Alkaline pressure oxidative leaching of bismuth-rich and arsenic-rich lead anode slime

A new alkaline pressure oxidative leaching process(with NaNO3 as the oxidant and NaOH as the alkaline reagent)is proposed herein to remove arsenic,antimony,and lead from bismuth-rich and arsenic-rich lead anode slime for bismuth,gold,and silver enrichment.The effects of the temperature,liquid-to-solid ratio,leaching time,and reagent concentration on the leaching ratios of arsenic,antimony,and lead were investigated to identify the optimum leaching conditions.The experimental results under optimized conditions indicate that the average leaching ratios of arsenic,antimony and lead are 95.36%,79.98%,63.08%,respectively.X-ray diffraction analysis indicated that the leaching residue is composed of Bi,Bi2O3,Pb2Sb2O7,and trace amounts of NaSb(OH)6.Arsenic,antimony,and lead are thus separated from lead anode slime as Na3AsO4·10H2O and Pb2Sb2O7.Scanning electron microscopy and energy-dispersive spectrometry imaging revealed that the samples undergo appreciable changes in their surface morphology during leaching and that the majority of arsenic,lead,and antimony is removed.X-ray photoelectron spectroscopy was used to demonstrate the variation in the valence states of the arsenic,lead,and antimony.The Pb(IV)and Sb(V)content was found to increase substantially with the addition of NaNO3.

φ-pH diagram of As-N-Na-H_2O system for arsenic removal during alkaline pressure oxidation leaching of lead anode slime

In order to illustrate the thermodynamic characteristics of arsenic during alkaline pressure oxidation leaching process oflead anode slime(NaNO3as oxidant;NaOH as alkaline reagent),theφ-pH diagrams of As-Na-H2O,N-H2O,As-N-Na-H2Osystems at ionic mass concentration of0.1mol/kg and temperatures of298,373,423and473K were established according tothermodynamic calculation.The results show that the existence forms of arsenic are associated with pH value,which mainly exists inthe forms of H3AsO4,24H AsO-,24HAsO-,H2AsO2-and As2O3in lower pH region,while it mainly exists in the form of3AsO4-when pH>11.14.High alkali concentration and high temperature are advantageous to the arsenic leaching.The alkaline pressureoxidation leaching experiments display that the tendency of arsenic leaching rate confirms the thermodynamic analysis resultsobtained from theφ-pH diagrams of As-N-Na-H2O system,and the highest leaching rate of arsenic reaches95.85%at453K.

Effect of NaNO3 concentration on anodic electrochemical behavior on the Sb surface in NaOH solution

The effect of NaNO_3 concentration on the anodic electrochemical behavior of antimony in 4 M NaOH solution was investigated using cyclic voltammetry(CV) and electrochemical impedance spectroscopy(EIS) analyses. The mechanism of NO_3^-concentration effect on the anodic electrochemical behavior of antimony was proposed, and its availability was confirmed by experimental results. The effect of NaNO_3 on the anodic behavior of antimony in Na OH solution can be interpreted as a stepwise formation of different antimony compounds with different NaNO_3 concentrations. Metallic antimony is apt to be oxidized into Sb_2O_3 within the NaNO_3 concentration range of 0–0.48 M. NaSbO_3 can be found on the antimony surface when the NaNO_3 concentration increases gradually. Insoluable NaSbO_3 inhibits the anodic oxidation of antimony due to its shielding effect on the mass transport of the reactants and products. Surface morphology and composition were analyzed by X-ray photoelectron spectroscopy(XPS), scanning electronic microscopy(SEM), and electron dispersion spectroscopy(EDS) analyses. Results indicate that the anodic oxidation layer is composed of Sb_2O_3, NaSbO_3, and Sb. The atomic proportion of antimony in the form of NaSbO_3 increases with increasing NaNO_3 concentration due to the powerful oxidizing property of NaNO_3.

ZNF582 hypermethylation promotes metastasis of nasopharyngeal carcinoma by regulating the transcription of adhesion molecules Nectin-3 and NRXN3

Background:Epigenetic regulation plays an important role in the development and progression of nasopharyngeal carcinoma(NPC).However,the epigenetic mechanisms underlying NPC metastasis remains poorly understood.We aimed to find functional genes which regulate the metastasis of NPC and identify therapeutic targets for NPC treatment.Methods:Bisulfite pyrosequencing was used to analyze zinc finger protein 582(ZNF582)methylation in NPC tissues and cell lines.Quantitative reverse transcription-polymerase chain reaction(qRT-PCR)and Western blotting were used to determine the expression of ZNF582.In vitro and in vivo experiments were performed to evaluate the biological function of ZNF582 in NPC.ZNF582-targeting genes were identified by chromatin immunoprecipitation sequencing(ChIP-seq)and were confirmed by ChIP-qPCR and luciferase assay.Results:ZNF582 promoter was hypermethylated in NPC,and both the mRNA and protein levels of ZNF582 were down-regulated in NPC tissues and cell lines.The restoration of ZNF582 inhibited NPC migration,invasion,and metastasis,while the knockdown of ZNF582 promoted NPC migration,invasion,and metastasis in vitro and in vivo.ZNF582 directly regulated the transcription and expression of adhesion molecules Nectin-3 and NRXN3.Both Nectin-3 and NRXN3 were identified as functional targets of ZNF582,and the restoration or abrogation of these genes reversed the tumor suppressor effect of ZNF582 in NPC metastasis.Conclusions:ZNF582 acts as a tumor suppressor gene in NPC by regulating the transcription and expression of adhesion molecules Nectin-3 and NRXN3,which may provide novel therapeutic targets for NPC treatment.

Correction to: ZNF582 hypermethylation promotes metastasis of nasopharyngeal carcinoma by regulating the transcription of adhesion molecules Nectin-3 and NRXN3

Following publication of this article[1],the authors noticed that the mismatched images were inadvertently included in Figure 5(migration assays of SUNE1-shNRXN3-#2 group in Figure 5I)and Figure 6(invasion assays of SUNE1-ZNF582+Nectin3 group in Figure 6A).This error has now been corrected online.