基于反冲洗铁泥制备的磁性吸附剂除砷及再生

Arsenic removal and regeneration of magnetic adsorbent prepared from backwashing iron sludge

为了解决除铁锰生物滤池的反冲洗铁泥作为吸附剂使用后难以收集的问题,利用溶剂热法将其制备成为一种磁性材料(magnetic powder adsorbent, MPA),考察其对As(Ⅴ)的吸附特性,结合FTIR表征明确其吸附机制,并探索吸附砷后的MPA最佳再生条件和再生后性能。研究结果表明:根据Langmuir等温吸附模型计算得到MPA在25,35和45℃下对As(Ⅴ)的吸附量分别为8.694,10.005和13.400 mg/g。MPA在吸附过程中发生专性吸附,与As(Ⅴ)形成稳定结合的内层络合物;极碱性溶液能够使吸附的砷发生解吸,以氢氧化钠溶液为再生液,其质量分数为1%时再生效果最好,温度为55℃时最有利于脱附;再生后的MPA吸附速率变快,但最终吸附量降低;3次再生后吸附量能够保持初始吸附量的71.1%,吸附剂可多次再生重复利用,且吸附性能耗竭的吸附剂能够达到直接填埋要求。

To solve the problem that the backwashing iron residuals in the iron and manganese removal are difficult to collect after adsorption as As removal adsorbent, solvothermal method was used to prepare a magnetic powder adsorbent (MPA). Its adsorption performances were studied and its adsorption mechanism for As(V) was investigated and cleared up by FTIR. In addition, optimum regeneration conditions of saturated MPA and performances of regenerated MPA were studied. The results show that the maximum adsorption capacity of MPA for As(V) calculated by Langmuir isotherm equation at 25, 35 and 45 ℃ are 8.694, 10.005 and 13.400 mg/g, respectively. Specific adsorption occurs and MPA forms stable inner complex with As(V). Under extreme alkaline conditions, the adsorbed arsenic can be easily desorbed from MPA. The optimal mass fraction is 1% using NaOH as regenerating solution, and the best temperature for desorption is 55 ℃. The adsorption rate of MPA after regeneration becomes faster, but the adsorption capacity decreases. After three regeneration cycles, the final adsorption capacity maintains 71.1% of the initial value. MPA can be reused for many times, and moreover, the exhausted adsorbent can meet the requirements of landfill without any other treatment.