改性海绵铁深度除磷及其再生磷回收方法

为了从污染水体中去除磷并有效回收磷资源,本文研究了海绵铁改性前后吸附除磷特性,并构建海绵铁除磷渗滤床,考察了其连续流除磷特性及再生活化方法,并探究再生废液中磷回收生成鸟粪石的工艺条件.结果表明:硫酸改性后的海绵铁对磷的最大理论吸附容量从改性前4.17 mg·g~(-1)提升至18.18 mg·g~(-1).吸附饱和的改性海绵铁,采用1 mol·L~(-1)氢氧化钠解吸和6%硫酸再活化后,能够达到98%的活化率.海绵铁除磷渗滤床在长达约200 d的连续流运行实验中表现出良好的除磷能力,在进水TP=10 mg·L~(-1),HRT=1 h条件下,磷综合去除率达30%～89%,累积单位容积磷吸附量达到6.95 kg·m~(-3).海绵铁碱再生后的废液可以用于回收鸟粪石,其最佳生成条件为:pH=10,n(Mg~(2+))∶n(PO_4~(3-))∶n(NH~+_4)=1.3∶1∶1.1.在最优条件下,磷回收率可以达到97.8%.本研究提供的方法对于污染水体中磷营养元素的去除及回收利用具有理论与实践意义.

Phosphorus removal and recovery based on modified sponge iron

In order to remove and recover phosphorus from polluted water, sponge iron was modified for phosphorus removal, and it was further packed into a filter for continuous phosphorus removal. The methods for phosphorus desorption from saturated sponge iron, activity regeneration and phosphorus recovery in the form of struvite were also investigated. Results show that the theoretical maximum phosphorus adsorption capacity of modified sponge iron increased from 4.17 to 18.18 mg·g^-1. The saturated sponge iron was regenerated with a 98% activity recovery after treatment using 1 mol·L^-1 sodium hydroxide and 6% sulfuric acid sequentially. The filter packed with the modified sponge iron performed well in removing phosphorus during nearly 200 days of continuous operation with a removal percentage of 30%~90% at influent phosphorus concentration of around 10 mg·L^-1 and hydraulic retention time (HRT) of 1 h. The accumulated phosphorus in the sponge iron attained 6.95 kg·m^-3. Phosphorus could be recovered from the desorption solution from the sponge iron regeneration in the form of struvite, and a maximum phosphorus recovery of 97.8% was achieved at the optimal conditions of pH=10, n(Mg²⁺):n(PO₄^3-):n(NH₄⁺)=1.3:1:1.The method provides theoretical and practical significance for the removal and recycling of phosphorus from polluted water.