Competitive sorption of selected anions on modified halloysite

• Autorzy: Prokop A. , Matusik J.
• Konferencja: XVth International Conference of Young Geologists Her'lany 2014 : Międzybrodzie Żywieckie, Poland, May, 8th-10th 2014
• Języki publikacji: EN

Abstrakty

EN

Halloysite is a polytype of kaolinite exhibiting a 1:1 layered structure with the chemical composition of Al4Si4O10(OH)8. Synthesis of new materials based on kaolinites has received wide attention recently (e.g. Dedzo et al. 2012). Soluble forms of chromium, arsenic and phosphorus found in excessive amounts in waters are toxic and/or carcinogenic and may cause health problems. Thus, the aim of this work was to investigate the sorption of aqueous Cr(VI), As(V), and P(V) on natural halloysite and halloysite grafted with diethanolamine. Halloysite (H) sample was obtained from the Intermark Company which exploits the Dunino deposits formed as a result of basalt weathering, located in NW Poland near Legnica. The modification consisted of two steps. Firstly, the intercalate of the mineral with dimethyl sulfoxide (DMSO) was prepared. For this purpose 12.5 g of the mineral was dispersed in a mixture of 90 mL DMSO and 10 mL H2O for 5 days at room temperature (HDMSO sample). Secondly, the HDMSO was refluxed with diethanolamine (DEA) (100 g/L ratio) for 24 h at 180°C under argon flow. The centrifuged product (HD) was washed with isopropanol and subsequently with water to remove unreacted DEA and DMSO remnants and dried at 65°C. The material was characterized using XRD, IR and SEM methods. Adsorption experiments were conducted at 5 mmol/L Cr(VI), As(V), and P(V) concentration in the single-element system for initial pH 3, 6, 9 and in mixed double-element system (1:1 anion molar ratio) for the initial pH 3. For the equilibrium studies, the H and HD samples were shaken in adequate solution (solid/solution ratio 20 g/L) for 24 h at room temperature. Afterwards, the supernatant solution was analyzed for anions. The Cr(VI) concentration was determined by 1.5-diphenylcarbazide method, while the P(V) and As(V) concentrations were determined by molybdenum blue method. The XRD confirmed the formation of an intercalate with DMSO as the characteristic d001 peak at 11.2 Å appeared. After DMSO treatment, the intensity of four distinct bands in the OH stretching region (3,700-3,600 cm-1), which are characteristic for the natural halloysite, changed as a result of interaction between the mineral and DMSO. Also the bands attributed to the C-H stretching vibrations of DMSO methyl groups were found at 3,021, 2,937 and 2,920 cm-1. The interlayer grafting of DEA led to fixing of basal spacing at 10.34 Å. After water washing the IR spectra showed only bands related to the grafted DEA molecules, which confirms the derivative stability (Matusik & Bajda 2013). As the cation exchange capacity (CEC) of the H sample is low, the adsorption process takes place mainly at the crystal edges. It was assumed that the protonated amine group of DEA will attract the anionie species. The results show that such modification does not improve the anion sorption properties of halloysite. The sorption increased only in case of Cr(VI) from 4 to 9 mmol/kg at initial pH 9 (single-element system). The highest sorption was observed in acidic system due to lack of competitive OH ions. In this case, sorption of Cr(VI) was 27 mmol/kg for H and 28 mmol/kg for HD. In contrast, the H adsorbed 108 mmol P(V)/kg in single-element system, while HD adsorbed only 50 mmol P(V)/kg. Adsorption of the As(V) was higher for the H sample and equal to 67 mmol/kg. A comparison of the obtained results for P(V) and As(V) to the sorption efficiency of HDT-MA-modified zeolites (respectively: 80 mmol/kg and 35 mmol/kg) and HDTMA-modified smectites (respectively: 75 mmol/kg and 45 mmol/kg) indicates, that the natural halloysite is a promising sorbent with regard to the studied anions (Mozgawa et al. 2011). In the single-element system the sorption increased as follows: P > As >>Cr. In turn, in the double-element system the competitive sorption was observed. Thus, the sorption of P(V) was lowered in the presence of Cr(VI), while in competitive P(V)-As(V) system the sorption of As(V) dominated. The mechanisms which contribute to the sorption were mainly surface complexation. Further investigation requires thermodynamic studies and the use of i.e. XPS (X-ray photoelectron spectroscopy).

Słowa kluczowe

EN

kaolinite; polytype; structure

• Wydawca: Wydawnictwa AGH
• Czasopismo: Geology, Geophysics and Environment
• Rocznik: 2014
• Tom: Vol. 40, no. 1
• Strony: 118--119
• Opis fizyczny: Bibliogr. 3 poz.

Twórcy

autor

Prokop A.

• AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection, Department of Mineralogy, Petrography and Geochemistry; al. Mickiewicza 30, 30-059 Krakow, Poland

autor

Matusik J.

• AGH University of Science and Technology, Faculty of Geology, Geophysics and Environmental Protection, Department of Mineralogy, Petrography and Geochemistry; al. Mickiewicza 30, 30-059 Krakow, Poland

Bibliografia

• 1. Dedzo G.K., Letaief S. & Detellier C., 2012. Kaolinite-ionic liquid nanohybrid materials as electrochemical sensors for size-selective detection of anions. Journal of Materials Chemistry, 22, 20593-20601.
• 2. Matusik J. & Bajda T., 2013. Immobilization and reduction of hexavalent chromium in the interlayer space of positively charged kaolinites. Journal of Colloid and Interface Science, 398, 74-81.
• 3. Mozgawa W., Król M. & Bajda T., 2011. IR spectra in the studies of anion sorption on natural sorbents. Journal of Molecular Structure, 993, 109-114