Fe0/海藻酸钙微球还原-Fenton氧化协同降解酸性红B

以海藻酸钠为固定基质制备了Fe~0/海藻酸钙微球,探讨基于Fe~0/海藻酸钙微球对染料还原-Fenton氧化协同降解转化的特性及机制.通过FT-IR、SEM、BET、XPS等方法对材料进行了表征,考察了不同还原氧化体系、Fe~0/海藻酸钙微球投加量、溶液p H等因素对酸性红B(ARB)降解效果的影响,以及Fe~0/海藻酸钙微球还原-氧化过程中Fe~0的稳定性和海藻酸钙微球重复催化性能.结果表明,Fe~0/海藻酸钙微球的多级孔道结构对染料有一定的吸附作用.在Fe~0/海藻酸钙微球还原染料阶段中,Fe~0投加量为0. 24 g·L-1,溶液初始p H为2. 96时,180 min后ARB的色度去除率可达到96. 8%.在后续的Fenton氧化阶段,加入10. 75 mmol·L-1H2O2后,ARB色度去除率达到99%,矿化程度提高至64. 7%.与Fe~0/海藻酸钙微球还原体系和Fe3+/海藻酸钙微球Fenton氧化体系相比,Fe~0/海藻酸钙微球还原-Fenton氧化协同体系能够实现ARB的有效脱色和矿化.由于海藻酸钙中羧基对Fe2+/Fe3+的配位作用,Fe离子从微球中转移到溶液中的量为微球中总铁量的3. 9%左右.由于Fe离子能够较好地固定在海藻酸钙微球中,在p H较高条件下,减少了Fe氢氧化物的生成,Fenton反应能够在较宽p H范围内进行,含有Fe2+/Fe3+的海藻酸钙微球表现出较好的重复催化氧化性能.因此,Fe~0/海藻酸钙微球还原-Fenton氧化协同技术为染料废水的处理提供了一种较好的解决方案.

Reduction Cooperated Fenton Oxidation of Zero-valent Iron (ZVI) Immobilized in Alginate Microsphere for Degradation of Acid Red B

The zero-valent iron (ZVI) immobilized in an alginate microsphere was prepared by using sodium alginate as a support material. The characteristics of the Fe⁰/alginate microsphere was characterized by FT-IR, SEM, BET, and XPS. The SEM and BET analyses showed that the Fe⁰/alginate microsphere had a multilevel porous structure and could adsorb ARB. Combined with Fe⁰ reduction and Fe³⁺/Fe²⁺ catalytic oxidation, the mineralization of ARB could be effectively realized. The ARB in the solution was discolored rapidly by the reduction of Fe⁰/alginate microsphere and then oxidized efficiently by the subsequent Fenton reaction. The discoloration rate of ARB in the reduction stage was 96.8%, with an Fe⁰/alginate microsphere dosage of 0.24g·L^-1 and pH of 2.96 after reaction time of 180 min. ARB was reduced to organics of lower molecular weight due to the degradation of azo groups by Fe⁰. In the subsequent Fenton oxidation stage, the mineralization degree of ARB increased to 64.7% after the addition of 10.75 mmol·L^-1 H₂O₂. The influence of the Fe⁰/alginate microsphere dosage, pH, reusability of the Fe⁰/alginate microsphere, and the stability of iron ions in the alginate microsphere were investigated. Due to the coordination of Fe³⁺/Fe²⁺ ions with -COO^--in the alginate, the iron ion in the solution was 3.9% of the total iron content in the microsphere. Iron ions could be well immobilized in calcium alginate microspheres, so the iron hydroxides were generated in lower amounts. The Fenton reaction can be conducted in a wide range of pH. The Fe²⁺/Fe³⁺immobilized in the alginate microsphere demonstrated good catalytic performance after it was reused four times. Therefore, the synergy of reduction and Fenton oxidation by the Fe⁰/alginate microsphere was a better strategy for dye degradation.