Enhanced Mn2+ solidification and NH4+-N removal from electrolytic manganese metal residue via surfactants

Abstract

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 °C, 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.