Enhanced Mn^(2+)solidification and NH_(4)^(+)-N removal from electrolytic manganese metal residue via surfactants

Electrolytic manganese metal residue(EMMR)harmless treatment has always lacked a low-cost and quick processing technology.In this study,surfactants,namely tetradecyl trimethylammonium chloride(TTC),sodium dodecyl benzene sulfonate(SDBS),sodium lignin sulfonate(SLS),and octadecyl trimethylammonium chloride(OTC),were used in the solidification of Mn^(2+)and removal of NH_(4)^(+)-N from EMMR.The Mn^(2+)and NH_(4)^(+)-N concentrations under different reaction conditions,Mn^(2+)solidification and NH_(4)^(+)-N removal mechanisms,and leaching behavior were studied.The results revealed that the surfactants could enhance the Mn^(2+)solidification and NH_(4)^(+)-N removal from EMMR,and the order of enhancement was as follows:TTC>SDBS>OTC>SLS.The NH_(4)^(+)-N and Mn^(2+)concentrations were 12.3 and 0.05 mg·L^(-1)with the use of 60.0 mg·kg^(-1)TTC under optimum conditions(solid–liquid ratio of 1.5:1,EMMR to BRM mass ratio of 100:8,temperature of 20℃,and reaction duration of 12 h),which met the integrated wastewater discharge standard(GB8978-1996).Mn^(2+)was mainly solidified as Mn(OH)_(2),MnOOH and MnSiO_(3),and NH_(4)^(+)-N in EMMR was mostly removed in the form of ammonia.The results of this study could provide a new idea for cost-effective EMMR harmless treatment.

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.