The concentration of seven Polycyclic Aromatic Hydrocarbons (PAHs) (namely Naphthalene, Acenaphthylene, Fluorene, Phenanthrene, Anthracene, Pyrene and Chrysene) were determined in 28 surface waters, 8 wastewaters, 26 soils and 26 surface sediments from the Msunduzi River, a major supply of portable water in KwaZulu-Natal (KZN) province, South Africa. Water samples were extracted using a conventional liquid-liquid extraction technique into Dichloromethane (DCM) while soils and surface sediments were extracted with an equal mixture of DCM and nhexane using the Soxhlet extraction technique. Purified extracts were analysed by Gas Chromatography-Mass Spectroscopy (GC-MS). Trace levels of PAHs were detected in some water, river bank soils and surface sediments. The concentration of PAHs was found to be comparatively higher in the soils and surface sediments than in the water. The concentration levels as well as distribution of the selected PAHs varied from season to season, however with no clear pattern. The occurrence pattern of PAHs along the river points to human-related activities as the major input sources of PAHs into Msunduzi water. Paired-up isomeric concentration ratios for surface sediments suggested pyrolysis as the major input source of PAHs, especially at sites closer to the city of Pietermaritzburg (PMB).
Mining activities are the main cause of generation of the voluminous sludge waste, loaded with metals precipitated from the treatment of acid mine drainage (AMD) and this is always disposed to the landfill. This study aimed at characterizing and suggesting the reusability potential of AMD sludge to reduce the environmental problem caused by its accumulation so that it could become a valuable material. The sludge was obtained after treating a synthetic AMD with a green oxidant sodium ferrate (VI) (Na
2
FeO
4
) that was prepared by a wet oxidation method. Chemical and physical characterization of a dried sludge generated after treatment was then performed using the Fourier Transform-Infrared and X-Ray powder Diffraction spectroscopy. Scanning Electron Microscopy-Energy Dispersive X-ray Spectroscopy also served to identify the surface morphology of the sludge. The sludge presented a high weight percentage of Fe and O and lower concentrations of other metals such as Al, Mn, Si, and Na. Nitrogen adsorption/desorption isotherms or Brunauer-Emmett-Teller (BET) was used to assess the surface area, pore volume and diameter of the sludge. The BET results showed that the surface area of the sludge obtained after treating the synthetic AMD using Na
2
FeO
4
was 31.50 ± 0.03 m
2
/g with pore diameter and volume of 52.50 nm and 0.41 cm
3
/g, respectively. However, the produced sludge could serve as an adsorbent to remove pollutants from water or to synthesize different magnetic nanocomposites due to its high surface area (>natural zeolite) and high composition of Fe and O.
Sodium ferrate solution was prepared by the wet oxidation process using liquid FeCl3 with NaOCl in a strong alkaline solution. The reference and the product were characterized using UV-visible, XRD and FTIR. The maximum concentration of Na2FeO4(VI) solution was 12.4 g/L (as FeO4 2-). Its stability was studied by recording the absorbances of several ferrate solutions at 505 nm on daily basis for a period of one month. The average rates at pH 12 were 3.19 × 10-11 M s-1 for K2FeO4 and 1.09 × 10-11 M s-1 for Na2FeO4. These average rates of degradation indicate that ferrate can last longer without conserving the ferrate solutions using different buffer solutions or phosphates. The peaks obtained
around 700, 769 and 879 cm-1 using FTIR confirmed the presence of Fe-O bond in the crystals, which is Na2FeO4 (VI). XRD patterns showed an isomorphism between the diffractograms of Na2FeO4 and K2FeO4.
A major problem in the active treatment of acid mine drainage (AMD) is the generation of large volumes of sludge through pH neutralization, oxidation of iron (II) and subsequent metal precipitation. The sludge settling rate, sludge volume index (SVI) and sedimentation process are ones of parameters identifying a good treatment of AMD. Sodium ferrate (VI) (Na2FeO4) is one reagent currently used to treat water due to its quick reaction rate, easy implementation and relatively low chemical and operational costs. However, very limited information is available in the literature related to the detailed characterization and dewaterability of Na2FeO4-treated AMD sludge. This study aimed at characterizing and monitoring settling rate and densification process of synthetic AMD sludge after treatment with Na2FeO4. The results confirmed a complete removal of iron from the synthetic AMD due to high oxidation strength of ferrate (VI) in acidic medium (Eᵒ = 2.2V) and showed the presence of different minerals formed in the sludge after treatment. The concentrations of the sludge collected at different intervals were justified by the densification process and high density of the sludge was obtained after 25 minutes while high weight percent of iron was found at 10 min and Fe and O dominated other elements in the sludge. The study demonstrated very good settling properties of the sludge and the low SVI value ranging between 30 and 60 mL/g TSS.
scite is a Brooklyn-based organization that helps researchers better discover and understand research articles through Smart Citations–citations that display the context of the citation and describe whether the article provides supporting or contrasting evidence. scite is used by students and researchers from around the world and is funded in part by the National Science Foundation and the National Institute on Drug Abuse of the National Institutes of Health.