Modified Nanorods Synthesis Of α-FeOOH And Their Adsorption And Heterogeneous Fenton-like Degradation Properties Of Methylene Blue

Goethite (a-FeOOH) is a widespread mineral in nature and plays a significant role on migration and transformation of organic and metal ions. A considerable amount of work has been developed to study its adsorption and heterogeneous Fenton-like degradation properties for water pollutants. Goethite as adsorbent and catalyst of water contaminants have been widely studied, but the adsorption capacity are low and the study which pollutants is thoroughly degraded after adsorbed is very little. In this work, we conducted the following research:The modified a-FeOOH nanorods were synthetic by hydrothermal method based on anionic surfactant sodium dodecylsulfate (SDS) as a structure controller and surface modifier. The effect of the important synthesis parameters on the crystal phase, morphology and surface characteristics of the samples were investigated. And the growth mechanism of a-FeOOH was discussed. The reasults showed that the a-FeOOH nanorods were prepared at pH12.00, SDS dosage1～3mM, hydrothermal time4～8h, and hydrothermal temperature80～160℃. When the pH was decreased to～9.01, the product tends to translate into a-Fe2O3. The growth mechanism of a-FeOOH nanorods included two stages of nucleation and growth.The adsorption and heterogeneous Fenton degradation properties of the prepared a-FeOOH nanorods was investigated by using methylene blue (MB) as the target compound. Effectiveness of important adsorption parameters of a-FeOOH dosage, pH, initial MB concentration and reaction temperature in adsorption system and effectiveness of important catalytic parameters of a-FeOOH dosage, H2O2dosage, pH and temperature in catalytic system were researched. The results show:The surfactant-modified a-FeOOH nanorods had high adsorption capacity. MB could be efficiently removed from solution at pH5.00, initial MB concentration200mg/L, a-FeOOH dosage0.5g/L and temperature30℃, with96.00%removal ratio. The adsorption capacity was found to be as high as385mg/g. The adsorption kinetic data could be described well by the pseudo-second-order model. The isothermic data was highly fitted to Langmuir isotherm. Meanwhile, the degradation efficiency of MB in60min was100%for the first oxidation when the initial conditions were [MB]=300mg/L,[a-FeOOH]=0.5g/L, pH=5.0,[H2O2]=4.89mmol/L and50℃. The MB degradation performance on the reused a-FeOOH showed a slight difference with the first oxidation cycle. The degradation efficiency of MB was85.94%for the fourth oxidation cycle.Natural a-FeOOH is often mixed with other metal ions, so the physicochemical characteristics and the adsorption and heterogeneous Fenton degradation of the metal(Mn, Co, Ni, Cr and Zn)-doped a-FeOOH were investigated. The results show that the addition of these metal ion have a certain impact on crystalline phase and morphology of the final product, and Cu-doped sample shows crystalline phase was converted to α-Fe2O3. Meanwhile, MB adsorption capacity of the metal-doped samples decreased and catalytic oxidation enhanced. The metal(except Co)-doped samples can remove100%300mg/L MB within60min.