligands for copper(II), zinc(II), cadmium(II), and lead(II) by liquid-liquid extraction were found to be in the order copper(II)> zinc(II) > cadmium(II) > lead(II). The ligands L1 and L2 showed binding efficiencies ranging from 78%-97% for copper(II), 75%-91% for zinc(II), 76%-92% for cadmium(II), and 59%-67% for lead(II). The extraction protocol was successfully applied to sewage effluent.

Ni(II) and chelated Ni(II) in wastewater are of environmental concern. This study explores the sequestration potential of structural Fe(II) in solid phase (≡Fe(II)) on Ni(II) and EDTA-Ni(II) using freshly prepared ferrous hydroxyl complex (FHC) as the Fe(II)-bearing mineral. The 1 mM Ni(II) could be completely sequestrated in 20 min by 3 mM FHC, although the sequestrated Ni(II) was partially released after 20 min. It is calculated that up to 156 mg Ni(II)/g Fe(II) can be sequestrated by ≡Fe(II) under neutral pH and anaerobic condition. According to the characterizations of the solid products, the large surface area for Ni(II) adsorption and the high ≡Fe(II) reduction capacity for Ni(II) reduction are the main contributors to the Ni(II) sequestration. After the reaction, the FHC is transformed to stable Fe-Ni layered double hydroxides. The concomitant ions can be either promotional or inhibitory to the sequestration performance depending on the ion type. The combination of FHC and Fe(III) can effectively sequestrate EDTA-Ni(II), whereas FHC alone has a low efficiency. Fe(III) substitutes Ni(II) from the EDTA-Ni(II), benefiting the subsequent Ni(II) sequestration by ≡Fe(II). This study demonstrates that ≡Fe(II) suspension is an cost-effective option for remediating Ni(II)-containing wastewater.

In this study, the redox homogeneous precipitation method was applied to synthesize hydrated manganese dioxide (HMO) and to study the removal performance of Cd(II) from wastewater. Moreover, a small amount of Mn(II) could still combine with HMO without causing the desorption of Cd(II). A novel discovery was that the synergistic effect of KMnO4 and Mn(II) could directly regenerate MnO2 to deeply remove Cd(II), realizing the recycling of MnO2. The influence of Mn(II) addition on the adsorption behavior of Cd(II) was discussed in terms of pH, Mn(II) addition mode, initial concentration of Mn(II) or Cd(II), and contact time. The adsorption of Cd(II) on HMO could be better in line with the Langmuir model, while that of Mn(II) accorded with the Freundlich model. The pseudo-second-order kinetic fitting results indicated that the removal of Cd(II) and Mn(II) on HMO belonged to chemisorption. SEM, XRD, FTIR, and XPS analysis demonstrated that Cd(II) was trapped by forming an inner-sphere complex on HMO, and the added Mn(II) and KMnO4 could regenerate MnO2 through oxidation-reduction reaction, wrapping outside of Cd(II) for a purpose of deep removal of Cd(II). HIGHLIGHTS: 1)A small amount of Mn(II) can bind to HMO without causing Cd(II) desorption 2)A large amount of Mn(II) can cause partial desorption of Cd(II) 3)Large amount of Mn(II) will partially bind to the surface of HMO or Cd(II) complexes 4)Deeply remove Cd(II) without eluting and regenerating HMO.