Removal of Phosphate Using Red Mud: An Environmentally Hazardous Waste By-Product of Alumina Industry

Abstract

The industrial waste, bauxite residue generated in the Bayer chemical process of alumina production, commonly known as red mud (RM) has been used as the adsorbent for selective removal of phosphate in aqueous solutions. RM collected from the storage area of alumina industry was characterized by chemical analysis and physical methods such as BET surface area, Scanning Electron Microscopy (SEM), particle size analysis, and X-ray diffraction (XRD) methods. Among the various red mud samples (0.2-200 ) studied, the samples treated with 1 M HCl for 2 h were found better for the selective adsorption of phosphate in comparison with untreated and heat treated RM samples. The presence of phosphate in the aqueous samples collected after adsorption studies with red mud was determined by standard spectrophotometric procedure using ammonium molybdate and ascorbic acid in nitrate medium at max 880 nm. The studies reported significant adsorption of phosphate on acid treated red mud in comparison with adsorption of phosphate on untreated and heat treated red mud, respectively. The adsorption of phosphate on raw red mud and activated red mud was further investigated with respect to stirring time, pH of the solution, dose of adsorbent, and varying phosphate concentration. Acid treated RM is observed as an efficient and cost-effective adsorbent for selective removal of phosphate in aqueous solutions.

Application of Mesopore-Activated Red Mud for Phosphorus Adsorption

“…Besides, the results of the physical properties analysis of M-ARM materials by the BET method were described in detail in Table 1. [18]; and (iii) the work of Li et al reported that the best pH value for phosphorus adsorption by RM was 7 [19]. From the above statements, there are some differences which, in our opinion, may be due to different RM activation methods.…”

Agricultural waste material Cotton Stack Activated Carbon as a suitable adsorbent for removing nickel (Ni++) ions, a heavy metal, from aqueous solutions: Synthesis, Characterization, and Isotherm Study.

“…Experiment results (Figure 8) further show that chemical treatment can considerably improve the adsorption capacity of raw activated carbon [39]. It also seen that up to 50mgL -1 of initial concentration (at Ce 30) it forms monolayer shown in graph but further more increasing nickel concentration, pressure of adsorption increases due to this it starts again adsorption in porous holes.…”

Exploring the Promotional Effects of K, Sr, and Mg on the Catalytic Stability of Red Mud for the Synthesis of Glycerol Carbonate from Renewable Glycerol

“…The XRD profiles of the fresh RM, RM-800, and RK-800 catalysts with K doping of 5% to 40% are shown in Figure a. Different crystalline phases found in the fresh RM sample were Fe 2 O 3 (at 2θ of 33.0°, 35.68°, 40.7°, 49.23°, 53.9°, 62.2°, and 64.9°), Al­(OH) 3 (2θ of 18.42°), SiO 2 (2θ of 37.6°), TiO 2 (2θ of 24.4°), and NaAlO 2 (2θ of 20.7°). − As reported in our earlier study, calcination of RM at 800 °C resulted in considerable increase in the surface concentration of Fe 2 O 3 and decrease in concentration of active NaAlO 2 , which resulted in low activity of the catalyst. It can be seen from Figure a that KNO 3 remained in well-dispersed phase on the surface of the RM at a lower percentage of K loading (5% to 15%), due to which there were no distinct XRD peaks of KNO 3 observed and Fe 2 O 3 remained as a dominant phase in the RK-800 catalysts loaded up to 15% K. This could be a reason for the low activity of the catalyst at low K loading.…”