| Iron (oxy)hydroxide is a common consitutent of soils, sediments, and aquifers. As a iron (oxy)hydroxide, goethite (-FeOOH) is the most abundant mineral in the surface environment which accounts for 15% of weight in laterite. Goethite is also abundant in Dong hai, the estuaries of Yangtse River and Yellow river. Owing to its stable property, high surface areas and high reactivity, goethite has good performance as adsorbent and so has prominent effects on the transportation, transformation, and precipitation for a large number of cations, anions, metal ions, and organic chelates in subsurface environment. So, It has many advantages such as good and inimitable compatibility as a material for the treatment of heav-metal-containing waste water.In this research sorption and de-sorption studies were conducted to investigate the adsorption and binding efficiency for the chromium-containing model solution and factual waste water with the biomineralized goethite. The aim of this study was to probe the feasibility with it as sorbent material in enigeered system in plant and in situ environmental remediation.At the optimized conditions, the medium pH is 7.00 for CrO42- and Cr2O72-and 5.50 for Cr3+. When the initial concentration of chromium is 10 mg/L the removal ratio is 89.33%, 88.27%, and 98.26% respectively. Re-adsorption under the conditions ibidem got the removal ratio 80% indicated that the material can be utilized for several times. 0.318% and 9.64% desorption for Cr3+ and CrO42- were found with the specimens sorbed at the initial concention of 20mg/L under the condition same with adsorption showed a good binding ability of goethite for chromium.Comparison study of chromium adsorption with natural goethite and specimen biomineralized in systems with macromolecule organic substances found distinct difference in their behavior. So, it is concluded that the interface interaction between goethite and heavy metal ions was notably affected byorganic materials such as polysaccharide, protein and its microstructure also plays important role in it and the specific surface area isn't the determinant factor.X-ray photoelectron spectroscopy (XPS) study of the specimem adsorbed with Cr3+ showing a weak Nls spectrum indicated the involving of NO3 in the sorption. The deconvolution of the Nls showed the deoxidization of NO3-. Apart of it, XPS analysis also found Cr (VI) chemical state besides Cr(III) which was the indication of the oxidation of. The deoxidization of NOs" may promote the oxidation of Cr (III). We also found Cr (III) in the XPS spectrum of the specimem adsorbed with C^O?2' besides Cr (VI). This is the evidence of the deoxidization of Cr2O72-.Scanning electron microscope (SEM) study showed that the micropattern of goethite and clays intermingled in the specimem also had distinct effects on the sorption of chromium. High content of -FeOOH on strawberry-like particles corresponding to high content of Cr (VI) demonstrated the strong binding ability of goethite for Cr (VI). However, the binding ability of goethite for Cr(III) is weaker than clay containing A^Os in the form of kaolin. TEM/EDX, SEM/EDX and XPS studies found the adsorption of Cr(III) on goethite non-homogeneously.
|
PDF Full Text Request