Waste Iron Dust Derived Iron Oxide Nanoparticles for Efficient Adsorption of Multiple Azo Dyes

Abstract

Herein, we have described a simple and viable approach to use the waste byproduct of steel industries: red iron oxide dust (IOD) for synthesizing its reduced version as reduced-IOD (r-IOD). The r-IOD possess active multiphases of iron oxides (Fe@Fe3O4@Fe2O3) and is used for the adsorption of three organic dyes. The surface area of magnetically active r-IOD is found to be ∼4.5 times than that of IOD and shows better mesoporosity. Due to having a larger surface area, r-IOD is used for the efficient adsorption of three organic dyes that include two anionic azo dyes, namely, RG 19 (Reactive Green 19), RO 16 (Reactive Orange 16) and one cationic MG (Malachite Green) dye, with maximum adsorption capacities of ∼2162.9, ∼2273.1, and ∼1400.2 mg g–1, respectively. Various batch experiments related to kinetics, isotherms, and adsorption thermodynamics are studied to understand the rate, order, type, and feasibility of adsorption. The effects of temperature, pH, loading, and concentration, on the adsorption process are also investigated. Moreover, the adsorption capacity of r-IOD is satisfactorily tested via an external spiking method toward the dye removal from industrial wastewater and laboratory wastewater.

Multiphase Reduced Iron Oxide Nanoparticles for Hydrogenation of Mono-, Di-, and Tri-Nitrophenols

“…It was found that only in the presence of r-IOD and NaBH 4 nitrophenols were successfully reduced to their corresponding products (∼99% PAP, ∼53% DAP, and ∼78% TAP), as shown in Figure e. The better reduction catalytic ability of r-IOD than that of IOD can be due to the presence of a higher surface area (better textural properties) and multiple active Fe-oxide phases. Further, various batch studies were performed to optimize the reaction conditions such as concentration of the reactant, catalyst loading, and the amount of reducing agents.…”

“…The r-IOD was synthesized using the previously reported methods, and discussed in the Experimental Section (see Supporting Information). The morphological changes observed after the chemical reduction process were analyzed by field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopic analysis (HRTEM). The low-resolution FESEM image in Figure a displayed the spherical morphology of IOD particles, and Figure b showed FESEM image of r-IOD particles having flake-like morphology, which can also be seen in the low-resolution TEM image of r-IOD in Figure c showing significant morphological changes after the process of chemical reduction.…”

“… The morphological changes observed after the chemical reduction process were analyzed by field emission scanning electron microscopy (FESEM) and high-resolution transmission electron microscopic analysis (HRTEM). The low-resolution FESEM image in Figure a displayed the spherical morphology of IOD particles, and Figure b showed FESEM image of r-IOD particles having flake-like morphology, which can also be seen in the low-resolution TEM image of r-IOD in Figure c showing significant morphological changes after the process of chemical reduction. The HRTEM of r-IOD displayed two types of interplanner spacing, i.e., 0.20 nm, corresponding to the (110) plane of Fe (0) and 0.24 nm, corresponding to the (311) plane of Fe 3 O 4 , as shown in Figure d.…”

“…Due to possessing high surface area and lower oxidation state of iron, r-IOD was utilized to reduce three model nitrophenols, namely, PNP, DNP, and TNP, in the presence of NaBH 4 as a reducing agent into their respective aminophenol, i.e., para-aminophenol (PAP), di-aminophenol (DAP), and tri-aminophenol (TAP), respectively, as shown in Figure a–d. Various control experiments were performed by adding IOD and r-IOD separately in the presence and absence of NaBH 4 , and the reduction reaction progress was monitored using a UV–vis spectrophotometer.…”