Enhanced recovery of high-purity Fe powder from iron-rich electrolytic manganese residue by slurry electrolysis

Iron-rich electrolytic manganese residue(IREMR)is an industrial waste produced during the processing of electrolytic metal manganese,and it contains certain amounts of Fe and Mn resources and other heavy metals.In this study,the slurry electrolysis technique was used to recover high-purity Fe powder from IREMR.The effects of IREMR and H2SO4 mass ratio,current density,reaction temper-ature,and electrolytic time on the leaching and current efficiencies of Fe were studied.According to the results,high-purity Fe powder can be recovered from the cathode plate,and the slurry electrolyte can be recycled.The leaching efficiency,current efficiency,and purity of Fe reached 92.58%,80.65%,and 98.72wt%,respectively,at a 1:2.5 mass ratio of H2SO4 and IREMR,reaction temperature of 60℃,electric current density of 30 mA/cm^(2),and reaction time of 8 h.In addition,vibrating sample magnetometer(VSM)analysis showed that the coercivity of electrolytic iron powder was 54.5 A/m,which reached the advanced magnetic grade of electrical pure-iron powder(DT4A coercivity standard).The slurry electrolytic method provides fundamental support for the industrial application of Fe resource recovery in IRMER.

Slurry electrolysis of ocean polymetallic nodule

The ocean poly-metallic nodule was leached by using slurry electrolysis process in HCl-NaCl medium.The leaching rates of Mn,Co,Cu and Ni in the ocean poly-metallic nodule are all above 97%.Meanwhile,the high purity of electrolytic MnO2 is also obtained as an anode product.The effects of electrolysis electric quantity,acidity,temperature,slurry density,grain size and iron ions concentration were studied.The results show that the ocean poly-metallic nodule can be treated economically in the slurry electrolysis process.

Anodic process of stibnite in slurry electrolysis:The direct collision oxidation

Mineral oxidation leaching in the anode area is the key step in slurry electrolysis.By adopting the slow linear potential scanning method during slurry electrolysis,this study investigated the steady-state polarization curve of a pure stibnite mineral on a graphite anode.In addition,the influence of the mineral particle size,liquid–solid ratio,stirring speed,and temperature on the collision oxidation of the mineral with the anode was studied.Based on the different oxidation reactions,the potential range can be divided into three intervals:the low-potential interval with a potential lower than 0.75 V,an intermediatepotential interval with a potential within 0.75–1.2 V,and a high-potential interval with a potential higher than 1.2 V.The collision oxidation of the mineral with the anode occurred in all three intervals.The oxidation of Sb(III)also appeared in the intermediate-and high-potential intervals,and chlorine evolution occurred in the high-potential interval.Therefore,the low-potential interval was determined to be a suitable potential interval for the slurry electrolysis process.In the low-potential interval,the particle size,liquid–solid ratio,and stirring speed had little effect on the oxidation rate of the minerals.As the temperature increased,the stibnite oxidation rate and exchange current density increased.Overall,the direct collision oxidation rate of stibnite was relatively low and the current densities under all the investigated conditions were lower than 0.4 mA·cm^(-2.This indicates that it is difficult to realize industrial production while relying solely on this process.

Copper fractal growth during recycling from waste printed circuit boards by slurry electrolysis

Superfine copper particles could be directly prepared from waste printed circuit boards by slurry electrolysis.Meanwhile,copper fractal growth could be observed.To better understand this phenomenon,the factors that affect copper dendrites in a point-cathode system were discussed in detail.These results showed that the fractal degree of copper dendrites increased as the increase of applied voltage and the decrease of copper sulfate and gelatin concentrations.Sodium lauryl sulfate and hydrochloric acid concentrations could not significantly impact the fractal degree of copper dendrites,while gelatin concentration could.The minimum copper fractal dimension was 1.069 when gelatin and copper sulfate concentration was 120 mg/L and 0.1 mol/L,respectively with an applied voltage of 11 V.Moreover,the results diffusion-limited aggregation model demonstrated that particle translational speed,particle numbers and binding probability significantly affected copper dendrite patterns.The scanning electron microscopy results indicated that the three additives greatly affected the refinement of the copper crystal.These findings contribute to enrich the theoretical study on metals recovery from e-waste by slurry electrolysis.