MgO改性赤泥复合材料对废水中氮磷的同步回收

Simultaneous recovery of nitrogen and phosphorus in wastewater by MgO modified red mud composite material

为处理高浓度氮磷废水同时实现赤泥资源化利用,通过赤泥负载氧化镁制备高效氮磷回收材料(MgO-RM),用以对废水进行氮磷同步回收.考察了废水初始pH值､废水氮磷比和MgO-RM投加量对氮磷同步回收效果的影响.采用动力学模型和等温吸附模型对回收特性进行了描述,在此基础上利用FTIR､XRD､SEM､BET测试手段对MgO-RM参与反应前后进行表征,以揭示其回收机理.结果表明:氧化镁可有效负载于赤泥表面,在最优条件下(初始pH值为3､废水氮磷比3:5和MgO-RM投加量4g/L)对氨氮和磷酸盐的回收能分别达到65%和90%以上.MgO-RM对氮磷的回收过程可用Langmuir模型和准二级动力学模型进行描述,吸附行为更符合单分子层吸附,化学吸附占主导地位,氨氮和磷酸盐理论最大回收量可达61.50和140.66mg/g.综合表征结果与回收特性推测,氮磷同步回收机制主要包括物理吸附､离子交换､络合反应和化学沉淀,其中以生成磷酸铵镁沉淀为主.

To treat high-concentration wastewater while realizing the utilization of red mud as a resource.The modified red mud composite material(MgO-RM)was prepared through the red mud loaded with magnesium oxide for efficient simultaneous recovery of nitrogen and phosphorus in wastewater.The effects of the initial pH,the mass ratio of nitrogen to phosphorus and the dosage of MgO-RM on the recovery performance were investigated,and kinetic models and isothermal adsorption models examined the recycling characteristics.Meanwhile,the recovery mechanism was revealed by characterizing the MgO-RM before and after the reaction through FTIR,XRD,SEM,and BET testing methods.The results showed that magnesium oxide was effectively loaded on the surface of red mud under an optimal condition:initial pH=3,nitrogen and phosphorus mass ratio=3:5 and MgO-RM dosage=4g/L.The ammonia nitrogen and phosphate recovery efficiency can be reached as 65% and 90%,respectively.Such a recovery process can be explained by the Langmuir model and the quasi-two-order kinetic model.The adsorption behavior was in line with the monolayer adsorption,in which chemical adsorption plays a dominant role.The maximum ammonia nitrogen and phosphate recovery capacity can be achieved as 61.50mg/g and 140.66mg/g,separately.The above results concluded that the recovery mechanism may include physical adsorption,ion exchange,complexation reaction and chemical precipitation,in which struvite precipitation is the dominant process.