Removal of wastewater contaminants by adsorption using iron on carbon foam.
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Date
2022
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Abstract
The dyes in textile effluents have a deleterious impact on water bodies and impede photosynthesis by decreasing sunlight penetration. This work examined the adsorption capacity of an iron oxide sorbent immobilised on carbon foam generated from natural sources for to remove organic methylene blue dye from water. In this investigation, the carbon precursor and iron oxide precursor were combined in a single tank and carbonised. The carbon foam created had a self-assembled structure with flour as a basic constituent. This study examined the thermal and mechanical properties of carbon-based foam created from an inexpensive, green, and template-free carbonisation technique using natural grain and pyrolytic char. In addition, the adsorption capability of an iron oxide sorbent immobilised on natural carbon foam to remove organic methylene blue dye from water and the adsorption of phenol was investigated. The preparation method for iron-based nanoparticles substantially impacts particle shape and size, size distribution, active sites, and subsequent applications. As the number of nanoparticles grew, the dye adsorption increased due to the increased number of active sites. At high temperatures, the molecules of the pigment worked together more efficiently, making it simpler to eliminate.
The possible application of magnetic nanopowder for phenol adsorption mobilised on natural grain carbon foam from an aqueous solution was also examined. Priority pollutants with high toxicity, even at low concentrations, are phenolic chemicals. A magnetic nanopowder was synthesised by dissolving an iron sponge in nitric acid to form iron nitrate, which was then added to a natural grain mixture consisting primarily of flour. Investigating the effect of starting concentration under constant adsorbent dosage revealed that absorbance values rose with increasing concentration. In each of these tests, the amount of phenol adsorbed increased as the original concentration rose. In addition, absorption increased when the carbon foam iron level increased. Using an equation relating to a pseudo first-order chemical reaction, a kinetic investigation determined that the phenol adsorption data sufficiently covered all carbon foam samples evaluated. The Freundlich, Langmuir, and Temkin equations were evaluated for modelling equilibrium adsorption isotherms, and it was determined that the Temkin model satisfactorily fit the experimental data.
Sorbents with 0, 6 and 15 wt iron were produced. Transmission electron microscopy (TEM) and Brunauer-Emmett-Teller (BET) techniques were utilised to analyse the physical characteristics and surface morphology of the synthesised carbon foam. In batch testing, the adsorption capacities were examined by identifying the effects of a rise in iron content, sorbent dosage, contact time, and dye concentration. Breakthrough curves were obtained by adjusting the height of the sorbent bed and varying the flowrate of the dye solution. A higher bed height equates to a bigger amount of adsorbent. With increasing bed height, the breakthrough and equilibrium adsorption capabilities were shown to rise. When the flow rate is high, the dye solution leaves the column before equilibrium, resulting in shorter breakthrough and saturation durations. Higher bed heights and lower flow rates resulted in excellent dye removal in the flow through the system. Breakthrough time increases as iron content rises. The 15 wt.% iron sample had more adsorption capabilities than the 6 wt.% iron sample, but the 0 wt.% iron control sample exhibited minimum adsorption properties. This investigation was best represented by the pseudo-first order kinetic model (R2 > 0.96), while the Freundlich isotherm best describes the adsorption equilibrium (R2 > 0.99). The results show that an iron oxide sorbent immobilised on natural carbon foam effectively removes blue methylene dye.
Variable amounts of iron, nitric acid and magnetite were added to each sample. Additionally, aqueous solutions with varying amounts of methylene blue dye were produced. Based on the change in Gibbs free energy, all samples demonstrated exothermic adsorption except for the magnetite sample, which displayed endothermic adsorption. As the temperature increases, the
viscosity of the dye mixture reduces, allowing more adsorbate to flow through the outer boundary layer and internal pores of the adsorbent. In the adsorption of methylene blue onto iron supported by carbon foam, intraparticle diffusion was not the single rate-limiting step for all samples; rather, the adsorption rate was limited by a multistep elementary reaction mechanism in which numerous processes happened simultaneously. The pseudo-second order kinetic model best describes this experiment (R2 > 0.96), while the Freundlich isotherm best describes the adsorption equilibrium (R2 > 0.999). According to the results, an iron oxide sorbent immobilised on natural carbon foam effectively eliminates methylene dye.
Description
Doctoral Degree. University of KwaZulu-Natal, Durban.