Xin He,Wutong Chen,Feiyun Sun,Zekai Jiang,Bing Li,Xiao-yan Li,Lin Lin
Flow-electrode capacitive deionization (FCDI) is a promising electromembrane technology for wastewater treatment and materials recovery. In this study, we used low-cost Na-modified zeolite (Na-zeolite) to prepare a composite flow-electrode (FE) suspension with a small amount of highly conductive carbon black (CB) to remove and recover NH4+ from synthetic and actual wastewater (200 mg-N/L). Compared with conventional activated carbon (AC), the Na-zeolite electrode exhibited a 56.2–88.5% decrease in liquid-phase NH4+ concentration in the FE suspension due to its higher NH4+ adsorption capacity (6.0 vs. 0.2 mg-N/g). The resulting enhancement of NH4+ diffusion to the electrode chamber contributed to the improved performance of FCDI under both constant current (CC) and constant voltage (CV) conditions. The addition of CB to the FE suspension increased the conductivity and facilitated Na-zeolite charging for NH4+ electrosorption, especially in CV mode. NH4+-rich zeolite can be easily separated by sedimentation from CB in the FE suspension, producing a soil conditioner with a high N-fertilizer content suitable for soil improvement and agricultural applications. Overall, our study demonstrates that the novel Na-zeolite-based FCDI can be developed as an effective wastewater treatment technology for both NH4+ removal and recovery as a valuable fertilizer resource.
Swine wastewater is a type of highly turbid wastewater with extremly high concentration of COD, NH 4 + , and total phosphorus. To address the drawbacks of commercial coagulants in the pretreatment of swine wastewater, such as loose flocs, slow settling rates, and the inability to remove NH 4 + , a novel Mg-Fe-Al hybrid magnetic coagulant (Mg/Fe/Al-MC) is prepared by using the high-pressure acid leaching (HPAL) technology based on iron tailings waste. Compared to atmospheric acid leaching (AAL), HPAL significantly increased the iron leaching rate from 22 % to 61 %. The specific surface area was increased from 5.1 to 9.2 m 2 /g. The study revealed the synergistic crystallization-coagulation-adsorption mechanism for the purification of swine wastewater. When the dosage of Mg/Fe/Al-MC was 2.5 g/L and pH was 9.0, the removal efficiency of NH 4 + reached 60 % by forming magnesium ammonium phosphate (MAP). Zeta potential results indicated that the coagulation mechanism of Mg/Fe/Al-MC is primarily based on electrostatic neutralization. After maturing Mg/Fe/Al-MC for 60 h, the content of essential polymeric Fe-Al hydroxide complexes [Fe(III)+Al(III)](b) reached 22.7 %. The insoluble porous particles exhibited a significant adsorption capacity, suggesting its important role in pollutant removal. Under the action of an external magnetic field, the settling velocity of Mg/Fe/Al-MC was significantly faster than that of polyaluminum chloride (PAC), with a much higher clear water yield of 75.5 %. This study provides new pathway for the enhanced pretreatment of swine wastewater.
危险品化学品经营许可证（带存储）