New insights into the activity of green supported nanoscale zero-valent iron composites for enhanced acid blue-25 dye synergistic decolorization from aqueous medium

Abstract

This work investigates how organic and inorganic support for innovatively modified nanoscale zero-valent iron (Fe0) as an integrated green technology to play a constructive role in the remediation of Acid Blue-25 (AB-25) dye in an aqueous solution. Silica gel and starch are used as a support material to solve the problem of aggregation and de-stabilization of Fe0 which has limited the application in an industrial scale. The modified Fe0 is successfully fabricated via a facile, one-step and environmentally-friendly approach. The systematic characterization, including SEM, TEM, STEM-XEDS and XRD for modified Fe0 compared with unmodified bare Fe0 is applied to study the morphological and structural properties. This study is also demonstrated that Fe0 and modified dosage, initial pH value, and reaction temperature and time have played an important role in the reduction of AB-25. Batch experiments showed that the removal efficiency of AB-25 has reached 100% at 6 min. under the optimum condition. Studies on the kinetics and isotherms of AB-25 reduction are well fitted using pseudo-first-order kinetics and Langmuir model, respectively. Thermodynamic studies indicated that these processes are endothermic, spontaneous and naturally favorable. Starch and silica do not only work as a carrier for Fe0 nanoparticles, but also contributes to the decolorization through an “adsorption–enhanced reduction, oxidative degradation, corrosion, and precipitation” mechanisms. The unmodified and modified Fe0 also exhibited easily regeneration and recycling at least for ten adsorption-desorption recycles. This study offers new insights into the promising green technology as a good performance for potential long term applications and magnetic separation for efficiently applied to dye-contaminated water.