Enhanced removal of Pb from electrolytic manganese anode slime and preparation of chemical MnO2.

Electrolytic manganese anode slime (EMAS) is produced during the production of electrolytic manganese metal. In this study, a method based on vacuum carbothermal reduction was used for Pb removal in EMAS. A Pb-removal efficiency of 99.85% and MnO purity in EMAS of 97.34 wt.% were obtained for a reduction temperature of 950°C and a carbon mass ratio of 10% for a holding time of 100 min. The dense structure of the EMAS was destroyed, a large number of multidimensional pores and cracks were formed, and the Pb-containing compound was reduced to elemental Pb by the vacuum carbothermal reduction. A recovery efficiency for chemical MnO2 of 36.6% was obtained via preparation from Pb-removed EMAS through the 'roasting-pickling disproportionation' process, with an acid washing time of 100 min, acid washing temperature of 70°C, H2SO4 concentration of 0.8 mol·L-1, liquid-solid mass ratio of 7 mL·g-1, calcination temperature of 60°C and calcination time of 2.5 h. Moreover, the crystal form of the prepared chemical MnO2 was found to be basically the same as that of electrolytic MnO2, and its specific surface area, micropore volume and discharge capacity were all higher than that of electrolytic MnO2. This study provides a new method for Pb removal and recycling for EMAS.HighlightsVacuum carbothermal reduction method was used for Pb removal in EMAS.The removal efficiency of Pb was 99.85%.Chemical MnO2 with excellent discharge performance was prepared using treated EMAS.This study provides a new method for EMAS resource utilization.

Copper (Cu2+) ion-induced misfolding of tau protein R3 peptide revealed by enhanced molecular dynamics simulation.

Tau misfolding plays a significant role in some neurodegenerative diseases such as Alzheimer's disease (AD). It is intrinsically disordered and highly soluble under normal physiological conditions. While the protein will aggregate to form paired helical filaments (PHFs) under copper homeostasis at pathological conditions, which is the main substance of neurofibrillary tangles (NFTs) in the brain of AD patients. However, the molecular mechanism underlying the copper (Cu2+) ion-induced tau misfolding is not fully understood. In this study, using the 1/2 third repeat fragment (R3 peptide) of tau protein (residues 318-335: VTSKCGSLGNIHHKPGGG) as a model, a Gaussian accelerated molecular dynamics (GaMD) method followed by efficient trajectory analysis was carried out to investigate the influences of Cu2+ on the tau about the protein fold and the free energy landscape along the simulation. The two-dimensional potential of mean force (PMF) profiles obtained from reweighting of the GaMD simulations as well as clustering analysis revealed the Cu2+ ion induced α-helix fold R3 peptide located at the low-energy wells of free energy map, which is in agreement with the reported experimental result. In contrast, there is no α-helix fold of R3 peptide that appeared during the GaMD simulation without Cu2+ ion existing. Furthermore, the definition of secondary structure of protein (DSSP) analysis indicated that the R3 peptide with Cu2+ ion forms a stable structure of the helix (Lys321-His330 interval of the peptide) at between 400 and 500 ns. Therefore, the structures and free energy profiles from GaMD simulations proposed that Cu2+ triggers the aggregation of R3 peptide into toxic PHFs through a stable α-helix fold form.