A green method for Mn2+ and NH4+-N removal in electrolytic manganese residue leachate by electric field and phosphorus ore flotation tailings

Investigating the Dewatering Efficiency of Sewage Sludge with Optimized Ratios of Electrolytic Manganese Residue Components

As an industrial waste residue, Electrolytic Manganese Residue (EMR) can greatly promote sludge dewatering and further particle-size optimization can significantly strengthen sludge dewaterability. In this study, the effects of ammonium sulfate, calcium sulphate dihydrate, and manganese carbonate in EMR on sludge dewatering performance were investigated using the response surface optimization method. It was found that the optimized ratio of three components in EMR was 1.0:1.6:2.2 based on capillary suction time (CST), specific resistance of filtration (SRF), and zeta potential of dewatered sludge. The composition ratio of particle-size optimized EMR was modified based on the above optimization, resulting in a significant increase in sludge dewatering performance (CST and SRF reduced by 8.7% and 11.2%, respectively). Compared with those in original sludge, the content of bound extracellular polymeric substances in the conditioned sludge with optimized ratio was drastically reduced while that of soluble extracellular polymeric substances was slightly increased, which was in accordance with the decline of fluorescence intensity. These findings indicated the disintegration of extracellular polymeric substances, the enhancement of hydrophobicity, and dewatering properties of the sludge. In summary, optimized EMR can effectively intensify the dewaterability of sludge, providing a competitive solution for dewatering and further disposal of sludge.

Enhanced green remediation and refinement disposal of electrolytic manganese residue using air-jet milling and horizontal-shaking leaching

The reclamation and reuse of electrolytic manganese residue (EMR) as a bulk hazard solid waste are limited by its residual ammonia nitrogen (NH4+-N) and manganese (Mn2+). This work adopts a co-processing strategy comprising air-jet milling (AJM) and horizontal-shaking leaching (HSL) for refining and leaching disposal of NH4+-N and Mn2+ in EMR. Results indicate that the co-use of AJM and HSL could significantly enhance the leaching of NH4+-N and Mn2+ in EMR. Under optimal milling conditions (50 Hz frequency, 10 min milling time, 12 h oscillation time, 400 rpm rate, 30 ℃ temperature, and solid-to-liquid ratio of 1:30), NH4+-N and Mn2+ leaching efficiencies were optimized to 96.73% and 97.35%, respectively, while the fineness of EMR was refined to 1.78 µm. The leaching efficiencies of NH4+-N and Mn2+ were 58.83% and 46.96% higher than those attained without AJM processing. The AJM used strong airflow to give necessary kinetic energy to EMR particles, which then collided and sifted to become refined particles. The AJM disposal converted kinetic energy into heat energy upon particle collisions, causing EMR phase transformation, and particularly hydrated sulfate dehydration. The work provides a fire-new and high-efficiency method for significantly and simply leaching NH4+-N and Mn2+ from EMR.

Study on mutual harmless treatment of electrolytic manganese residue and red mud

Electrolytic manganese residue (EMR) and red mud (RM) are solid waste by-products of the metal manganese and alumina industries, respectively. Under long-term open storage, ammonia nitrogen and soluble manganese ions in EMR and alkaline substances in RM severely pollute and harm the environment. In order to alleviate the pollution problem of EMR and RM. In this study, the alkaline substances in RM were used to treat ammonia nitrogen and soluble manganese ions in EMR. The results confirm the following suitable treatment conditions for the mutual treatment of EMR and RM: EMR-RM mass ratio = 1:1, liquid-solid ratio = 1.4:1, and stirring time = 320 min. Under these conditions, the elimination ratios of ammonia nitrogen (emitted in the form of ammonia gas) and soluble manganese ions (solidified in the form of Mn3.88O7(OH) and KMn8O16) are 85.87 and 86.63%, respectively. Moreover, the alkaline substances in RM are converted into neutral salts (Na2SO4 and Mg3O(CO3)2), achieving de-alkalinisation. The treatment method can also solidify the heavy metal ions-Cr3+, Cu2+, Ni2+, and Zn2+-present in the waste residue with leaching concentrations of 1.45 mg/L, 0.099 mg/L, 0.294 mg/L, and 0.449 mg/L, respectively. This satisfies the requirements of the Chinese standard GB5085.3-2007. In the mutual treatment of EMR and RM, the kinetics of ammonia nitrogen removal and manganese-ion solidification reactions are controlled via a combination of membrane diffusion and chemical reaction mechanisms.

Comprehensive effects of grain-size modification of electrolytic manganese residue on deep dehydration performance and microstructure of sludge

As the by-product accompanied by sewage treatment, sludge has complex composition and high moisture content, therefore, its reutilization and disposal are still a challenge. In this paper, five kinds of quartz sand conditioners with different particle sizes (denoted as QS1, QS2, QS3, QS4 and QS5, respectively) were used to explore the effect of particle size distribution of conditioners on sludge dewatering performance. The moisture content, capillary suction time (CST), time to filter (TTF), specific resistance of filtration (SRF), particle size distribution curve, pore distribution law, scanning electron microscopy, isothermal adsorption-desorption curve and extracellular polymeric substances distribution were employed to characterize the modified sludge and explore the improvement mechanism. The results show that the particle size distribution of the conditioner significantly affects the efficiency of sludge dewatering. The wt% of sludge regulated with QS1 (QS1-S) could be reduced to 52%, and its CST value, TTF value and SRF value is 57.93 s, 278 s and 1.84 × 10⁸ s² g^-1, respectively. The conjecture about the effect of difference of particle size distribution on sludge dewatering performance was verified with the original Electrolytic Manganese Residue (EMR) and the grain-size modified Electrolytic Manganese Residue (EMR6). Compared with those of the EMR-conditioned sludge, the CST, TTF and SRF of EMR6-conditioned sludge was decreased by 8.7%, 22.3% and 11.2%, respectively. According to analysis of surface microstructure, the surface of the sludge cake modified with QS1 is rough and sparse with rich pore structure. Compared with those of the undisturbed sludge (A0), the pore volume and specific surface area of the sludge modified with QS1 was increased by 61.65% and 38.62%, respectively. After grain-size modification, the dehydration effect of EMR6 (D10 4.25 μm, D50 19.65 μm, D90 73.26 μm) was significantly enhanced, and the D10, D50 and D90 value was close to that of QS1. It can be concluded that the particle size of QS1 (D10 3.27 μm, D50 15.66 μm, and D90 62.23 μm) can improve the dewatering performance of sludge by shearing the sludge particles to change the original sludge particle size distribution and improving the blockage of sludge dewatering channels.