镁盐改性生物质炭的合成及其在废水氮磷资源化中的应用研究

Synthesis and characterization of magnesium modified biochar for ammonia and phosphorus immobilization from simulated wastewater

通过直接沉淀-热改性法将纳米氢氧化镁晶体(Mg(OH)_2)负载在生物质炭(BC)上,系统研究了该改性材料(Mg(OH)_2-BC)对模拟废水中氮、磷的固定特性,并探讨了投加量、反应溶液pH、接触时间对吸附过程的影响.结果表明,Mg(OH)_2-BC在投加量为0.3 g·L^(-1),反应溶液初始pH为7,反应时间≥40 min时对氮、磷的固定效果最佳,最大吸附量分别达到58.8、130.0 mg·g^(-1).Mg(OH)_2-BC对氮、磷的吸附过程均符合准二级动力学模型,吸附过程受化学吸附机理的控制.通过SEM、XRD、FTIR等对反应产物进行表征分析,结果表明,Mg(OH)_2-BC对氮、磷的固定机制主要为鸟粪石结晶沉淀,也即化学沉淀.

A magnesium hydroxide modified biochar（ Mg（OH） 2-BC） composite was developed as a novel adsorbent by impregnating nano-size magnesium hydroxide（ Mg（OH） 2 ） particles on the surfaces of Biochar（BC） through a thermal-precipitation modification method. The nutrients removal mechanisms of ammonium nitrogen and phosphorus, from simulated wastewater by the adsorbent was discussed after investigating and evaluating the influence of adsorbent dosage, pH and contact time. The results show that Mg （OH）2-BC exhibited a high removal capacity with a maximum of 58.8 mg· g-1 for ammonium nitrogen and 130.0 mg·g-1 for phosphorus at adsorbent dosage of 0.3 g·L-1 , initial pH 7 and contact time of 240 min. The kinetics curve of both ammonium and phosphorus adsorption process followed the pseudo-second-order kinetics model, implying that the adsorption process was mainly controlled by chemical adsorption. The recovered precipitates were characterized by field-emissian scanning electron microscopy （SEM）, X-ray diffraction （XRD） and Fourier transform infrared spectroscopy（FTIR）. The results show that the main mechanism for ammonium and phosphorus immobilization by Mg（OH） 2-BC was through chemical precipitation of struvite crystals.